Gears for 37's and auto

[Crowbar]

2.0 owners - what are you running for gears with 37's and automatic? And what is you opinion of what you're running? Don't want to hear about gear calculators or theories. Looking for real world feedback from 2.0 owners.

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[CarbonSteel]

I'm running a 3.6L/ZF8/5.13s/37's.

With a 2.0T/ZF8/37's, 4.88's would be a good combination.

 

[conFUcius]

Same as @CarbonSteel - I beat a CRV off the line at a light, I’m happy

 

[Crowbar]

Same as @CarbonSteel - I beat a CRV off the line at a light, I’m happy

I'm currently debating between a 2.0 and 3.6. I have a JTR with the 3.6, 37s, and 5.13's. Perfect gear for the 3.6. Wondered what the 2.0 liked since it had a completely different torque curve. How do you like the 2.0?

 

[conFUcius]

I'm currently debating between a 2.0 and 3.6. I have a JTR with the 3.6, 37s, and 5.13's. Perfect gear for the 3.6. Wondered what the 2.0 liked since it had a completely different torque curve. How do you like the 2.0?

I have a 3.6 but I did a prolonged drive with two different 2.0s (2+ hours) - one with 37s and no re-gearing and one with 39s and 4.88s. My humble opinion is the 2.0 will tolerate being OEM longer because of the boost but you don’t need as short of a gear for that engine. If I had a 2.0 with 37s, I would’ve done 4.88s to preserve gas mileage and not use as small of a pinion.

 

[CarbonSteel]

I have a 3.6 but I did a prolonged drive with two different 2.0s (2+ hours) - one with 37s and no re-gearing and one with 39s and 4.88s. My humble opinion is the 2.0 will tolerate being OEM longer because of the boost but you don’t need as short of a gear for that engine. If I had a 2.0 with 37s, I would’ve done 4.88s to preserve gas mileage and not use as small of a pinion.

^^^^^ this ^^^^

 

[David P.]

I'm running a 3.6L/ZF8/5.13s/37's.

With a 2.0T/ZF8/37's, 4.88's would be a good combination.

^same as @CarbonSteel. My 3.6 also has an e-torque - helps with smooth shifting.

 

[ML7]

I have the 3.6 Auto ESS and 4.88 with 37s and just put on some winter tires that are 315s, I wouldnt go with the 5.13's if you want to spend a lot of time in low range, the smaller pinion and gear teeth mean greater changes of breakage. I like the 315s with 4.88 it pops off the line and goes quick through the first few gears. For normal use the 4.88 with 37 I think is perfect, I can average over 19 mi/gallon with 37s on the freeway.

 

[Old Jeeper]

What are you running for gears with 37's and automatic? And what is you opinion of what you're running? Don't want to hear about gear calculators or theories. Looking for real world feedback.

37s and 4:88 are a very happy couple. They are happy with an auto or Std trans and I have run both. I will say the 5 sp auto is not as comfortable with 37s/4:88s as is the 8-speed auto, not so much as to be an issue but gain better performance from the 8 sp setup.

I point you to forums that UNLIKE THIS ONE(at least so far) lack the HONESTY that I have seen on here.

On other forums bragging on how your 3.55 axle works GREAT with you 40 in tires, gives you 29 mpg and has not affected performance at all. In fact one said he drove across the country and averaged 85 mph and 27 mpg.

I would tell that most Jeep forums a high % of nonowners posing as owners and Jeeps. I have not sensed that in this forum, prob one best forums out there...

You can run 4:10 with 37s, not a happy drive, 4:56 will improve the performance and 488 the happy camper.

 

[Zandcwhite]

The 8 speed auto allows you to over or under gear with minimal consequences. The 1st gear is so low compared to any auto ever offered in a Jeep it's almost comical. A jk with an auto would require 5.13 gears just to match a stock JL Rubicons 1st gear drive ratio. The double Overdrive does the opposite on the top end. A JK with 4 10's would have the same freeway rpm as a JL with 4.88's. In our 2019 we drove, wheeled, and roadtripped for 37k miles on 37's and stock 4.10s and never felt a need for more gearing. When we went to 38's, I decided to regear. My jump in head first personality got the best of me and we went all the way to 5.38's. Way too low period. It was in 8th gear all the time. At freeway speed it felt like it needed to shift but there was nowhere to go. Destroyed fuel economy, somehow was slower 0-60, and just didn't cruise on the freeway as well. I could see 4.88's but absolutely no lower. With the new XR, I won't even consider regearing from the 4.56's.

