To sum it up, I sometimes hear a thump from the rear end when I let go of the gas and coast/decelerate. It almost seems like slack being picked up until it catches (thus the thump I can feel and hear).

Last year I had the pinion bearings replaced on my differential (due to a whining I was hearing). The car drove like a dream and everything was perfect after that - no more noise from the back and I could totally tell there was very little slack in the driveline. It no longer thumped when I decelerate/coast. I was happy.

As the new parts of whatever broke in, I am back to where I started (minus the whining sound). When I take my foot off the gas, it will sometimes make a thump. When the car is jacked up, there is considerable movement from when I spin the tires until the driveshaft starts to spin.

Is this backlash? I've read quite a bit about it and I definitely don't want to mess with it too much, but would tightening the pinion nut - even if a tiny bit- help me out and reduce some of the play? I suspect some of the issues arose when the shop originally did work on my rear end and did not reinstall the pinion nut correctly (torqued it rather than putting it back on in the same position). If I tighten the pinion nut, will I reduce the backlash?

My issue seems similar to:
http://web.camaross.com/forums/showt...light=backlash

Just as a point of reference from one of my original posts: http://web.camaross.com/forums/showthread.php?t=462546

Thanks!!!!!!!!!!!!!!!!!!!

 

Have you checked the carrier mains? I had a similar problem when I first got my car, and popped the cover off to find the drivers side mains completely loose one nut about to fall off, and one stud backed out way way to far. I tightened it down and the thump was gone.

Could be they didnt use locktite on them and they have just now gotten to the point you noticed it.

 

Perhaps the shop didn't torque the pinion nut enough, and it's starting to slack off? You "could" snug it up a bit, but the problem is, you would have no way to gauge how much pre-load you're putting on the bearings, UNLESS you pulled the diff apart, pulled the carrier, and checked it properly! Sorry, but that's the fact of the matter.

IF you go to that extent, maybe you might want to consider putting in a solid pinion spacer instead of the factory style crush collar. There's a little more work involved in setting up a solid spacer, but if, in fact, it is the pinion giving you grief, it shouldn't move once it's setup with the solid spacer.

As for backlash, I think you would actually increase the amount of backlash you have by pulling the pinion in tighter . Backlash adjustment is done by shimming the carrier left/right. But sounds like maybe your issue is with the pinion?

 

Thanks for the idea, will definitely look into that!

 

Ahh - thanks, thats the kind of response I was looking for... I cannot tighten up the gears/reduce backlash without ripping apart the differential.

What about this - the differential looks like there is gear lube/oil all over the top half of it. I checked the drain plug and it is on and tight. How the heck can the lube get out of there? If it were the plug, I wouldn't think there would be lube anywhere other than "line of sight" of the plug. Is it common to find lube all over the top of the differential?

I guess this means I need to take it apart to have a look. While its open, is there anything I should be looking for? Lets say there is a lot of backlash, should I be able to slide the ring gear back and forth with my hands? Another thing I saw this weekend while installing new shocks is that I can push and pull the wheels in and out (horizontally along the driveline), but very minimally - this is normal, right?

 

The oil all over the housing may be from the diff being filled up too much with oil, and when it gets hot, it spurts out the vent on top of the housing.

If/when you have it apart, you won't be able to slide/move the carrier or anything ... all you can do is turn the gears!! Although the way you talked about pushing the axles in & out, that is normal for a small amount of end play ... no worries.

 

Again, thats exactly what I was looking for - there is a vent or opening on the top so oil there is "normal" :-) Thanks!

So to sum up your comments (thanks by the way), there isn't anything I can really check in the differential without having a tool to measure backlash and/or have a good understanding of rear ends - right?

 

Well, if you want to "check" the pinion to see if it's still snug, you can do that by hand. You'd have to have the carrier pulled though. Problem is, it might "feel" ok, but under load is when it's actually showing a problem ... and you may not be able to tell if something isn't right (ie: if the crush sleeve isn't maintaining pressure and space between the bearings any more, or if the pinion nut is slightly loose).

If you could get a dial indicator, you could check the backlash without pulling anything but the cover. Also, if you've got it opened up, double check that the bearing caps are still torqued in place (65#). "Maybe" your backlash is way off?!