Im posting this in the right section this time. :rolleyes: Im having a problem (I'm think) with the posi unit in the 69 coupe. Here is the deal. The rear suspension is totally rebuilt, new bushings,shocks,springs,etc, so I dont think that is the issue. The rear gears are the original ones that came in the car. I purchased a rebuilt gm posi unit from ebay. I could tell it had been rebuilt but the quality may or may not be questionable, as I dont know what to look for. I had a pro set up the backlash as the pinion was never removed, just put the ring gear on the new carrier and installed. I filled it with oil while it was out of the car. I put the gear oil in first,then put a bottle of posi addative, well I over filled it and after the rear was installed I removed the fill plug and let the excess oil drain out. This is where I think the problem lies, since the posi oil was the last added and it hadnt mixed yet, it was all on top, so removing the fill plug it MAY have let most of the posi oil drain out. now the problem, when the rear oil is cold, I dont have a problem, but after driving the car for a while and getting it hot, if I turn to the right (hadnt noticed it happening when I turn left) the rear end makes a popping sound you can hear and feel. I can stop, back up a few feet, and put it back in drive and the problem goes away or it will go away after driving straight for a little ways. I was advised to add more posi oil when I posted in another forum and I've purchased 2 bottles of posi fluid, but I wanted to get some more opinions before I fill with gear/posi oil and replace the seal if it sounds like maybe another problem, I dont want to pull the cover and drain the oil again. Sorry for this being so long, but I wanted everyone to know the whole story behind what is happening. thanks in advance. graemlins/thumbsup.gif

How many miles are on the rebuild? If it has done it from the start, the posi oil has nothing to do with it. When you turn, does it try to spin the inside tire befor the pop?

Originally posted by Dragn70:
How many miles are on the rebuild? If it has done it from the start, the posi oil has nothing to do with it. When you turn, does it try to spin the inside tire befor the pop? It has done it from day one,I have about 150 miles on it, and I really cant tell if it tries to spin the inside tire or not since it only does it when I turn right.I mean, I cant hear or feel the tire spinning that I can tell.

I had a simialar problem with my 12 bolt. It popped and felt like a 4WD on dry pavement trying to turn the front wheels, but it only did it when I turned to the left. This is pretty common if you don't have posi additive in the rear. put some additive in and go to a parking lot very slowly turn left and right repeatedly to work the additive into the clutches. HTH

The additive is an acid that keeps the clutches clean. Some of the new eaton's have carbon fiber clutches and don't need the additive. Sounds to me like a loose bolt is popping when put in a bind. Check all the control arm bolts and maybe a rear coil spring. If you have lost some alignment shims out of the front end you could get a popping sound going through the frame. In some cases the end play on the right axle could be on the big side and you hear the c clip slamming into the carrier.

Use something to pull some of the oil out of the rear end and put in some more additive. Drive it for a while and the problem should go away.

My rear end is a rebuilt posi. Thoguh I got at least 7k miles on it before it started "popping", it did only do so once warm. I put in one bottle of the GM posi lube and it went away. No problem for the last few months.

Give the posi lube a shot.

If not, do some testing with a friend. Just cut the wheel hard lock and go slowly and see/feel what you can from that.

Big Gear Head is the man on this stuff but I would like to throw in here with my own take on this. The 12 in my 67 was doing the same thing after you know who pulled it out, replaced the alex bearings a put it back together. It would pop going around corners, one of the side gear shims slipped out of placed and was floating around in the gear oil a additive. Metal on metal not good graemlins/clonk.gif graemlins/clonk.gif

Fished the concave shim out, puzzled out how to get it back in there, problem fixed graemlins/hurray.gif

Good point Wally, those thrust washers fall out easily and it is a very common problem.

well, I added 2 bottles of posi fluid and filled with gear oil and its still pops. I do believe its a left wheel bearing. It didnt do it before I added a posi, but maybe it was because the open diff. didnt turn the left tire so there was no load on it???? I'm just guessing because Im not really familiar with posi's. this is my first.anyway, Im not going to be able to change the bearings for 2 weeks.

Go to a big parking lot and do some tight figure 8's. Do them slow so the cops don't mess with you. This will get the additive worked in good and maybe help pin point the problem if the additive does not get it.

Give it a little time and see if it gets better.

Marty and big gear head. I will do as you recommended and give it some time to work in. thanks for all the adivce guys. graemlins/thumbsup.gif

When I had the posi in my 12-bolt rebuilt years ago I chose slightly stronger springs. I have put in the GM additive religiously any time I change the oil and my axle still pops a bit when I'm moving slow and turning sharp. I suppose this means my posi will wear out faster than it should. The popping I experience isn't too bad so I've learned to live with it, at least I know it's still working.

But now Wally's post now makes me want to pull the cover and take a look at those shims..........

Those shims are sneaky, thet slide out and don't make any noise graemlins/angry.gif

Mine made a nice noise. When we did the posi I had Mr. rear end man set it up tight so you can inagine the popping it made graemlins/clonk.gif

Wally, what are you talking about when you say "side gear shims"? Are you refering to the carrier shims that go on either side of the carrier bearings?

Nope. There are two shims, between the carrier housing and the side gears of the posi. They are dished like a bowl. The axle passes through the carrier, the shim and the side gear. That damn shim falls out when it feels like it, not all the time, and that clunking noise when you do corners is the end result, or it was in my 12 bolt.

Where is Big Gear Head, I'll bet he has a picture of the thing.

10 and 12 bolt posi (http://www.hotrod.com/techarticles/42584/)

Wally,
You actually had a picture of it on the link that you provided. http://www.hotrod.com/techarticles/42584/
It is above the caption
"Test fit the large center pin through the
case to ensure that the brass washers and
spider gears line up properly. Work
carefully to prevent damaging the soft
brass washers. Then remove the pin."

just wanted to update.... It seems the 2 bottles of posi fluid worked after about 3-5 days of letting it work in. thanks for the help guys.