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View Full Version : Clunk...drivetrain play??


ParadiseXJ
September 4th, 2010, 10:32
I've been having a "clunk" issue when slowing, downshifting AND accelerating, upshifting. My D35 is an open diff. so when I have the back end on a jack & turn the tire the opposite tire turns the opposite way, normal. It's just that there is a lapse of time before the tire I'm turning kicks in with the other tire turning.

Motor & trans mounts are fine. What else should I look for to eliminate that play OR is that play normal and I should look elsewhere for the clunk??

I have the rear up on jackstands now to change T/C fluid and front diff, wanna go wheeling (30 mile trail) on Monday. Any ideas??

GrimmJeeper
September 4th, 2010, 10:53
how did you check the trans mount? did you drop the crossmember and see if it comes apart? It can *look* fine, but be completely torn off of the metal mounting part, mine has done that twice, and still looked fine until I dropped the cross member.

ParadiseXJ
September 4th, 2010, 11:35
how did you check the trans mount? did you drop the crossmember and see if it comes apart? It can *look* fine, but be completely torn off of the metal mounting part, mine has done that twice, and still looked fine until I dropped the cross member.

Visual check only. It LOOKS good but now I s'pose I should look a little harder.
On dropping the cross member...Easy job? any tips? I've never done it.

GrimmJeeper
September 4th, 2010, 11:51
its easy, just put a jack under the trans and unbolt the crossmember from the frame. if it falls off the tranny mount is bad :D

ParadiseXJ
September 4th, 2010, 12:38
OK, the trans mount is OK, BUT, I found that the diff end U-joint has quite a bit of play in it. When I rotate it it clicks from one direction to the other (bad eh??). I see how the u-joint comes apart but is THIS a major project or???

I do believe that's the source of my clunk.

GrimmJeeper
September 4th, 2010, 12:41
there should be no play at all in a ujoint, i'd say that's a good place to start. changing a ujoint is pretty easy just make sure you dont let the needle bearings inside the cap fall inwards when you're putting the new one back in. a blob of thick bearing grease helps keep em standing up where they belong.

joe_peters
September 4th, 2010, 12:44
Chime in on the tranny mount--it shouldn't have any movement in it. My quick and dirty test is to put a jack with a piece of wood under the transmission and while observing the mount/crossmember/trans give the jack a pump--you shouldn't see much if any movement of the trans without the crossmember making the same upwards movement.

I would drop the DS and check/replace that u-joint. For that matter, if its time to replace one, I would do both on that DS.

Post up pictures of your wheeling trip!

ParadiseXJ
September 4th, 2010, 13:07
OK I'm going with u-joint.

The MJ came with several extra parts, one of them being a Spicer U-joint, straps and strap bolts. Printed on the strap is Spicer 2708.

Anyone know if that's the right part # or do I have to go shopping??

NAPA - "Precision" $16
Autozone - "Duralast Gold" $13

...and is the same u-joint front & rear?

GrimmJeeper
September 4th, 2010, 13:32
I would go with the NAPA unit, precision makes decent joints. Dunno who makes the Duralast version though. Who knows these days everyone is sourcing the same manufacturers. I'm biased though, I'm at work (in my NAPA store) right now :D

both ujoints on the rear drive shaft are the same, as well as the one at the axle up front.

ParadiseXJ
September 4th, 2010, 14:08
Spicer 2708.
Anyone know if that's the right part # or do I have to go shopping??



Can you cross reference that P/N

GrimmJeeper
September 4th, 2010, 14:12
Nope, but if that's stamped on the strap its just a number for the strap itself, not the ujoint.

The NAPA part number for the joint you need is P369

ParadiseXJ
September 4th, 2010, 15:01
Nope, but if that's stamped on the strap its just a number for the strap itself, not the ujoint.

The NAPA part number for the joint you need is P369

Thanks, I picked up a P369. I'll compare it to the other.

heyhar
September 4th, 2010, 15:14
If the shaft is out, and your hands are dirty, do both. they have both seen the same work load, and in my experience, I've had the front ones go first quite often.

Maybe unrelated, but my '96 had a clunk just after letting off the brake after a stop, turns out it was axle wrap, the front rotating down due to braking, and clunking back to normal position after releasing the brake. I 'fixed' it with leaf spring clamps, preventing the leaves from spreading. The real cause is tired springs, just another item on the to-do list.

ParadiseXJ
September 4th, 2010, 17:10
I see the concensus is to do both. I didn't, I'll do the other next week. The clunk is gone, gone, gone. I got a chance to lube up the slip yoke shaft and TC output. I thought this was going to be MUCH harder. Took me an hour, including the trip to NAPA and breaking my POS Harbor Freight vise.

Load up the XJ, we're goin' to the woods!!! Thanks for the help guys.

40* 02' 08.20" N 121* 26' 18.31" W No phones!!

xcm
September 4th, 2010, 17:18
axlewrap CAUSES worn u-joints, they go hand in hand, at least they did for me while i was running an AAL, if you have the AAL, try doing burnouts in various types of dirt. if you can get the rear end to play the bongo's, youve got axlewrap.

whats the rear suspension?

ParadiseXJ
September 4th, 2010, 17:56
whats the rear suspension?

The rear is a 3.5" full pack lift with an extra (MJ) leaf. I said good-bye to axle wrap a couple years ago. I have the angles and suspension pretty well dialed in. No vibes or other ill effects. Just that friggin' clunk! (past tense)

I've had the Jeep for 7 years and I've never changed a u-joint. I paid to have my front axles done last year. The rear u-joint was t-t-toast. It fell apart in my hands as soon as I pulled the shaft out. I believe it was original equipment as my Dad had the Jeep from new and never really did anything to it.

heyhar
September 4th, 2010, 18:17
Sounds like you caught it in the nick of time! Have a good vacation.....