Overfill TH400?

[Frankenchevy]

I recently wrapped up some work on my truck. I installed a deep aluminum pan on my Th400 and Hughes XTM torque converter. I fired up the engine, shifted from park to 1 and everything in between. Crept around the driveway a bit in both directions for 10 minutes while waiting for the engine to come to full operating temperature. I kept putting in atf 1 quart at a time. Took about 3-3.5 gallons if I recall correctly.

Finally got the fluid into the hash marks on the dipstick. My mistake was not having the trans at full operating temperature, I guess. It’s really hard to see the clean fluid on the dipstick. At the end of a 100ish mile round trip, I pulled the truck into a gas station, put it in park with the engine still running and checked the level again. Now it seems high—again very hard to see with brand new fluid. I have to run a paper towel down the dipstick slowly until I see wetness.

The trans shifts quickly and smoothly, there is no foaming of the fluid or vapor coming from the dipstick.

Is it worth draining some off?

Are there immediate signs of a dangerously overfilled Th400?

Thanks in advance.

 

[Frankenchevy]

No seepage to be found around the pans mating surface and nothing coming from the vent tube either.

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The Hughes XTM TC is supposed to pump significantly more fluid per minute. Maybe that will throw fluid slightly further up the dipstick?

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[75Monza]

Usually overfilled causes overtemp of fluid and foaming, I only worry about it if it's severely obvious. I added the same converter to my 86 with a slightly different deep pan with a port on the side so I put a temp gauge there. First few days, I had the same issue trying to get it full and then overdoing it. I used one of these quick change valves on my pan, makes it less messy when I want to drain it. https://www.nospillsystems.com/

 

[HotRodPC]

If you're no more than a quart over full, it should be fine for a Th400. If it were a problem, it would be foaming and spitting out the vent tube.

 

[QBuff02]

that amount of fluid seems, excessive.. How much fluid did you put in the converter before you installed it into the transmission? My 2,400rpm stall I got about 2.5 qts dumped into it before I slid it into place and I put 6 qts in to top the level off after changing filter. But that converter looks like a stock diameter so it will take a fair amount more to "fill". Couple that with your deep aftermarket pan and I could see 3 or more gallons going in easily. But I digress, if it was indeed too much it would be puking it out of the vent tube on the top of the transmission! Don't ask me how I know.. Lol Unless mud daubers or something have the vent plugged off but I think you'd see an issue elsewhere. check it after a few drives just to be safe. But I'd say run it!

 

[Frankenchevy]

that amount of fluid seems, excessive.. How much fluid did you put in the converter before you installed it into the transmission? My 2,400rpm stall I got about 2.5 qts dumped into it before I slid it into place and I put 6 qts in to top the level off after changing filter. But that converter looks like a stock diameter so it will take a fair amount more to "fill". Couple that with your deep aftermarket pan and I could see 3 or more gallons going in easily. But I digress, if it was indeed too much it would be puking it out of the vent tube on the top of the transmission! Don't ask me how I know.. Lol Unless mud daubers or something have the vent plugged off but I think you'd see an issue elsewhere. check it after a few drives just to be safe. But I'd say run it!

I only put a quart in the tc before installing. I drove it around my property for a bit with 3 gallons and it was barely touching to very tip of the dipstick. That’s when I started slowly adding a little at a time.

I also have a fairly large derale stacked plate cooler, about 10 additional feet of 3/8” tube and the larger diesel radiator may hold more in the side tank than the smaller bbc or sbc radiator.

Between the transmission and transfer case, I purchased 5 gallons of ATF. I still have about a quart left.

I’ll take it on another cruise tonight. But after 100+ miles straight I didn’t find fluid coming from anywhere. Fingers crossed.

 

[DoubleDingo]

I think you'll be fine. Worse come to worse you can open the drain plug and let some out.

 

[Rusty Nail]

Between the transmission and transfer case, I purchased 5 gallons of ATF. I still have about a quart left.

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[Matt69olds]

Drill a couple tiny holes in the dipstick, at the add and full marks. Then maybe you can see the fluid. If it’s a fresh rebuild, with empty cooler, lines, converter, etc and a deep pan I wouldn’t be surprised at 3 gallons of ATF.