I have a 400 turbo it is in a race car with a transbrake, I launch the car go through the gears come down the return road back into the pits and then shut the car off, when I shut the car off fluid comes out of the vent tube on top of the tranny, I ran a hose from the vent tube into the car and drilled a hole in a pop bottle big enough to put the hose in it, thats how I know its coming from the vent tube, its been leaking for about 3 weeks but it didnt start until I changed the fluid and filter in the tranny, I know its not over full what else could cause this?? I am running a deep pan and tranny cooler, Someone please give me advice. Thanks!

It only started after you changed the fluid & filter??? How do you know it is not over-full? Here is the order that I would start checking:
You say you switched to a deep pan-are you using the proper filter for that pan? When you put a deep pan on the trans. you also need to use a deep style filter that will sit lower in the pan.
Normally venting is associated with an over-full condition and/or aeration. If for some reason that filter is pulling in air-it will also cause it to vent as the frothy fluid will take up more space. When you changed the filter-what did you do about the seal that was stuck in the valve body? Did you pull the old one out and insure that the new one was in place? Are you certain you did not put a new seal up against the old seal? Check the neck portion of the filter where it goes into the valve body for hairline cracks. Check/confirm your dipstick is correct for the application.

The last issue is heat. Sometimes when transmissions get really hot they will vent as well. If a bearing is failing, or some other hard parts are experiencing abnormal wear they can generate tremendous amounts of heat which will may cause it to vent. If possible hook a temperature gauge up to the trans pan to see what the temperature is at when this condition is occuring. That would be a great place to start diagnosing what is happening. Good luck.

Shoot the pan with an IR gun.

It started after I changed fluid and filter, when I bought the tranny it already had the deep pan on it, I have ran the tranny all year, when I changed the fluid it had a normal everyday filter in it so I just replace it with another stock filter, I checked when I changed it to make sure the filter seal wasnt still there. as far a dipstick length its the dipstick that has always been with the tranny. I guess I will pull the pan and see if I can get a filter for a deep pan, did you say they make on for deep pans, you wouldnt have a part number or brand would you?? Thanks!

eric,

I only have 1 question. Did you have the deep trans pan before doing the fluid & filter change or was that added on there at the time of the fluid & filter change?

On my first 1969 Camaro the pan was the problem and I know someone else who had the same issue because the trans was overheating. The best thing to do in my humble opinion is get the biggest trans cooler you can find. I think mine was rated for an 18,000 lb vehicle or some crazy thing like that way back around 1989 or 1990. Then get a trans temperature gauge. I had mine mounted on the center console with a slight tilt toward the drivers side. It was a B&M guage and a B&M trans cooler.

I knew of very few people way back 15+ years ago who had trans temperature gauges for their THM 400 or even THM 350. Trust me on this the trans cooler & trans temp guage will make your life alot easier. That way you know when and if it's over heating and it will help you figure out what is up. Trans coolers (the big ones) & the temperature gauges should be installed on every car. Even on the cars built today or in 1999 & 2000 you don't see trans temp gauges.....I'll say it again put a huge trans cooler & a trans temp gauge on it. It well help it run cooler & you will know what your trans temperature is at. The whole thing parts and labor even with today's prices should run you $200 tops. It's well worth it!! Good Luck!!

P.S. Fortunately or unfortunately depending on how you look at it I just bought another 1969 Camaro and this car has a manual trans (4 spd T-10)

"When you changed the filter-what did you do about the seal that was stuck in the valve body? Did you pull the old one out and insure that the new one was in place? Are you certain you did not put a new seal up against the old seal? Check the neck portion of the filter where it goes into the valve body for hairline cracks. "

??? The TH filter uses a tube that connects it to the case, not the valve body ???

Make sure to use two orings on the case end of the filter pickup tube so it won't pull in air. With a deep pan there should be a means to help support the filter to keep it near the bottom of the pan. Most kits use a bolt/sleeve arrangement to accomplish this. Fluid level should be no higher than the pan/case junction with things running and warmed up. As mentioned, check the dipstick for correct level markings. The only difference in the filters is some old TH's used a metal style long filter, while later ones used the conventional one most are used to seeing. The later ones are fine, and some like to use the Allison style filter. I've had no issues building them with the normal style filters. If you need more help just email me.