Possible to overfill tranny? TH350 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jmil1974 · 11-04-2002, 05:31 PM

I dropped the tranny a tad to put my motor in. Pan is totally empty and TC is maybe half empty. How important is it to not overfill the tranny?

**COBALT** · 11-04-2002, 05:51 PM

Not nearly as important as NOT having it empty. Since your transmission is basically a hydrolic system too much fluid could cause excessive pressure on the internals, and may cause slippage to the clutch plates just if its too hot or doesn't have enough fluid.

I think the rule of thumb is to dump a quart into the torque converter if its empty before putting it on the transmission, and then 3 quarts down the tube before starting the truck and adding more gradually until you're at the low point of the dipstick, then add the last 1/2 quart. Remember that only 1/2 a quart exists between empty and full. Finally, run the tranny through all gears and check it a final time to make sure the fluid level is constant. You may have to add a little more...

jmil1974 · 11-04-2002, 05:56 PM

Thanks, Cobalt!

Longhorn Man · 11-05-2002, 12:49 AM

I would like to add that you should drive it a bit and get it up to operating temp before going for the final bit of fluid.
You want it on the full line when warm.
If over filled, you will airate the tranny fluid, and the bubbles will make it a frothy foamy mess that will not cool your tranny very well. In essence, air will be on your clutch packs instead of fluid, and it would bve the same as running it low.
Plus what he said about high pressures too.

11-04-2002, 05:31 PM	#1
jmil1974 Ain't we cute? Join Date: May 2002 Location: Friendswood, TX Posts: 700	Possible to overfill tranny? TH350 I dropped the tranny a tad to put my motor in. Pan is totally empty and TC is maybe half empty. How important is it to not overfill the tranny? __________________ 69 C10 2WD LWB Fleet 350/350 power front disc conversion (6 lug disc kit from gmcpauls) and new engine, PS, A/C, fresh fluids, SHE DRIVES! FOR SALE $3900

11-04-2002, 05:51 PM	#2
COBALT Senior Member Join Date: Sep 2001 Location: Seattle, WA, USA Posts: 5,817	Not nearly as important as NOT having it empty. Since your transmission is basically a hydrolic system too much fluid could cause excessive pressure on the internals, and may cause slippage to the clutch plates just if its too hot or doesn't have enough fluid. I think the rule of thumb is to dump a quart into the torque converter if its empty before putting it on the transmission, and then 3 quarts down the tube before starting the truck and adding more gradually until you're at the low point of the dipstick, then add the last 1/2 quart. Remember that only 1/2 a quart exists between empty and full. Finally, run the tranny through all gears and check it a final time to make sure the fluid level is constant. You may have to add a little more... __________________ '69 3/4 ton C20 2wd-350ci/TH400 '69 3/4 ton Custom 20 2wd-350ci/4sp Manual '99 2wd 5.7 Chevy Tahoe Seattle, WA.

11-04-2002, 05:56 PM	#3
jmil1974 Ain't we cute? Join Date: May 2002 Location: Friendswood, TX Posts: 700	Thanks, Cobalt! __________________ 69 C10 2WD LWB Fleet 350/350 power front disc conversion (6 lug disc kit from gmcpauls) and new engine, PS, A/C, fresh fluids, SHE DRIVES! FOR SALE $3900

11-05-2002, 12:49 AM	#4
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	I would like to add that you should drive it a bit and get it up to operating temp before going for the final bit of fluid. You want it on the full line when warm. If over filled, you will airate the tranny fluid, and the bubbles will make it a frothy foamy mess that will not cool your tranny very well. In essence, air will be on your clutch packs instead of fluid, and it would bve the same as running it low. Plus what he said about high pressures too.



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.