Gear ratios and bad advice

Should I open a can-o-worms asking about gear ratios for high compression stroker motors/ V8's/ diesel swaps?
 
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2002 TJ - 3 speed automatic - per the build sheet it has 3.73 gears

Currently riding on pretty worn 245/75/16 tires the PO put on there with the moab rubicon wheels

My question is this: will I feel a noticeable decline in performance if I move up to 265/75/16? (3.9% increase in diameter per tire size calculators ... which maybe translates to a 5-6% increase if you factor in the tread wear on the old tires vs the brand new tires)

I really love the way it drives right now so I am a little hesitant to move to the bigger tire. I'm not embarrassed to admit that my reasoning to go bigger is admittedly aesthetics. I've seen some builds with a 2-2.5 inch lift and 265's and I think that profile / stance looks awesome.

What do you guys think?
 
2002 TJ - 3 speed automatic - per the build sheet it has 3.73 gears

Currently riding on pretty worn 245/75/16 tires the PO put on there with the moab rubicon wheels

My question is this: will I feel a noticeable decline in performance if I move up to 265/75/16? (3.9% increase in diameter per tire size calculators ... which maybe translates to a 5-6% increase if you factor in the tread wear on the old tires vs the brand new tires)

I really love the way it drives right now so I am a little hesitant to move to the bigger tire. I'm not embarrassed to admit that my reasoning to go bigger is admittedly aesthetics. I've seen some builds with a 2-2.5 inch lift and 265's and I think that profile / stance looks awesome.

What do you guys think?

You'll be fine.
 
2002 TJ - 3 speed automatic - per the build sheet it has 3.73 gears

Currently riding on pretty worn 245/75/16 tires the PO put on there with the moab rubicon wheels

My question is this: will I feel a noticeable decline in performance if I move up to 265/75/16? (3.9% increase in diameter per tire size calculators ... which maybe translates to a 5-6% increase if you factor in the tread wear on the old tires vs the brand new tires)

I really love the way it drives right now so I am a little hesitant to move to the bigger tire. I'm not embarrassed to admit that my reasoning to go bigger is admittedly aesthetics. I've seen some builds with a 2-2.5 inch lift and 265's and I think that profile / stance looks awesome.

What do you guys think?
If you have 3.73 gears, you should be fine. 3.07s, which were common with the 32RH would give you trouble.

3.73 would put you at about 2700 RPM at 70 mph, which is roughly the same as a factory TJR equipped with the NSG370.

This is assuming you have a 6 cyl
 
2002 TJ - 3 speed automatic - per the build sheet it has 3.73 gears

Currently riding on pretty worn 245/75/16 tires the PO put on there with the moab rubicon wheels

My question is this: will I feel a noticeable decline in performance if I move up to 265/75/16? (3.9% increase in diameter per tire size calculators ... which maybe translates to a 5-6% increase if you factor in the tread wear on the old tires vs the brand new tires)

I really love the way it drives right now so I am a little hesitant to move to the bigger tire. I'm not embarrassed to admit that my reasoning to go bigger is admittedly aesthetics. I've seen some builds with a 2-2.5 inch lift and 265's and I think that profile / stance looks awesome.

What do you guys think?
If it were me, and I planned to be driving it on the street a lot with the265's, planned on keeping it that way for a while, I would go ahead and swap to 4.10's. This would get it geared a bit better for street driving to include hills.

It's in my opinion that's it's better to be a little over-geared rather than under geared for street driving.
 
i think I've finally found the answer to a question I have been struggling with. I have an 04 tj 5spd. just regeared to 4.56 in preparation to lift and bigger tires. If I am reading and understanding right. 33' tires would be perfect for daily driving and weekend trail riding.
How did that regear work out for you? I have a 06 sport 4.0L, auto w/3.73 gears on 33" tires. Daily driver for my daughter.
 
I guess that's a no...

More horsepower is going to really help with the .69 over drive ratio in the 42RLE.
Tundra comes with a double overdrive 0.55 5th gear, and 4.10 rear end but it has a 5.7L...
so if the 42RLE will handle a V8 or Diesel.... more power would resolve part of the 42RLE compromises.
 
