4.10 Re-gearing - 2025

[Rene_05]

Thanks Cheddar, I have the Eaton 912A553 - Detroit TrueTrac. Will have to look back through everything and see what I’ve missed. No turning back now, just hoping it isn’t an insane amount to drill the LSD. I vaguely remember an old Tommud post that might speak to this I will try to find.

Finally got the rear finished today. For anyone in the future that has a 2005-07 :
- Most new 4.10 ring gears appear to come double drilled with 10mm and 3/8 holes. The Yukons in my part list did.
- The master service kit for my 05 came with 10mm bolts.
- The Detroit TrueTrac 912a553 came drilled with only 3/8 holes, so I ordered the below bolts that ended up working out and I didn’t have to have the DTT holes drilled.
- YG 33035 (3/8 x 24 thread, .866 long)

Cheers and thanks to the forum in helping figure this out. Now to pull the front out

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[CheddarGau]

You will love the 4.10 gears. Drives so much better.

 

[Rene_05]

I’m actually looking forward to going on all of the little gear break in drives .

Speaking of break in, I haven’t found a consistent answer to this:
- Should I wait to break in the rear until the front is finished and just break them both in at the same time? Know the higher speed/highway break in doesn’t apply, but at least for the lower speed cycles?
- Since I imagine the front needs to be under load, I assume this needs to be done in 4wd. Is this safe to do on pavement if the road doesn’t have turns/is straight?
- Since they are Dana gears up front, do they really even require break in?

 

[CheddarGau]

I’m actually looking forward to going on all of the little gear break in drives .

Speaking of break in, I haven’t found a consistent answer to this:
- Should I wait to break in the rear until the front is finished and just break them both in at the same time? Know the higher speed/highway break in doesn’t apply, but at least for the lower speed cycles?
- Since I imagine the front needs to be under load, I assume this needs to be done in 4wd. Is this safe to do on pavement if the road doesn’t have turns/is straight?
- Since they are Dana gears up front, do they really even require break in?

Just drive it easy for the first 500-1000km. You are pretty much allowing time for the gears to mesh and work their pattern in. Change real oil around 500-1000km, and add lsd additive if applicable. fronts will just hang out and work in slower, but think of it as a brand new vehicle. Those gears aren't broken in either and never have issues.

 

[Rene_05]

Just drive it easy for the first 500-1000km. You are pretty much allowing time for the gears to mesh and work their pattern in. Change real oil around 500-1000km, and add lsd additive if applicable. fronts will just hang out and work in slower, but think of it as a brand new vehicle. Those gears aren't broken in either and never have issues.

Thanks, figured I was thinking about the front too hard, just don’t want to mess up after all the work. Planning to follow this guide for the rear:

Ring and Pinion Break in Procedure

Help your new ring and pinion gear set last longer by following this recommended break-in procedure from Revolution Gear & Axle to avoid premature wear

revolutiongear.com

 

[CheddarGau]

Thanks, figured I was thinking about the front too hard, just don’t want to mess up after all the work. Planning to follow this guide for the rear:

Ring and Pinion Break in Procedure

Help your new ring and pinion gear set last longer by following this recommended break-in procedure from Revolution Gear & Axle to avoid premature wear

revolutiongear.com

Yeah that works too. I did highway not long after. The main thing is just don't abuse it right out of the gate.

Yeah the fronts will just hang out and wear drive and coast side as you drive normally. Will take longer, but they arent used much so the break in isn't as crucial.

You're going to love the drive after.

 

[CheddarGau]

How do you like the drive so far? I found it gave instant gratification.

 

[Rene_05]

How do you like the drive so far? I found it gave instant gratification.

Can confirm that I should have done this a long time ago. It’s like I can feel the rest of the components breathing a sigh of relief, since they don’t have to work as hard. Will be really interesting to do the highway speed break in next!

 

[CheddarGau]

Can confirm that I should have done this a long time ago. It’s like I can feel the rest of the components breathing a sigh of relief, since they don’t have to work as hard. Will be really interesting to do the highway speed break in next!

