pre-war differential overhaul

[chris davis]

Can anyone suggest a Western Pennsylvania/Eastern Ohio shop to overhaul a 1941 Cadillac differential?

[Doug Houston]

The unfortunate problem here is that Cadillac never had specs for what you want. Until about 1970, Cadillac serviced the entire differential and carrier assembly (the pig) as a unit, and this item was not intended to be serviced. They had some kind of special precise fixtures of calibrating the assemblies, and no mortal has any of the set-up data.

I wish I had better information, as I have several such cars myself.

[Doug Houston]

The unfortunate problem here is that Cadillac never had specs for what you want. Until about 1970, Cadillac serviced the entire differential and carrier assembly (the pig) as a unit, and this item was not intended to be serviced. They had some kind of special precise fixtures of calibrating the assemblies, and no mortal has any of the set-up data.

I wish I had better information, as I have several such cars myself.

[Bruce Reynolds # 18992]

Gday Doug,

Well, as far as getting the data, it wouldnt take much to take the necessary measurements and preload settings from carefully dismantling a known good one.

I cant help here in this regard as I dont have access to such a beast, but, there must be someone out there with one that they arent likely going to use.

Bruce,
The Tassie Devil(le),
60 CDV

[Richard Goulden]

Well I dont know much about pre war diffs, but I took the diff head and axles for my 59 to my local diff place here in New Zealand. I said can your do it ?, they said , have you got the bits ?. ( bearings seals etc ), I said yes and they said no problem. When I picked it up, one of the staff said "thats the diff they said we couldnt do", and laughed.
Price was almost cheap, and the head guy, it would have been cheaper, but to dissasemble it they had to mill out some part on one side  that is supposed to come off with a puller.
Im real glad I had it done, when they showed me the bearings that they removed. It runs quiet and perfect.
They didnt blink an eyelid when I bought it in, seemed to be all in a days work. Gears seemed to be in very good condition, but bearings were on the way out. I shudder when I think of the thousands of old cars still driving arround, with worn out bearing in their diffheads.

[Bruce Reynolds # 18992]

Gday Richard,

It is good to see that there are still people that will tackle the "untouchable".   I am also one of those.

And yes, if the bearings are shot, or even wearing out, constant use will render the CW & P totally uesless.   Once it is incorrectly worn, then it would require re-lapping in, and there arent many places that can do that operation.

Banana skins and/or sawdust only work for a short time.

Bruce,
The Tassie Devil(le),
60 CDV

[Mike Simmons]

I am currently fighting to remove the "retainer" or cover that contains the pinion seal on a 1940 differential. On a 46 unit that I removed from a parts car, one can see another big problem for a rebuilder-it does not use "main caps" like a Ford 9-inch. The ring gear and carrier are rotating within the actual casting. I dont know how one gets the ring gear/carrier out so as to remove the pinion gear to get at the bearings. This style rear was utilized into the early 50s but I dont know for how much longer. Obviously not through 1959.

[Mike Simmons #938]

Oops-shouldnt have added that last bit. Looking at the cross section pic in the 59 shop manual suggests the same way of holding the ring gear carrier, though the overall shape of the center section is different.

[Bruce Reynolds # 18992]

Gday Mike,

Yes, those 9" Ford diffs are one of the easiest ones to work on.   Maybe that was why Ford did it that way.   And, they break easily as well.   I have rebuilt dozens of them, and thrown out lots of broken parts.

The Chev and Ford Salisbury Diffs use shims to give sufficient preload, and I have done heaps of the Ford F250 types, and they are easy as well, with the correctly made-up shim inserting tool that I made.

As I have never pulled an early Cadillac Diff to pieces, I cant really comment, but if the Factory could rebuild them, then with the right equipment, and/or the knowhow, I wouldnt have any hesitation in tackling one.

The biggest hurdle will be the re-riveting of the CW to the carrier.

The Workshop Manual doesnt give a good enough diagram of what is involved.

