Stuck posi clutches
 

Sherri and I worked on the 69 Z for a good 10 hours today.

First time on the road. Drove 25 miles (open headers - maybe I am just getting old, but too loud for me!!!) to my brother's shop so I could mount new tires, and can do exhaust work tomorrow, as well as some fine tuning on the engine.

Posi unit was rebuilt with all new clutches. Bought it maybe 10 years ago, so it sat for awhile, but always in climate control, and it had zero rust anywhere. In hindsight, I probably should have disassembeled before installing it.

Used GM posi additive for first fill after going through the rest of the rear.

I am guessing that once the cluthes release the first time, they will start to break in and get better.

Right now, problem is they are stuck. No differential movement around corners. So far, I have only driven on OLD dry rotted tires, so maybe with new rubber they will break loose around the first corner. If they don't, anyone have any tricks for getting them freed up the first time?

Re: Stuck posi clutches
 

On my Ford 3/4 ton, 4x4 Van, the clutchs locked up from non-use. I changed the gear lube to synthetic, then took it to a big parking lot and did figure eights. They slowly worked themselves free. Never had that problem again.

Re: Stuck posi clutches
 

Just like what Tony said;
Lynn, you can cure this with a trip to "Wallmart".
If you go late at night and find an open area with the space,
Then crank the wheel hard to one side, slowly
Do 3 or 4 full turns and then the same the other direction, it
Will get the gear lube worked into the clutch.
After doing rearend rebuilds for 30 years I have seen this manny times,also
I am not a fan of Syntheic's but that is up to you, just make sure you get the "GM"
posi additive.
It is a "Must" have!!
I have never found an aftermarket that work even close.
Just my thoughts,Joe.

Re: Stuck posi clutches
 

That was exactly my plan unless I got another suggestion.
I think it will help once I get some real rubber in the back.
Eric is sending me some Hoosier Quicktime rear tires. That ought to do it.
Just mounted some original type Firstones yesterday, but not sure that thosee E70's will be enough.

Thanks.

Re: Stuck posi clutches
 

I had the same problem but mine only cleared up a little doing the fig 8's. Somewhere I read
to add another small bottle of the GM posi additive and to do the fig 8's in reverse. I am
glad to say all rearend noise is gone.

Tony

Re: Stuck posi clutches
 

I tried the figure 8's with my bias ply 70 series Firestones. No go.

Lots of burning rubber smell when I got back to the house.

I have some 275 60 15 Hoosier Quicktimes, but after test fitting, they are just too darn close to the lip to do fig 8's.

May have to wait to put some bigger rear tires on the back.

Re: Stuck posi clutches
 

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 67rs/ss</div><div class="ubbcode-body">I had the same problem but mine only cleared up a little doing the fig 8's. Somewhere I read
to add another small bottle of the GM posi additive and to do the fig 8's in reverse. I am
glad to say all rearend noise is gone.

Tony </div></div>


I'll second the figure 8's IN REVERSE to free up the rear.

Re: Stuck posi clutches
 

Taking the driveshaft out tonight and dropping it off to have it re-tubed tomorrow.

Will put one more bottle of posi lube in there and try the f8s backwards after I re-install the driveshaft.

Sherri got to take it for a spin this evening. Her first time behind an old muscle car (her daily driver is a M Roadster, so it isn't like she hasn't experienced performance).

Re: Stuck posi clutches
 

Put some modern radials on and did the fig 8's and lots of circles both left and right.
No go.
Took the carrier out last night &amp; removed the spring pack. Couldn't get the side gears to move on the bench. Was getting late, so I sprayed penetrating oil on the clutches from every angle and put it back together without the springs pack. More grease and another bottle of GM posi additive.

Was 11 by then, so didn't take the time to go do figure 8's. Drove home the 30 miles and the clutches are still stuck. Hmmm... I am starting to think the buy that &quot;blue printed&quot; this rear maybe got things a little too tight. Didn't measure clearances on the side bearings and spider gears, but suspect that may be my issue.

