VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc 1936 Master differential

I am finally getting ready to assemble the dropout and torque tube section for my 1936 Pontiac (same design as 1936 Chevrolet Master) rear axle. As I am writing this, I am putting a Filling Station order together that will hopefully be all the remaining parts. I have a few questions.

I already have the carrier bearings, pinion bearings, a new staking nut, and the two bushings that support the driveshaft at the universal joint end. Bolts for the ring gear are on the way.

Here's what I have on the list for the Filling Station so far.

FS54a carrier gasket
FS54 pan gasket
FS1030 pinion rivet
RW110 metric seal (front of driveshaft)
AF367 dowel pin for driveshaft bushing
FS125 torque ball shim kit with cork seals

No mention is made in the manual of the fork-shaped tool that is used to seat the rear pinion bearing (Hyatt bearing) when installing the pinion on newer Chevrolets. In 2 of my parts rearends the Hyatt bearing was either never seated, or had come out of the bore and crashed into the pinion. The Filling Station has the tool available (AF-656). Is that tool the right answer for seating the bearing on a 1936 Master rearend?

What about the seals for the torque ball? In older threads some posters have advocated using an o-ring on the ball. Also I believe Gene mentioned that the original seal on the threaded collar was felt. Are these available anywhere? I will be ordering the FS-125 shim kit, and I believe it comes with cork. Is there anything else I should be getting?

The pinion rivet FS-1030 is listed for 1930-1933, but when you read the description it says it fits clear up into the 1980s. I am not sure why this part would even exist in the 1980s. It is 1/4" x 2-1/8". Is this the right part for 1936 Master?

Does anyone stock pinion bearing shims for this axle?

Have I forgot anything? Thanks!

I ran across some pinion shims the other day in my hoard, do you happen to have a part number ? I think some were marked as to thickness.

Dave

bloo,

With the same amount of work you could convert it to 3.55 rear gears. I couldn't post information with photos here on how I did that job at home because I'm not a VCCA member but a forum member who does have photo posting privileges solved the problem:

https://vccachat.org/ubbthreads.php/topics/334876/1936-chevy-3-55-rear-gear-conversion.html

My '36 PU (same rear axle as '36 Master car) still doesn't keep up with highway traffic with the 3.55 gears but it comes a lot closer than with 4.11 gears.

Ray W

brino,

We talked about this in another thread, maybe 2 years ago, and I did find the PDF with the pictures.

I had read about that previously. I don't think there is any better way to get to 3.55, and although I may regret it.... I bought a set of the elusive 3.82 economy gears from another member here. The project stalled first because I did not have a usable diff case to rivet the gear to, and then the riveter backed out. The current plan is to bolt it with aircraft close-tolerance bolts and lots of Loctite. I hope it works out. From simple calculation I think I would have preferred 3.55 to 3.82, but many have questioned whether the Pontiac 6 can pull 3.55. It is 4.89 now, and can pull any hill in high gear. That makes it very hard to estimate how much torque it actually has.

I wanted to make as little change to the car as possible, and when the 3.82 became available I jumped. This has now drug out 2 years, and I'm pretty sure If I had opted for your method I would have been done a long time ago.

I

Thanks for responding! I don't know which thickness I need yet, as I haven't started assembling. I believe I do have the part numbers somewhere. I hope to assemble this before winter is over, so I should know soon.

As I understand it, the factory shimming was almost always the same 2 shims, but one of my parts units was missing the shims. Also, the ring and pinion is aftermarket. I think it is very likely that I wont have the right shims. I've not found any on Filling Station or any of the other major vendors.

The shim part numbers are
372359 .012" 1929-1936 cars and 1/2 ton trucks + 37-39 1/2 ton trucks

372361 .018"

372360 .015"

The book does not list the inner and outer diameter of these shims but does list these numbers for the 1937-1954 shims, They are 2 3/8" ID and 2 13/16" OD These shims would be easier to locate.

What ratio did you find?

3.82!

Will be interesting to get your reaction after some driving. Will be like geeting a whole different engine.

