exactly which part/parts Are/ is responsible for preventing the converter from draining back and over filling the pan?
I'm not a big automatic person but I don’t think anything stops it from draining back, thats why the level is checked with the engine running. Phil
I thought it had to do with the seal on the torque converter. I have done several searches in the past on this issue, and its not just a T350 thing. Higher capacity pans seem to be a band aid in regards to control. I have never had it happen but my late brothers 31 Ford had it happen for years. I read a fix talking about the seal on the TC and thought it made the most sense. I did not know how old the trans or the converter was in his coupe to tell.
I expect it has mostly to do with the bushings in the pump, and the condition of the torque converter hub, as well as the condition of the pump gears and housing. Also, the input shaft where it rides in the bushing in the stator support (aka the pump cover). But that's just a guess. Those parts are usually worn in a used TH350. Wear in those parts will let air get into the converter, so the fluid can drain out.
I always thought the red stuff on the floor was as a result of a self levelling device in there somewhere! Universally fitted. Chris
I’m not a transmission guy, But now isn’t a transmission guy supposed to change those out? Is checking and perfecting those surfaces and bushings and gears part of a standard rebuild process? Seems there’s a county wide epidemic of leaking TH350s.
It was at the shop I worked at almost 40 years ago. But that was one of the better shops...there are quite a few that don't bother. Also these transmissions are 40-50 years old now, and parts and expertise for them are getting harder to find.
Some drainage of the converter is just nature...it's called...gravity. It would have to be that every part is perfect that is connected to the tube that comes out of the converter and drives the pump. There is NO inner seal to prevent some oil from draining. Just the pump guts itself. The better the pump is, the less converter drain, the looser the pump guts are, the more converter drain there will be. Is the trans. too full of oil when checked ? Is it checked correctly to begin with ? Mike
Another issue is that in the old days, any car that had a TH350 in it was a late model, daily driven car. Now most of them are in old cars that have to sit for a while between drives. The drain back takes a while to happen, usually a week or more, although less if the trans is worn out. Used to be that the cars never sat long enough to have a chance to leak that way. Now they almost always do.
yes, good point... mine starts to leak after sitting 3-4 months. Not a drop on the floor if it´s driven once a month, same with my Powerglide or SP 400.Sitting over the winter will result in a mess...
The transmission isn’t supposed to leak even if the converter drains back You need to fix the point it leaks from (most likely the transmission pan gasket, or the seal where the shifter arm comes out, or the kickdown cable exit) hope this helps
There are about a dozen places a 350 can leak. We've discussed it several times here. A well built 350 won't leak. There are a lot of places to screw up. Sent from my Trimline
It takes about 4 weeks for the TC to drain back into the Powerglide in my A pickup to the point that it starts to leak. When I notice the spot on the floor I know I need to get her fired up. The longer it sits, the more the spot will spread out. It's the car's way of making me feel guilty for not driving it.
The stator bushings are the culprit for rapid (overnight) converter drainback. Even if it drains back, it shouldn't leak on the floor if all the seals were installed correctly. When I build a 350, I install a bushing kit (all the bushings are replaced).
It’s not in the car. It’s on a dolly in the corner. Might have 100 miles on the rebuild. Pan was drained when it came out in October. Unnoticed and Quietly leaking a giant fucking mess. Inadvertently and before a pan got under it the dip stick tube came out of the case and then we had a trans fluid fountain Making a once big mess into a huge mess. It might not of pissed me off so bad If floor was not brand new.
My 400 TH does the same thing. Let it set a month without starting it and I have a trans fluid puddle under the car. The converter drains into the trans and comes out of the front seal. There is nothing wrong with the transmission, just start the car and let it run a little bit every couple of weeks.
I generally put a used torque converter on my "tear down bench" and let it drain as much as it will, before putting it into storage, whatever that storage may be. Sucks that a fresh trans did that. Live and learn, I guess.
My glide ,350 ,375 & 400 will drain back if not driven or started up between afew days to a week , I use the grommet seal Not O ring dip stick , I use The Lokar Braided , After seeing trains fluid , thinking it was pan or converter seal , My Leak comes from the braided Hose & fitting @ case . After setting .the drain back will fill up the Tube / house about a Inch or so above case grommet. Miner leak , I live with it for now ,My cars are on a lift once a week , so i clean it & check out things , because I run my cars hard. I do not like Leaks
I had this with a fresh rebuilt T350, and after speaking with a local trans shop found that my culprit was the O ring seal on the filler tube. After lubricating the floor in the workshop with a couple of litres of ATF, I was told that they will all eventually drain back, and as the level in the pan goes up, it will find the lowest spot to leak. I thought "easy fix, replace the "O" ring, maybe put some goop around there as well", but it is virtually impossible to remove the dipstick tube hold-down bolt (which is a trans to engine bolt) with the engine in the car (bad planning on my part). So we came up with this solution: Fill the trans to the right spot, run it, and leave for a couple of weeks with a big drip tray underneath. Each time it is stopped for a week or so , a little bit will drip, until it eventually stops dripping. I ended up with about 1 cup of fluid in the tray. The level is now down the bottom of the dipstick, the leak has stopped, the trans runs nice (no foaming or noises). I will eventually work out how to re-seal the dipstick tube, just need new batteries in my thinking hat.
Make sure the bushing in the pump body where the converter slides in is a new one . Makes a difference . Some shops don't install a new one .
On the TH 350, the main pressure regulator valve controls fluid flow to the converter. When the engine is shut off, the valve closes on the fluid in side. However, after the fluid goes through the cooler it is used to lubricate the gear train. There is a bushing between the input shaft and main shaft and I've seen many of these bad; but you must understand that the gear train lube system is a calibrated leak. If the trans isn't operated for a week or so, the converter is going to drain back. As long as all the seals are good, it shouldn't leak even if the converter has drained back. I've got a TH 400 in my Model A and it does leak when the converter drains back. It looks like an oil pan leak but it is leaking at the selector shaft seal and I put a new one in when I rebuilt it. Looks like I get to do it again. The Powerglide in my old truck never leaks.
Another problem is that alot of our cars are raked which with gravity causes the fluid to 0verload the front of the pan. That coupled with the poor O ring seal equals a constant dribble of fluid when our cars sit for days at a time. The sleeve type seal does a much better job than the O ring type .Later Bill
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