Help: Change Muncie Tranny Oil

I want to change the gear oil in the 4 speed Muncie. I looked at the tranny and there are 2 plugs on the passenger side, one near the bottom but NOT exactly on the bottom, the other is a couple of inched higher on the side of the tranny.

I'm thinking the upper plug is for filling and the bottom one is the drain. It would appear that the bottom one will not allow ALL the old oil to drain out. Is this a problem?

Also, what gear oil (Brand & Weight) do you reccomend for Florida temperatures (Hot).

Thanks!

 

Your thinking is correct on the plugs. I think the case is just thick on the bottom so nothing to worry about with all of it draining out. I would run 90W on the street or strip. Any name brand is fine.

 

I run Amsoil 75w-90 Severe Gear oil (GL-4) in my M21.

Works great!

 

You can get a suction gun at NAPA for ABOUT $11.00, it looks like a grease gun. Just get a piece if tubing to go on the end of the gun that is flexible enough to get to the bottom of the trans. You can use it to get the old oil out and to install the new.

Bert

 

Thanks guys... I'll be heading to NAPA for the "Suction Gun" in the morning and then change the oil. How much oil do I need for a M20 Muncie?

Anyone runing synthetic oil in the Muncies?

Thanks!

 

I don't think you are supposed to use synthetics in the
vintage Muncie---I think some experts can chime in on this--I read something
on the Chevelle sight but can't reference it for you. Pete

 

The Amsoil I run is synthetic.

2+ years, and it works great.

 

Based on my personal experience stay away from the synthetics in a vintage Muncie.

I do a lot of pure stock racing and tried synthetics 2 different times. Broke 2 transmissions within a very short period of time. I went back to non-synthetics and have not had a problem.

The only explanation I can come up with is that the gears were designed at a time when synthetics were not available. There have been a lot of advances in metallurgy since the 70's that allow the use of synthetics in newer transmissions. Even with new gears in the Muncies I will not run synthetics.

The synthetics will shift easier when cold, will reduce friction losses, will leak easier and do not cling to the gears to provide a cushion like the non-synthetics.

If you never race it or run it hard you will be ok, any sort of hard usage could lead to premature disaster.

 

David, hope this gets to you as I am new to the site. I need your input on reverse lockout hardware for my 70 Stage 4 spd car. I am the Arizona Larry that talks to you at the GSCA nats each year. Also bought hood latch from you last year. please contact me.