"I wanted to make as little change to the car as possible, and when the 3.82 became available I jumped. This has now drug out 2 years, and I'm pretty sure If I had opted for your method I would have been done a long time ago."

bloo

I thought of using the 3.82 gear set but the MPH gain at the same RPM, about 2 MPH on the freeway, seemed like too much work for too little change so I did the 3.55 conversion instead. The 3.55 gears really do make my '36 much more suitable to the roads of today. It could easily pull a numerically lower gear ratio. Now I see why the Model A guys like Volvo overdrives grafted into their torque tubes. Even those low horsepower 4 bangers have no trouble pulling high gear overdrive according to their owners.

When I tell people the rear axle in my '36 PU originated in a '37 car they tell me they would have never known if I hadn't told them.

Ray W

Well, if no one sees anything missing in that list, I am gonna go ahead and place the order. Hopefully I can get this differential built by spring. We just got another 5 inches of snow yesterday...

Thanks to all who responded!

Have you given any thought about the axle bearings and seals?

I found them again, let me know what you need and your address.

Well.. Yes.

I suppose this is going to come back to bite me, but it isn't leaking now, and I am tempted to leave it alone (and hope I don't accidentally destroy the seals when I pull the axles).

One or two of my parts axles had the original seals, and they are made of leather or felt or something. They do not have a sharp lip, and did not groove the axle surface. I like that. If that is what I find in the car I hope to just leave it alone.

Also, I am putting a modern positive seal on the driveshaft, to prevent leakage from the transmission to the differential, and the differential has no vent. As long as some of the seals are the old kind, I don't think I need one. If I seal it up tight I probably do. I would prefer not to drill the axle housing.

Another concern is that modern gear oil will be less viscous, and just slop out.

If I find a bad bearing, that will make it academic, but nothing is loose or noisy.

WOW, that was quick. Thank you for digging them out. I will contact you just as soon as I figure out what I am missing.

Bloo
The leather or felt seals often didnt leave a groove like the modern style as there was no lip edge as such. I would look to tightening the seal to axle contact or replacing while you have the axle out as oil on the brakes is not fun.
Tony

I remember seeing in another thread (that I cannot find now) that the front pinion bearing (the double-row ball) was updated at some point, and the new one needed to be installed differently than the old one. Something about the notch the balls are loaded through.

Gene, do you remember this? I have a NORS New Departure bearing bought back when I first started this project. I will post a picture later, probably tonight. I am wondering which way to put it on.

Yes, that pertains to 1937-1951 modes.

Oh! I thought it was the same bearing. No wonder I couldn't find it searching for 1936.

Test assembled it to check for shims, and the pinion is way too far out. The shop manual says that the top of the pinion teeth should align with the ends of the ring teeth on the inner diameter of the ring gear.

I checked the shims and the washer. .016, .016 and .190. OOPS. Parts book says the washer is .120 . I guess that explains it.

OOPS. I misread the parts book.

I ordered another spacer on Ebay, actually a lot of several #328198. They arrived, and apparently .190 is normal. I only see one possibility listed in the parts manuals online. It's group 5.460 in Chevrolet.

http://chevy.oldcarmanualproject.com/parts/1929_41/41cp137.html

http://chevy.oldcarmanualproject.com/parts/1929_54/347.htm

My Pontiac parts book also calls for #328198.

This just isn't going to work. Do any other (thinner) thicknesses exist?

It sounds like the pinion assembly may not be seated completely in the bore. Make sure the bore is good and clean and give the pinion a good tap to seat it.

I am fairly sure it was seated and the wedge bolts were tight. I am going to try again later today. I hope you are right. Last might I was checking dimensions on the gears and bearings, versus some other ring and pinion sets I have, and everything seemed to match. That would suggest the bore depth is wrong. I hope not.

Would the .012, .015, and .018 I have pictured above be to thin?

Dave

There is a thick washer that goes under the shims (328198) and supports them. I was trying to get this figured out so I could ask you about shims. For the moment I am stymied, but I am going to have another try this afternoon.