Gear ratios and bad advice

ChrisTJ98 said:
Freaking overwhelmed reading this post about gears. Still unsure what the hell to do. 98 TJ 4.0, ax-15, 3.07 gears. I will probably search for a dana 44 to re gear myself but with 31x10.50x15 all terrain bf Goodrich that say they measure an actual 30.5 inches, is 3.73 good enough or should you really go to 4.10's I understand, running at higher rpms is not a bad thing because you do want to run in the middle or slightly higher rpm range of whatever your engine is designed for. It's the same have experienced with outboard motors going with different props. I do want close to maximum mpg as I don't go offload that much anymore. I do live in a very FLAT state.

I guess my question here will 4.10's and this tire size end up eating a lot more into my mpg? Should I just stay with 3.73 gears?
Click to expand...
I have an 04 4.0 running KO2 32sx12.5... I have not regeared yet. Ive got 3.73 going and it's fine on the highway and flats. When I drive up in the mountains on the highway even I'm struggling a bit. But if it's just a daily driver in the city 3.73 might be ok. I'm still revving 2500rpm going 100km in 4th...
 
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jjvw said:
42rle/37.5"/5.38=2495rpm@75mph
Could be better.
Click to expand...
Maybe a little but I prefer being able to talk to my passengers :p with a flowmaster exhaust it would be way too loud getting up to 3000...2500ish still has over 80-85% of max torque and whenever I hit a hill too steep to pull in OD it just downshifts and accelerates back to 70 no problem...I am in East Texas though...only guys in the mountains would need lower...also losing more and more gear strength when you go deeper especially in small ring gear axles...also options above 5.38 are scarce unless you have 60s...so 5.38 is the logical ceiling for most even if you go bigger than 35s
 
Brantley said:

Please know what you're talking about before making a video to the entire world about something. While the intentions of this video are good, and Bleepin' Jeep usually has good information for its viewers, I don't think I've ever groaned more over a Jeep topic than I did watching this video.

This video is full of misinformation. The worst part about it is the multitude of comments from people who had no idea what gear to run and are now thanking him for "helping" them pick out what they should run. Those will be some sorely disappointed folks when they realize how bad his advice was.

He starts by teaching one how they "should" calculate their new gear ratio. He bases his calculations off of stock gears (3.07 in several cases) and uses 29" tires as the basis for his calculations. This is problematic for several reasons.

1) 3.07 was a horrible gear ratio, even for stock tires. On 29" tires with the AX15, you end up right at 2200 RPM at around 70 in 5th gear which lugs the engine. Not good.

He ends up doing the math for 33's which results in him giving 3.55 as a recommendation for 33" tires. I don't know if any of you have tried that ratio, but it sucks.

So, he's already basing his recommendation off of a pretty poor example. If you want to do the math equation, start with Rubicon gearing. The 5-speed manual Rubicon TJs were really the only Jeeps properly geared from the factory in my opinion. The automatic should have had 4.56 for 31" tires, not 4.10 like its manual counterpart.

2) He adds nothing to compensate for larger, heavier tires, extra weight on the Jeep, lift height pushing it into the wind stream, etc. The lift height is almost negligible but the other items I mentioned make a huge difference.

3) His 2.5 example is flawed for several reasons.

First, he starts with using his YJ as an example. He uses 29" tires and 4.10 gears to describe why his 4.88 on 33" tires has the RPM "through the roof".

The flaws begin with the tire size. The largest tire size on a 2.5 YJ was 205/75R15 (27.1"), not 29". There was an option for 215/75R15 (27.7") which my 4.0 YJ had but I believe that was for the 4.0 only. So, he's already nearly 2" off on his calculation method. That makes a huge difference in what he's going to recommend.

Next, he does his math using 29" tires and 4.10. He ends up getting a number of 4.95 for 35" tires. Rather than going to the lower option of 5.13, he chooses to drop back to 4.88. Bad decision, that means if his Jeep came stock with 4.10 and 29" tires, he would now have even less gearing with 35's than he did stock on those 29" tires that don't exist on the YJ model.

He follows this up by saying he regeared to 4.88 expecting to run 35's but ended up with 33's instead because of a deal he got or something. He proceeds by saying his RPM is way too high and that he hits 3000 RPM at 55 mph. False, that setup doesn't reach 3000 until about 69-70 mph.

