Chris Wilson

I have a 93 Formula with about 115K on it with a stock rearend. When I go around a corner at fairly slow speeds (<30mph) it makes a squealing noise. It sounds almost like sqeeky springs. I pulled it out and have taken the cover off but visually the posi looks ok. Is there anything that I should specifically look for? The seal on the yoke was leaking a little but I know there was enough fluid in it. The only thing that I am not sure of is how much additive there was, if any. The other problem I was having is a whinning under deceleration. This is the only time that I hear it. I was thinking that maybe a bearing? While I was searching I also saw the the stock posi is not rebuildable, but I found a spring retainer service kit and a pinion gear service kit on auburns website. Any solutions?
Thanks,
Chris

Chris Wilson

I checked the backlash tonight and it was .006". I wonder if I have a bearing going that is making the whinning. Any ideas? Anyone?
Thanks,
Chris

tanmanski

the whining is pretty common, mine does it, most of us have investigated it, as you are now and have decided it's "normal"
I don't know why our posi diff's would show anywhere as "non rebuildable" - maybe that particular vendor just didnt want to deal with them? My driveline shop had no heartburn working on mine
the squealing differential around corners is a more serious (IMO) issue. I would start with a fluid change & new posi additive in the correct amount, let it work in for a few miles then re-evaluate & see if the sound is differnt or gone.

Chris Wilson

Right now the rear is out of the car and another 10 bolt is in it. I would prefer to put the original back in since it has 3.23 instead of the 2.73 rear I just swapped in. I would think that .006" backlash is about factory spec so I wouldn't think that is causing the whine. I guess that I am more worried about the posi noise. Will the posi additive really quiet it down that much? The owner before me posted that he was having problems with "unlimited slip" so I thought maybe it was a more serious problem than just no additive.
Thanks,
Chris

tanmanski

Chris, I can tell you from direct experience is that the correct lube, amount & additive do make a difference in the noise & functioning of the posi unit. Whether there's more wrong with yours than that will remain to be seen, but I suggest it because it's the basic first step in diagnosing your situation. I feel your pain, but really, swapping rear axle assy's is one of the easier jobs on our cars, so I think it's what I'd do first. I was intrigued by your post that the previous owner had problems with it. Maybe you can get more details out of him about what he experienced with it. Let us know what you find out.
FYI my diff had 110k on it, the posi clutch pucks were pretty worn, the springs were a bit weak & it generally felt a bit sloppy. My driveline shop installed new pucks, springs & verified or set all the gear lashes back to spec for $300. It still whines a bit in some situations, but it feels solid & doesnt grab or chatter going around tight corners. These diff's are pretty basic really.
Maybe for peace of mind you might just take the removed unit to a reputable driveline shop & have them check it to see if they can find anything wrong with it. The key to giving a shop this kind of carte blanche is to be able to trust that they're going to not go looking for stuff to replace just because it is not brand new (worn) but really not broke. I think that's why most of us prefer to do our own mtx, but sometimes it's nice to have an expert look at something for you.
good luck,
Ian

Chris Wilson

I think that I will swap it back in and try new fluid and additive. I may put in new pinion bearings, seal, and crush sleeve since I have it out. Another question, how are the stock posi units? Do they generally hold pretty well?
Thanks again,
Chris

tanmanski

it seems to be all about the HP levels you're at & how hard you're launching on it. Personally I haven't had any probs with mine, but I'm basically stock HP & I don't drag race, just street hammering. I think the general consensus of most on the board is, once you go over 400HP, the 10 bolt is living on borrowed time, but it CAN be trashed at stock HP levels if you go with drag radials & aggresive suspension & launch technique. I'm going to retain my 10 bolt until it grenades, then rebuild or replace it. There are some things you can do to beef up the stocker, but I haven't done them & am not sure how effective they are, i.e. better rear end hardware & girdle type reinforcements that try to limit movement/shifting of internals. I guess the bottom line is, most guys see it as a weak link in the car.

Chris Wilson

I guess the only reason that I still question rebuilding the posi (instead of trying additive and new fluid) is because the previous owner posted that he was at an autocross and out of a corner he left a 25' one wheel peel. I am going to be doing a trackmasters driving school (2 days) and I want the formula to be in as good of shape as possible. But I will say that I have hung the back end out on more than one occation so both tires must be getting power then Has anyone had luck with rebuilding their stock posi?
Thanks for the replies!
Chris