49 Cadillac differential

[STEVE CLC #16187]

To make a long story short, the other day my pinion  nut spun off now I don't how in came loose after all they are torqued at 200 ft. lbs. anyway I removed the differential and there seems like no damaged ring gear and pinion, however the ring gear has some very slight and I mean slight flaking of the hard facing , The diff was very quiet and the bearings are good .  I installed axle bearings and seals when I did the brakes. So my question is,  do I or should I replace the ring gear and pinion and can I use the old crush sleeve if I cant find a new one? and where do I find parts for the Cadillac differential? I need to do something soon as this is my daily driver and it is hard to be without it. Ironically I rebuilt everything in this 49 except the differential. Thanks for your suggestions and information.

steven

[Dave Shepherd]

I would certainly get a new crush sleeve, but inspect thoses gears very carefully, try getting the pinion play out with the old sleeve, check the backlash, if ok I would try running it, get the new sleeve in and set the the preload. Clean out the housing of course.

[Jay Friedman]

A comment.  You can't take these differentials apart.  They are held together internally by pins of some sort which are destroyed of you dis-assemble it.  Aside from replacing the seal and pinion bearing, if any internal parts are defective such as the ring gear or pinion, you must replace the whole unit.  Fortunately, except for the ratios, they are the same from '41 (and possibly earlier) until '56 (and maybe later), so are not too difficult to find.  If your '49 has Hydramatic the ratio is 3.36, which are the most common.

[STEVE CLC #16187]

Jay, your confusing me, are you saying I shouldn't take it apart ? or anybody ? how do they rebuild the replaced unit? can you get the pins to rebuild them? I do have a 41 diff and the ring gear & pinion look good. I know this fellow that does all kinds of diffs in his garage part time and seems to now what he is doing. Btw can I get a rebuilt unit ?


steven

[Dave Shepherd]

Basically the ring gear is sort of riveted to the diff case, in any case there are no ring and pinion gear sets available anyway, so another good diff would be your only recourse if they are bad.

[Steve Passmore]

Jay is correct. This topic was discussed in great length a year or so back as I recall.  These units were never meant to be rebuilt. Your manual will give you a clue as everything written on the axle amounts to 1/2 page and they say, "Go back to your dealer for a replacement"  even the dealers had no information.

Two main difficulty's.
   One,     there are four specific tools made just by Cadillac needed to take it apart as there are no caps or nuts to the crown wheel bearings as on a normal diff.     The bearing support posts have to be expanded with one of these tools.      People who had tried it with levers have been known to break the cast off like a carrot.      There is no shaft through the housing but two sleeves on each end, so the next special tool has to fit in and take their place in order to remove the carrier and for measuring and replacing shims..  The third tool extracts the sleeves.   The forth tool measures the depth to the Pinion for bearing pre load.

Two.  There are no dimensions written anywhere on the correct setting to re assemble so if you get this far you are flying by the seat of your pants.

I have searched for many years for these special tools and have only found one so far because Buick adopted this design in later years and gave their mechanics the tools and dimensions to fix the axles.

The good this is there are many diffs out there but I don't see anything in you first comments that would make me change the diff at this stage. I would have to try it first and see if it was noisy. Don't fix it unless its broke.

[Jay Friedman]

A friend of mine, an expert car restorer/machinist/mechanic, once tried to rebuild one for me.  I watched him work, and while trying to take it apart, as S Passmore said, he broke something "off like a carrot" though I can't remember exactly what it was that broke.  I had told my friend that the '49 shop manual clearly says the diff must be replaced, not repaired, which he didn't really believe till he tried.

On the good side, besides there being lots of them out there, in my experience even if they are a bit noisy they will last many years anyway.  In the mid 1980s I installed one with a 3.77 ratio in my '49 (with a manual trans) which did hum somewhat.  It was mildly annoying, but since they are heavy and hard to handle it wasn't loud enough to make me want to go to the trouble of changing it.  Finally, 20 years later and after tens of thousands of miles I was offered another diff with a 3.36 ratio for not much money, which I figured besides being quieter, would lower the engine rpms and save gas.  I installed it in the car, and luckily it doesn't hum or leak.  I then sold the hummer real cheap to another CLC member who installed it in a Series 75 limo and who, ironically, reports that in his car it doesn't make noise at all.  Go figure??

If you do buy another one, the ratio can be ascertained without going to the trouble of counting gear teeth.  On a diff with a 3.36 ratio for '49 Series 60, 61 or 62 cars with Hydramatic, the number 6 should be stamped on the bottom of the case below the center of the pinion shaft.  On a diff with a 3.77 ratio for '49 Series 60, 61 or 62 cars with a manual transmission or Series 75 limos with Hydramatic, either no number or number 7 will be stamped on the case.  There are also diffs with a 3.07 ratio for '52 to '56 Series 60, 61 or 62 cars with Hydramatic which have the number 3 stamped on the case and diffs with a 4.27 ratio for Series 75 limos and hearses/ambulances with a manual transmission with the number 4 stamped on the case.   

[Bill Ingler #7799]

To add to what Jay has posted, the picture below shows the flat area on the bottom of the case where you will find the number indicating the ratio of the gears. I have seen several rear ends that you are almost certain were never marked as the stamped number is very difficult to make out. A good wire brushing will bring out the number as was the case with the rear end below.   Bill

[Jay Friedman]

A couple of more points:

1. If I remember correctly, the nuts which hold the diff to the axle housing have special washers under them which seal in the gear oil, so don't lose or replace these;

2. You can buy a new gasket which goes betwen the perimeter of the differential and the axle housing from Olson's Gaskets in Washington State.