Th350 spews fluid

[Old Blu]

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?

 

[NickTransmissions]

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?

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.

 

[Old Blu]

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.

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

 

[NickTransmissions]

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

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.

 

[Old Blu]

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.

thanks again for the advice, will get the research going on part numbers.

 

[Matt69olds]

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.

 

[Craig Nedrow]

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.

 

[Ricko1966]

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.

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.

 

[DoubleDingo]

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.

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?

 

[Ricko1966]

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?

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

 

[Old Blu]

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

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.

That’s the stuff I looked up online also, good to know it worked for you. I should be able to pick some up at the local Napa.

 

[Old Blu]

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

Hose and or string both make sense, I’ll do both just to confirm the measurements. Might also start looking at wrecking yards for a 350 dipstick to compare or replace.
No shop space in my world so this will have to happen on a day between PNW rain storms!

 

[squaredeal91]

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!

 

[Old Blu]

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!

Yeah....happened to me a few years ago but it did’nt catch fire, just smoked like crazy. Used simple green to clean up everything under the hood. Took out the plastic vent and now the fluid blows out there. So will do the flush and check dipstik length, hope that works. I’ve also read somewhere that the worn out bands can cause overheating the fluid. That would mean rebuild or replace.

 

[Grit dog]

If it self levels and quits spewing fluid and still works then you’re probably overfilling. If it pukes until the trans starts slipping then you have an issue.
JMO
Have you run it til it stops puking?
And presuming the vent is clear.