1960 Posi Differential Question

[Mark P.]

I am having a posi rear end built to replace the non-posi unit installed in my car.

I bought a correctly numbered and dated posi case, an Eaton posi unit, a US Gear 3.70 R & P and the Master rebuild kit (Timken bearings, seals, shims, bolts, crush sleeve, etc).

Thought I had everything until the rebuilder informed me the pinion yoke was pretty worn. This is also referred to as a Companion Flange in the Shop Manual but seems this term isn't used much thesedays.

Do pinion yokes need to be replaced very often ?

Any preferences on brands or vendors ?

I was thinking of getting this one. Anyone ever buy from Denny's Driveshafts ?

http://www.dennysdriveshaft.com/p58_1955_to_1964_chevrolet_pinion_yoke_1310_series_17_spline.html?submit=More+Information

[John T.]

Re: 1960 Posi Differential Question

I have had several positive experiences with Denny's.

Good luck

John

[Gary C.]

Re: 1960 Posi Differential Question

Mark, posi axles are shorten in overall length than non-posi axles. Gary....

[Mark P.]

Re: 1960 Posi Differential Question

Gary - Has anyone ever just ground off 1/8" off the splined end of the axel like some of the hot rod sites say ?

Thanks,

Mark

[Gary C.]

Re: 1960 Posi Differential Question

Mark, check with Rev. Mike Ernst or someone who has more knowledge about 1959-62 posi axles. Hopefully they will chime in on this thread. P&A Group 5.420 doesn't have separate listing for posi and non-posi 1959-62. Do know originally there was a .10 spacer used between the wheel bearing and axle housing. The 57-8 posi axles are 1/8 inch shorter than non-posi's and according to the P&A it doesn't look like there was any axle difference starting with 1959. Sorry, can't be more helpful. Gary....

[John N.]

Re: 1960 Posi Differential Question

Gary - Has anyone ever just ground off 1/8" off the splined end of the axel like some of the hot rod sites say ?

Thanks,

Mark

Mark
I have been through this a number of times and the 1/8" cut may do it.
I will put the third member in the car with two fasteners after puting oil on the cross shaft area on both sides where the axle ends could contact. Next use solvent on axle ends to remove any oils. Put about .150 thickness of clay on each axle end and install axles. Remove axles and check for thickness of inprint. If necessary have axles machined to give you a minumum of .125 end clearence. Usually you have more problems with the left axle.
Regards

[Stewart A.]

Re: 1960 Posi Differential Question

Is the idea of the shorter axle meant to give the axle greater torsional strength by reducing it's length in a Limited slip differential scenario. Stewy

[John N.]

Re: 1960 Posi Differential Question

Is the idea of the shorter axle meant to give the axle greater torsional strength by reducing it's length in a Limited slip differential scenario. Stewy

Stewart
Nothing that exotic. The cross section of the posi unit is wider than the std open diff. If you use std axles with a posi unit the axles may ride directly against the cross shafts in the posi and break them. This creates the need to check the end play or clearance and make adjustments.
Regards

[Roger W.]

Re: 1960 Posi Differential Question

Stewart
Nothing that exotic. The cross section of the posi unit is wider than the std open diff. If you use std axles with a posi unit the axles may ride directly against the cross shafts in the posi and break them. This creates the need to check the end play or clearance and make adjustments.
Regards

Does anybody out there have the axle length measurements for the Posi axles? My 59 had a posi unit originally, but when I got it the there was a non posi replacement. I put a new posi unit in. I don't recall having any dificulty with the axles.

[John N.]

Re: 1960 Posi Differential Question

Does anybody out there have the axle length measurements for the Posi axles? My 59 had a posi unit originally, but when I got it the there was a non posi replacement. I put a new posi unit in. I don't recall having any dificulty with the axles.

Roger
The 61 P&A shows replacement, both posi & open for 59:
left 28 7/18 O.L.
right 30 3/16 O.L.
I would not have expected you to have a problem. Assuming you had the original axles, spacers if used on that year with posi, bearing width, bearing retainer flange, etc. I went 36 years changing components on these early rear ends before I had the first problem that I knew of. I lost left rear axle splines on California Street in San Francisco during the 1995 California Mille on the 1956 Sebring team car. The axles had been shortened at Sebring for the width of the Lyeth limited slip diff and I had installed a posi. Then I found others which were primed for problems, ie axles rubbing on cross shafts etc.
Regards

[Roger W.]

Re: 1960 Posi Differential Question

Roger
The 61 P&A shows replacement, both posi & open for 59:
left 28 7/18 O.L.
right 30 3/16 O.L.
I would not have expected you to have a problem. Assuming you had the original axles, spacers if used on that year with posi, bearing width, bearing retainer flange, etc. I went 36 years changing components on these early rear ends before I had the first problem that I knew of. I lost left rear axle splines on California Street in San Francisco during the 1995 California Mille on the 1956 Sebring team car. The axles had been shortened at Sebring for the width of the Lyeth limited slip diff and I had installed a posi. Then I found others which were primed for problems, ie axles rubbing on cross shafts etc.
Regards

Thanks for the info. The next time that I take the rear end apart, I will the axel lengths.