I found highway to be very enjoyable, power up hills is great, much less gear hunting. slightly higher RPM at cruising speed, but i feel that it's not impacting fuel economy, since it would have been in a similar range with the smaller tires and 3.73. The overdrive still loves to stay engaged on hills, and requires decent throttle input to disengage, but that's more of a programming thing from factory.

City driving (99% with hills and a lot of stop and go) I found to have a major impact. Acceleration from stand still was great, with far less throttle input required to move. My observation is fuel economy is better than before the bigger/heavier tires and has more torque. Autistic son loves the car for some reason ( I suspect it's the round headlamps) and if he decides to play around in it and accidentally breaks something, new parts are cheap and used ones are plentiful. All and all I'm not allowed to sell it because of him hahaha.

For those on the fence it is a worth while upgrade, especially if you plan to keep the vehicle. Technically no money put into a vehicle will help it's resale value, but in order to buy anything newer with same same specs/performance may cost significantly more money than upgrading. My view is (mechanic point of view) is to repair and upgrade a vehicle of this type, since in general it's replacement parts are very affordable. In the long run you come out ahead. An example of the costs associated with new vehicles.... a tail lamp or headlamp lens with factory LED's often run in the $500-$5000 range. Depends on brand, trim, and if sensors are in the lens of course.

 

[CheddarGau]

Can confirm that I should have done this a long time ago. It’s like I can feel the rest of the components breathing a sigh of relief, since they don’t have to work as hard. Will be really interesting to do the highway speed break in next!

Not sure if you noticed this on your new gears (and old), but there are markings with a number and + and - on them. There are there to be used with the marking on the existing gears and the existing shims (marks are on the pinion of new and old) to allow you to do a calculation that will give a good estimate of of much to add or remove. It's not perfect, but gets you very close. Mine wasn't perfect, but was close enough, that I just threw it in without adding shims to the pinion.... I was on limited time with only a couple hours to do the removal and install/ pattern adjustment.... don't judge me

 

[u2slow]

Fwiw, we don't all need 4.10. That's a side effect of the auto having a very tall OD ratio.

I regeared from 3.54 to 3.73. (6spd). Swapped complete diffs from an automatic. It was the perfect correction for the tire size change.

 

[Rene_05]

I found highway to be very enjoyable, power up hills is great, much less gear hunting. slightly higher RPM at cruising speed, but i feel that it's not impacting fuel economy, since it would have been in a similar range with the smaller tires and 3.73. The overdrive still loves to stay engaged on hills, and requires decent throttle input to disengage, but that's more of a programming thing from factory.

City driving (99% with hills and a lot of stop and go) I found to have a major impact. Acceleration from stand still was great, with far less throttle input required to move. My observation is fuel economy is better than before the bigger/heavier tires and has more torque. Autistic son loves the car for some reason ( I suspect it's the round headlamps) and if he decides to play around in it and accidentally breaks something, new parts are cheap and used ones are plentiful. All and all I'm not allowed to sell it because of him hahaha.

For those on the fence it is a worth while upgrade, especially if you plan to keep the vehicle. Technically no money put into a vehicle will help it's resale value, but in order to buy anything newer with same same specs/performance may cost significantly more money than upgrading. My view is (mechanic point of view) is to repair and upgrade a vehicle of this type, since in general it's replacement parts are very affordable. In the long run you come out ahead. An example of the costs associated with new vehicles.... a tail lamp or headlamp lens with factory LED's often run in the $500-$5000 range. Depends on brand, trim, and if sensors are in the lens of course.

It has been a great vehicle for me over the years and is relatively straightforward to work on. My main reason for keeping it was being able to learn how to wrench without additional up front cost. What I’ve learned has made it worth it for me. My mom also has a 2003 limited and refuses to get something else, so it helps knowing a good bit about these. Your posts have helped a lot of folks out, so I’m glad your son isn’t letting you sell your (his) Jeep .

Did you program the computer with the larger tire size, revolutions per mile and/or updated pinion ratio? After scouring different posts, seems like a programmer at a dealership would be needed.