I like it when the Manual says that the whole pumpkin has to be returned to the factory for repair.   This would be one good reason for not owning one outside USA if they really gave any strife.   Personally, I havent heard of any going bung here in Australia, but someone will hopefully tell be different.  I have a 66 Diff complete that I am busting to pull it to pieces, but havent been able to get to it, and too many other things to do before tackling it.   It is LSD as well.

Bruce,
The Tassie Devil(le),
60 CDV

[John Tozer #7946]

Hi guys,

I am in the middle of refurbishing my 37 75 series diff, have seen several 36 and 37s pulled down and have a 38 sitting on the garage floor. The 36 / 37 diffs were famous as "glass" diffs in Australia and a very large number of old Caddies from this era have been located with no rear end at all (including mine) or with tell-tale oil leaks from the rear axle - thats a long story but suffice it to say they were not great diffs.

Bruces point about "If they can build it, we can fix it" is pretty right if you can source the parts. The 36/37 diffs were the last of the spiral bevel cut diffs and they do come apart quite easily. You just need to punch mark the starting location of the bolts etc. as you proceed. I cant swear to how easy/difficult getting the pinion out is as I havent got that far yet but I have a procedure for this provided to me by a Club member some months ago. Happy to share it if anybody wants a copy.

These diffs were also pre-loaded with up to two brass shims (actually large washers) either side. The missing ingredient is "What determined how many shims each diff got and of what thickness?" The hard part of refurbishing these diffs are the bearings - they were a special tapered roller bearing and the few that are left are horrendously expensive. The bearing cups, on the other hand, are 20 bucks each!

I am at a bit of a loss to understand why you would de-rivet the crown wheel unless it was completely shot in which case a whole new diff centre would probably be easier to find .... I drove 8,000 km around the States in a rental car with one on the back seat free from a great Cadillac friend in Illinois.

Regards,


John Tozer

[Len Sholes]

Regarding the comments about dismantling the early differential that does not have caps on the carrier. A friend of mine just went through this on his 40 LaSalle diff. What you have to do is to pull the bearing retainers out of the bearings on each side of the carrier. What he did was made up a tool that consisted of two pins that fit into the two puller holes in the retainers, he then made a puller style bolt that had holes in one end to accept the two pins, then once he had the bolt in place with the two pins engaged in the puller holes he used a piece of pipe for a sleeve and then with a strong back across this he pulled the bearing retainers out of each side of the carrier and you can then drop out the crown gear assembly. Once you have this out of the way it is not problem to remove the pinion. GM must of had a special puller tool for this procedure but we could not find any information on what it looked like so my friend made his own. I hope this helps you.

[Chris Davis]

Its been some time since this thread was active so I thought it was timely to weigh in with the same inquiry as well some additional information I've been able to glean from some different sources.

In my case I have no idea what condition the differential is in as the car was parked in 1959.  The differential is original and appears to have never been apart.  It does seem to me there is excessive play/backlash (basically by rotating the yoke back and forth) that suggest wear or possibly an adjustment issue.  As I am now (finally!) ready to re-assemble the chassis and re-install the body my preference is to re-build.

Stating the obvious (and repeating what other members have pointed out), none of the Master Chassis or factory shop manuals reflect anything beyond replacing the entire assembly.   

However, the Motor repair book from the early 50's shows dis-assembly and repair (but notes Cadillac units are factory supplied).  Also Hollingers shows information on bearings, as does a 1946 NAPA parts catalog - seemingly because they can be replaced(?).  I have also determined the Timken bearing numbers are still vaild and available.

Which brings this to the point - does the notion of dis-assembling and rebuilding a differential fall in the "too hard/can't be done" category?   

[homeonprunehill]

05-22-07
Chris.If you have basic mechiancal ability go for it !It's not that hard. Replace the seals while you have the diff. out. You will need a hyd.press to change the bearing & seals.
HTH
Good Luck,JIM