The Stovebolt Site Forums The Shop Area Engine Shop tranny/differential fluid change

Does anybody have any a-z tips on changing the fluid in the transmission and differential on a '50 3100? The service manual doesn't even address how to do this, only that it needs to be done. I can't find anything on this site that addresses it in detail.

I guess my biggest question/concern is, if there's only one port (drain/filler plug) on the differential, how can you drain it and fill it through one hole? It defies physical logic.

Thanks!

You use a siphon pump like this one:

[img]http://www.laroke.com/larryk4674/2001/bb032001ct.jpg[/img]

Bigger Picture Here

This is a fifties version but there are newer models of this tool still on the market today.

Try taking the lower bolt out of the differential cover.Should drain,the hole goes all the way through. If not,you'll have to remove the cover. Make sure to put some thread sealer on the bolt when you replace it.

Thanks. How about tips on changing the transmission gear oil?

Mine has a drain plug and a fill plug. There is also a small plug on top of the trans at the rear to add lubricant to the u-joint after removing the trans/clutch/u-joint. I use Quaker State in a long bottle that pours in nicely if you hold the end right up against the floorboards.

You can see my methods for changing tranny and pumpkin gear oil here:

Gear Oil Change


You may notice that I am currently using Synthetic Gear Oil in the tranny and standard gear oil in the differential. That is because my rear end leaks some (not a personal problem ) and the tranny doesn't. Synthetic Gear Oil may leak out of places where regular gear oil won't.

Laroke;
My old manual says 50 wt motor oil in my 3 speed tranny. Used that and it still whines. What brand of synthetic tranny oil you using and where did you get it? I read somewhere that you shouldn't use hypoid oil in the tranny because of the brass. if you were to use regular tranny oil, do they make a non-hypoid oil which is readily available at the local Parts depots? If so, same weight? Thanks in advance.

I am using Valvoline in the 75-140 wt., Geezer. Here's the product spec

Valvoline Full Synthetic Gear Oil


Don't know enuf to know if I'm causing damage to the tranny or not with this stuff. Maybe someone who knows more will jump into the thread.

I'm using the same gear oil in both the tranny and the diff. Quaker State 80-90W and the label specifies it is good for manual trannys and differentials.

GM has a synthetic transmission and differential oil. Used the special non slip differential oil in a Nissan manual transmission and avoided taking it out for an overhaul. Fixed up a 'sticking' shift into second gear.

Also, this product might be fine.

http://www.desertrat.com/redline_oil/redline.htm

cheers, George

Many thanks to all!!!!

Mystic JT 6 is the best gear lube available it should be available at most parts stores.this stuff will keep a tranny or differential alive for 1,000,000 plus miles in class 8 vehicles( BIG TRUCKS)i use it exclusively in all standard trannies and differentials.