1936 Fleetwood 75 Rear Axle Oil Leakage

[Tom Hirn CLC#22260]

Dear Cadillac Enthusiasts,
I am pretty new to the club and since a few weeks the proud owner of a 1936 Fleetwood 75.
After my last ride I saw that oil leaks out of the left side of the rear axle where the axle housing ends and the brake base starts. The brake itself is not affected by the oil (yet).
I think that the left oil seal of the axle shaft in the housing caused this leakage. Are there any other possibilities of failure how could oil get there ?
I saw in the parts manual that the 36 models have only one oil seal for the axle shaft, which is located closely to the differential, while newer models have it behind the wheel bearing.
Can anybody give me a procedure how to change the oil seal ? Do I need to disassemble the entire rear axle to reach the seal ?
Also, can anybody give me the dimensions ( Outer diameter , inner diameter and width ), material ( felt, leather, rubber etc. ) and a supplier address where I can get those ? I live in Germany, so it might be a little bit more complicated to get the seal(s).......

I appreciate any help I can get !

Best Regards,

Thomas Hirn CLC#22260

[Harry Scott (4195)]

Tom, To access the seals you need to disconnect the drive shaft pull the axles out and then remove the center section from the housing. At this point the seals are accessable. I cant locate the replacement part number, however, there is a modern seal that works fine. You will also need to be sure the ventilation system is clear and functioning. On the top of the inner housing there is a baffle with filtering material in it which releives the pressure to the outer housing. That pressure is releived by small holes near the drain plug on the bottom of the housing. If these holes are plugged the lubricant will be forced out of the axle ends like you describe. If I can find the seal information I will either email you or put it on the board. Good Luck

[Tom Hirn]

Harry, many thanks for the info. I checked the vent holes and they seem to be ok. The previous owner had to change one axle shaft and I think the oil seal got damaged during this operation. However, I will check / change the oil seal when the driving season is over.
If you could find / send me the seal info, it would be just perfect.

Thx and Regards,

Tom CLC 22260

[John Tozer #7946]

Tom,

I will leave the advice on the internal oil seal for Harry to answer but you should also be aware of a problem that occurs with these diffs that can also cause the diff oil to leak out through the wheel.... and it is far more ominous.

These diffs have a very bad habit of becoming sloppy over time as the shims used to pre-load the diff wear thin. All the sun gears, bearing cups and bearings are held in place by a male threaded plug about 3/4 inch thick that screws into a female thread on the inside of the diff/crown wheel casting. These are either crap metal or the threading is a lousy job because, as the shims wear, the plug begins to float within the threads. In a catastrophic situation, the entire thread is stripped off either or both the plug and housing and the lot lets go! I have seen six of these diffs so far - all of them had the problem to some degree and at least one (mine unfortunately!) had let go big time.

This problem causes the oil leak as follows:

As the plug floats in the housing, the inboard (diff centre end) of the axle floats with it and prescribes an oval path as it rotates, not a circular one. This oval path, over time and in serious cases, ovals out the oil seal housing cup. With the old spring loaded leather-lipped oil seals, it also tears the leather housing of the seal - ergo, your now ovalled oil seal doesnt seal to the circular axle shaft and you get diff fluid leaking past the seal to the wheel - there is no other seal before the outboard wheel bearing.

You can test for this and for just how serious it might be by:

1.    When you have got the axle and diff centre out as Harry has described, place the diff centre on its back on the bench (i.e., the crown wheel parallel to the bench top);

2.    Check both axles one at a time(the worst side always seems to be the left) by inserting the axle back into the splines in the diff centre to its full extent;

3.    See how much play there is at the diff centre end as you try to prescribe a circle (i.e., not by rotating the axle in the diff but by trying to prescribe a circle with the wheel end of the axle WITHOUT rotating it.

If you cant prescribe a circle, you dont have a problem. the bigger the circle you can prescribe, the bigger the problem you have at the other end of the axle!

4.    Remove the first axle, turn the housing over and insert the other axle in the other side and make the same checks.

I appreciate that this is hard to put into words but if you have trouble understanding the process, let me know and I will scan some sketches and send them to you.

As a general principle, if the play is only slight, replace the oil seal (a modern neoprene one will beat the old spring leather ones any day) and rest easy.

Hope this is of some help;


John Tozer

[Harry Scott]

Tom, I have looked everywhere and cant find the part numbers for the seals. You might try Olcar Bearings 135 James Creek Southern Pines, NC 28387 910-693-3324. He has the part numbers and also can supply the old style or new style seals. When you have it apart it would be good to check for more serious problems as John describes. Well keep our fingers crossed that it is only a bad seal. Harry

[Tom Hirn]

John,
many thanks for the info. Since it is also my left side that leaks I am very courious what I will find when I open the diff.
Yes, it is hard to put it into words and also, I have to confess, hard to understand for me without sitting in front of the dismantled axle. If you could sketch something and send it over it would be very helpful for me !
One last question : In case I will find a big circle in the diff. what can I do to get it back into business ?

Best Regards,

Tom

[John Tozer #7946]

Tom,

That was the obvious question... I figured I had probably frightened the ........ out of you with the description of the problem without getting into the cure.... and you mighnt need it.

I have been counselled by many that, if it isnt TOOO bad, just leave it and replace the seal, which as I said , is probably the old leather one, with the new neoprene ones as Harry advised.

Most of these old girls wont put on enough miles in their remaining lives to warrant it. I COULD have left my replacement alone, for example, but I had spent so long looking for a new one, (finally travelled 8,000 km around the US of A with it sitting on the back seat of a hire car before I got it home to Australia) seen so many with the problem in the States that I couldnt help myself - I had to strip it down and find out why? You should also note that the shop manuals advise you to send it back to your Cadillac Service Centre rather than attempt it yourself! Thats not quite possible, especially in my case.

I will write up both the dagnosis and the cure that has been recommended to me by two V12 owners and get it across to you. Probably take a day or two but I will no doubt beat the time it takes you to do what you have to do to get the diff center out.

Good luck with the 36 - I had one as a rotten parts car for my 37. They are lovely high art deco vehicles before they became big and bulbous!

Regards,


John Tozer

[Tom Hirn CLC 22260]

Hi John,
no you hadnt frightened the ........ out of me  :-). I am doing this hobby since 20 years now and restored a few total wrecks in the past. I learned there is almost nothing you cant fix with a lathe, a milling machine and a bunch of good connections.
Take your time, sending me the description, it is still nice weather in Germany so I will still drive a little until I examine the rear axle.
Yes , these cars are definetely high art deco !! I like the style very much. Unfortunately pre-war Cadillacs are seldom like 10 ct diamonds lying on the street here in Germany. I am probably the only one that owns a 1936 model.

Again many thanks and Best Regards,

Tom Hirn