 

[CarbonSteel]

The 8 speed auto allows you to over or under gear with minimal consequences. The 1st gear is so low compared to any auto ever offered in a Jeep it's almost comical. A jk with an auto would require 5.13 gears just to match a stock JL Rubicons 1st gear drive ratio. The double Overdrive does the opposite on the top end. A JK with 4 10's would have the same freeway rpm as a JL with 4.88's. In our 2019 we drove, wheeled, and roadtripped for 37k miles on 37's and stock 4.10s and never felt a need for more gearing. When we went to 38's, I decided to regear. My jump in head first personality got the best of me and we went all the way to 5.38's. Way too low period. It was in 8th gear all the time. At freeway speed it felt like it needed to shift but there was nowhere to go. Destroyed fuel economy, somehow was slower 0-60, and just didn't cruise on the freeway as well. I could see 4.88's but absolutely no lower. With the new XR, I won't even consider regearing from the 4.56's.

If and only if the engine produces enough torque because the transmission does not compensate for the loss of/lack of torque. Yes, you can "get away" with using a higher gear with certain engines, but you cannot with others (such as a 3.6L). While I agree that 5.38 would be too low with 37's, I will bet a steak dinner these combinations are the sweet spot for drivability and fuel economy in a D44:

3.6L/ZF8:

33's = 4.56
35's = 4.88
37's = 5.13
38+ = 5.38

2.0T/ZF8:

33's = 4.10
35's = 4.56
37's = 4.88
38+ = 5.13

 

[Ed95Pont]

I have an 3.6 E torque XR with 4.56 and 37's . Plenty of on road acceleration, Holds 8th gear on the highway. Does fine off-road.

 

[Mtenna99]

I’ve been contemplating gear changes as well. Sounds like everyone is saying for a 2.0 auto on 37s they recommend 4.88.

I tow a 3,000 lb camper so I figured 5.13 may be a better move. Thoughts?

 

[Zandcwhite]

If and only if the engine produces enough torque because the transmission does not compensate for the loss of/lack of torque. Yes, you can "get away" with using a higher gear with certain engines, but you cannot with others (such as a 3.6L). While I agree that 5.38 would be too low with 37's, I will bet a steak dinner these combinations are the sweet spot for drivability and fuel economy in a D44:

3.6L/ZF8:

33's = 4.56
35's = 4.88
37's = 5.13
38+ = 5.38

2.0T/ZF8:

33's = 4.10
35's = 4.56
37's = 4.88
38+ = 5.13

It all depends on driving style. where I live, 85mph is average on the freeway. The 4-1 transfer case insures plenty of gearing off road. For me personally, freeway speed is the critical component and therefore I’d adjust all of your ratios across the board up one. The 4.56’s on our current XR with stock 35’s are boardline too low for me and it is a 3.6L. If you’re the type of Jeep owner who rarely exceeds 70mph, theres no penalty for gearing too low.

 

[grimmjeeper]

If and only if the engine produces enough torque because the transmission does not compensate for the loss of/lack of torque. Yes, you can "get away" with using a higher gear with certain engines, but you cannot with others (such as a 3.6L). While I agree that 5.38 would be too low with 37's, I will bet a steak dinner these combinations are the sweet spot for drivability and fuel economy in a D44:

3.6L/ZF8:

33's = 4.56
35's = 4.88
37's = 5.13
38+ = 5.38

2.0T/ZF8:

33's = 4.10
35's = 4.56
37's = 4.88
38+ = 5.13

An automatic can compensate somewhat for a lack of low RPM torque. The stall speed of the torque converter makes all the difference.

If you have a high stall converter, the engine will rev up to a higher RPM at low speeds before the Jeep gets moving. This gets it up to a place where it can make more torque. When that happens, the perception is that it's accelerating just fine even with mismatched gears. And it's why so many people claim you don't need to regear.

That being said, I'd agree with your recommended ratios.

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