Interesting thread that talks about it here. “Pinion reset” appears to be the key phrase.
https://www.jeepkj.com/threads/gas-milage.48243/post-534699

https://www.jeepkj.com/threads/tire-size-to-regear-or-not-to.62593/post-

https://www.jeepkj.com/threads/pinion-reset.48652/post-540732

Looks like you all talked a little about it in your thread too, didn’t notice that before. I’m not overly concerned about it now since it is relatively flat here, but I want to be closer to the mountains asap.

https://www.jeepkj.com/threads/4-10-gear-finally-installed.81534/post-817024

 

[Rene_05]

Not sure if you noticed this on your new gears (and old), but there are markings with a number and + and - on them. There are there to be used with the marking on the existing gears and the existing shims (marks are on the pinion of new and old) to allow you to do a calculation that will give a good estimate of of much to add or remove. It's not perfect, but gets you very close. Mine wasn't perfect, but was close enough, that I just threw it in without adding shims to the pinion.... I was on limited time with only a couple hours to do the removal and install/ pattern adjustment.... don't judge me

Interesting, I will have to take a look at the old gears. Would have been neat to do myself, but a little too much risk in messing something up for my appetite.

 

[Rene_05]

It has been a great vehicle for me over the years and is relatively straightforward to work on. My main reason for keeping it was being able to learn how to wrench without additional up front cost. What I’ve learned has made it worth it for me. My mom also has a 2003 limited and refuses to get something else, so it helps knowing a good bit about these. Your posts have helped a lot of folks out, so I’m glad your son isn’t letting you sell your (his) Jeep .

Did you program the computer with the larger tire size, revolutions per mile and/or updated pinion ratio? After scouring different posts, seems like a programmer at a dealership would be needed.

Interesting thread that talks about it here. “Pinion reset” appears to be the key phrase.
https://www.jeepkj.com/threads/gas-milage.48243/post-534699

https://www.jeepkj.com/threads/tire-size-to-regear-or-not-to.62593/post-

https://www.jeepkj.com/threads/pinion-reset.48652/post-540732

Looks like you all talked a little about it in your thread too, didn’t notice that before. I’m not overly concerned about it now since it is relatively flat here, but I want to be closer to the mountains asap.

https://www.jeepkj.com/threads/4-10-gear-finally-installed.81534/post-817024

Welp, first dealership I tried on my way home wanted 500 to do the programming. Surely that can’t be what it should cost today right? Would a non dealership mechanic with a high end programmer be able to do this?

 

[u2slow]

My speedo was more correct after bigger tires. YMMV.

 

[CheddarGau]

Welp, first dealership I tried on my way home wanted 500 to do the programming. Surely that can’t be what it should cost today right? Would a non dealership mechanic with a high end programmer be able to do this?

HAHA FUNNY. Should be able to do it with a typical snap on scan tool if the option is even there. Still haven't looked in our witech and snap on... been busy.....

 

[Rene_05]

HAHA FUNNY. Should be able to do it with a typical snap on scan tool if the option is even there. Still haven't looked in our witech and snap on... been busy.....

No worries, not urgent or important, I mainly stopped for giggles and to get an idea. I def got the giggles. I will try the shop that did my gears again, now that I have a better idea of what I’m asking for.

 

[Rene_05]

Fwiw, we don't all need 4.10. That's a side effect of the auto having a very tall OD ratio.

I regeared from 3.54 to 3.73. (6spd). Swapped complete diffs from an automatic. It was the perfect correction for the tire size change.

That’s fair, I’m more hoping to do it for the transmission’s sake. Don’t really mind the speedo being off.

 

[u2slow]

That’s fair, I’m more hoping to do it for the transmission’s sake. Don’t really mind the speedo being off.

How much additional correction is needed?

I mean, the VSS reads the axle speed (corrected by the r&p ratio already) and the shift points are already set for the vehicle speed (which is now more correct with bigger tires).

Its not like many other vehicles where driveshaft speed is read and the trans "doesn't know" the axle ratio changed.

 

[Rene_05]

How much additional correction is needed?

I mean, the VSS reads the axle speed (corrected by the r&p ratio already) and the shift points are already set for the vehicle speed (which is now more correct with bigger tires).

Its not like many other vehicles where driveshaft speed is read and the trans "doesn't know" the axle ratio changed.

It appears to be off ~4-5 mph per my phone GPS. 50 is about 54 for example.

I have 265/75/16 (I know we aren’t supposed to go this big, but I did) and now the 4.10 gears.