Not much time to work on it this week, so may have to wait a week on this. Sure cuts down on the driving enjoyment. Here I have this killer Z that runs very well, and it feels and sounds likecrap going around a corner. When pulling out of the gate, I normally just punch it so at least all I am getting is tire spin.

Re: Stuck posi clutches
 

Anyone have a part number for the spring plates? One of mine needs to be replaced.

Re: Stuck posi clutches
 

#3869320

Re: Stuck posi clutches
 

Thanks

Re: Stuck posi clutches
 

WOW, 25 miles with open headers? You are a brave man! Somebody made your posi into a spool. It will never break or slip going straight. HA! And....you are NOT to old!

Re: Stuck posi clutches
 

Yeah, problem is I like going around corners from time to time.

Will pull it back out in a week or two.

Zack is graduating this weekend and we have relatives coming in from out of town, so I will just have to put the car on hold for a while. Although I know Sherri's dad will have to go for a ride.

Re: Stuck posi clutches
 

I had a Trans Am when I was a teenager that had noisy posi clutches and I went to the Pontiac dealership and talked to the old mechanics about how to fix it. They told me to put in a bottle of GM additive and do a burnout with the right wheel on the grass and the left wheel on the pavement, then do a burnout with the left wheel on the grass and the right wheel on the pavement. I did and no more noise! I have used that trick for years on many cars and trucks. I miss those old days when you could go to the dealership and talk to the mechanics and they would be glad to help a broke kid fix his car.

Re: Stuck posi clutches
 

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: supercar</div><div class="ubbcode-body">I had a Trans Am when I was a teenager that had noisy posi clutches and I went to the Pontiac dealership and talked to the old mechanics about how to fix it. They told me to put in a bottle of GM additive and do a burnout with the right wheel on the grass and the left wheel on the pavement, then do a burnout with the left wheel on the grass and the right wheel on the pavement. I did and no more noise! I have used that trick for years on many cars and trucks. I miss those old days when you could go to the dealership and talk to the mechanics and they would be glad to help a broke kid fix his car. </div></div>

That's a great idea. What's your address? I will be right over. Don't want to tear up my own yard.

Actually, I probably would try that if it wouldn't sling grass and dirt all over my clean wheel wells. Not sure I could find a good place. I like all my neighbors.

Re: Stuck posi clutches
 

LOL! We would not do it anybodys yard. We would do it on a country road where there wasn't much traffic. Good luck with the fix.

Re: Stuck posi clutches
 

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: supercar</div><div class="ubbcode-body">LOL! We would not do it anybodys yard. We would do it on a country road where there wasn't much traffic. Good luck with the fix. </div></div>

Yeah, I figured. Just being a bit of a smart arse.

I have already reseigned myself to disassembling the unit.

Re: Stuck posi clutches
 

Finally disassembled the unit. Soaked it in WD40 for several days, submerged. Still stuck.
Clutches were not stuck from sitting. Whoever put this together just used too many shims. Total of .053 on each side. It was a bear getting it apart. Had to use a 1 inch thick brass drift.

I did not have a shim assortment, and there wasn't a sufficient assortment of shims in there to shuffle around. Thought it would be sitting in pieces until I could buy an assortment.

Remembered I had an OLD NOS set of Moroso spyder gears and side gears still in the box. Just on a whim, tried them to see if they might be a little thinner than the factory gears. Sure engough. Ended up with .002 (manual calls for .001 to .006) backlash. Put it back together and it works great. Success.
Guess I ought to buy a shim assortment for future use. Also need a set for the side bearings and pinion bearings. I have a set of 4.88 gears for future use.

Thanks for all the suggestions. I am sure they would have worked had they simply been stuck from sitting.

Re: Stuck posi clutches
 

Might help to watch this, very good info... [img]<<GRAEMLIN_URL>>/biggthumpup.gif[/img]

https://www.youtube.com/watch?v=CGq15JBBUQw

https://www.youtube.com/watch?v=UwxLHFZq6QA

Mike