1990 245, M47

Symptom: Play in the rear u-joint.

I replaced my rear driveshaft u-joint with an OEM unit on Saturday. No real hardship - used a large hammer with a variety of sockets to be out with the old and in with the new. I checked the new u-joint after installing it (before installing the shaft), and found it to be pretty tight. Tight enough that it doesn't "flop" when I flip the driveshaft over (make sense?). I can move it with a small bit of force. No especially tight spots in the articulation - smooth all-around, but tight. Figured it might just need to "wear in" a little.

Installed the driveshaft in the car - drove it for several miles throughout the day and noticed a really low vibration - very "bass-y" - above ~25 mph. Seems to be a little louder when I put some torque to the wheels.

Took the shaft back out Sunday and made sure the flanges didn't look bent in. Smacked 'em a couple times with a hammer and brass drift. Still pretty tight - seems slightly looser (maybe..). Reinstalled, and drove it to work this morning. Same "bass" noise.

What's the deal? Are the snap rings too thick? I installed the driveshaft in the same orientation it was in before I removed it. Should new ujoints be totally "floppy", or tight? Could a new u-joint unveil some other driveline issues? The old one wasn't mortally wounded - but it was definitely on its way out.

I don't know. Very frustrating.

I use sockets and press the new cups using a bench vise to avoid vibrations that may displace the needles.

On the other hand I remember years ago I used thinner snaprings to get a new rear U joint get enough play to fix rear axle vibrations.

Hope you did not get a misplaced needle.

Make sure the front drive shaft in alined properly with the rear. If their out of sink that can cause a vibration.

Ron J

Tight enough that it doesn't "flop" when I flip the driveshaft over

Shouldn't be that tight to my way of thinking.

Do they have a grease fitting? If so they need to be lubed.

Did you install yourself? You may have dropped one of the needle bearings but in that case I think you would not be able to install the joint at all.

What part # did you use?

--
'80 DL 2 door, '89 DL Wagon

They should not be as tight as you describe. Sometimes when new u-joints are installed you need to do this to make them loose---recruit an assistant--set the driveshaft with one joint yoke flat on a an anvil surface and strike the yoke half facing up with a good sized hammer (strike the yoke itself--not the cup) and strike it good and square -- now set the other set of yokes on the anvil and do the same. For whatever reason that method seems to get the yoke assembly "stretched" to allow free movement of the u-joint. Always works for me. -- Dave

Thanks for all of the advice guys.

When I got off work, I pulled the driveshaft back out (getting pretty good at removing those 4 bolts efficiently).

The u-joint was still tight - but seemed like it was loosening up a bit (after having driven ~50 miles). I pulled all of the snap rings out, and hammered on it the way Volvo from Heck recommended. Everything loosened up. Had to hammer it all back together to fit the snap rings, and of course it tightened back up.

Then I found there was a scuff in the flange's groove, where the snap ring "snaps" in. Seems like I would've had to (and did on Saturday) hammer the one ujoint cup in further to engage the snap ring groove. I took a chisel to it (lightly), and reassembled. Still tight, though.

Started hitting, turn 90 deg, hitting, turn 90 deg, etc etc (thanks again Volvo from Heck)- and it loosened up pretty nicely! Went to put it back in, and realized I didn't have the two driveshaft halves properly aligned for the past 3 years.

Anyway - all seems to be well. Still have a low bass sound above 45 mph (definitely better, though) which is more pronounced when I give it some gas. I think I am just going to leave it all alone - perhaps its just the IPD exhaust droning.

On to maintaining the wife's '98 XC

What Volvo from Heck was saying was to bang the Yokes in a way that it will push the Caps outward toward the snaprings. The Snap rings need to be assembled, not taken off.

Low rumble. Hmmm, check your Differential fluid level.
--
'75 Jeep CJ5 345Hp ChevyPwrd, two motorcycles, '85 Pickup: The '89 Volvo is the newest vehicle I own. it wasn't Volvos safety , it was Longevity that sold me http://home.lyse.net/brox/TonyPage4.html http://cleanflametrap.com/tony/

Tony is correct in that what I suggested was meant to be done with the clips in place. As for the rumble and alignment---keep in mind there are visually two correct ways to assemble the two halves (unless you've found the origiinal markings)--but only one of those is correct balance wise. -- Dave

Yeah I had intended on pulling the u-joint out of the shaft and checking for dropped needles. After hammering for a few minutes I remembered you said to do it with the snap rings IN, the whole point being to push the cups as far out against the snap rings as possible.

Regarding assembling the two halves - I used the factory/original markings.

I pulled the diff plug when the driveshaft was out, and fluid dribbled out - definitely full.

Trans fluid level is fine. I pumped a little bit of grease into the center support bearing with a needle fitting after I did the work yesterday.

Regardless - this bass noise wasn't there before I replaced the u-joint. So either:

1. U-joint was bad out of the box
2. U-joint was installed incorrectly
3. A tight, new u-joint revealed another problem in the driveline (old joint had play)

#1 is not likely - all needles were present, and it spun smoothly.
#2 has been the current topic of discussion/research - I seem to have fixed that.
So that leaves #3..

Checked:

Diff fluid level (yesterday). Fluid is new from 6 months ago (Amsoil)
Trans fluid level (yesterday). Fluid is new OEM from 6 months ago.
Guibo (yesterday) is new from ~6 months ago
Front u-joint - no play. smooth.
Trans mount - replaced with proparts 5k miles ago. Pretty soft..but intact

I guess that leaves the center support bearing. The rubber surround piece is getting pretty cracked - but the bearing is SKF, replaced 1.5 years (30,000 mi) ago. I guess it could be time again..

Thanks everyone for the responses. Sorry if my replies are long and "stream-of-consciousness" - I am trying to be as informative and thorough as possible.

The u-joint caps have to be pushed outward against the snap rings after installation. Brace the horz. yoke with blocks on each side. Tape on the vert. yoke until the top cap flexes the snap ring slightly outward. Repeat in all four directions.

Low bassy sound might a wheel bearing or center shaft support bearing.

I agree this is an important step with installing u-joints.

You must also make sure Yoke is assembled (clocked) in the same exact position as they were before removing old joint, the yoke is attached to the differential as it was originally, and the rear drive shaft is aligned correctly where it slides into the front drive shaft.

Dan

"You may have dropped one of the needle bearings but in that case I think you would not be able to install the joint at all. "

May be surprised. I know I did this very thing, and in the intervening 45 years have met several who have done likewise. Muscle and perseverance, and I believe you could get the snap ring in with a needle laying in the cup.
--
Art Benstein near Baltimore

You can say any foolish thing to a dog, and the dog will give you a look that says, 'Wow, you're right! I never would've thought of that!'
- Dave Barry

You have more perseverance than I do, Art.

But if it's possible to install that way, it could be the problem.

--
'80 DL 2 door, '89 DL Wagon