He also says his poor gas mileage comes from running 3000 RPM, also false, the 2.5 did more than that stock and it sure didn't ever hurt gas mileage. That's the nature of the beast on a 2.5.

4) Real world vs. math. Numbers are good but gear ratios on paper are nowhere close to realistic when you actually drive the Jeep with all the variables the world throws at it.

You can't tell me that 3.55 gear ratio he recommended for his 33's will end up driving well or even close to it.


To end this long rant, don't listen to the people telling you to use your stock gear ratio to determine a new gear ratio for a larger tire. It may add up on paper but it doesn't translate properly in the real world.

The only good combination from the factory was the 5-speed Rubicon and then some of the 32RH combinations.

One other combo that was okay when stock was the 5-speed 3.55 package that came with about 27.7-28" tires. However, you can't follow this for larger ties because it'll end up at 4.10 for 33's, 4.56 for 35's, etc., which aren't ideal setups.

There should have never even been 3.07 offered at all in my opinion.

I sure hope that YouTube guy has played around with his ratios and tires a few more times since the production of this video and has figured out that his advice was very misleading not ideal in the slightest.

Things like this where the people giving out info seem very knowledgeable end up convincing people who don't know an better that they can listen to the person who speaks in confidence, even if they aren't right. Since this guy had some confidence in the things he said, I wouldn't be surprised at all if he lead quite a few people down the wrong road of picking the proper gear ratio if they chose to regear their axles.

Bottom line, listen to people who have real world experience with all the different ratios and tire sizes, not the guy on YouTube using math to figure out what he'll run. There are quite a few very experienced guys out there who can steer you to the exact ratio you want off of the top of their head. Those are the guys you want to listen to.

Rant over.

Just to provide something useful out of this post, here are what I and many other forum members have determined to be the best ratios for Wranglers older than 2007 that have the 4.0L, 2.5L, or 2.4L engines.

4.0L engine

5-speed manual (AX15/NV3550)

31's - 4.10 (this is how the Rubicon came)
33's - 4.56
35's - 4.88
37's - 5.13 or 5.38 (personally I'd choose 5.38 which adds about 100 RPM to help for the larger 37" tires)

3-speed auto (32RH) used 1987-2002, deemed the TF999 in older 1987-1991 YJ Wranglers

31's - 3.73
33's - 4.10
35's - 4.56
37's - 4.88

4-speed auto (42RLE) used 2003-2006, actually used longer in the JK but I'm not including JK Wranglers.

31's - 4.56, even though the factory Rubicon used 4.10 unfortunately
33's - 4.88
35's - 5.38 (Rubicon's have to change carriers to support this deep of a gear ratio)
37's - forget about it unless you get axles that support 5.89.

6-speed manual NSG370
31's 3.73 more street, 4.10 more trail or mountainous/hilly highway
33's - 4.10 more street, 4.56 more trail or mountainous/hilly highway
35's - 4.56 more street, 4.88 more trail or mountainous/ hilly highway

2.5L & 2.4L engine

5-speed AX5/NV1500

31's - 4.56/4.88 (either is good, 4.88 really helps keep speed on the highway)
33's - 4.88
35's - 5.38 if you have the axle for it, otherwise 5.13

3-speed auto 30RH

31's - 4.10
33's - 4.56
35's - 4.88

4-speed auto 42RLE

31's - 4.88
33's - 5.13 or 5.38 if you can run them.
35's+ - wouldn't even consider it.
Click to expand...
Great points...man that video is misleading....great breakdown by transmission this helps tons...wish this was on YT...I might just have to make a video :O
 
Navy Seal said:
Maybe a little but I prefer being able to talk to my passengers :p with a flowmaster exhaust it would be way too loud getting up to 3000...2500ish still has over 80-85% of max torque and whenever I hit a hill too steep to pull in OD it just downshifts and accelerates back to 70 no problem...I am in East Texas though...only guys in the mountains would need lower...also losing more and more gear strength when you go deeper especially in small ring gear axles...also options above 5.38 are scarce unless you have 60s...so 5.38 is the logical ceiling for most even if you go bigger than 35s
Click to expand...

You're running 38s on stock axles?
 
