84 C4 trans fluid change question
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Joined: Oct 2018
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84 C4 trans fluid change question
I am in the process of bringing back to life an 84 c4 that had sat for 9 years. I redid the fuel system as per advice from this forum, (85 fuel pump, pressure adjusted to 14lbs) and it now starts and runs great. Don't know how it drives out yet but it sure sounds good. I changed the oil and filter Saturday. My next project is to the drain the trans fluid and change the filter. I drained the fluid tonight and was happy to find no metal or signs of unusual wear. The fluid was of course dark red and had a funky odor but didn't smell burnt so I am going with the fluid and filter change only for now. I have done some research and looked here on old posts about what type of fluid to put back in the tranny but was unable to find what I felt to be the definitive answer. Since I am only doing a fluid change 4-5 quarts is what I am anticipating. The question is, do I use full synthetic or standard Dexron III? I have 5 quarts of each from prior projects so the cost factor is not an issue. Any advice would be greatly appreciated.
Zen Vet Master Level VII
Joined: Mar 2016
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From: Southlake, TX
Le Mans Master
Joined: Sep 2013
Posts: 6,192
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From: near the thumb in the mitten
There really isn't a set amount of fluid used to refill. Add 4 quarts, start engine and let idle, then add as necessary until full. Fluid needs to be hot (hot to the touch) to ensure it's full.
Add fluid.
Cycle shifter from park to low and back to park stopping in each position.
Recheck and repeat as necessary.
Stop adding when fluid is towards the bottom of the full hash marks.
Then take car for a spin 10-20 minutes and recheck add fluid to middle of "full" hash marks.
If you add to top of full hash marks before road test the fluid level could be off; low or over. As oil circuits refill/apply fluid level drops. The fluid expands when it gets hot leading to over full. The quick spin allows transmission to go through its operation and warm fluid to operating temp giving a reliable reading on dipstick.
Add fluid.
Cycle shifter from park to low and back to park stopping in each position.
Recheck and repeat as necessary.
Stop adding when fluid is towards the bottom of the full hash marks.
Then take car for a spin 10-20 minutes and recheck add fluid to middle of "full" hash marks.
If you add to top of full hash marks before road test the fluid level could be off; low or over. As oil circuits refill/apply fluid level drops. The fluid expands when it gets hot leading to over full. The quick spin allows transmission to go through its operation and warm fluid to operating temp giving a reliable reading on dipstick.
Race Director
Joined: Apr 2003
Posts: 17,700
Likes: 1,667
From: moraga ca
If you just drop the pan you will need at most 4 quarts. I have left my tranny dripping for over a month and was able to get almost 2 quarts extra because the converter slowly bleeds some fluid out.
Team Owner
Joined: Jul 2004
Posts: 28,432
Likes: 3,285
From: Hartford WI
I am in the process of bringing back to life an 84 c4 that had sat for 9 years. I redid the fuel system as per advice from this forum, (85 fuel pump, pressure adjusted to 14lbs) and it now starts and runs great. Don't know how it drives out yet but it sure sounds good. I changed the oil and filter Saturday. My next project is to the drain the trans fluid and change the filter. I drained the fluid tonight and was happy to find no metal or signs of unusual wear. The fluid was of course dark red and had a funky odor but didn't smell burnt so I am going with the fluid and filter change only for now. I have done some research and looked here on old posts about what type of fluid to put back in the tranny but was unable to find what I felt to be the definitive answer. Since I am only doing a fluid change 4-5 quarts is what I am anticipating. The question is, do I use full synthetic or standard Dexron III? I have 5 quarts of each from prior projects so the cost factor is not an issue. Any advice would be greatly appreciated.
