How much "slop" in the driveline is normal?

Question

Jeep-meisters,I bought a '98 TJ Sport, currently lock stock, w/ 54k miles on it.  It seemsto me to have too much play in the rear drive line.  This is felt mostly asdrive-line snap when running along and decelerating and then accelerating.It is especially bothersome when running in a low gear at low speeds, suchas when off-roading.  It makes it want to buck around under theseconditions.  Obviously something I want to eliminate.If I put the t-case in neutral and manually rotate the drive shaft by hand,about how much rotation should I get?  On mine, the rear driveshaft turnssignificantly more than the front one, which leads me to believe that theP.O. has messed around in  the rearend (ring, pinion, diff, ??) and notshimmed things up right afterward.I have the factory manuals which go into setting the preload and the otherdifferential shims up, but nowhere does it mention how much lash is normalas viewed from outside.Any thoughts?TIA,Fred W. remove allspam from address to reply

L.W.(ßill) · Accepted Answer

Hi Fred,     Every four wheel drive has that "snap" slack in the drive train,because their out put shafts are not directly connected like two wheeldrive cars, so they may be disconnected and switch into the lowercompound gears of the transfer case.      The rear should feel very much like the front. It is normal to feela lot of slop, maybe close to an quarter of an inch at the yoke radiusbecause you are not only taking up the slack of the ring and pinion(practically negotiable) but through the clearances of the differentialspider gears and axle splines. I wouldn't worry about it, unless itstarted to howl. Check their fluid levels while you're thinking aboutit.         God Bless America, ßill O|||||||Omailto:     "Fred W." wrote:

Mike Romain · Answer

The snap you are describing also can come from a broken or weak trannyor engine mount...Mike86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '0088 Cherokee 235 BFG AT's"Fred W." wrote:

CRWLR · Answer

Like Bill, my advise is to not worry about it. But, I would have given a different story.

When you turn the drive shaft, you have to take up all the slop in the carrier as well as the R&P gears, which should be near nothing, but the slop in the carrier can be considerable on a relative basis. The rear carrier is physically larger than the front, and will by virtue of size have more slop. I wouldn't be alarmed if the slop is in the range of between 1/16th and

1/8th turn.

Add to the slop in the carrier the slop in the tcase, and trans, and you have a normal condition that you are complaining about.

accelerating.

Bob · Answer

When I just did my tailshaft conversion, I also took note of how much "slop" was in both the front and rear diff while I had my driveshafts off. I noticed more in my front than my rear, but both were very minimal.

And on the other end, the output flange on the rear of the transfer case is solid, while the output flange for the front driveshaft has some play in it, due to the chain in the t-case.

I don't know how to measure the slack on the rear diff you are referring to, except to just say it is very minimal for me. Hope yours is nothing serious!

I would also note, though, the wrangler's gas pedal is pretty twitchy in my experience, and can be very prone to that "bucking" when quickly pressing or releasing the gas, especially in lower gears, even with a rock solid diff. But you sound like you know your stuff (referring to the backlash and such), so I'm going to assume your issue is not just that simple.

L.W.(ßill) · Answer

You have the limited slip traction device in the rear.         God Bless America, ßill O|||||||Omailto:      wrote:

CJimmie in Iowa · Answer

Bill; Is that not also true of a locker acting that way?Jimmie;

L.W.(ßill) · Answer

There's a lot of play in the Detroit Lockers I've played with, wherethe clutches in a limited slip is under a lot of pressure and won't giveat all, unless under the weight of a two ton vehicle.         God Bless America, ßill O|||||||Omailto:

Tookie · Answer

I had almost no slack in my rear, until I installed a LockRight.With these, you don't have to mess with the carrier or gears,but it now has over 1/8 of a turn of slack in it.Jack both rear tires off the ground, turn one of them.If the other  tire turns the opposite direction, you have an opendifferential. If it turns the same direction, the PO has installed alimited slip or locker, which could be causing your slackTookie - 88YJ,"Money Hungry"4" lift, 33" TSLs, Lock-RightsPosiLock, 4.10s

CJimmie in Iowa · Answer

Bill:  That's why I just had to ask. I have never had either one, so all Iknow is what I can read up on them. And as you know that's not the same ashand's on.  Thank's...Jimmie;

Jerry McGeorge · Answer

If you put the e-brake on, place the trans in neutral there should a SLIGHT amount of "backlash", or play as you twisyt the driveshaft. It will feel like a lot, but in reality it's only about .010" at the ring & pinion. Now, if you add lockers to the equation, then there's an additional amount of "take up" in the side gears. However, you should be able to feel the small amount of play between the pinion and ring gears.

If in doubt, compare it to another similar vehicle.

Fred W. · Answer

Thanks Mike,I was thinking of that too and will take a close look at the tranny andengine mounts.Also, thanks to all the other replies to my question.  I will certainly posta follow up to anything I figure out..-Fred W

How much "slop" in the driveline is normal?

Join the Discussion

Didn't find your answer?