I have a flow master exhaust. 4.88 35's with the 6 speed. Sit right about 3100 rpm at 75 mph. And the wind noise is still more than exhaust, engine and tire noise
 
Navy Seal said:
You should just stay with 3.73s....4.10s are not enough difference to go through the gear change...31s and 3.73s will get you better mpgs than 4.10s but the 4.10s will get you a little more power in 5th...although the 4.0 mpg is really not that great to begin with lol...
Click to expand...
I have 3.07 and 31's now regardless I need a gear change. I'll ride in a friends jeep with 3.73 and 31's and go from there. He pretty much has everything the same as mine as far as transmission tires and engine. I'm in Louisiana it's flat as shit here unless I go to shreveport and it gets kinda hilly.
 
ChrisTJ98 said:
I have 3.07 and 31's now regardless I need a gear change. I'll ride in a friends jeep with 3.73 and 31's and go from there. He pretty much has everything the same as mine as far as transmission tires and engine. I'm in Louisiana it's flat as shit here unless I go to shreveport and it gets kinda hilly.
Click to expand...

If you're going to regear, be sure not to sell yourself short and not go deep enough.
 
jjvw said:
If you're going to regear, be sure not to sell yourself short and not go deep enough.
Click to expand...
I'm gonna re gear it myself. I have a couple people around me I could probably ask to double check my work. I have pretty all the tools to do it, so I look at it like if I mess up I'll gear it to the right gear anyways. I know what you mean though I don't want to under gear it but shit 373 or 410 gotta be way the hell better then what I have now anyways. This thing is gonna most likely be just a daily driver with little to no offload.
 
Street vs off road doesn't matter. You are gearing for the highway. And if you gear properly for the highway you will also have better gears for off road.

Keep in mind that the Rubicon came with 4.10 to turn 31" tires. Also keep in mind that the 42rle was always undergeared from the factory and should never be used as a baseline for good gearing. If anything, look at the 32rh.
 
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Hi all, new to the group and dragging up an old thread... Have a TJ with the 32R 3 spd auto and 3.73 ratio diffs.
This is an off road only so will rarely get into high range, Or travel at highway speeds. What we call in New Zealand a trailer queen . Its stock std at the moment .
Was toying with fitting 33's ... but would really like to run 35's. Now the question is .... change the diff ratios to ??? or splash out on a crawler box and just throw that in ....... What say you all.... experiences ... ideas.... Thanks in adance
 
Brantley said:

Please know what you're talking about before making a video to the entire world about something. While the intentions of this video are good, and Bleepin' Jeep usually has good information for its viewers, I don't think I've ever groaned more over a Jeep topic than I did watching this video.

This video is full of misinformation. The worst part about it is the multitude of comments from people who had no idea what gear to run and are now thanking him for "helping" them pick out what they should run. Those will be some sorely disappointed folks when they realize how bad his advice was.

He starts by teaching one how they "should" calculate their new gear ratio. He bases his calculations off of stock gears (3.07 in several cases) and uses 29" tires as the basis for his calculations. This is problematic for several reasons.

1) 3.07 was a horrible gear ratio, even for stock tires. On 29" tires with the AX15, you end up right at 2200 RPM at around 70 in 5th gear which lugs the engine. Not good.

He ends up doing the math for 33's which results in him giving 3.55 as a recommendation for 33" tires. I don't know if any of you have tried that ratio, but it sucks.

So, he's already basing his recommendation off of a pretty poor example. If you want to do the math equation, start with Rubicon gearing. The 5-speed manual Rubicon TJs were really the only Jeeps properly geared from the factory in my opinion. The automatic should have had 4.56 for 31" tires, not 4.10 like its manual counterpart.

2) He adds nothing to compensate for larger, heavier tires, extra weight on the Jeep, lift height pushing it into the wind stream, etc. The lift height is almost negligible but the other items I mentioned make a huge difference.

3) His 2.5 example is flawed for several reasons.

First, he starts with using his YJ as an example. He uses 29" tires and 4.10 gears to describe why his 4.88 on 33" tires has the RPM "through the roof".

The flaws begin with the tire size. The largest tire size on a 2.5 YJ was 205/75R15 (27.1"), not 29". There was an option for 215/75R15 (27.7") which my 4.0 YJ had but I believe that was for the 4.0 only. So, he's already nearly 2" off on his calculation method. That makes a huge difference in what he's going to recommend.

