lift kit and drive shaft alignment

[dirtster]

I'm new to this so bear with me please. I have been considering a 2.5 - 3" lift kit for my newly acquired 2000 XJ (mainly so I can use 30 or 31" tires). I have been doing some research and asking around. The companies who sell lift kits seem to be rather vague about the question of drive shaft alignment.

I talked to the shop foreman of a local brake and alignment shop whom I trust and have done business with in the past. I asked him about the subject of lift kits. He said, "We don't install them here but we have taken them off for customers who had driveshaft problems and rear differential problems." He was citing a case of a 6" lift on a Wrangler.

The kit companies suggest tilting the differential upwards to better align the driveshaft after the lift kit install. The guy at the brake shop says this can eventually cause failure of the differential when the vehicle is used on pavement as a daily driver. He speaks from experience.

I don't know if a mild lift like I am considering will be problematic, but I don't want to learn an expensive lesson either.

I would appreciate the experience and help from this forum to help me solve this issue in my mind before I proceed or just bag the whole idea.

 

[Bounty__Hunter]

Your current rear driveline is setup like the below pic, you want to maintain this geometry after the lift.

This is easily done on your jeep, and can generally be accomplished by simply lowering the transfer case crossmember 1/2". I did this on my '99 XJ when I lifted it 3", never had a vibration or angle problem. I made my own transfer case drop from 1/2" thick steel, simply drilling two holes to space down the crossmember from the unibody chassis.

 

[dirtster]

Thanks Bounty H. That helps a lot and the drawing is an extra effort that I appreciate.

The drawing brings up another picky question though: the transmission is designed to sit in the calculated position set up by the auto engineers. If I alter that angle to align the driveshaft after the lift, will that mess with the transmission over time? It seems like the small amount that I am talking about (not more than .5") would make little diff. I hope I'm right. I may consult with a local transmission shop.

Sorry I'm being so cautious. :redface: It seems better to check all this out in advance than to just dive in blindly.

 

[Bounty__Hunter]

It's a widely accepted practice to lower the transmission end of the drivetrain slightly to alleviate drivetrain angles. Some even install motor mount lifts to raise the opposite end of the drivetrain.

If you're that worried about the calculated position of the transmission, sounds like you're forever destined to drive a stock vehicle.

 

[dirtster]

Yes, Bounty H., you make a good point about my caution and you may be right. I know there are many successful lifts if done properly. Yet a stock vehicle is not all bad if one knows the limitations and drives accordingly.

I have taken my stock XJ on some fairly gnarly BLM unmaintained roads and the vehicle is quite amazing in its stock form.

You and others on this forum have helped me tremendously. Thank you for your patience and responses.

 

[Bounty__Hunter]

Stock jeeps are very capable, even more so when you add limited slip or locking differentials to one or both axles.

 

[dirtster]

Locking differential: is this what it means when I read the term "lockers" in articles about Jeep set ups? Is this conversion best done by a shop that does that kind of work? Which is better, locking differential or limited slip?

Thanks again.

 

[bobcat481]

Locking diffs. are better for sure. Limited slip means exactly that. One side is allowed to slip , before the other side grabs hold. With a locker, both wheels are locked together with the driveshaft. No slip, no give on either side. That's the way to go. There are many types, brands, and such. Installation is too awfull bad if you have a decent set of tools, and read up throughly before you start. If hesitate about your abilities, then have someone else do it. The price to have one installed is less than the price of a broken, new one. Something to think about is what your stock axle can handle. A stock D-35 is NOT the best axle to try to up-grade with a locker. They can and will handle it, but for how long....who knows.

 

[dirtster]

Thanks Brad. I have a Chrysler 8.25 in the rear with 3.73 gearing and a Dana 30 in front. There is a "Powertrax no-slip locker" on eBay for $453 including shipping for a Chrysler 8.25. That sounds pretty reasonable. Is that what I need? Ever hear of a Powertrax?

