For those wondering about 38s and 4.10 gears. Video inside.

[Chocolate Thunder]

I've personally found the 2.0/8-speed to be an overall great combo. The low and mid range torque of this relatively lightweight engine makes the Jeep feel lighter than it really is. My JLUR is sitting 5.5" above stock height in the front and 6" in the rear, with 40x13.5's. Still rocking the stock 4.10's.

A few months back, I was at Windrock Park in Tennessee. I hit a couple of trails that included 7 and 8 rated obstacles and it walked right over everything with ease, and I was purposely aiming for the harder lines. Even though it had just rained hard the day before, I didn't need to bump it at all.

The biggest thing that makes me hesitant to swap to shorter gears, other than putting more money into these axles than I already have, is ending up with too little of gear mesh due to the smaller diameter pinion gear. I'll wait till I upgrade to a set of 60's, which will have larger ring gears to better support 5.13's or 5.38's.

4" lift and 38x13.5's...

5.5"/6" lift and 40x13.5's...

Clearly your rig is awesome and more capable than mine. Than most of ours probably. So take this with love when I say GET THAT THING REGEARED! For me I felt that the stock 4.10 were fine before I changed. But afterward I wished I’d done it sooner. In my case I didn’t know what I was missing until I did it. I only have 37s and I went to 4.88. Could have went to 5.13. With 40s I’d think that 5.13 is the bare minimum you’d want. It’ll make the 8 speed so much better in regular driving and while wheeling.

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[Headbarcode]

Clearly your rig is awesome and more capable than mine. Than most of ours probably. So take this with love when I say GET THAT THING REGEARED! For me I felt that the stock 4.10 were fine before I changed. But afterward I wished I’d done it sooner. In my case I didn’t know what I was missing until I did it. I only have 37s and I went to 4.88. Could have went to 5.13. With 40s I’d think that 5.13 is the bare minimum you’d want. It’ll make the 8 speed so much better in regular driving and while wheeling.

I don't at all doubt how much better it'd be with shorter gears, but I have too much in these axles already. If I dig into the carrier for gears, it would snowball to also include air lockers. I'm weak when it comes to the while you're in there mentality.

Resale is the other reason for me to refrain. My current axle upgrades would hold a value in the eyes of the next person, but not if I gear them too short for most people.

And thanks for the kind words! This forum is filled with many awesome Jeeps, and a lot of very knowledgeable people that could run circles around me, so I'll never presume to have a leg up on anyone.

Cheers, Jeremy!

 

[Northridge4x4]

Have you upgraded your axle shafts? I put DANA SPICER DANA 44 ADVANTEK REAR CHROMOLY AXLE SHAFT M220 in a couple weeks ago. Apparently one of the seals got damaged in shipping that went unnoticed. Sat for a week in my garage with no leaks. During a recovery operation I was pitched 20% and when I completed the recovery, a couple table spoons of oil was all over my wheel. northridge4x4 is shipping me a new seal & bearing for that axle.

Which side is leaking?

 

[Chocolate Thunder]

I don't at all doubt how much better it'd be with shorter gears, but I have too much in these axles already. If I dig into the carrier for gears, it would snowball to also include air lockers. I'm weak when it comes to the while you're in there mentality.

Resale is the other reason for me to refrain. My current axle upgrades would hold a value in the eyes of the next person, but not if I gear them too short for most people.

And thanks for the kind words! This forum is filled with many awesome Jeeps, and a lot of very knowledgeable people that could run circles around me, so I'll never presume to have a leg up on anyone.

Cheers, Jeremy!

But when (not if) you inevitably go ahead and upgrade to D60 or D80s, the regeared axles and all the other goodies you’ve done will hold a lot of value and you’ll recoup all of the thousands you’ve spent on them! I know this is true because I’ve had to explain it to my wife so she understands that money I dump into my Jeep isn’t frivolous, it’s a wise INVESTMENT!

 

[J0E]

Which side is leaking?

Left
Parts on the way
Thx

 

[dragoneggs]

Minus does the same. I have to cruise at 65 or 85 to hit 8th. I’ve found those to be the sweet spot on my JL.

Me too… since moving to 35s unless it is super flat highway and/or a tailwind. I also noticed the OPs RPMs seem to be a few hundred lower than mine running in 7th and 8th. Also a 3.6L w/4:10s

 

[Atom631]

Ive got 38s with the 3.6 auto and NEVER saw 8th. not once. I barely saw 7th. and I live on Long Island, arguably one of the flattest places in the country.

 

[lowmpg]

I get asked the question a LOT about how my Jeep runs with 38s and 4.10s. I decided to shoot a video the other day while I was driving up to the campsite. So far I am very happy and surprised. I know how to setup gears and have re-geared in the past so that is not holding me back. I hope this helps answer some questions.



-Eli

Thank you for this!!!!

 

[Old Jeeper]

I've personally found the 2.0/8-speed to be an overall great combo. The low and mid range torque of this relatively lightweight engine makes the Jeep feel lighter than it really is. My JLUR is sitting 5.5" above stock height in the front and 6" in the rear, with 40x13.5's. Still rocking the stock 4.10's.

A few months back, I was at Windrock Park in Tennessee. I hit a couple of trails that included 7 and 8 rated obstacles and it walked right over everything with ease, and I was purposely aiming for the harder lines. Even though it had just rained hard the day before, I didn't need to bump it at all.

The biggest thing that makes me hesitant to swap to shorter gears, other than putting more money into these axles than I already have, is ending up with too little of gear mesh due to the smaller diameter pinion gear. I'll wait till I upgrade to a set of 60's, which will have larger ring gears to better support 5.13's or 5.38's.

4" lift and 38x13.5's...

5.5"/6" lift and 40x13.5's...

Till you ya have dated her you don't how good Suzy Easy really is.

Run them all from 3:07s to 6:14s.

The question to be asked is: Where is Mr Torque live at?

GENERALLY speaking, higher up in the rpm is where torque hangs out then you need deeper gears.

The TJR sweet spot is 37's and 4:88s, that straight 6 torque shows up at 1500 rpm and is as flat from there as my first GF without her bra on. If you told me you were going to run 39/40s I put in 5:13s on a TJR due to weight,

JLUR, big tall tire, wide tire and the heavy weight of the JLU I would lean towards the 5:38s. Those 40s & your wheels got to be pushing 125 lb+. That is a LOT of rotating mass to be spinning. I HOPE you have upgraded BIG TIME to Heavy Duty Pads and disks...I run EBC Green or Yellow Pads and EBC disks, you would be stunned the first time you hit the brakes the difference is amazing.

Not sure where your torque curve is with the 2.0 but your happy place might be in the 5's. Take in consideration, Weight of JLR, Tires, type of wheeling, rock > Low rpm Vs Mud/Sand > higher rpm.

Few shops do it but tuning your is the last step of a build and it takes a couple of days. When I had my shop I will tell my customers, I don't build Jeeps, I engineer them so that they work in concert with all the components.

Now go do it you got what it takes...

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