Next, he does his math using 29" tires and 4.10. He ends up getting a number of 4.95 for 35" tires. Rather than going to the lower option of 5.13, he chooses to drop back to 4.88. Bad decision, that means if his Jeep came stock with 4.10 and 29" tires, he would now have even less gearing with 35's than he did stock on those 29" tires that don't exist on the YJ model.

He follows this up by saying he regeared to 4.88 expecting to run 35's but ended up with 33's instead because of a deal he got or something. He proceeds by saying his RPM is way too high and that he hits 3000 RPM at 55 mph. False, that setup doesn't reach 3000 until about 69-70 mph.

He also says his poor gas mileage comes from running 3000 RPM, also false, the 2.5 did more than that stock and it sure didn't ever hurt gas mileage. That's the nature of the beast on a 2.5.

4) Real world vs. math. Numbers are good but gear ratios on paper are nowhere close to realistic when you actually drive the Jeep with all the variables the world throws at it.

You can't tell me that 3.55 gear ratio he recommended for his 33's will end up driving well or even close to it.


To end this long rant, don't listen to the people telling you to use your stock gear ratio to determine a new gear ratio for a larger tire. It may add up on paper but it doesn't translate properly in the real world.

The only good combination from the factory was the 5-speed Rubicon and then some of the 32RH combinations.

One other combo that was okay when stock was the 5-speed 3.55 package that came with about 27.7-28" tires. However, you can't follow this for larger ties because it'll end up at 4.10 for 33's, 4.56 for 35's, etc., which aren't ideal setups.

There should have never even been 3.07 offered at all in my opinion.

I sure hope that YouTube guy has played around with his ratios and tires a few more times since the production of this video and has figured out that his advice was very misleading not ideal in the slightest.

Things like this where the people giving out info seem very knowledgeable end up convincing people who don't know an better that they can listen to the person who speaks in confidence, even if they aren't right. Since this guy had some confidence in the things he said, I wouldn't be surprised at all if he lead quite a few people down the wrong road of picking the proper gear ratio if they chose to regear their axles.

Bottom line, listen to people who have real world experience with all the different ratios and tire sizes, not the guy on YouTube using math to figure out what he'll run. There are quite a few very experienced guys out there who can steer you to the exact ratio you want off of the top of their head. Those are the guys you want to listen to.

Rant over.

Just to provide something useful out of this post, here are what I and many other forum members have determined to be the best ratios for Wranglers older than 2007 that have the 4.0L, 2.5L, or 2.4L engines.

4.0L engine

5-speed manual (AX15/NV3550)

31's - 4.10 (this is how the Rubicon came)
33's - 4.56
35's - 4.88
37's - 5.13 or 5.38 (personally I'd choose 5.38 which adds about 100 RPM to help for the larger 37" tires)

3-speed auto (32RH) used 1987-2002, deemed the TF999 in older 1987-1991 YJ Wranglers

31's - 3.73
33's - 4.10
35's - 4.56
37's - 4.88

4-speed auto (42RLE) used 2003-2006, actually used longer in the JK but I'm not including JK Wranglers.

31's - 4.56, even though the factory Rubicon used 4.10 unfortunately
33's - 4.88
35's - 5.38 (Rubicon's have to change carriers to support this deep of a gear ratio)
37's - forget about it unless you get axles that support 5.89.

6-speed manual NSG370
31's 3.73 more street, 4.10 more trail or mountainous/hilly highway
33's - 4.10 more street, 4.56 more trail or mountainous/hilly highway
35's - 4.56 more street, 4.88 more trail or mountainous/ hilly highway

2.5L & 2.4L engine

5-speed AX5/NV1500

31's - 4.56/4.88 (either is good, 4.88 really helps keep speed on the highway)
33's - 4.88
35's - 5.38 if you have the axle for it, otherwise 5.13

3-speed auto 30RH

31's - 4.10
33's - 4.56
35's - 4.88

4-speed auto 42RLE

31's - 4.88
33's - 5.13 or 5.38 if you can run them.
35's+ - wouldn't even consider it.
Click to expand...
Brantley said:

Please know what you're talking about before making a video to the entire world about something. While the intentions of this video are good, and Bleepin' Jeep usually has good information for its viewers, I don't think I've ever groaned more over a Jeep topic than I did watching this video.

