[torqhead]

Long story short, trans built by 3rd party, pan leaked 3 times, last time pan replaced with new one by 3rd party. Found it leaking again, after it's sat for awhile in the garage while I've been doing my winter project (complete suspension replacement). It seems to leak at the front passenger side always and been validated multiple times it's not the front seal and pump. I ordered a replacement gasket, found recommendations using search here, but looking for any other things to check since I'm going to do it for hopefully the last time for a few years!!!

[Chief of the 60's]

It might be the selector shaft seal or dipstick tube O-ring. But if it is the pan, buy an aluminum one.

[torqhead]

Originally Posted by Chief of the 60's

It might be the selector shaft seal or dipstick tube O-ring. But if it is the pan, buy an aluminum one.

I'll do a thorough inspection now, just received the gasket. The new pan is an aluminum one with a drain, so if anything he didn't go cheap on the pan and the drain is a nice upgrade!

[Chief of the 60's]

I chased a selector shaft seal for over a year and 3 seals only to find a tiny wear groove in the shaft. Could not see it until it was removed, then it was clear as day.

[torqhead]

Originally Posted by Chief of the 60's

I chased a selector shaft seal for over a year and 3 seals only to find a tiny wear groove in the shaft. Could not see it until it was removed, then it was clear as day.

I'll check that while I've got it open. I forgot to mention it goes for months without a leak after it was fixed, basically through the summer and while I'm driving it. Sits for months through the winter in the garage and when I find it leaking. Did that on the last two changes across the past two summers. I've just taken it to the trans shop and had them fix it.

I'll get it up high and do a thorough inspection to see if it's coming from somewhere else besides the pan.

And ironically this is my 1000 post here, what a milestone after 14 years!

[mgarblik]

If you really want to get serious and find the leak I can tell you how to find it in about 2 minutes. If you have any connections at a new car dealer or a good modern independent shop. See if you can rent or borrow an EVAP (evaporative emissions) smoke tester for evap leaks. You rig up a couple hose adapters and attach the smoke machine to the dipstick tube and turn it on. It will fill the entire transmission with harmless smoke in about a minute. Then with the car in the air and an intense light you can find very quickly where the smoke is escaping. You should get a little from the transmission vent. That's all. I generally put a wad of clay over the vent once I see it coming out there. That verifies the transmission is full of smoke. Then plug it with the clay. The leak point will show itself 100% of the time. What choice does it have? This is a great method for finding all kinds of leaks. I fill the exhaust system from the tailpipe to find exhaust leaks. Fill the engine from the oil fill for oil leaks, power steering leaks, and of course for EVAP leaks which is what the tool was designed for. It is designed to find EVAP leaks as small as .005" in diameter. Otherwise, finding small, intermittent leaks is a bit of a guessing game. Good luck.

[69 Limelight]

In your first post you say it's (seems to be) leaking front passenger side. that pretty much eliminates selector shaft seal because it's on driver's side. In your last post you say it's dry during summer months when you drive it frequently.

I'd be looking at your dipstick tube seal. When it sits for long periods of time fluid drains back out of your convertor and fluid level is above hole in casting that dipstick tube goes in. If the seal around dipstick tube (probably either o ring or rubber bushing thing that looks like a hat with brim and hole in middle) isn't doing it's job fluid will leak out then run down oil pan lip and drip off.

[Cardo]

He could have a pin hole in the converter weld. Seen that happen before. Only leaked if the hole wasn't on top.

[torqhead]

Originally Posted by mgarblik

If you really want to get serious and find the leak I can tell you how to find it in about 2 minutes. If you have any connections at a new car dealer or a good modern independent shop. See if you can rent or borrow an EVAP (evaporative emissions) smoke tester for evap leaks. You rig up a couple hose adapters and attach the smoke machine to the dipstick tube and turn it on. It will fill the entire transmission with harmless smoke in about a minute. Then with the car in the air and an intense light you can find very quickly where the smoke is escaping. You should get a little from the transmission vent. That's all. I generally put a wad of clay over the vent once I see it coming out there. That verifies the transmission is full of smoke. Then plug it with the clay. The leak point will show itself 100% of the time. What choice does it have? This is a great method for finding all kinds of leaks. I fill the exhaust system from the tailpipe to find exhaust leaks. Fill the engine from the oil fill for oil leaks, power steering leaks, and of course for EVAP leaks which is what the tool was designed for. It is designed to find EVAP leaks as small as .005" in diameter. Otherwise, finding small, intermittent leaks is a bit of a guessing game. Good luck.

