veeeight

Hi All,

1966 C2
A very simple question. I want to change my transmission oil (gearbox), is there a drain plug on the bottom of the gearbox or do I have to suck the oil out through the level plug.

Thanks Phil

DZAUTO

I can only guess that you have a Muncie 4sp (since you didn't specify manual or automatic transmission).
The answer is NO, you cannot drain it (I
DO NOT know why in God's green earth GM didn't install a drain plug). Thus, as you mentioned, it will have to be sucked out. All Muncies have a boss for a drain plug, but up until 1970, ONLY the M22 got a drain plug. On every Muncie that I rebuild, I install a magnetic drain plug, which CAN BE done with the transmission in the car, but it is a little tedious.

veeeight

Thanks DZ.
Yes it is a 4 speed manual Muncie.
Madness that they did not provide a drain facility.
Phil

GTOguy

The same thing with Automatic transmission pans of the period, and even most domestics now. I guess the cost of a plug was too high. Sucking gear oil with a pump gun out of a trans or diff is tedious and incomplete work. The worst stuff, at the very bottom of the case, always remains. When I had a 1930's Chrysler, the factory repair manual said to use flushing oil when servicing the trans or diff. Apparently, this was a very light engine oil with some mineral spirits mixed in, no doubt to cut the crud in the cases. My own solution would be to install a drain plug like DZ said, and drain it warm.

Nowhere Man

67 powerglide has a drain plug

DansYellow66

It can also be tough getting the suction line worked down past the gear train to the bottom of the case but with some twisting and shoving it will go. I think I used a vacuum pump the last time I did this.

Frankie the Fink

Yes. And filling the tranny in the car is no picnic either. AmSoil makes a nice plastic hand pump that fits their fluid bottles that lets you pump the goop into that tight space with no mess. Only a few bucks and well worth it

DansYellow66

Oh yeah - that too. I think I actually pumped the new fluid in with my vacuum pump. But, there is a definate opportunity to make a big mess all over your garage floor in filling the transmission.

Powershift

Step 1: Put your oil drain pan under the transmission to catch any overflow..

Step 2. Use a plastic funnel with a 3-4 ft piece of 1/2 ID x 5/8 OD clear Tygon tubing. Place end of tubing into trans fill hole and route the other end with the funnel up to the engine compartment where you can reach it.

Step 3: Pour trans fluid into the funnel until trans is filled.

Same technique for the rear axle, except the tubing is shorter and you access/pour from the right wheel well.


Larry

MikeM

I have one Muncie that still has the factory fill in it from 1966. Another from 1968. Should I change the oil? What does the owner's manual say?

Personally, I'd leave well enough alone instead of stirring up all that hardened stuff that's settled to the bottom of the transmission case unless I could open the transmission and give it a good cleaning.

tuxnharley

Why start now................?

cdub327

M20 and M21 have no plug. I put a drain plug in my 67 without pulling tranny. Not the easiest job without a lift. I only tapped to 3/8 pipe, I will open it to 1/2 inch pipe when I do the clutch.

vettsplit 63

And when you refill the fluid, resist the temptation to pump a bunch in real fast, and plug the hole with your thumb til you locate the plug. You will wind up with a leak on the floor from hell. Ask me how I know this.

MikeM

Sounds like it's a hassle to even fool with it? What's the downside to just leaving it alone?

DansYellow66

I would agree but I put synthetic in my transmission after a rebuild and I decided that was a mistake - so I had to drain and refill it with dino GL-4 transmission fluid.

GTOguy

IMO, like Mike M, no downside to leaving it alone as long as it's full and clean. It really doesn't 'wear out' or 'go bad', in my experience.

GCD1962

Autogear Muncie's have a drain plug

BD104X

Remember to loosen the fill plug BEFORE you drain it so if the fill plug strips or is frozen the vehicle isn't stranded with no lube in the trans and no way to refill.

Riccal

I have a 67 (no drain) I read somewhere that if you unbolt the tranny and linkages and speedo cable and rotate it 'til the filler plug is on the bottom it will drain. Is this feasible?

Rick

ohiovet

If you are going to do all that you mind as well pull the trans and install a drain plug.