Advice on Transmission Fluid Change for 1980 C10

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Grit dog

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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

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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

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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.
 

Camar068

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10 yrs Air Force
Dex III is the same as Dex/Merc from what I've read.
 

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