The Stovebolt Site Forums The Shop Area The HiPo Shop Turbo 400 Overfilled Symptoms

Can too much transmission fluid cause sluggish shifting, slippage, and delayed reverse engagement when hot? It's also leaking pretty good. I'm not sure about the history of this transmission as the truck has been inoperable for many years. I had to add about 5 quarts just to make it go. After driving it for about 20 minutes, it started doing all of the above. I pulled out the dipstick while it was running and it shows about 1 1/2 inches above full.
Just driving it around the neighborhood a few times, I noticed that the pan was occasionally dripping. After this longer drive, the leak is much worse now.

If its to full you can get a foamy fluid which makes them act funny. 400's are tough and its pretty hard to hurt one. Try changing the pan gasket, governor gasket, and the speedometer gear adapter o-ring. Any one of the three could be leaking. Add fluid slowly tills up to the full mark when cold, or full mark when hot, some have both marked. It should hold about 11 quarts when dry, but just dropping the pan will be around 6 or 7 quarts. Start with five and add if needed.

Joe

you are over full on fluid.also changing the filter could help with the shifting.

The worse thing you can do is overfill any automatic transmission. I would rather see one a quart low when it comes into my shop. If it is overfilled my recommendation is lower the fluid level now. When the fluid heats up from driving it causes undue strains on seals and governor valve bodies. None of which is cheap to repair.
Normbc9

Thanks for the tip, it has been sitting since my post. When I get the time I will draw some fluid out and see how it responds.

John

John, one of the the worst things about overfilling apart from leaks is it can also cause aeration problems,(the foamy fluid Joe H mentioned)this is due to the fluid being churned up by the drums and planetary gears.
Aerated fluid takes longer to pressurize the hydraulic circuits.

It can also cause problems with the valve body,causing slippage and consequently making the trans run hotter,which leads to sludge and varnish problems.

Remember: There is only 1 pint difference between the add and full marks,it should be between the two at running temp.

You get the picture......

Just disconnect one of the cooler lines, put it into a quart bottle, and crank the engine up. If you guess right, the fluid will come out of the line, not the hole in the radiator. If not, get ready to clean up a puddle. It's surprising how fast a quart of fluid can run out of a cooler line!
Jerry

Hey J

Just rebuilt a TH400 for my project sounds like low oil pressure to me I am no expert but thats the common thing between all the symptoms you can get to the pressure relief valve with the pan removed, worst case the pump is worn out. I found the TH400 easy to work on and parts are cheap if you fix it yourself, good luck

cheers Paul

The tranny problems that you're experiencing may be the reason the truck has been sitting. With my luck, no tranny problem has an easy fix like being over full, it's usually catastophic!...haha,
Scott

my 1990 c1500 pick up has a 3 speed turbo 400 and wont shift out of 2nd gear its a fresh rebuild. the pan and fluid are clean and everything works just no third gear.

You'll get more responses if you post a new question rather than piggybacking on a 3 year old thread. If it's a fresh rebuild you might want to talk to your rebuilder.