VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 differential fluid change ?

Okay... dumb question of the day. Is there a dedicated drain plug for the differential ? I know enough to stay away from the pinion bearing lock nut bolts.

There are no leaks and I don't want to remove the rear cover, unless necessary.
I assume to check the level, simply remove the 3/4" plug on the rear facing cover plate, insert pinky, check for fluid, but I'd like to drain it all out and replace with fresh 600w since I have no idea when it was last changed. I was thinking of using my electric dipstick oil changer pump that I could snake down into the 3/4" inspection hole and suction the oil out.
After having the car 4 months now, I've been working my way aft, checking things as I go. Almost done. Thanks guys.

I had to have mine suck out!! if you do it your self, do it on a hot day !!

I suggest taking off the differential cover so you can inspect the inside and scrape out any sludge. The bottom bolt hole for the cover is the drain hole.

When I first drained the differential from my '27, there was a lot of sludge. I sprayed WD40 in there as a cleaning fluid and used a parts cleaner brush to clean the gears.

Make a new cover gasket, put it back on, and fill with Mobil 600W.

Cheers, Dean

Just remove the bottom bolt and it will drain. Will flow faster if the filler plug is out and oil warm.

Thank you. I wouldn't have thought a bottom bolt. Simple. The FS can probably ship me a replacement gasket faster than I could make one.

Positioning my hot 500 watt halogen light under it will warm it up nice before I drain it. Temperature at my garage floor level is about 40 degrees, 32 outside here in CT. Winter just won't end !

Removing the bolt will not harm the gasket.

By the look of the bolts and gasket they have been fairly recently installed. Just pull the bottom bolt and drain and then check to see what the drained oil looks like. If it looks like mud then remove the cover and give everything a good cleaning. I am betting the oil will be super clean.

Good plan. I just gave the undercarriage and rear end a good scrubbing with a citrus cleaner. It looks great, but it could have been 20 years since the fluid was changed. I believe the car saw minimal use, but yeah, if it looks dirty upon draining, time for some new oil.

Clean or dirty change the oil. If the drain oil is cruddy then pull the cover. If it's clean then I would just refill with new oil.

When I did mine, I pulled the plug, then put a pan under the rear end and pulled the bottom bolt. The bolts are Thru bolts, so when you pull it out the Fluid will ooze out. Rear End

I made a new gasket, cleaned up the cover and gasket surfaces. Flushed out the rear end and then put in new oil.

I just drained it. Photo shows old oil on the left. A splash of new 600w on the right. I've seen worse, but I may pull the cover and clean it up proper. It's more like 25 years now that I think of my '32 's restoration history. I have the time, no excuse

Since the cover bolts go through into the differential oil chamber, make sure that you put some sealant on the threads when you put the bolts back in. Otherwise, the oil has an opportunity to leak via the threads.

This is covered well in Ray Holland's "School in Session" series. Mandatory reading for gearheads.

Cheers, Dean

The color means nothing. Some brands are much darker than others depending on the additives which can darken the fluid..
If it were mine I wouldn't loose any sleep over it.
At any rate both are 100 per cent better than what was available in 1932.

The new 600W gear oil that I have for my car is the same color as the oil featured on the left of the photo. The oil that is out of your differential looks good to me.

Yeah, but would you put it on your pancakes ? I fished out some sludge, cleaned up the innards and most importantly, have peace of mind. New owner, new fluid !
Thanks all for helping out a Shade Tree Mechanic. When do I get promoted around here anyway ??

You won't get promoted to Back Yard Mechanic until you achieve 200 posts.

Now it will be good for another 20yrs! Got to get it ready Charlie. We're going to put some miles on our cars once the weather clears and I can get my car done. Had my restored 83'Blazer out today. Buddy got his truck stuck in the forest checking his deer stand. There is still 2' of snow in the woods and with the trails in bad shape, the cruise through was an adventure. Got him out though so that's a good thing.

To me they both look fine and as Chevnut posted the color can vary depending on manufacturer. I bought some from a F**D vendor a couple of times and one time it was dark and the next time light. If you had drained out some oil that looked like molasses and smelled to high heaven then it would have been some real old stuff.

the stuff i got from TFS is pretty dark as well, like the one on the left...