Where's the drain on my rear end?

[55 ledsled]

Hello,
I am wondering how one replaced the rear end oil on my 55 sedan? There is not a drain hole as far as I can see, but only a fill hole. One does not have to completely remove the pinion to drain? Help would be helpful. Thanks

[Lexi]

Not my year of Caddy, but if memory serves me correct, there is no drain plug-just a fill hole about mid-way up, gas tank side. You could use a suction gun to remove the oil through the fill hole, or if there is a gear covering remove it to gain access, (but don't think your car has an easy access plate either). Clay/Lexi

[The Tassie Devil(le)]

The only way to drain out the oil is to either remove the Pumpkin, which means removing the axles, or remove one axle, and tip the car up on its' side.   But, this method is not really desireable.

There is no need to replace the diff oil unless there is something wrong inside the diff, or if the rear axle has been submerged in water, and water has entered the housing.

Bruce.

[cadman56]

You wouldn't want to at least remove some of it with a suction gun and replace with new?  60 yr. old oil.  Just asking.  BTW, which axle would you suggest?
Love the humor.

[The Tassie Devil(le)]

You could remove some with a suction gum, and then have a look at it to check its' condition.

Got to have humour when dealing with such a horrible thing as diff oil, as this stuff REALLY STINKS.   I have rebuilt very many diffs in my time, especially the Ford 9", and the smell takes a long time to leave the garage.

As for which axle, the one opposite the fuel filler car, so you lose nothing from the fuel tank.

Bruce.

[gkhashem]

I did this on my 1964 Oldsmobile 98, with an anti-spin differential. I was getting some strange noises and binding feeling while rolling at low speed in the parking lot. It happened only after the car was good and warm. Say after a 30 minute to 1 hour ride. I am guessing the oil was breaking down and the additive was useless to help the anti-spin workings.

So we used an air compressor and created a vacuum in a collection bottle. The stuff came out black and dirty looking. I think we got most of it out about 2 quarts I guess and added some AC Delco ant-spin additive and some new gear oil.

However the stuff is thick and will take some time to get out. I would say it took a good 10-15 minutes to get the 2 quarts. I used a dip strip to see how much was left and there was only about 1/4 to 1/2 inches left in the bottom of the pumpkin. So it seemed to do what I wanted. I would say you would need an air compressor that can provide a decent psi in order to create enough vacuum to move the heavy gear oil.

Seems to have worked no noises since.

[Lexi]

Sadly, if there is any metallic debris or other foreign matter in the pumpkin even the siphon gun might miss it. There are hand vacuum pumps that could probably be used with some finesse (and time), but an air driven siphon gun with an appropriate diameter pick up hose should do it. Probably best to have driven the car first to heat up the oil to be drained to increase flow potential. The gun would need a good cleaning afterwards to remove the heavy dif oil and the smell! Clay/Lexi

[David Greenburg]

This sounds like a personal problem.😀 But seriously, is it not possible to disconnect the driveshaft and then unbolt the front of the housing?  My '61 appears to be leaking at that point, and I assumed there was a seal there.

[gkhashem]

I think that's called a pinion seal, I think you can remove this without taking everything apart.

[Jeff Rosansky CLC #28373]

I don't know for sure but I would think if you have to remove the pinion seal you are going to lose a good amount of fluid at that time anyway. You should be able to just combine both jobs...... just have plenty of cardboard, etc down. It will stink abd hard to clean up. Did it on the 70 and I have a feeling it will need to be done on the 55 as well.
Jeff

[The Tassie Devil(le)]

CAUTION.

If you remove the pinion flange and seal, then you will need to re-install the pinion, and try to get the correct pre-load on the pinion bearings.

Once this pre-load is disturbed, it is virtually impossible to get it back to what it was without re-building the centre.

If in doubt, it is easier, and faster to drop out the pumpkin and clean up the mess, including the old oil within the housing, install a new gasket and put it all back together.

While everything is out, and visible, and "feelable", then everything should be inspected.   Nothing may need replacing, apart from the oil and the gasket, but at least you will be satisfied in the knowledge that all is good.

Bruce.

[55 ledsled]

Thanks everyone for your help! I will suction that out...warm it up a bit so its a little easier to get out. Thanks again!