3.6L, 8 AT, 37”: 4.88 or 5.13?

[SleepEatJeepRepeat]

Just ordered 4.88's...I am running 35" KO2's on a 3.6 JLR with stock 4.10's and rarely if ever see 8th, even on flat hi-ways. (Yes, I had the dealer calibrate for 35's right after install) I told myself 35's were as big as I would ever go...Now I plan to go with 37" KO2's as soon as the new load range C (developed for the new Ford Raptor) are available-hopefully end of April or early May.

Silly me, when I first ordered my JLR I thought 33's would be fine...Before she even arrived I had bought her a set of 35" KO2's. Fast forward one year and she's getting 37's, 4.88's, chromoly axles...However, I am blaming this latest upgrade bug on Jeep corporate for definitely telling the GM at my dealer that they are not making a 2-door V8!

My 2 cents:
For those with JLUR's running heavier tires and wheels or those who might someday jump to 38's or 39's, 5.13's would probably be a better choice.

Oh man I was about to order 37” ko2 d’s thanks for saying that, I am totally going to wait for the c ply..

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[Kurt0]

That’s a huge help, thank you for the details. I’ve never gotten mileage like that even stock except once on a straight trip going 63 mph the whole way. Got 19.xx. Now with the 2.5” lift, 37s, and 4.10 I get 15.5-17 on the highway.

its because the engine is tuned too lean. Reprogramming with something like livernois or a superchips makes a considerable difference.

 

[Kurt0]

That’s a huge help, thank you for the details. I’ve never gotten mileage like that even stock except once on a straight trip going 63 mph the whole way. Got 19.xx. Now with the 2.5” lift, 37s, and 4.10 I get 15.5-17 on the highway.

just looked at my receipt. 20.3 was my quick in the head math. It was actually 20.6 on the hand calc.

 

[Tdog495]

Just got 4:88’s and in the break-In period. My first impressions is it shifts way better and faster than 4.10s.
Other than the shifting change you pretty much just go up one gear. Meaning when ur usually at 5th, now you’re at 6th, usually at 7th, now your at 8th. Also it hold the gears stronger.
Drove my friends jeep with 5:13’s yesterday. It feels like his jeep goes directly to 2nd and operates on a higher RPM (felt good). Then I tested his passing power going 70 in 8th gear and it instantly went into 5th. That’s the only downside I found. He said it frustrates him all the time. No passing power at that speed at all

 

[SleepEatJeepRepeat]

Just got 4:88’s and in the break-In period. My first impressions is it shifts way better and faster than 4.10s.
Other than the shifting change you pretty much just go up one gear. Meaning when ur usually at 5th, now you’re at 6th, usually at 7th, now your at 8th. Also it hold the gears stronger.
Drove my friends jeep with 5:13’s yesterday. It feels like his jeep goes directly to 2nd and operates on a higher RPM (felt good). Then I tested his passing power going 70 in 8th gear and it instantly went into 5th. That’s the only downside I found. He said it frustrates him all the time. No passing power at that speed at all

how much with labor does it cost to go to 4.88?

 

[Tdog495]

I

how much with labor does it cost to go to 4.88?

It was done at, The Custom shop NYC. I believe it was $1800 for just labor. I brought in my own gears

 

[zeebo56]

how much with labor does it cost to go to 4.88?

I just got 4.88s in mine. I would recommend it with 35s and I have a plan to go to 37s at some point. Felt it was a good compromise. Feels great and mpg has improved in the few days I have driven it. Still breaking it in.

If you call Mobile gear installers they would likely do yours with parts for under $1600. Only mentioning them since they helped me a decent amount when I was doing my gears and they seem knowledgeable.

 

[zeebo56]

Just got 4:88’s and in the break-In period. My first impressions is it shifts way better and faster than 4.10s.
Other than the shifting change you pretty much just go up one gear. Meaning when ur usually at 5th, now you’re at 6th, usually at 7th, now your at 8th. Also it hold the gears stronger.
Drove my friends jeep with 5:13’s yesterday. It feels like his jeep goes directly to 2nd and operates on a higher RPM (felt good). Then I tested his passing power going 70 in 8th gear and it instantly went into 5th. That’s the only downside I found. He said it frustrates him all the time. No passing power at that speed at all

what size tires are you both on?

 

[Djhyper66]

I just got 4.88s in mine. I would recommend it with 35s and I have a plan to go to 37s at some point. Felt it was a good compromise. Feels great and mpg has improved in the few days I have driven it. Still breaking it in.

If you call Mobile gear installers they would likely do yours with parts for under $1600. Only mentioning them since they helped me a decent amount when I was doing my gears and they seem knowledgeable.

I’m so excited to get my gears redone on my jl sport , going 4.88 .. 2 weeks till my appointment.. I have only had my new rims and tires for a month now but I’m ready to re-gear them.

 

[zeebo56]

I’m so excited to get my gears redone on my jl sport , going 4.88 .. 2 weeks till my appointment.. I have only had my new rims and tires for a month now but I’m ready to re-gear them.

You will love it. Big difference from the 3.45s we have stock. Highway driving is more pleasurable. I'll find out about some offroading this weekend

I had the 35s for almost a year before I did the 4.88s last weekend.

 

[Tdog495]

what size tires are you both on?

I’m on 37x 13.50 cooper STT pros

 

[Tdog495]

I’m so excited to get my gears redone on my jl sport , going 4.88 .. 2 weeks till my appointment.. I have only had my new rims and tires for a month now but I’m ready to re-gear them.

Def a good decision. I have no issues with these gears whatsoever

 

[tjeeper]

I made an appointment with my local shop to get my JLUR regeared. The owner is recommending 5.13s. He seems to think my Jeep will be in 8th gear more on the highway with 5.13s than 4.88s. Maybe it is a regional thing, the higher altitude here, more hills, or maybe the 80mph speed limit. I don't know- I'm still leaning towards 4.88s. I don't want to gear too low, I want it to be like it was when it was stock.

 

[zeebo56]

I made an appointment with my local shop to get my JLUR regeared. The owner is recommending 5.13s. He seems to think my Jeep will be in 8th gear more on the highway with 5.13s than 4.88s. Maybe it is a regional thing, the higher altitude here, more hills, or maybe the 80mph speed limit. I don't know- I'm still leaning towards 4.88s. I don't want to gear too low, I want it to be like it was when it was stock.

What size tires are you running. I think with 37s 4.88 or 5.13 both work well. 5.13 if you will be towing. I did 4.88s with my 37s and they seem to work well. I think 5.13s would have been a good choice as well. At 80 you will be at slightly higher rpms but probably not enough of a difference to matter much.

 

[tjeeper]

37s, like everyone else

In all the research I've done, I haven't found anyone who wasn't happy with their choice. I'm probably splitting hairs at this point. I don't plan on going to 40s on these axles, so I don't have to worry about that. I don't tow with my JL- I have a large SUV for that. Still leaning towards 4.88s.

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