This video is full of misinformation. The worst part about it is the multitude of comments from people who had no idea what gear to run and are now thanking him for "helping" them pick out what they should run. Those will be some sorely disappointed folks when they realize how bad his advice was.

He starts by teaching one how they "should" calculate their new gear ratio. He bases his calculations off of stock gears (3.07 in several cases) and uses 29" tires as the basis for his calculations. This is problematic for several reasons.

1) 3.07 was a horrible gear ratio, even for stock tires. On 29" tires with the AX15, you end up right at 2200 RPM at around 70 in 5th gear which lugs the engine. Not good.

He ends up doing the math for 33's which results in him giving 3.55 as a recommendation for 33" tires. I don't know if any of you have tried that ratio, but it sucks.

So, he's already basing his recommendation off of a pretty poor example. If you want to do the math equation, start with Rubicon gearing. The 5-speed manual Rubicon TJs were really the only Jeeps properly geared from the factory in my opinion. The automatic should have had 4.56 for 31" tires, not 4.10 like its manual counterpart.

2) He adds nothing to compensate for larger, heavier tires, extra weight on the Jeep, lift height pushing it into the wind stream, etc. The lift height is almost negligible but the other items I mentioned make a huge difference.

3) His 2.5 example is flawed for several reasons.

First, he starts with using his YJ as an example. He uses 29" tires and 4.10 gears to describe why his 4.88 on 33" tires has the RPM "through the roof".

The flaws begin with the tire size. The largest tire size on a 2.5 YJ was 205/75R15 (27.1"), not 29". There was an option for 215/75R15 (27.7") which my 4.0 YJ had but I believe that was for the 4.0 only. So, he's already nearly 2" off on his calculation method. That makes a huge difference in what he's going to recommend.

Next, he does his math using 29" tires and 4.10. He ends up getting a number of 4.95 for 35" tires. Rather than going to the lower option of 5.13, he chooses to drop back to 4.88. Bad decision, that means if his Jeep came stock with 4.10 and 29" tires, he would now have even less gearing with 35's than he did stock on those 29" tires that don't exist on the YJ model.

He follows this up by saying he regeared to 4.88 expecting to run 35's but ended up with 33's instead because of a deal he got or something. He proceeds by saying his RPM is way too high and that he hits 3000 RPM at 55 mph. False, that setup doesn't reach 3000 until about 69-70 mph.

He also says his poor gas mileage comes from running 3000 RPM, also false, the 2.5 did more than that stock and it sure didn't ever hurt gas mileage. That's the nature of the beast on a 2.5.

4) Real world vs. math. Numbers are good but gear ratios on paper are nowhere close to realistic when you actually drive the Jeep with all the variables the world throws at it.

You can't tell me that 3.55 gear ratio he recommended for his 33's will end up driving well or even close to it.


To end this long rant, don't listen to the people telling you to use your stock gear ratio to determine a new gear ratio for a larger tire. It may add up on paper but it doesn't translate properly in the real world.

The only good combination from the factory was the 5-speed Rubicon and then some of the 32RH combinations.

One other combo that was okay when stock was the 5-speed 3.55 package that came with about 27.7-28" tires. However, you can't follow this for larger ties because it'll end up at 4.10 for 33's, 4.56 for 35's, etc., which aren't ideal setups.

There should have never even been 3.07 offered at all in my opinion.

I sure hope that YouTube guy has played around with his ratios and tires a few more times since the production of this video and has figured out that his advice was very misleading not ideal in the slightest.

Things like this where the people giving out info seem very knowledgeable end up convincing people who don't know an better that they can listen to the person who speaks in confidence, even if they aren't right. Since this guy had some confidence in the things he said, I wouldn't be surprised at all if he lead quite a few people down the wrong road of picking the proper gear ratio if they chose to regear their axles.

Bottom line, listen to people who have real world experience with all the different ratios and tire sizes, not the guy on YouTube using math to figure out what he'll run. There are quite a few very experienced guys out there who can steer you to the exact ratio you want off of the top of their head. Those are the guys you want to listen to.

Rant over.

Just to provide something useful out of this post, here are what I and many other forum members have determined to be the best ratios for Wranglers older than 2007 that have the 4.0L, 2.5L, or 2.4L engines.

