How to drain trans fluid

[Monzadude]

Might seem like a dumb question but I cant seem to figure out how to drain the fluid out of my transmission. It's the factory 4 speed mated to a 3.8. I checked the fluid and its up ok but I want to drain and replace it. The car sat for 25-30 years so I'm changing all fluids. The trans is the last one. I'm sure I'm missing something but I couldn't see it. I posted this in the trans and drive line section. 19 views so far and no replies so I’m trying here. Any ideas?

[cosvega76]

If it's a Saginaw trans, remove the lowest tailshaft housing-to-main case bolt.


Chuck

[Monzadude]

Thank you Chuck. As far as I know it's a Saginaw. One more quick question. What oil should i use. Its red and looks like ATF right now.

[cjbiagi]

It should not be automatic trans fluid. It should be a GL4 80W90. I use Brad Penn "classic" transmission gear oil. https://penngrade1.com/products/gear-lu ... ae-80w-90/ It takes 3 pints, do not overfill or it will leak through the shift shaft seals. It should be about a 1/4" below the fill hole.

[Monzadude]

Thanks for the help. The fact that the oil is reddish and you're saying it should be 80w just confirms it needs to be changed.

[Monzadude]

So I have another question. I drained the oil out of the trans. It was red and thin like automatic trans fluid. Definitely not 80w oil. Since there is probably some residue of the old stuff left, is it ok to just put the heavier oil in and let it mix? Why would it have auto fluid in it? I was also thinking maybe filling it with 80w and running it for a bit and then changing it again.

[283vega]

just asking but could it be a synthetic gear lube?

[Monzadude]

I'm not sure if it's a synthetic. As far as I know this car has sat for the past 25-30 years. I'm not sure what if anything was done to it.

[cjbiagi]

If in doubt, flush it out!