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Discussion Starter · #1 ·
I just changed my transmission fluid for the first time. I have a c6 3 speed automatic. Napa said it calls for 12 quarts, I question this because they gave me the wrong filter/gaskit kit. I put in about 11 1/2 quarts and the dip stick reads way up the stick, but this could be excess fluid from pouring it in. Does any one know how much fluid to put in this trans? My gears slam in harder then normal. Its been at least 20,000 miles since the fluid has been changed. I purchased it that many miles ago and have been doing a lot of hauling. Also what kind of fluid. I used dercon 3 but I heard type F goes with the c6.
 

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The correct fluid for an '89 C6 is MERCON. Most MERCON fluids will also have a DEXRON III rating, and that's fine. Don't use MERCON V! That could screw up the trans.

Did you drain the converter and the pan? If so, it should take close to 12 quarts. If you only changed the pan you are MANY quarts overfilled.

In the future you could try THIS method. It was written for the newer trucks with the 4R100, but the C6 is close enough that it will work for this trans, too. You'll need about 13 quarts to do a C6 with this method.
 

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Exactly, that is the capacity with the converter drained. If you have not started the truck, it's a simple matter to drain the converter of the old oil, then start the engine to refill it. If you have already run the engine, thge old and new oil is mixed. You have the choice of changine it again, or just draining out the extra oil from the trans or converter.
 

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Discussion Starter · #4 ·
O.K. I droped the pan and changed that fluid again. I didn't evan bother looking for a drain plug on the trasfer case. I feel its been diluted enough for another 10,000 miles. I put in 5 quarts this second time and it reads a half a quart over the full line. Thats o.k. with me, better the 4 inches over the full line. I reused the same cork gasket, no leaking yet. I tightened the bolts more and smashed the gasket out. Next time I'll buy a reusable rubber gasket. So that means the first time I changed my transmission fluid I drained the pan (5-6 quarts) then put in 11 quarts, so I was 5 quarts over filled!! /ubbthreads/images/graemlins/laugh.gif
 

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Just my opinion for what it's worth.

I would suck out transmission fluid until it is exactly at the full mark when you are at operating temps.

As you know, F**d vehicles have traditionally been senistive to old transmission fluid.

I would try to make sure that you adhere to the maintenence schedule on your tranny. I learned my lesson on an F150. Was having crazy tranny problems that were solved by a total tranny oil change.

Yardbrew
 

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The correct fluid for an '89 C6 is MERCON. Most MERCON fluids will also have a DEXRON III rating, and that's fine. Don't use MERCON V! That could screw up the trans.

Did you drain the converter and the pan? If so, it should take close to 12 quarts. If you only changed the pan you are MANY quarts overfilled.

In the future you could try THIS method. It was written for the newer trucks with the 4R100, but the C6 is close enough that it will work for this trans, too. You'll need about 13 quarts to do a C6 with this method.
Ford issued a TSB updating the fluid from Mercon to Mercon V
 
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