3.55 diff rebuild advice needed.
Thread Starter
Melting Slicks
Joined: Oct 2012
Posts: 2,156
Likes: 273
From: Dunedin NZ.
3.55 diff rebuild advice needed.
I have a 3.55 diff head that I want to use to replace the 3.08 fitted. The crown wheel and pinion are good but the half shaft end float is 25 thou. Can this be corrected to the suggested 5 - 10 thou by replacing the posi clutches and re shimming without disturbing the crown wheel and pinion or should I just run it as is?
The half shaft inner ends look good and the circlips are in place.
Clearance between the half shaft inner ends and the centre pin in the posi unit is almost nil < 2 thou.
The half shaft inner ends look good and the circlips are in place.
Clearance between the half shaft inner ends and the centre pin in the posi unit is almost nil < 2 thou.
Race Director
Joined: May 2005
Posts: 10,674
Likes: 122
From: Millington Illinois
St. Jude Donor '08-'09
I have a 3.55 diff head that I want to use to replace the 3.08 fitted. The crown wheel and pinion are good but the half shaft end float is 25 thou. Can this be corrected to the suggested 5 - 10 thou by replacing the posi clutches and re shimming without disturbing the crown wheel and pinion or should I just run it as is?
The half shaft inner ends look good and the circlips are in place.
Clearance between the half shaft inner ends and the centre pin in the posi unit is almost nil < 2 thou.
The half shaft inner ends look good and the circlips are in place.
Clearance between the half shaft inner ends and the centre pin in the posi unit is almost nil < 2 thou.
Last edited by 63mako; Oct 26, 2014 at 03:16 PM.
Thread Starter
Melting Slicks
Joined: Oct 2012
Posts: 2,156
Likes: 273
From: Dunedin NZ.
I'm getting back to working on this diff. My main concern is the half shafts hitting the centre pin, the circlips are good, so wear is in the clutch packs or the half shafts or both. What happens if I have the half shafts metal sprayed on the yolk ends to build them up and reduce the clearance?
Race Director
Joined: Aug 1999
Posts: 18,126
Likes: 174
From: WI
I'm getting back to working on this diff. My main concern is the half shafts hitting the centre pin, the circlips are good, so wear is in the clutch packs or the half shafts or both. What happens if I have the half shafts metal sprayed on the yolk ends to build them up and reduce the clearance?
Thread Starter
Melting Slicks
Joined: Oct 2012
Posts: 2,156
Likes: 273
From: Dunedin NZ.
Hi Redvetracr, that seems odd to me I would have thought that any side load should be borne by the bearing where the yoke would be pressing against it. Is there any reference that I can read up on as to the pin being the point where the load is taken up? Not saying you are wrong just trying to learn as much as I can before I do a diff swap.
Le Mans Master
Joined: Dec 2007
Posts: 6,422
Likes: 591
From: McHenry Illinois
Redvetracr is correct. When going in a straight line the yoke end and the pin are rotating the same speed, so no wear or friction. The only time they turn at different speeds is during a turn when one wheel must travel slightly faster than the other. The spindle/wheel assembly pushes against the half shaft, which in turn pushes the side yoke inward, the center pin is the contact area.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
I would not install something with that much slop in it. Play causes accelerated ware. You probably need the before mentioned yokes and or possibly the posi unit. When yokes ware it puts a lot of metal in the oil
Last edited by gkull; Nov 29, 2014 at 04:49 PM.
Thread Starter
Melting Slicks
Joined: Oct 2012
Posts: 2,156
Likes: 273
From: Dunedin NZ.
There is no wear other than the 25 thou of clearance between the C clip and the gear or in other words between the yoke shaft and the pin at full extension. When the shaft is pushed towards the pin it is just touching. There are no marks on the pin and the end of the yoke is unworn also. I'm going to pull the yokes out and have a better look.
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Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
There is no wear other than the 25 thou of clearance between the C clip and the gear or in other words between the yoke shaft and the pin at full extension. When the shaft is pushed towards the pin it is just touching. There are no marks on the pin and the end of the yoke is unworn also. I'm going to pull the yokes out and have a better look.
Thread Starter
Melting Slicks
Joined: Oct 2012
Posts: 2,156
Likes: 273
From: Dunedin NZ.
Thought I would advise the outcome with this diff. I had the half shafts modified with hardened button inserts in the ends so that they will wear better (this is what truck diffs have in them). The buttons sit 12 thou proud of ends of the shafts so this decreased the clearance as well. I fitted new oil seals, a drain plug, Castrol 80-90 weight limited slip oil and Wynns friction modifier for posi diffs (this is what the GM dealer uses here) GM stuff not available here. Everything seems to be working well and the 3.55 diff is a better ratio to work with the 200R4 than the 3.08 at least on the hilly terrain hereabouts. I'm keeping the 3.08 in case I ever change the motor to a 383 which could better cope with this gear.