Went for a little cruise yesterday nothing serious, just one burnout; nothing that I dont usually do. LOL. Parked the car. Then, walked out a couple of hours later to see about 1/2 quart of AFT on the ground under my Skylark. It looks like it came out of the top of dipstick tube (evidence of spray on the underside of hood and the firewall). The level hasn't been touched since I installed the transmission last summer (fresh rebuild) and has always been spot on. Anyway, I unplugged the kickdown switch (more on that later) and drove the car home. It ran fine and didn't puke anything more, but does look like it tried to leak a little. I wiped everything down and everything was still clean this morning. Did some quick googling last night and saw that I should check a few things: 1) Breather tube at top of tranny (could be, will check) 2) Vacuum line from intake to vacuum modulator on transmission (could be, will check; modulator is new from last summer) 3) Check O-ring on the dipstick tube (could be, will replace either way just to rule out) 4) Possible over-heating (pretty sure this is not the case here fluid is clean and no funny smells and it runs fine) 5) Possible over-filled transmission (doubt it it was a low when I got home last night and I had to rev the motor a hair to get it in reverse when I left to go home) Anyway, the reason Im posting this before checking 1-3 is because there is one thing Ive done to the transmission within the last two weeks - install the electrical downshift switch on the gas pedal. I dont see how that could cause a problem with the ATF, but wanted to throw it out there to see if anyone else has experienced a correlation between the two. I mean, it drove fine three times after I put in the switch and then this happened (fourth drive). Any ideas?
I hope I am not bad luck! Don't see it caused by overheating, not that long of a drive. I don't like that having to rev a bit to get in reverse, it would have to have lost a bit more ATF than a 1/2 qt to be that low. I'll ask my tranny guy about it.
LOL. No, you're not bad luck. If it was going to happen it was going to happen. Could have been more than 1/2 quart too. I'm not too worried about it yet; it's probably a simple fix. The worse case scenario is I'd have to fall back on the 24month/24,000 mile warranty. Hot rods. Gotta love 'em! ou: :laugh:
You mean the cover for the torque converter and flexplate? I don't have one on their. The converter didn't have much oil on it, just what you'd expect from some transfer from the wind making a mess underneath the car. What are you thinking?
Im thinking maybe the bottom of your tube is leaking (o-ring needs replaced). Seems consistent with the amount youve lost. Althought its a bit of a stretch to say the flexplate flinged it up all the way to the firewall. I had a firebird that would just puke out fluid when it felt like, I found out the dipstick tube wasnt bolted to the transmission, and would just pop out sometimes. But it lost just as much fluid as youre describing, and then stopped.
Assuming it's the dipstick O-ring (or some other easy fix) how do you guys feel about locking dipsticks? I may pick one up while I'm at it here. I think I'm lucky the manifolds weren't hot like headers can get. ATF is flammable.
Not sure what caused your problem, but I know here in Canada, GM did have an 'official' recall on '89 Chevy/GMC PU's for that exact reason, (ATF being forced out the filler tube on ST400 auto tranny equipped trucks). They sent owners a new replacement dip stick that sealed the filler/dip stick tube opening with an expanding seal that plugged the opening, and locked into place with a flip style, locking lever cap. o No:
Those dip stick tube O rings are marginal. If the tube is at all distorted, or moves around (not properly bolted near the top), you could have a leak. Bolt it if it isn't, and some gasket forming stuff on the O ring surfaces might cure it. I have switched to the later style tube using a sort of rubber funnel at the seal, to avoid these issues. Bruce Roe
UPDATE: I crawled under the car and took a look at things today. 1) Hooked up a vacuum pump to the breather tube on top of the transmission. It pulled some good vacuum, but nothing came out. I then stuck some wire in the tube and was only able to get about 2-1/2" into the tube. So, does this mean it's plugged? I thought the pump shouldn't get any vacuum if it's not blocked. 2) Took a look at the vacuum line between the modulator and the intake. It was blocked up near the intake. It's the original tube from the 455 and was also crimped (looked to be factory) near the intake end. I cut off that portion of the line and then re-installed it. 3) I wiped everything down and it took just under one quart of ATF to get it back to normal level. Took it for a short ride and checked it; good. Took it for a longer ride and gave it a little workout. The transmission shift MUCH better at part throttle than it ever did before I fixed the vacuum line. And the electrical switch works great at WOT. 4) Parked it in the garage and kept a close eye on it for about an hour and all I could see was a little ATF right at the O-ring of the dipstick tube. It's been parked for about the same amount of time now as it was when it puked ATF the other day. It appears to be seeping just a little from that O-ring, so I'm going to get a new tube and dipstick for it. 5) Here's the funny part: the outside of the dipstick tube is completely dry this time, but there is some evidence of spray on the hood and firewall again, right near the top of the dipstick. The dipstick was not loose when I parked it and there is no evidence that any ATF came up the inside of the tube. So, that kind has me scratching my head. Anyway, still not sure why it puked the other day, but we'll see what a new, locking dipstick does. What do you guys think about that breather tube - does it sound clogged? BTW, my modulator is adjustable, but my 3" exhaust is too close to it for me to get a screw driver in there. Can I remove it from the transmission to make adjustments without dumping ATF?
BJ, I think that adjustable modulator uses a allen wrench to adjust it, might be able to use the bent end of one to get in there! Could that spray be leftover juice from the original puking?
if my car sits for a lengthly time i get fluid up through the dipstick.after the car sits for days or months the fluid in the convertor drains down and makes the fluid level much higher than normal.and i get a small puddle under the car.its been doing this for yrs.i was told 400s sometimes do this.everything else is dry.i put a new style locking dipstick like on new vehicals..and this is also manditory in a lot of nhra classes now
I had a fresh T-400 on the shop bench and threw a vacuum pump on the breather tube, could not pull vacuum. Was able to get about 3 1/2 inches of wire in the tube. Sounds like the breather tube is blocked. Hopefully a pro will chime in and give us a clue as to what could block it. Hope this helps!
Some kind of mud wasp is all it took to block mine. Luckily it was plugged in the downward portion of the tube, so as I gently pushed a fine wire into the tube, the debris fell out rather than in. Devon
It definitely sounds like the breather tube is my problem. It was the first thing that kept coming up on google searches too. I certainly don't want to push anything inside the tranny, so will have to figure out a good way to clear it out. Maybe I need a stronger vacuum pump. Thanks for the input, guys.
All GM trannies will do this to various degrees, when they sit for an extended periods. The excess tranny oil from the torque converter drains and overfills the oil pan, where it seeps out the filler tube, or past the rear extension housing seal. :TU:
I might have to pull the transmission to do that. I can barely reach up there as it is with the exhaust in the way. It's very close to the floor of the car too. If it comes right down to it, I'll probably just take it in the the shop that rebuilt the things and let them monkey with it.
