I'm lifting my 2007 Libby (Rusty's coil) and am buying a new set of tires for it (either BFG ATs for Grabber AT2s) Looking around the forums, I've found that most people round these parts throw 245/75/R16s on their rigs. With the bigger tire size and increased tire weight (+16-18 lbs. per tire over stock), how does this affect the longevity of the 42RLE tranny (and drivetrain in general)? I will be doing lots of trail running with some rocky climbs (no extreme rock climbing but steep and rocky nonetheless.) Obviously, the increased tire weight and rotation will put more stress on the drivetrain, but will it still be operating within the capacity of the drivetrain? I am completely aware of the fact that I'm throwing my warranty out the door by modding the Libby, but with the wimpy 36/30k warranty of the 2007s, it's like not having one anyway...hehe. I'm completely independent of mechanics (I do all of my own car work...I have no problem pulling an engine), so replacing a tranny or transfer case is not that big of a deal...BUT, I'd like to know in advance if I'm doing something that could leave me stranded on a hillside somewhere 50 miles from civilization.

Thanks,
Scoobybri
2007 Libby Sport 4x4 Off-Road and Towing Packages
Rusty's 2.5" Coil Lift On The Way

I think the front diff is more likely to leave you stranded than the transmission. Lots of people have cracked the front diff by having it suddenly gain traction, so watch out for that situation.

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DIRTY KJ :: flickr photostream
"Primitive life is very common and intelligent life is fairly rare ... some would say it has yet to occur on Earth" --- Stephen Hawking

I don't mean to hijack, but I believe someone here was looking into putting a steel diff up front to fix that problem, just a thought.

Stephen

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04 5sp. with mods

http://www.cardomain.com/ride/798121

Yea i agree the tranny is pretty good, I would def. worry more about the front diff. but there is a diff. collar out that as far as i know has prevented the diff cracking. Someone correct me if im wrong but no one that has bought the diff colar has cracked their diff. And as far as warranty goes, Its really according to what kind of dealership you go to cause some don't give as much crap about having a lift and some tires.

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Drop what your doin, and go drive your jeep!!!!
03 Jeep Liberty Limited
4X4

After seeing other peoples rig and wanting to mod my own the front diff is the only really weak link in the KJ but you guys are right to just know your situation and avoid spinning the front wheels like crazy because if u pick up traction good night diff. I have seen some kj's pics in some stuff way beyond what I would be doing IE Jeepin Al and a few others. If the trails get tricky I plan to add a locker and DTT in the front for traction to avoid the spinning the tires like a Barbarian to get to the top. From my driving a little 4x4ing the motor and tranny seem good. Out of the motor and tranny area expect the motor to go first IE valve spring.

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02 prelowered jeep kj limited select-trac
aftermarket rad (crack in stocker)
235/70/16 michelin LTX
Mopar hooks and Skids
BDS lift
dynomax super turbo

It's hard to prove the effectiveness in this way because:

a. The people who buy the collars are the kind that worry about diff breaking, therefore it follows that they will be more gentle.

b. We haven't had a report of failure with the collar on, however, all it takes is one cracked diff with the collar on to disprove the hypothesis. But, until then, it's not conclusive prove.

I guess that to prove this you would have to get similarly-equipped Liberty to tackle a spot that's known to crack diff. But, even here, it's difficult. I was on the same path that someone cracked his front diff, and eventhough I did not go up it myself at the time, it did not look to be especially challenging. We may never know ...

(yes, I ordered a collar anyway )

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DIRTY KJ :: flickr photostream
"Primitive life is very common and intelligent life is fairly rare ... some would say it has yet to occur on Earth" --- Stephen Hawking

So what I'm reading is that the tranny and transfer case is ok with the increased stress, but that the front diff is the issue. If saving the front diff is a simple as slapping a collar around the pinion input shaft, I'll order one and be done with it.

So no one here with big tires and a lift has had drivetrain failure? (Ignoring front diff problems...we know that is a problem.)

Scoobybri

KJ-BOL hadn't put his on yet, but still managed to explode his front diff. So I'm not sure I agree with your theory about us collar owners being gentle. Heck, the reason for the collar is to push the limits

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My opinions & advice are taken at your own risk.
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2002 Patriot Blue KJ - Coming soon!
2006 Black LJ (Wrangler Unlimited), auto, custom skids, 3.5" Rubicon Express, Aussie D30, Rocker Guards & Cooper AT3 235x85r16
2009 Patriot Blue D2500, 5.7L Hemi, 4x4, Quad Cab
1967 Alberg 37' Masthead rigged Sloop

245'S aren't really all that big, if the tranny couldn't handle those, it shouldn't be in a jeep, "well", maybe a compass hee hee.

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06 jeep liberty 4x4 65th aniver edition

04 ranger xlt sc 4x4, 4.0 sohc, 5-speed, gibson dual sport, cai, udp, bama tune, BFG's, and tru-trac

07 redfire mustang GT, 4.6 3V, 5-speed

One other point on the Diff collar - I think Mutt had one on when he broke his CV joint, without breaking the Diff housing
and um.......... I'm not sure that would be gentle.....

http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?t=12328&postdays=0&postorder=asc&start=0

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2005 CRD
stuff
Skeptic quod gratis asseritur, gratis negatur

Any time you put more stress on the drivetrain, its not going to last as long. No, it wont just up and break on the trail, but in the long run, its not going to last as long as if you had stock tires on it.

Thats one reason I have two sets of wheels. I also only got the 245/70 and not the 75's. I only noticed a small amount of lost torque.

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LOST KJ'S
Where are you going???
Current Jeep: 2004 Jeep Liberty
-Atlantic Blue
-Air Ride Rear Suspension ; OME/Rustys Lift ; Powertrax Locker ; Moog Lower Ball-Joints ; 245/70/16 Yokohama Geolander A/T-S's on MOABS ; Flowmaster 50 SUV
Lost #007082
http://www.cardomain.com/id/jeepjeepster

The tranny is the same one used in the TJ, ZJ, and WJ from some time, including the Rubicon. It's also used in the new JK. The t-case is also the same that has been use in the TJ, XJ for a long time

A lot of these people run 35" tires and I haven't seen many complaints. A 245/75R16 is not that large really.

Yes any increase in load is going to shorten the life of parts, but it's probably negligible. There alot of factors that would effect longevity more, such as maintenance and how hard you drive. I wouldn't worry about it.