sidneyhop

I just picked up a rear end that I want to switch out my current one with, but after I got home I realized its missing the springs that I always thought made it a limited slip.

It has an OH stamping on the cover which is a 78 or 79 and being after a 70 should automatically make it a posi, but I dont know the history of it. Could have been rebuilt or who knows what.

Thanks for any help!

wombvette

Sorry

...Roger...

Some guys leave the springs and plates out.

sidneyhop

So this is a posi unit, but just without the springs and plates?

I was reading some other threads and one said if you turn the pinion and both side axles turn the same direction then its a posi, but then another thread said the opposite. One should turn the other direction.

...Roger...

If one wheel turns opposite direction its not a posi.

ajrothm

It could still be a posi if the clutches are setup to spec (ie. tight) and not relying on springs/plates to provide preload.....

BUT if you spin the pinion or one of the side yokes, the other side yoke may spin the opposite direction because there is no springs/plates to preload the clutches....BUT once you put real torque into the pinion from the engine, the clutches will lock...

Problem is, you don't know if the clutches have been setup like that or not....Most rebuilders do not take the time to do this..... Tracdogg2 and GTR1999 both setup or "tune" the clutches like this and do not use springs/plates for preload...This is something that has to be measured out and shimmed.

Tracdogg just built my super 10 bolt and it doesn't use springs/plates....If I turn one side yoke, the other goes backwards....but I guarantee you my posi is working......I just made 5 passes at the strip....

...Roger...

I don't know if I have ever seen an open C2-C3 rear end BUT I don't see the clutch plate guides in his rear end. They usually hang out a little from the case.

Rally68

The case is relieved for the clutch tabs & keeper on a posi diff. You can see the half-circle relief and the clip for the clutch tabs clearly in the second picture

sidneyhop

ok, just check the rotations. Pinion turns both axles the same direction. If I turn one axle the other turns the same direction. I can hold one axle still and turn the pinion and the other axle rotates.

I guess this is a definite indication that its a posi thats been 'tuned'. Did the 78 and 79s all have springs and plates?

sidneyhop

Damit! I just read another thread where if you're able to hold one axle steady and turn the pinion and the other rotates its an 'open' differential and NOT a posi. So which ever one has the least amount of resistance moves.

...Roger...

Interesting and makes sense. So.... just a guess but it sounds as if on dry ground the diff without preload springs will do fine but if the same diff is on an icy surface it might act as an open rear end.

...Roger...

You can solve this by looking in to see if the side gears have clutches behind them. You should also be able to see if the clutch guides are there.

sidneyhop

I dont know a lot about differentials. Would the clutches be inside the carrier shown with the arrow? Where would the clutch guides be?

Thanks

...Roger...

Yes inside where you have the red arrow and on the other side under the side gear.
One of the guides will be just under the point of the red arrow,its a half of of tube looking thing that holds the ears of the clutch plates.

sidneyhop

Are these the clutches? A standard 'open' differential wont have these?

...Roger...

Yep thats the guides and the posi clutches. Is that yours ?

sidneyhop

Yep, thats mine. Seems as if someone has taken the springs out from what Ive been reading. Question is has it been 'tuned' correctly or even at all? I tried to take a better pic of the carrier to ask if its been polished. This would be a sign that its been tuned and possibly correctly??

There isnt a lot of slop in the spider gears, no rattle back and forth if I turn the axles. One interesting note is when I turn the pinion and hold the drivers side everything else rotates freely. When I hold the passenger side however it binds up and is difficult to turn. Could this mean the clutches or bearings need attention?

...Roger...

I sent Gary a PM ,hopefully he will chime in and answer your latest questions.

sidneyhop

No word yet from Gary.

I did notice that the clutches that were used were the snowflake variety so replacing them with solid clutches should give me a definite reason to start breaking it down. Whats the best brand and place to get them, and also the shim kit to?

Alex

Mike Ward

Gary is no longer on CF. Try DC or CAC.