Your idea sounds like a potential good investment, would you think something like this would be sufficient to do general testing as you described?

https://www.amazon.com/AutoLine-Pro-.../dp/B06XHRBKTM

[torqhead]

Originally Posted by 69 Limelight

In your first post you say it's (seems to be) leaking front passenger side. that pretty much eliminates selector shaft seal because it's on driver's side. In your last post you say it's dry during summer months when you drive it frequently.

I'd be looking at your dipstick tube seal. When it sits for long periods of time fluid drains back out of your convertor and fluid level is above hole in casting that dipstick tube goes in. If the seal around dipstick tube (probably either o ring or rubber bushing thing that looks like a hat with brim and hole in middle) isn't doing it's job fluid will leak out then run down oil pan lip and drip off.

Yeah, that supposedly has been checked before and I did previously. Doesn't mean that's not happening now and will check that. Thanks!

[torqhead]

Originally Posted by Cardo

He could have a pin hole in the converter weld. Seen that happen before. Only leaked if the hole wasn't on top.

Would that sling it everywhere? It's literally on the rim of the pan and then of course traverses it's way to the low point to drip off of...

I also found one of the bolts stripped in the rear when I tried to snug it up before ordering the gasket, so will have to fix that while I'm in there. Always cleaning up someone else mess it seems.

[Sirrotica]

Check the dipstick tube as you said it was right front location. Two places to look, the dip stick tubes sometimes crack when they swedge the tube on the top of seal to case, or where they make an indentation for the O ring seals and I have seen them crack there also.

The best sealing seal is the boot type that fits the whole lower length of the tube, much better than the O ring seals.

Here's a video that shows different seals and tubes to solve this problem:

https://www.youtube.com/watch?time_c...&v=NIIynnd9I78

The tube is probably the most overlooked point of leaks on auto transmissions.

Also the cooling lines are in that area, might check for a cracked flare fitting on the cooling lines.

Also the breather is on the right side, if the transmission is overfilled, the fluid will run out of the breather tube after it is shut down. The fluid returns to the lowest point in the system, the sump, and the level will rise after shutdown.

A few of the problems I've run into over the years on the passenger side of the case.

[Scott Thelander]

I chased mine on my 4x4 700r4 front seal pan gaskets dip stick tubes

it was

the pump gasket to the case ,,,,

passenger front also

[mgarblik]

I have heard those "paint can" type smoke machines can be dangerous so I DO NOT recommend buying those cheap models. They heat the fluid to produce the smoke. So some home-made looking deal made from a paint can sounds potentially dangerous. I wouldn't want you to damage your prized car or worse with one of those. A proper EVAP smoke machine is expensive, near the $1000.00 range. That's why I suggest trying to rent or borrow one for your car. I have been looking for a decent used one for myself for a year or so. No luck yet. But I have one available to borrow anytime I need it. If I had one here in my shop, I would probably use it once every couple of weeks. Very helpful. The OTC "Leak Tamer" is the least expensive one I see every now and then used. Typically 3-400 dollars used. Still an investment. See if you can borrow one if other methods don't work out. If you really think it is the pan again, I have had the best luck with a quality cork or silicone gasket formed on a metal core type gasket. Tightened carefully with an inch Lb. torque wrench.

[jeff chmura]

Check the TV cable....there's a o ring seal for that also.
The transmission will fill higher than the pan with more fluid when it sits. The oil from the valve body,clutch drums drain back to the pan, so if it leaks after it sits a bit,look for a leak above the pan rail.

[hgerhardt]

I bought a magnesium pan for my 200-4R from Art Carr years ago and had to machine it flat before I could use it. Might want to check that on yours.

[torqhead]

Well now that I finally just do the job myself. Here's what I found causing the leak on the trans pan that the trans shop didn't solve after 3 times! The cast has been damaged pushing out against the pan by a 1/32", so gasket can't completely seal in this area.

[torqhead]

Guys is this normal for about 10 thousand miles

[poncho447]

Originally Posted by torqhead

Guys is this normal for about 10 thousand miles

Yes, that amount of "dust" is normal.

[Carmine]

I chased a leak on my '71 GTO TH400 transmission, it seemed forever. I changed pans and gaskets I can't tell how many times. Then I discovered the leak was coming from behind the dipstick tube. Bottom line is, it wasn't seated properly in the transmission main body and allowing leaks after being shut off. I think this happened because of the converter drain off filling the pan with more fluid. I didn't drive the car every day. Sometimes it sat for a few weeks. To me, Pontiac made it almost impossible to attach the filler tube to a bolt on the bell housing. Ridiculous. What I did was square up the filler tube in the body and fabricated a bracket at the top, attaching it to the tube and to the firewall. Painted it the Pontiac blue and it holds the tube in place. Looks like to belongs there. No more leaks ever. Just my personal experience, Carmine.