4.0L engine

5-speed manual (AX15/NV3550)

31's - 4.10 (this is how the Rubicon came)
33's - 4.56
35's - 4.88
37's - 5.13 or 5.38 (personally I'd choose 5.38 which adds about 100 RPM to help for the larger 37" tires)

3-speed auto (32RH) used 1987-2002, deemed the TF999 in older 1987-1991 YJ Wranglers

31's - 3.73
33's - 4.10
35's - 4.56
37's - 4.88

4-speed auto (42RLE) used 2003-2006, actually used longer in the JK but I'm not including JK Wranglers.

31's - 4.56, even though the factory Rubicon used 4.10 unfortunately
33's - 4.88
35's - 5.38 (Rubicon's have to change carriers to support this deep of a gear ratio)
37's - forget about it unless you get axles that support 5.89.

6-speed manual NSG370
31's 3.73 more street, 4.10 more trail or mountainous/hilly highway
33's - 4.10 more street, 4.56 more trail or mountainous/hilly highway
35's - 4.56 more street, 4.88 more trail or mountainous/ hilly highway

2.5L & 2.4L engine

5-speed AX5/NV1500

31's - 4.56/4.88 (either is good, 4.88 really helps keep speed on the highway)
33's - 4.88
35's - 5.38 if you have the axle for it, otherwise 5.13

3-speed auto 30RH

31's - 4.10
33's - 4.56
35's - 4.88

4-speed auto 42RLE

31's - 4.88
33's - 5.13 or 5.38 if you can run them.
35's+ - wouldn't even consider it.
Click to expand...
I know this is an old post and on a TJ forum, but I have a YJ with an AX-5 2.5L and wanted to know if what you have listed above also goes for the YJ. I have 33's and was wanting to upgrade to 35's. When you stated that you recommend 5.38 if you have the axle for it. What axle do you recommend? Thanks for any help.
 
Ron Mueller said:
I know this is an old post and on a TJ forum, but I have a YJ with an AX-5 2.5L and wanted to know if what you have listed above also goes for the YJ. I have 33's and was wanting to upgrade to 35's. When you stated that you recommend 5.38 if you have the axle for it. What axle do you recommend? Thanks for any help.
Click to expand...
5.38 generally requires Dana 44 (or larger) axles front and rear, at least among TJ and YJ factory axles. The highest ratio available for either the Dana 30 or Dana 35 is 5.13, so either of those axles will limit you to 5.13. 5.13 would be a bit taller than optimal for that engine/transmission/tire combination, but probably not unbearable.

My personal opinion is that swapping axles just to get that bump from 5.13 to 5.38 is not worth the cost unless you plan to go to significantly larger axles regardless. If you do swap to D44s, which would require significant fabrication for YJs, 5.89 also becomes an option, and may make more sense if you aren't using repurposed factory Rubicon lockers.

Assuming you have factory axles, I would focus on a Super 35 kit for the rear, maybe a Super 30 kit for the front (or at least chromoly 27 spline axles), and 5.13 gears, as well as quality chromoly axles. Other upgrades like a 15" big brake kit, fresh bearings and ball joints, and other upgrades may also be worth considering.

With the AX-5, 4th gear and 5th gear are very close together, so when you need a bit of extra torque, downshifting is easily completed. With 5.13s and 35s, 3rd gear would potentially be usable at lower freeway speeds (65 mph or less approximately) and would be the appropriate gear for passing or climbing steeper hills.
 
As above but focused just on your rear Dana 35 axle, it's not strong enough in stock form for 35" tires. With 35's or 33's with a locker it will snap an axle shaft. The good news is it's easy to upgrade that axle with a Super 35 kit so it would be strong enough for both 35's and a locker. Go with 5.13 gearing since that's as low of a ratio as can be installed into either of your axles. Otherwise I'd say go with 5.38 gears.

But if it were me with the 2.5L engine I'd stick with 33's and the 5.13 gearing.
 
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Steel City 06 said:
5.38 generally requires Dana 44 (or larger) axles front and rear, at least among TJ and YJ factory axles. The highest ratio available for either the Dana 30 or Dana 35 is 5.13, so either of those axles will limit you to 5.13. 5.13 would be a bit taller than optimal for that engine/transmission/tire combination, but probably not unbearable.

My personal opinion is that swapping axles just to get that bump from 5.13 to 5.38 is not worth the cost unless you plan to go to significantly larger axles regardless. If you do swap to D44s, which would require significant fabrication for YJs, 5.89 also becomes an option, and may make more sense if you aren't using repurposed factory Rubicon lockers.

