What type of rear differentials do our trucks have?

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Eric Fischer

Member
Open rear or limited slip?

I tried searching this forum but was not able to determine a clear answer.

If it's supposed to be a limited slip then mine is completely shot, because while holding one wheel, I can easily spin the other wheel by hand. It acts as though it's an open rear.

Thanks.
 
myclone

myclone

Donating Member
Re: What type of rear differentials do our trucks have?

Eric Fischer said:
Open rear or limited slip?

I tried searching this forum but was not able to determine a clear answer.

If it's supposed to be a limited slip then mine is completely shot, because while holding one wheel, I can easily spin the other wheel by hand. It acts as though it's an open rear.

Thanks.
Click to expand...

Thats normal operation for the type limited slip we have.. What we have is a "Gov-Lock" which requires X amount of wheel speed difference between the two rear wheels before it engauges. Thats why the "jack up rear end and spin one wheel" test isnt effective 99% of the time.

As was mentioned gov locks are a complete pile of poopy.. If yours has actually failed then call up Auburn or whoever you prefer and get a posi for a 7 5/8" ring gear 10 bolt to replace it. No fuss no muss.
 
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Eric Fischer

Member
Re: What type of rear differentials do our trucks have?

myclone said:
Thats normal operation for the type limited slip we have.. What we have is a "Gov-Lock" which requires X amount of wheel speed difference between the two rear wheels before it engauges. Thats why the "jack up rear end and spin one wheel" test isnt effective 99% of the time.

As was mentioned gov locks are a complete pile of poopy.. If yours has actually failed then call up Auburn or whoever you prefer and get a posi for a 7 5/8" ring gear 10 bolt to replace it. No fuss no muss.
Click to expand...

Thanks, that explains alot. Considering that the stock differential is a "pile of poopy" you would think more people would rip it out and replace it with something better....
 
myclone

myclone

Donating Member
Re: What type of rear differentials do our trucks have?

Eric Fischer said:
Thanks, that explains alot. Considering that the stock differential is a "pile of poopy" you would think more people would rip it out and replace it with something better....
Click to expand...

Ive already broken one gov lock/rear diff myself but I got a complete syty rear diff for a replacement cheaper than I could buy a Auburn/Moroso/whatever so thats the ONLY reason I still have one.

I have lotsa 3rd gen F body buds who went through them by the truck load until they just swapped out the gov lock ten bolt for a complete 8.5 ten bolt diff.
 
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Eric Fischer

Member
THEMADTYPH00N said:
Anyone ever try the 100 dollar torsen unit that SLP sells? I hear a lot of S-series guys like em.
Click to expand...

I'll let you know how it works out. I just ordered one :D. For $100, I figured I can't go wrong.

I am hoping that the torsen differential will solve a problem that occasionally occurs when launching a SyTy - when building boost, the left rear wheel starts to spin. I can see why the Gov Lock differential would allow that to occur, since the difference in wheel speed is probably less than 100 RPM. The torsen should minimize this problem because the locking torque will increase when building boost against the brakes.

Also I have noticed occasionally on launch that the truck will lurch sideways (I think to the left). Perhaps this is a direct consequence of the Gov lock locking up??? Again this might be eliminated with the torsen. Who knows, but I will find out and report back...
 
E

Eric Fischer

Member
THEMADTYPH00N said:
Awesome, let me know how it works out.
Click to expand...

Well I got the Torsen unit from SLP. Although it does come with carrier bearings, one side was damaged so I had to replace them.

Also for anyone working on the GM 7.625 rear end, take note that the ring gear bolts are left hand thread. I never saw that before, and it nearly ruined my day but luckily I was able to recover with a new bolt from GM.

Finally I didn't expect the Torsen to drop right in without changing the carrier shims and my expectations held true - the Torsen is about 0.005" wider than the stocker resulting in too high of a preload on the bearings. So I had to order some adjustable shims from Reider racing.

I will report back when I get the shims.
 
E

Eric Fischer

Member
Merk said:
Eric-

Any update on this?

Merk
Click to expand...

Yes. With the adjustable carrier shims I was able to set the backlash and carrier preload with no problems. However, for some reason on my particular setup, I am having trouble getting the c-clips to go in. See here:

http://syty.net/phpBB2/viewtopic.php?p=248305

I didn't want to post this update because I was afraid it would discourage people from performing this mod. Apparently others have performed this mod with very little trouble - new shims are generally not needed, and although tight, others are able to install the c-clips without issue.

I am planning on milling down the reluctor rings about 0.060" to make insert/removal of the c-clips easier.
 
D

davecalidad

New member
Eric Fischer said:
Merk said:
Eric-

Any update on this?

Merk
Click to expand...

Yes. With the adjustable carrier shims I was able to set the backlash and carrier preload with no problems. However, for some reason on my particular setup, I am having trouble getting the c-clips to go in. See here:

http://syty.net/phpBB2/viewtopic.php?p=248305

I didn't want to post this update because I was afraid it would discourage people from performing this mod. Apparently others have performed this mod with very little trouble - new shims are generally not needed, and although tight, others are able to install the c-clips without issue.

I am planning on milling down the reluctor rings about 0.060" to make insert/removal of the c-clips easier.
Click to expand...

I have one in the Turbo S10 and it is BADAS$ on the street and the track.
It works real well, although I still have a tough timekeeping he straight with 8 psi launches and 245 55 18 KDWS BFG's.....it's an animal!!
 
E

Eric Fischer

Member
Eric Fischer said:
I am planning on milling down the reluctor rings about 0.060" to make insert/removal of the c-clips easier.
Click to expand...

For those of you that are following this thread, I used a lathe to mill off about 0.050" off the surface of ABS exciter rings. Now the c-clips go in with ease. :D. I was able to FINALLY finish assembling the rear.

Next test will be to ensure that the ABS signal still works. I am sure that it will (I don't think removing 0.050" on a 0.500" wide target will hurt the signal).

Unfortunately I can't drive the truck because the forward clutch in the tranny broke, but that's a different thread!
 
E

Eric Fischer

Member
Eric Fischer said:
Next test will be to ensure that the ABS signal still works. I am sure that it will (I don't think removing 0.050" on a 0.500" wide target will hurt the signal).

Unfortunately I can't drive the truck because the forward clutch in the tranny broke, but that's a different thread!
Click to expand...

Final update:

The truck is back on the road finally. The ABS works fine even after removing 0.050" off the exciter ring.

The Torsen works very well too. What seems most noticeable is that if the truck does lose traction (like on a very high boost launch) it will still track nice and straight where with the stock differential the truck would dart to the left/right (presumably as the gov lock kicks in).

I highly recommend this mod, it was well worth the $100.
 
thesyguy

thesyguy

Member
I just installed a torsen setup in my Sy and it was a direct bolt in. No modifications needed at all. I have yet to test it since it has been snowing here for the last 3 days!
 
canadian

canadian

sy in progress
anybody have any tips or step by step instructions for removing the old unit? i tried doing the search, but didn't find much. what's the best way to remove the cross bolt holding the pin in the gearset? don't want to strip the bolt head.
 
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