[David Young]

I have a 57 with a Muncie M-20 and stock rearend housing, axles and non-posi 3.55:1 carrier.

I came across a late 3-serries posi case (thin ring gear flange & left hand thread case bolts). But one of the plates is wrecked, all four tangs were ripped off, it has five plates/discs per side.

I want to put the posi in the 57 3.55 carrier but it needs new clutches or at least the one bad plate, the rest don't show wear.

What are the clutch arrangements? Reading one of the service manuals it shows and talks about putting two internal splined discs together with the two external tanged plates on either side of them for moderate street driving or alternately stacking them plate, disc, plate, disc for maximum non slip traction. It only shows an early four plates/discs per side case.

For a late case, which uses five and one is cupped/beveled, do I start with an internal splined disc or tanged plate next to the gear retainer and where do I place the tanged cupped/beveled plate?

This is for a very street driven weekend pleasure cruising 57.

Also, can I install 58-64 axle bearings on 57 non-posi axles to take up that extra 1/8” that might interfere with the posi cross shafts?

 

[Rick_L]

I can't answer your clutch plate questions, I would like to know that info myself.

Only the 55-56 axle shafts need to be shortened, the 57 shafts do not.

If you were to use the wider bearings, the retainer plate would not seat down onto the brake backing plate, and you'd bend it up as you attempted to tighten the bolts.

 

[Bihili]

Posi Trac manual:
http://chevy.oldcarmanualproject.com/booklets/57top30/5730smindex.html
Page 22

parts:

http://www.tomsdifferentials.com/catalog.asp?pg=14

 

[David Young]

Thanks Rick,

I had read on one of these posts that 57 non-posi axles were an 1/8” longer than posi ones and needed to be ground off or they MAY hit the cross shafts and prevent engagement.

Thanks Bill,

That service manual is for early 57-59 8 (4 each side) disc cases.

It does, on Page 21, explain the “best arrangement for average driving” (which is what I want) and to start with an external tanged plate next to gear retainer, then two internal splined discs together in the middle and end with another external tanged plate.

But it does NOT address where to place the third (beveled) plate used in late 60-64 10 (5 each side) disc cases. That’s what I’m trying to find out.

But thanks guys for the links and help.

 

[Rick_L]

You might go over to chevytalk.com and do a search. There is a guy over there that goes by DZAUTO, he is an expert on these things, and has posted a lot of info. I don't recall anything about the clutches but I'll bet he's posted about it. Or just ask your question over there and he'll probably reply.