4.56 or 4.88 gears?

[AndyG]

Biggest concern with 4:88 is picking up a bad vibration , which seems to be some how linked to higher driveline rotation . It can happen , and can be hard to chase down or even eliminate.

4:56 is great for a 5 speed (nv 3550) and 4:88 is most commonly recommended for the automatics.

Regearing is awesome , you will enjoy the Jeep a lot more .

 

[ac_]

I'm also considering regearing to either 4.56s or 4.88s. I have a 5 speed manual and my 5th gear is useless on the highway, can't hold speed. I've got a heavy right foot too so my usual 80mph on the highway is around 2900 RPMs, and I need to get that lower. I have 35's too, so we're in the same boat.

This is my opinion FWIW.
I have a 98 with a Ford 8.8 rear and 4.88 gears. I am running 33's, and I can do 80 on the freeway quite easily with my 4.0 5sp. Since you are running 35's I would suggest the 4.88's I don't think you will be disappointed. Especially if you do any offroading at all.

The Jeep drives like any normal car that is underpowered getting to 80 and sucks gas like you wouldn't believe. Really there isn't too much terribly different between 4:56 and 4:88. I don't think you would ever really notice much of a difference except for 4low. You will really notice it then.

I truly believe in your case if you go 4:56 you will always wonder what 4:88 is, but if you go 4:88 you won't care what 4:56 is like. Unless you never go offroad and mainly drive on the freeway. If that is the case, you might like 4:56 slightly better, but I don't think you will even notice the difference.

4:88's will get you out of the hole quicker. That is my .02 worth.

 

[TJJeepGirl]

You mentioned that you have a stock Dana 30 in the front. Are you keeping that, or do you plan on upgrading it in the foreseeable future? I'm only asking because you said you just installed an 8.8, I'm guessing to upgrade from a Dana 35.

As of now the plan is to keep the Dana 30 and just install new gears and a locker. But I did have the Dana 35 in the rear.

 

[TJJeepGirl]

Thank you everyone for the info! I think I'm going with the 4.56. I do have a AW4 sitting in the floor just waiting on me to install it. I was planning to wait until my 3 speed gave out before installing it. But if it gives me trouble with the new gears I'll yank it out and go ahead and put my other in. Thank again for all the help guys! Once I get them in I'll let everyone know how I like them

 

[mrblaine]

Thank you everyone for the info! I think I'm going with the 4.56. I do have a AW4 sitting in the floor just waiting on me to install it. I was planning to wait until my 3 speed gave out before installing it. But if it gives me trouble with the new gears I'll yank it out and go ahead and put my other in. Thank again for all the help guys! Once I get them in I'll let everyone know how I like them

If you swap in the AW-4 and want to run 35's, you'll have to install 5.13's and you'll wish you could get 5.38's in there.

Also be aware that all you get with the AW-4 is an OD and some reliability. That comes with the expense of a shorter rear driveshaft, pretty high inefficiency, lots of heat production, and a trans pan that is lower than it could be.

I have that conversation with every owner of every swap I have done. The first week they tell me how great it is, then after about a month the questions start. How do I cool this thing down some?
Is there any way to make it a bit more peppy?
Why doesn't my cruise control work?
Does it really hang down that far?

Not saying you should or shouldn't install it, just be prepared for the reality that is the AW-4.

 

[Jerry Bransford]

You mentioned that you have a stock Dana 30 in the front. Are you keeping that, or do you plan on upgrading it in the foreseeable future? I'm only asking because you said you just installed an 8.8, I'm guessing to upgrade from a Dana 35.

For most of us, there's no need to replace the front Dana 30. WIth nothing more than replacement 27 spline 4340 alloy inner/outer axle shafts that axle is more than up to being locked with 35" tires doing very tough trails. That's what I i did with my previous TJ's Dana 30 after breaking one of its factory shafts on a tough trail.

 

[JMT]

For most of us, there's no need to replace the front Dana 30. WIth nothing more than replacement 27 spline 4340 alloy inner/outer axle shafts that axle is more than up to being locked with 35" tires doing very tough trails. That's what I i did with my previous TJ's Dana 30 after breaking one of its factory shafts on a tough trail.

I'm all about saving money. I must have read this advice a hundred times now and will save you time and money. I'm plenty happy with my Dana 30, PowerTrax No Slip and stock axles for now. If I break one I'll just upgrade to the 4340 chromoly. Focus on the rear...

 

[Jay P]

I'm all about saving money. I must have read this advice a hundred times now and will save you time and money. I'm plenty happy with my Dana 30, PowerTrax No Slip and stock axles for now. If I break one I'll just upgrade to the 4340 chromoly. Focus on the rear...

I was about to ask about that same locker in front with stock shafts and 33x12.50s until I can upgrade to chromoly. If you’re running it and no issues I’m going to try it. I do have a set of spare shafts also.


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[JMT]

I was about to ask about that same locker in front with stock shafts and 33x12.50s until I can upgrade to chromoly. If you’re running it and no issues I’m going to try it. I do have a set of spare shafts also.


