Advice on Transmission Fluid Change for 1980 C10

[Grit dog]

If it’s operating fine then absolutely change it. Sounds like a good truck if it’s never been apart and still is truckin.

If you don’t pump it out the cooler lines to get the majority of old out, I’d get a pan with a drain plug and change it about 4x depending how much comes out. That’ll effectively replace about 90% of it.

 

[Grit dog]

If it’s operating fine then absolutely change it. Sounds like a good truck if it’s never been apart and still is truckin.

If you don’t pump it out the cooler lines to get the majority of old out, I’d get a pan with a drain plug and change it about 4x depending how much comes out. That’ll effectively replace about 90% of it.

Unless you’re lucky and there’s a drain plug in the tq converter but it’s not likely.

 

[Turbo4whl]

Unless you’re lucky and there’s a drain plug in the tq converter but it’s not likely.

The only factory torque converter that had a drain plug in them were old Fords. (I've only ever seviced trucks, don't know about cars.) Aftermarket converters may have a plug, but the OP stated he believed the trans was not apart.