Posi case question
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Joined: Apr 2007
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Posi case question
Good day Gentlemen
Installed my new clutch plate and adjusted per Tom's tune-up sheet. With .040 shims on either side I can spin the unit by hand. With .045 shims I cannot spin the unit by hand.
So I installed the .040 shims. Then I installed the 4 springs and plates. Now the differential will not turn by hand.
Is this normal?
Thanks Everyone
Dan
Installed my new clutch plate and adjusted per Tom's tune-up sheet. With .040 shims on either side I can spin the unit by hand. With .045 shims I cannot spin the unit by hand.
So I installed the .040 shims. Then I installed the 4 springs and plates. Now the differential will not turn by hand.
Is this normal?
Thanks Everyone
Dan
Tech Contributor
Joined: Aug 1999
Posts: 15,188
Likes: 4,010
From: Connecticut, USA
When tuning a posi you place the springs and plates in the trash. Even when the posi is factory built and sloppy at times the springs will load the clutches all the time. If the lash it too tight you're going to get hammer or breakage. Go back and either tune or setup stock.
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Joined: Apr 2007
Posts: 69
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Thanks Gary
Should I pitch the springs and plates, and just go with my .040 shims on either side?
Can you tell me if my tuning procedure is correct?
1) Lube clutch plates and shims and install in case (no springs/plates at this point)
2) Put the case on an old axle that is in the vice.
3) Grab case with both hands and try to turn.
4) Could not turn with .045 shims. Installed .040 shims and then could turn.
5) Added springs/plates and could not turn.
6) Posted on Corvette forum.
I am curious especially about #3. Should I be using a spanner instead of just hand (6 inches? 12 inches? 2 feet?) to turn the posi case?
Thanks again
Dan
Should I pitch the springs and plates, and just go with my .040 shims on either side?
Can you tell me if my tuning procedure is correct?
1) Lube clutch plates and shims and install in case (no springs/plates at this point)
2) Put the case on an old axle that is in the vice.
3) Grab case with both hands and try to turn.
4) Could not turn with .045 shims. Installed .040 shims and then could turn.
5) Added springs/plates and could not turn.
6) Posted on Corvette forum.
I am curious especially about #3. Should I be using a spanner instead of just hand (6 inches? 12 inches? 2 feet?) to turn the posi case?
Thanks again
Dan
Tech Contributor
Joined: Aug 1999
Posts: 15,188
Likes: 4,010
From: Connecticut, USA
Shim size will vary with every case. Some use 030 other up to 050" The amount of wear on the spiders, the depth of the bores in the case and the correct "feel" all add into the job.
I set them till they bind, back off 005 then grind shims in between to get the correct feel. No plates or springs used.
I set them till they bind, back off 005 then grind shims in between to get the correct feel. No plates or springs used.