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I'm running it with 33x12.5's and wheel it hard with no issues. It rarely clicks, only a couple of times on the trail, never on the street. It's also DIY if you take a little time and follow the excellent instructions.

 

[Jerry Bransford]

I was about to ask about that same locker in front with stock shafts and 33x12.50s until I can upgrade to chromoly. If you’re running it and no issues I’m going to try it. I do have a set of spare shafts also.

My previous TJ's front locker was a No-Slip, it was great... no clicking or ratcheting sounds when turning corners like other lunchbox lockers make. Pretty much silent with perfect manners on the road when in 2wd.

 

[Jay P]

I'm running it with 33x12.5's and wheel it hard with no issues. It rarely clicks, only a couple of times on the trail, never on the street. It's also DIY if you take a little time and follow the excellent instructions.

You just solved my procrastination issue.


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[Jay P]

My previous TJ's front locker was a No-Slip, it was great... no clicking or ratcheting sounds when turning corners like other lunchbox lockers make. Pretty much silent with perfect manners on the road when in 2wd.

This is the route I have chosen. Should be done and ready to go the first week of January. Thanks!


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[Rob5589]

Like Blaine mentioned, if going to the AW4 you will want deeper for 35's. Unfortunately that puts you in a situation, being that you currently run the 32RH. Either install the AW4 now or hold off on the re-gear. Or just stick with 4.56 and the 32RH and ditch the AW4 idea.

 

[jjvw]

Which leads to the question of why an AW4 over the 32rh? Is it just for the OD?

 

[luk4mud]

I replaced stock 4.10's with 4.88's recently, went thru the same analysis.

The 4.88's seemed like the better option for me- auto trans (42RL), 35's and a fair amount of time in the dirt. I dont drive that fast on the freeway, 70 max usually so it doesnt wind out.

HTH

 

[jjvw]

I replaced stock 4.10's with 4.88's recently, went thru the same analysis.

The 4.88's seemed like the better option for me- auto trans (42RL), 35's and a fair amount of time in the dirt. I dont drive that fast on the freeway, 70 max usually so it doesnt wind out.

HTH

How did you arrive at 4.88 with 35s/42rle?

 

[Jerry Bransford]

I replaced stock 4.10's with 4.88's recently, went thru the same analysis.

The 4.88's seemed like the better option for me- auto trans (42RL), 35's and a fair amount of time in the dirt. I dont drive that fast on the freeway, 70 max usually so it doesnt wind out.

It's still lugging at times with 4.88 with 35's with your 42RLE. Better would have been 5.13. I have a Rubicon so I was able to replace my 4.88 gears with 5.38 which cured my engine's lugging problems and actually bumped my mpg from <12 mp to almost 15 mpg. I would have said 5.38 would have been better for you but 5.13 is as low as non-Rubicons can be regeared to.

I only bring up the 5.13/5.38 as the more recommended ratio for 35's with the 42RLE transmission those who read this thread in the future.

 

[luk4mud]

It's still lugging at times with 4.88 with 35's with your 42RLE. Better would have been 5.13. I have a Rubicon so I was able to replace my 4.88 gears with 5.38 which cured my engine's lugging problems and actually bumped my mpg from <12 mp to almost 15 mpg. I would have said 5.38 would have been better for you but 5.13 is as low as non-Rubicons can be regeared to.

I only bring up the 5.13/5.38 as the more recommended ratio for 35's with the 42RLE transmission those who read this thread in the future.

Looking at the actual teeth in a 4.88 vs 5.13 there is a material difference. My gear guy indicated that he's seen a few 5.13's go bad with my set up but rarely any 4.88's. I have no plans for 37s either.

And yeah, its a little sluggish on hills but not much, and the lower RPMs are nice. I'd rather have the safety factor of the 4.88's I guess.

 

[Jerry Bransford]

Looking at the actual teeth in a 4.88 vs 5.13 there is a material difference. My gear guy indicated that he's seen a few 5.13's go bad with my set up.

Your gear guy is guessing and making statements based solely on rumors he heard. 5.13's and 5.38's have been thoroughly tested and in use for years now in our Wrangler axles. No problems. Some claimed the same thing when 4.88's came out for the Dana 30 many years ago. If there were problems we wouldn't be installing 5.13 and 5.38 gearing, me included with 5.38's, and using our rigs strenuously with them.

5.38 gear teeth are actually the same size and strength as the 5.13. Some smart engineers figured out a way to change the 5.13 gear tooth count and spacing slightly to give the 5.38 ratio with no loss in strength.

 

[ac_]

years ago in the early 90's I was replacing my gears on my YJ to 4:56, and I was working at a transmission shop at the time. The owner told me the same thing. He told me never go over 4:11 because that is the lowest gear factory makes. Everybody I knew was running 4:56's and I installed them, and never had an issue.

I agree it seems like everytime they go lower new rumors come out. Now 4:56's are standard and they still aren't a factory gear. BTW I am running 4:88's now as stated earlier.

@Jerry you had me at 15mpg WTF? I was getting 13 with 3:73 - 31's and now with 4:88s - 33's still 13. Probably because I can beat people out of the hole now, so I do, whereas before I knew I couldn't so I never tried. I can actually pass people around town now.