Changing Transmission Fluid

[Barnwood]

We drained the transmission fluid, which is very thick and black. How do we make sure the transmission is clean and free of grit?

[mcgarrett]

Without removing the transmission from the car, I would do the following:


-Put the transmission in neutral and remove the shift tower.

-Place a drip pan under the tranny and remove the drain plug.

-Put a gallon of mineral spirits into a pump-up garden sprayer and rinse the insides of the transmission thoroughly while rotating the gears by hand.

-Let it drain and allow the mineral spirits a day or so to air-dry completely before adding gear lube. If you prefer, use compressed air to help the drying process.

-Reinstall the bottom drain plug and while the top of the tranny is still open, remove the filler plug on the side of the tranny case and add your fresh gear lube directly into the open tranny case at the top, being sure to drench all the gears while moving them back and forth on the shafts to make sure new lube gets into all the crevices, bearings, and shafts until the level reaches the filler plug opening and starts to overflow it.

-Reinstall the filler plug and shift tower and you should be good.

Others may have their preferred method, but this seems to work fine.

[Barnwood]

Originally Posted by mcgarrett

Without removing the transmission from the car, I would do the following:


-Put the transmission in neutral and remove the shift tower.

-Place a drip pan under the tranny and remove the drain plug.

-Put a gallon of mineral spirits into a pump-up garden sprayer and rinse the insides of the transmission thoroughly while rotating the gears by hand.

-Let it drain and allow the mineral spirits a day or so to air-dry completely before adding gear lube. If you prefer, use compressed air to help the drying process.

-Reinstall the bottom drain plug and while the top of the tranny is still open, remove the filler plug on the side of the tranny case and add your fresh gear lube directly into the open tranny case at the top, being sure to drench all the gears while moving them back and forth on the shafts to make sure new lube gets into all the crevices, bearings, and shafts until the level reaches the filler plug opening and starts to overflow it.

-Reinstall the filler plug and shift tower and you should be good.

Others may have their preferred method, but this seems to work fine.

Thank you

[JayJay]

I have found that mineral spirits generally need some intense mechanical agitation to clean gear lube effectively. Parts washing brush, toothbrush, etc. you might follow the mineral spirits with a thorough spraying of everything with brake cleaner, allowing it to drain into your catch pan. Figure at least one 14-oz can of brake cleaner. You can’t overclean.

Dry as suggested, fill as suggested, run it and drain and refill after say 250 miles. You can do this refill through the side hole.

[Synchro909]

As above but I put a magnet on the drain plug and I'm pleased to say it hasn't done much. The less metallic debris it collects, the better. When I replace the oil, I only have to wipe the magnet and refill. It's much easier in the long run and I like easy.

[Gene F]

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DO NOT START THE CAR with the top of the transmission off!!!!!!!!!!!!!!!!!!!!

[Kurt in NJ]

Drain it immediately after driving at least 20 miles, let it drain overnight—- the debris will either be suspended and come out with the oil or laying in the recess of the drain plug

[eagle]

I agree with Kurt, simply let it drain overnight. Refill in the morning. I refill mine with Lucas Oil Stabilizer, its the best I've found for smooth silky shifting.

[400A]

I also remove the shift tower to access the gears. I use kerosene to wash everything down and help the process along by scrubbing a bit with an old toothbrush. I always use 600W oil as seems to slow the gears down quicker for smooth shifting.

[Bob Bidonde]

I measured the oil levels in the transmission and rear axle.

[Y-Blockhead]

Originally Posted by Bob Bidonde

I measured the oil levels in the transmission and rear axle.

Thanks Bob for confirming that. I see in some popular publications (one being the "Red Book"), the capacity for the transmission is listed as 1.5 pints.

[rotorwrench]

What works well is to drain the gear lube out and put low cost motor oil in there and preferably as heavy an oil grade as possible. SAE 10W40 would likely do but a person isn't going to leave it in there all that long. Run the vehicle around for fifteen minutes or so at low speeds then drain that out and refill with the proper viscosity and grade of gear lube.

This is known as a gearbox flush on some helicopter main rotor transmissions. On those we just run it up for 15-minutes or so then drain it.