Th350 spews fluid

Old Blu said:

Looking for expert advice. My Th350 blows fluid out of the dipstick tube. I checked the vent, seems clear. I removed the vent altogether and now the fluid blows out there onto the ground. Have to top off the fluid fairly often. Not a daily driver but making monthly dump runs. Otherwise the trans seems to wrk fine.
Is it time for a rebuild?

Click to expand...

NickTransmissions said:

Something is forcing fluid out, it's usually one of two things (high level):

1. Fluid is overfilled by at least a quart or under-filled by a couple quarts and remaining fluid is super heated causing gas-pressure driven venting at the base of the bell housing
2. There's a restriction somewhere in the system (internal transmission or external) that's creating an overpressure condition that's relieving itself via the vent tube

I'd flush your lines and internal transmission cooler in the radiator to see if #2 is relevant for your situation. If not and fluid level is correct then it may have to come out to determine the cause of all that venting.

Click to expand...

Old Blu said:

Nick, Thx for the info, I'm not sure if I have the right Dipstick, have heard that can be an issue. Any way to tell if it is for a TH350 or TH400? Maybe a spec'ed length?
So I checked, and the Trans cooler is outside the radiator and the lines accessible. Will look at how to flush, any suggestions?
A

Click to expand...

NickTransmissions said:

That could be; wrong dipstick leading to inaccurate fluid level reading, etc.

I believe they have different part numbers so may be worth looking up the part numbers on Rock Auto to see if you can cross ref yours against what you see.

I use brake cleaner on the lines and cooler but i think there's purpose built flush tools available. And you dont have to flush the transmission itself, just the lines and cooler. But id first determine if your dipstick / tube is correct for the TH350.

Click to expand...

Matt69olds said:

The Full mark on the dipstick should be even with the parting line of the case/pan. Obviously, this will require pan removal to verify.

Click to expand...

Ricko1966 said:

This^^^ but you can run a piece of string from
the top of the dipstick tube to where the tube meets the case on the outside edge ad 1 1/4 inches that should be parting surface depth. I suppose a person could run a piece of fuel hose down the dipstick tube to the bottom of the pan, mark the hose when it bottoms in the pan,subtract the pan depth.

Click to expand...

DoubleDingo said:

Hose would definitely be easier/better than string. Or were you meaning using string to basically string-line from one side of the case to the other with the pan off?

Click to expand...

Ricko1966 said:

String down the outside edge of the tube to get tube length top to where it enters the case, then ad 1 1/4 inches because that's how much more drop there is to the case/pan seam

Click to expand...

Craig Nedrow said:

I used this when I rebuilt my 350, as there was a bunch of broken parts. I like that this will screw right onto your lines, and flush the whole system. Then just blow out with compressed air.

Click to expand...

Ricko1966 said:

String down the outside edge of the tube to get tube length top to where it enters the case, then ad 1 1/4 inches because that's how much more drop there is to the case/pan seam

Click to expand...

squaredeal91 said:

Might not at all be the issue but be sure that your vent tube is clear. Once upon a time on a th350 that vent was plugged up with mudd dobber and blew atf out of the stick suddenly on the highway and caught fire on the headers!

Click to expand...