Chris J

My TH 400 is leaking fluid from the top of the dipstick tube. I have done some reading and it sounds like this is often caused by a clogged vent tube. Can anyone tell me the best way to check the vent tube for blockage and what the best way is to clear it. Any help with this problem is appreciated.

TripDeuces

Vent tube is on the passenger side above the cooling tubes. Just rotating it will remove it. Sounds more like the trans is overfilled. Fluid should ideally be at or just below the pan sealing surface when full. Over filling can lead to what you are describing.

droldsmorland

TOP of the dipstick tube! Yikes! Way over filled. Or do you mean bottom of the tube where the tube fits into the case? If the latter, then the rubber seal grommet that seals the tube to the case is shot. Replace it.
You could use a suction gun or your mouth with a hose attached to the vent tube to verify its not restricted. Id advise not blowing compressed air into it. If somethings in there it will contaminate the trans.

Chris J

No its the top of the tube when the engine starts. I assume now its either got to much fluid in it or it has a blocked vent tube. I'm going to check the fluid level first, I will make sure it is at the top of the pan. If that's not the cause I'll move to the vent tube. As soon as I figure it out I will let you know what it was.
Thanks for the help

droldsmorland

Other things that can cause this is a kinked trans cooling line or over heating due to slippage. Is it shifting properly?

rjohnson442

Leaking or puking from the dipstick? If continuously slowly leaking from tube I'd say overfilled. If it's puking out onto the intake and filling the valley I'd say clogged vent tube. Mud dobbers like to nest in the tubes depending on where you live. The tube is on the top of the trans and kinda a pain to reach in the car.

Chris J

Update
I put a vacuum pump on the vent tube and it would not hold vacuum so I'm assuming it is clear. Next I removed the vacuum modulator to check the fluid level. I figured it was just above the top of the pan so if my fluid was to full it would drain out form that hole, and it did just that drained about a quart out. Started the car put it in drive and reverse, no leaks at all. Was not able to dive the car yet as the roads are still crappy! But I'm hopeful this was the problem. Thanks for the help!
Chris

CRUZN 66

If you were actually overfull, why didn't your trans fluid indicator show the proper level (or actual level)?? Do you have the correct fluid level indicator? You might consider draining the trans fluid, refill with correct amount of fluid and make sure the indicator is reading correctly...

droldsmorland

Hate to sound sarcastic....but....read the instructions on the dipstick(indicator?) and or the owners manual. Car level, warm, in park, engine idling.

oldcutlass

And engine running

droldsmorland

Yikes! missed that key piece of info. tx Eric.

Chris J

Thanks for your help, checked fluid level with the car running on level ground at temperature, I'm not an expert but I do know a few things, this is why I was surprised and asked for help here. The dipstick actually indicated I should ad a pint. So after reading your reply's it was obvious I needed to verify the fluid level so I removed the vacuum modulator and as I said in my last post, to much fluid. So now I need to figure out why the dipstick is not giving me an accurate reading and fix that.