 

[Bounty__Hunter]

I believe a Powetrax may use clutch discs inside which will wear out over time and provide less traction as they wear. The best limited slip on the market is the Detroit Truetrac which is a gear driven limited slip, nothing to wear out.

A limited slip isn't bad, it's a traction improvement over stock and they're invisible onroad. Auto lockers can be a bother because they lock and unlock depending on acceleration/deceleration, which can cause some unnerving noises and unexpected lane changes. Selectable lockers are nice but often cost prohibitive.

 

[dirtster]

I did some research on Powertrax. It is an automatic locker like a Detroit Locker. I may take the leap on this one. $453 including shipping is a decent price.

BTW, I have pretty much decided to do a 2" lift for now and shoot for 30" X 9.5" tires with the stock alloy rims. As I get more into this and gain some experience I can always do something more radical later. Thanks again for all your input and good advice.

Yesterday I installed the Mopar gas tank skid I got at the salvage yard for $25. I had to eliminate the factory heat shield (but the skid serves that purpose) and I had to change the rear tailpipe hanger. A muffler shop changed the hanger for $28. The overall job turned out great for a total of $53 and a lot of grunt and sweat.

 

[Bounty__Hunter]

I did some research on Powertrax. It is an automatic locker like a Detroit Locker. I may take the leap on this one. $453 including shipping is a decent price.

It's only like a Detroit Locker in that they're both automatic lockers, locking up with a touch of the throttle. However the similarities end there. The Detroit is a full carrier replacement, while the Powertrax simply replaces the spider gears inside the carrier. The Powertrax is also known as a lunchbox locker. See what you can find on the Aussie Locker, similar to the Powertrax but may be much more affordable.

 

[dirtster]

Okay, Bounty H, I will check into the Aussie Locker. The Powertrax locker is said to be locked all the time and "rachets" when doing tight corners. Hummm, I wonder about that. Anyone using the Powertrax unit?

 

[Bounty__Hunter]

The Powertrax locker is said to be locked all the time and "rachets" when doing tight corners. Hummm, I wonder about that. Anyone using the Powertrax unit?

All the lunchbox lockers operate basically the same way, unlocking and ratcheting when in turns and off the throttle. Accelerate through a turn and chances are it will stay locked, chirping the inside tire, or locking up part way through a turn, causing a discerning bang and some squirrely handling.

 

[blown XJ]

i highly recomemded the detroit truetrac. i got one in the front of my xj with a spool in the back. 99% when wheelin both front tires are spinning and it is invisable while in 2wd on the street. for a daily driver/weekend wheeler i would suggest gettin a trutrac in the rear. or getting one front a rear. dont get me wrong i love the spool in the back but its hell on tires and has some bad handling charaistics i daily drove my jeep with a spool for 3 years now it has been retired to wheeling only..

 

[dirtster]

Thanks, Blown XJ. I will check that out more. The old Buick slogan of many years ago was "Ask the man who owns one."

 

[blown XJ]

just trying to help a fellow jeep guy out.. i know this site helped me out a ton as i was working on my jeep

 

[firestarter]

So, the diagram makes perfect sense but do you really have to consider re-alignment for small lifts (3.5 and under). It seems to me that there is plenty enough tolerance on the joints to allow for the diff to be rotated a bit.

Maybe I'm missing something here? What would the harm be in having the rear diff at a slight angle?

 

[Bounty__Hunter]

You won't notice slight misalignment, it's the large differences that create a noticeable vibe. Although any misalignment will likely shorten the life of the ujoints even without a noticeable vibe.

 

[dirtster]

I ordered the 2" lift kit yesterday. I'm going to take careful measurements of the driveshaft angle before and after the lift. Even though it wouldn't be absolutely necessary to lower the transfer case I will have the info to make some slight adjustments if needed. It couldn't hurt anything to at least consider a slight adjustment and it doesn't look that difficult to do.