Assuming you have factory axles, I would focus on a Super 35 kit for the rear, maybe a Super 30 kit for the front (or at least chromoly 27 spline axles), and 5.13 gears, as well as quality chromoly axles. Other upgrades like a 15" big brake kit, fresh bearings and ball joints, and other upgrades may also be worth considering.

With the AX-5, 4th gear and 5th gear are very close together, so when you need a bit of extra torque, downshifting is easily completed. With 5.13s and 35s, 3rd gear would potentially be usable at lower freeway speeds (65 mph or less approximately) and would be the appropriate gear for passing or climbing steeper hills.
Click to expand...
Thank you. I really appreciate your help.
 
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Steel City 06 said:
5.38 generally requires Dana 44 (or larger) axles front and rear, at least among TJ and YJ factory axles. The highest ratio available for either the Dana 30 or Dana 35 is 5.13, so either of those axles will limit you to 5.13. 5.13 would be a bit taller than optimal for that engine/transmission/tire combination, but probably not unbearable.

My personal opinion is that swapping axles just to get that bump from 5.13 to 5.38 is not worth the cost unless you plan to go to significantly larger axles regardless. If you do swap to D44s, which would require significant fabrication for YJs, 5.89 also becomes an option, and may make more sense if you aren't using repurposed factory Rubicon lockers.

Assuming you have factory axles, I would focus on a Super 35 kit for the rear, maybe a Super 30 kit for the front (or at least chromoly 27 spline axles), and 5.13 gears, as well as quality chromoly axles. Other upgrades like a 15" big brake kit, fresh bearings and ball joints, and other upgrades may also be worth considering.

With the AX-5, 4th gear and 5th gear are very close together, so when you need a bit of extra torque, downshifting is easily completed. With 5.13s and 35s, 3rd gear would potentially be usable at lower freeway speeds (65 mph or less approximately) and would be the appropriate gear for passing or climbing steeper hills.
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Thank you. I really appreciate your help.
 
Jerry Bransford said:
As above but focused just on your rear Dana 35 axle, it's not strong enough in stock form for 35" tires. With 35's or 33's with a locker it will snap an axle shaft. The good news is it's easy to upgrade that axle with a Super 35 kit so it would be strong enough for both 35's and a locker. Go with 5.13 gearing since that's as low of a ratio as can be installed into either of your axles. Otherwise I'd say go with 5.38 gears.

But if it were me with the 2.5L engine I'd stick with 33's and the 5.13 gearing.
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Thank you. I appreciate the advice. I will definitely look into the super 30 and 35 kit and consider sticking with the 33's and go to the 5.13 gearing. The reason I was looking at 35's is to get a bit more ground clearance for my axles. I got stuck in some ruts where jeeps with 35's were getting through. Got my pride hurt a bit. However, I only have one locker in the front but if I can put a locker in the rear with the super 35, and then also regear that may be the equalizer.
 
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Ron Mueller said:
Thank you. I appreciate the advice. I will definitely look into the super 30 and 35 kit and consider sticking with the 33's and go to the 5.13 gearing. The reason I was looking at 35's is to get a bit more ground clearance for my axles. I got stuck in some ruts where jeeps with 35's were getting through. Got my pride hurt a bit. However, I only have one locker in the front but if I can put a locker in the rear with the super 35, and then also regear that may be the equalizer.
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If your front locker is in good condition, skip the Super 30 kit and just add in chromoly 27 spline shafts when you get the chance. Otherwise you'll need a new locker for the front if you do a Super 30. Revolution Gear and Axle makes decent USA-made chromoly shafts that use JK u-joints for extra strength. Other companies also supply decent imported axles. RCV is another great option but probably the highest price of any option. The new shafts can be installed at any time.

The Super 35 is highly recommended, however. Due to the design of the Dana 35's axle shaft bearings, it is exceptionally difficult to produce a chromoly shaft with a hard enough surface to last with a bearing, thus installing chromoly shafts is generally not recommended. The Super 35 kit gives you larger diameter axle shafts instead using typically a 1541H alloy, which gives a decent boost in strength both from the alloy and the larger diameter. The Super 35 kit requires a new differential carrier, so you're best off doing it during your locker install and regear.
 
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