4.88s on 35s Anyone?

[homebrew]

So I want/ need to regear my rubi (3.6 auto) currently running 35s. I plan on moving up to 37s in the next year once these tires wear out. I do tow a travel trailer on occasion as well. My question now is how upset will the jeep be with the 4.88s and 35s on the highway? I know 4.56 will get me back in the sweet spot but I don't want to pay for gears twice and I cant afford gears and tires at the same time. I am doing a 2000+mile road trip with some offroading in moab and cali and would like to get the gears done before the trip. Any help is appreciated.

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[mtnbiker73]

If you are going to run 37s, then go with the 4.88 gears. The only thing you'll notice on the highway is higher revs, but with the 8-speed auto, it won't be bad at all.

 

[Brian_18JLUR]

I know lots of people with 37s and the 4.10 gears and loving it. I have 39s and have the 4.88s. I absolutely love it! Feels a hair over stock and MPG is amazing at mixed driving with 17.5 all day long! the 8-speed is amazing but with this transmission you don't have to go as high with the gears like the JK.



Best Video on the Web for this! I followed this on all my jeeps and never had an issue or regret.

 

[DesertsJL]

35” tires and 5.38 gears here. I know that I’m a bit over geared, however the Jeep runs great on the highway and doesn’t feel bad at all. The 8th gear is really tall for an overdrive anyway. I live in a hilly area and I think that the extra gear ratio helps a lot. I do plan to go bigger with the tires eventually so it made sense for me to only regear once.

 

[LLRubylady]

35” tires and 5.38 gears here. I know that I’m a bit over geared, however the Jeep runs great on the highway and doesn’t feel bad at all. The 8th gear is really tall for an overdrive anyway. I live in a hilly area and I think that the extra gear ratio helps a lot. I do plan to go bigger with the tires eventually so it made sense for me to only regear once.

I have an appointment to regear to 4.88 with my 6 spd rubicon. I’m a little afraid honestly as to the unknown. I don’t want to make a mistake. I was told not to do 4.56 with 35s.
I think it’ll run ok. I guess I just worry about anything long term down the road that could result. But I guess if I don’t do it i’ll Never know.

 

[UKCATS]

I have an appointment to regear to 4.88 with my 6 spd rubicon. I’m a little afraid honestly as to the unknown. I don’t want to make a mistake. I was told not to do 4.56 with 35s.
I think it’ll run ok. I guess I just worry about anything long term down the road that could result. But I guess if I don’t do it i’ll Never know.

You will be fine. For a 6 speed manual, that will be a great combo. Follow the break-in procedure, and check the lockers to make sure they are still hooked up right.

 

[Jeepjunkie]

I have an appointment to regear to 4.88 with my 6 spd rubicon. I’m a little afraid honestly as to the unknown. I don’t want to make a mistake. I was told not to do 4.56 with 35s.
I think it’ll run ok. I guess I just worry about anything long term down the road that could result. But I guess if I don’t do it i’ll Never know.

Let us know how it turns out for you. I’m waffling between 4.56’s and 4.88’s for when go to 35” tires (also a 6-Speed manual). I like the lower gearing for off road of the 4.88’s (I have the 2.76 t-case) but understand the 4.56s will rev at a pleasant 2400 in 6th at 75mph. I do a lot of highway driving in the JL.

 

[cocaine_white]

I know lots of people with 37s and the 4.10 gears and loving it. I have 39s and have the 4.88s. I absolutely love it! Feels a hair over stock and MPG is amazing at mixed driving with 17.5 all day long! the 8-speed is amazing but with this transmission you don't have to go as high with the gears like the JK.



Best Video on the Web for this! I followed this on all my jeeps and never had an issue or regret.

Any trouble getting it to shift into 8th? Im on 37's and factory gears and it wont hardly shift into 8th at all. But im about to put on 39's and want to do 4.88's instead of 5.13's since my 40 mile commute is mostly highway and i dont want to grenade my mpg's

 

[CarbonSteel]

Any trouble getting it to shift into 8th? Im on 37's and factory gears and it wont hardly shift into 8th at all. But im about to put on 39's and want to do 4.88's instead of 5.13's since my 40 mile commute is mostly highway and i dont want to grenade my mpg's

I am currently on 35's with 4.10's but will be re-gearing to 4.88 later this month. My MPG took a dump because the engine is not running in its optimum RPM range (it is lugging). A slight headwind will have you in 7th in the blink of an eye and any hills will have you in 6th. I struggled with this (though not quite as bad) with 33's and 4.10's--especially when traveling from Houston to CO/WY/MT.

For me, while I may be slightly over-geared, I would rather have the extra gear and not need it rather than vice-versa. I have said before that gas engine automatic Rubicons should come from FCA geared as 4.56 instead of 4.10.

In your case, "I feel" like with 4.88's and 39's, you are going to be about where I am with 35's and 4.10's and you will wish you had geared it with 5.13's. Some of the other guys who have done this should chime in soon.

 

[zeebo56]

I just put 4.88s on my JLU sport with 35s. Currently breaking it in. I did a few heat cycles yesterday and today. Did some trips today on the highway but stayed under 65 mph. I did notice certain areas going uphill were a breeze compared to before.

Mpg seems to not be much better yet but I'll find out more when I can go to 75 on the highway like I usually do.

It's funny ill be in 7th gear cruising in town at 35 and hit 8th gear at 40. Rpms are around 2000 at 60-65 mph in 8th.

I do plan to go to 37s at some point in the future which is why I chose 4.88 over 4.56. I feel it was the right choice and seems to work ok with the 35s as well.

 

[Joe_S]

I just put 4.88s on my JLU sport with 35s. Currently breaking it in. I did a few heat cycles yesterday and today. Did some trips today on the highway but stayed under 65 mph. I did notice certain areas going uphill were a breeze compared to before.

Mpg seems to not be much better yet but I'll find out more when I can go to 75 on the highway like I usually do.

It's funny ill be in 7th gear cruising in town at 35 and hit 8th gear at 40. Rpms are around 2000 at 60-65 mph in 8th.

I do plan to go to 37s at some point in the future which is why I chose 4.88 over 4.56. I feel it was the right choice and seems to work ok with the 35s as well.

Is the downshift more noticeable when you're coming to a stop? I just had my JLU sport regeared to 4.88 on 35s. The shop said the downshift would be more noticeable and it's normal on JLs. I'm trying to get used to it, but it's a little annoying.

 

[zeebo56]

Is the downshift more noticeable when you're coming to a stop? I just had my JLU sport regeared to 4.88 on 35s. The shop said the downshift would be more noticeable and it's normal on JLs. I'm trying to get used to it, but it's a little annoying.

Maybe once in a blue moon I'll notice it but still seems pretty smooth to me. Maybe @chevymitchell will ask more questions to get an idea of what you are experiencing.

 

[CarbonSteel]

Mine just came out of the shop after re-gearing to 4.88 with 35" tires. Complete night and day difference between the 4.10's and the 4.88's. No more constant up and down shifting, it stays in 8th gear like it should, and I have not noticed any harsher down shifting.

With the exception of 1st and 2nd gear being shorter (but not to the point of making it feel weird), it operates as it did with the 4.10's in it. I am very happy with the results.

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