Gears for 37" tires

[Jim1119]

If you do the math there is only a 10% gearing change when going from 33 to 37. The 33 to 37 tire size works out to a 200 rpm change at 70MPH. What you did on your JK is of no relevance on your JT. I had a JK Sport on 35s with 4.56 and it was geared too low for adequate highway performance

Do you think I could put 37s on my overlander and do mostly highway/city driving with mild off roading? 3.73 axle ratio.

Sponsored

 

[MrKnowitall]

Do you think I could put 37s on my overlander and do mostly highway/city driving with mild off roading? 3.73 axle ratio.

You CAN. It’ll go down the road fine and the 8spd will make it work. That said, it WILL be slower and you probably won’t use 8th gear as much.
AEV now specs a 4.56 gears for their JL370 package. It’s probably more needed with the Wrangler 3.45 gears, but the Gladiator is heavier, too. If you’re going to regear, go as deep as you can tolerate. With the 8spd, on 37’s, 5.13 will give you totally fine highway cruising rpm.

 

[Jim1119]

You CAN. It’ll go down the road fine and the 8spd will make it work. That said, it WILL be slower and you probably won’t use 8th gear as much.
AEV now specs a 4.56 gears for their JL370 package. It’s probably more needed with the Wrangler 3.45 gears, but the Gladiator is heavier, too. If you’re going to regear, go as deep as you can tolerate. With the 8spd, on 37’s, 5.13 will give you totally fine highway cruising rpm.

Thanks! I would plan on upgrading the gears later so that I could do a little more serious off roading. I’m very handy, can build almost anything, but I’m not a mechanic. Think I could do it myself?

 

[MrKnowitall]

Thanks! I would plan on upgrading the gears later so that I could do a little more serious off roading. I’m very handy, can build almost anything, but I’m not a mechanic. Think I could do it myself?

Gears in Dana axles are not a simple DIY. It requires special tools- bearing press, in-lb torqure wrench, dial indicator, shim selction. Since its a Slaisbury type axle (not a banjo, like Ford 9” or Toyota), you have to do the work under the truck or pull the entire axle. You have to set pinion depth, ring gear pattern and preload for both. Then once its all together, you’re on your own if you didn’t get it quite right and it starts to howl, or worse.

 

[Jim1119]

Gears in Dana axles are not a simple DIY. It requires special tools- bearing press, in-lb torqure wrench, dial indicator, shim selction. Since its a Slaisbury type axle (not a banjo, like Ford 9” or Toyota), you have to do the work under the truck or pull the entire axle. You have to set pinion depth, ring gear pattern and preload for both. Then once its all together, you’re on your own if you didn’t get it quite right and it starts to howl, or worse.

Gotcha. I think that reinforces my opinion that if I go with 37s, I’ll have to take it easy off-road until I can afford to upgrade the axles.

Thans for the help and advice!

 

[MrKnowitall]

Gotcha. I think that reinforces my opinion that if I go with 37s, I’ll have to take it easy off-road until I can afford to upgrade the axles.

Thans for the help and advice!

Honestly, with the deep 1st and low range, off-roading will be less of a problem than the on-road. There’s zero harm in trying out the 3.73gears first, and then deciding if deeper gears are worth the $2000.

 

[Jim1119]

Honestly, with the deep 1st and low range, off-roading will be less of a problem than the on-road. There’s zero harm in trying out the 3.73gears first, and then deciding if deeper gears are worth the $2000.

Even better!

 

[wiredup60]

So, I have 38's and just regeared from 3.73 to 4.88's. I am in the break in period. I have the jscan and adjusted for tires, have not changed any gear settings, or changed shift points. The main thing I have noticed is that below 50mph, the gears climb quickly to 7th and even stay in 8th at 45mph. So, since in higher gears, often, the engine is typically below 2000 rpms, hovering around 1500 most the time when not on the gas. They downshift quickly when I step on it, does that seem normal? do I need to change a gear setting or shift points?

 

[Renegade]

So, I have 38's and just regeared from 3.73 to 4.88's. I am in the break in period. I have the jscan and adjusted for tires, have not changed any gear settings, or changed shift points. The main thing I have noticed is that below 50mph, the gears climb quickly to 7th and even stay in 8th at 45mph. So, since in higher gears, often, the engine is typically below 2000 rpms, hovering around 1500 most the time when not on the gas. They downshift quickly when I step on it, does that seem normal? do I need to change a gear setting or shift points?

You probably need to adjust the axle ratio in your computer via J-scan. There's not an actual "shift points" adjustment to be made.

 

[Flux]

Well, I got my Rubi Gladiator a month ago and already had the dealership install the Evo 2.5" lift, adjustable F/R track bars, and Patagonia 37s. I have the Tazer 2 mini installed for necessary adjustments. In case you're wondering....... I had the dealer do the install so they would have to honor any warranty work and couldn't try to void anything from the lift and tires (I have this documented with them). Clearly, having them do the install wouldn't have been my first choice which is apparent since I've already had to take it back for a couple of adjustments; they installed the front lower control arms on the wrong sides causing the tires to rub, they didn't adjust rear upper control arms to get the pinion angle in line with the driveshaft.......
After considerable research and going off previous experience, I ordered the front and rear Yukon 5.13 gears and install kits yesterday. I've already contacted a place here in Austin (Just Jeeps) to do the install which will be $500 per axle. I'll let y'all know how it goes.
Edit; I have the auto tranny.

 

[Flux]

Woohoo! Gears and install kits just arrived!

 

[Jim1119]

Woohoo! Gears and install kits just arrived!

Damn that was quick!

 

[Flux]

Damn that was quick!

I know! I ordered them on April 30th from Northridge. I didn’t think they’d get here so fast. I should have called the place I’m going to have install them today and schedule a time for the install.

 

[Jim1119]

I know! I ordered them on April 30th from Northridge. I didn’t think they’d get here so fast. I should have called the place I’m going to have install them today and schedule a time for the install.

post some pics when you’re done. I want the same tires. Congrats!

 

[Jim1119]

I know! I ordered them on April 30th from Northridge. I didn’t think they’d get here so fast. I should have called the place I’m going to have install them today and schedule a time for the install.

or I could just come down to Austin and we could put your rig to the test in the hill country.

Sponsored