Ready to change the trans gasket and filter on my 80 350 auto transmission. I have a 1980 Corvette shop manual that says it takes 10 qts. Any imput would be appreciated.







1980 claret/claret

Up to 10 quarts is with an empty transmission. Your's won't be empty. You will only get about 1/2 of the fluid out. Much will stay in the torque converter. You may want to turn the engine a few times after the pan is off, and you may get a bit more fluid. Just crank it, don't start it.

When you tighten up the gasker, watch the gasket edges. When the gasket just starts to "squish" stop tightening. If you go too far the gasket will split and leak like mad.

When you refill, put 3 quarts in and start the engine. Drop it in drive. If it does not kick in gear, add another quart and try again. Once it does grab a gear, run it through all the gears to make sure everything is full of fluid. Then let it warm up, and then top off the fluid by the dipstick reading. If you fill it cold, it will actually be a bit high. Trans fluid expands quite a bit as it warms.

Ken Styer

About 3 quarts. The converter holds about 10 quarts but isn't affected by draining just the pan. A trans. flush would change all the fluid but that scares me with an older transmisson. I've heard some horror stories about flushing. Any input on this? I'm thinking about doing the wife's 90K mile Malibu. Bought the filter and fluid, think I'll just go that route. Do ya believe the filter instructions say to REUSE the gasket! Don't think so. Mike

Ken, what are your thoughts about trans. flushing? Mike

In my experience with trans flushes, I don't recommend it on a car with over 75,000 miles unless is has been properly maintained from day one. Too many times, I have seen vehicles that had high mileage and a trans flush return within 1-2 months needing a transmission. Just drain the body and change the filter and see how it is. You can always do another drain and refill another few months down the road which will acomplish giving you more clean fluid.
Reid '72 T-top

Trans flushing is always good, but can sometimes lead to early demise. It's the same thing as synth oil. If the only thing holding the seals togther is the crud, then the seals can start to leak, leading to low pressures, leading to slippage.

But, it's not the flushing that does the extra cleaning at the seals, it's the new fluid. It takes some time to clean up the crud. Trans fluid is the strongest solvent that can run on a regular basis in an oil system. ( you can add a qt to the engine and run it as a engine flush before an oil change ) Flushing replaces almost all of the old fluid (up to 90 percent)instead of less than 50 percent.

In the vast majority of cases, the trans was on the verge of failing anyway. The flush may have helped it along by perhaps as much as 1000 miles sooner, but that's usually it. When a flush was done then it fails, people point at the flush. When it wasn't done there was nothing to blame the failure on, and oh well it went bad. A regular service can do the same thing, but perhaps a bit slower due to less clean fluid. (that's how old wives tales start, and few old wives work on C3's)

If the trans was going to fail, it would fail anyway. Fluid change or not. If it is okay, it's okay, and changing the fluid is always a good thing.

Always change the filter and use a new gasket when servicing the transmission. A flush will NOT clean out the filter. At least no where near the condition of a new one. Flush first, then filter. IF you change the filter first, you shove dirt into the new filter. The better flush machines can suck the fluid back out after a flush, and allow you to change the filter, then refill the trans.

Here is the flip side. If it's been a long time from a fluid change, NOT changing fluid can lead to a failure, that could be prevented by changing fluid. So either way you are taking a chance with old fluid. I will always take the chance of going with clean. It's always better than dirt and grit.

So my best recommendation? Flush it and change the filter, use a new gasket. Second best, regular trans service, new filter, gasket, and as much fluid as possible. Or you can leave it alone, it will die sooner or later on it's own.

Ken Styer

what brand of tran fluid do you guys recommend?

mark v

Thanks for the imput guys. Since my 80 only has 18000 miles on it, think I will change my filter and gasket only. DextronII is whats recommended. Gotta work on a leaky caliper first.