Tundra comes with a double overdrive 0.55 5th gear, and 4.10 rear end but it has a 5.7L...
so if the 42RLE will handle a V8 or Diesel.... more power would resolve part of the 42RLE compromises.
The answer is and always has been horsepower. If the Jeep made 300-350 it would fully take advantage of the .69 and go somewhat unnoticed.
 

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.

I am in a weird situation and was wondering if I could get some advice on what gearing ratio I should change to. I recently bought a 2004 TJ Wrangler with an 4.0L I6 engine swap. After searching the VIN, it turns out that the Jeep was originally a TJ Wrangler SE, meaning that it came stock with a 2.4L I4 and the respective body components. It has a custom front and rear bumper, I just gave it 35" wheels with a 4" lift, and we sometimes use it to plow. Also, 5th gear can barely get up to 80 mph, so I never use it. As a result, I decided that I definitely need to change the gearing. What do you recommend I change to? I was thinking 4.88 or 5.38. Should I look into getting a new transmission as well?

Current Setup:
4.0L I6
NV1500 Trans
Dana 35, 3.07 Rear Axle
Dana 30 Front Axle
35" Wheels
4" Lift
 
I am in a weird situation and was wondering if I could get some advice on what gearing ratio I should change to. I recently bought a 2004 TJ Wrangler with an 4.0L I6 engine swap. After searching the VIN, it turns out that the Jeep was originally a TJ Wrangler SE, meaning that it came stock with a 2.4L I4 and the respective body components. It has a custom front and rear bumper, I just gave it 35" wheels with a 4" lift, and we sometimes use it to plow. Also, 5th gear can barely get up to 80 mph, so I never use it. As a result, I decided that I definitely need to change the gearing. What do you recommend I change to? I was thinking 4.88 or 5.38. Should I look into getting a new transmission as well?

Current Setup:
4.0L I6
NV1500 Trans
Dana 35, 3.07 Rear Axle
Dana 30 Front Axle
35" Wheels
4" Lift
Are you sure the transmission wasn't swapped as a part of the engine swap? Seems more common to install a bolt in transmission than retrofit a smaller one. If you have a NV1500, you could go with 4.88 or 5.13. NV3550 or AX-15, go with 5.13.

Unless you have front and rear D44s or aftermarket axles, you can only go as high as 5.13 in the front Dana 30.

Since you use it to plow, go straight to 5.13 regardless. And since you might end up swapping transmissions, 5.13 will provide adequate gearing for both the NV1500 and whatever replaces it. Do it once, and do it right. Better than paying for two regears.

Also, if you're considering installing limited slip or locking differentials on either axle, regearing is the best time to do so. Front and rear lockers help immensely off road, and will likely also help you plow in deep snow. Instead of spinning two wheels, you can spin all 4 and get up to twice the forward traction.
 
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Are you sure the transmission wasn't swapped as a part of the engine swap? Seems more common to install a bolt in transmission than retrofit a smaller one. If you have a NV1500, you could go with 4.88 or 5.13. NV3550 or AX-15, go with 5.13.

Unless you have front and rear D44s or aftermarket axles, you can only go as high as 5.13 in the front Dana 30.

Since you use it to plow, go straight to 5.13 regardless. And since you might end up swapping transmissions, 5.13 will provide adequate gearing for both the NV1500 and whatever replaces it. Do it once, and do it right. Better than paying for two regears.

Also, if you're considering installing limited slip or locking differentials on either axle, regearing is the best time to do so. Front and rear lockers help immensely off road, and will likely also help you plow in deep snow. Instead of spinning two wheels, you can spin all 4 and get up to twice the forward traction.

Thanks so much for the help. After doing more research I did realize that 5.13 is the biggest for the diffs I have. Also, I'm unsure which trans I actually have, but I guess I'll find out when I fix a rear engine seal leak.
 
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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

I'd like to add I'm 37s, 5.13, and even supercharged. I drive daily on flat ground and I would never want 4.88s. 5.13 is perfect for street and more than flexible enough for offroad in low.
 
awesome thread guys/gals.
i have a 97 2.5l 30rh dana35 dana30 running 35's with stock 3.73 gears. its amazing horrible lol im in the process of gathering parts for a 4.0 ax15 swap next winter and what im gathering is 4.88 gears would be good with the current set up and the 4.0 ax15 set up? or would you suggest 5.13s?