TH 400 leaking fluid out of dipstick - Chevelle Tech
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Transmission & Driveline Transmissions and Differentials

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  #1  
Old Oct 2nd, 06, 3:44 PM
lester lester is offline
 
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Default TH 400 leaking fluid out of dipstick

Recently purchased 396 ss TH400. Drives fine, but pukes trans fluid out of top of filler tube - usually noticed upon arriving back home. Fluid is very clean and does not seem overly hot. Previous owner had told me it has a "slight trans leak" Level checked and is fine. Could it be wrong dipstick/tube...? What is the length of dipstick. Or, could it be a clogged vent? Where is the vent tube located? Thanks for any help
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  #2  
Old Oct 2nd, 06, 10:29 PM
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Default Re: TH 400 leaking fluid out of dipstick

Check the vent on top of the tranny.
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  #3  
Old Oct 3rd, 06, 7:21 AM
Oldani Motorsports Oldani Motorsports is offline
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Default Re: TH 400 leaking fluid out of dipstick

Also make sure it's not overfilled. Level should be no higher than the case/pan interface point. Also make sure there are two orings on the case end of the filter pickup tube. It can pull air in there and foam the fluid, which will also let it puke out the dipstick or vent possibly. You can run a small piece of wire into the vent tube to make sure it's open. If all else fails it may be a front pump machining issue but that's not common.
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Old Oct 3rd, 06, 2:59 PM
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Default Re: TH 400 leaking fluid out of dipstick

This happened to mine one time, I found a dirt dobber had filled the vent tube.
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Old Oct 3rd, 06, 9:08 PM
lester lester is offline
 
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Default Re: TH 400 leaking fluid out of dipstick

Thanks for the suggestions - I will check vent tube first.
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  #6  
Old Oct 6th, 06, 2:22 AM
lester lester is offline
 
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Default Re: TH 400 leaking fluid out of dipstick

The vent tube was clear... I took a level to the bottom of the pan and jacked the car till level. While cool - I dropped pan slightly and let excess fluid run - about a quart collected. I then tightened and marked dipstick. I hope this was problem - wrong dipstick causing bad reading. I still need to test drive...no time yet - Have wife and screaming kid in the house.....or is that ...kid and screaming wife. I get confused....lol
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Old Oct 6th, 06, 2:59 AM
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Default Re: TH 400 leaking fluid out of dipstick

I sure hope one of those fixes it.
I'm kind of leary about the tube cause it's so much higher than the top of the trans it would need preasure to push the oil out the top.
Now that I think back on it mine happened about 14 years ago but not long after I had to overhaul and change out the sprag if I remember right.
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Old Oct 8th, 06, 12:21 AM
lester lester is offline
 
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Default Re: TH 400 leaking fluid out of dipstick

Wasn't that lucky...still puked out the tube, but now takes forever to get into drive or reverse...maybe level too low now. Either way I have problems... Sticking valve? I think next step will be dropping pan, and maybe valve body to see if anything obvious. As mentioned - just bought the car - Fluid is VERY clean which I suspect previous owner recently changed which is probably not a good sign. I guess worst case is I have to put in rebuilt...good thing TH 400's are fairly cheap.
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  #9  
Old Oct 8th, 06, 1:10 AM
Cecil Cecil is offline
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Default Re: TH 400 leaking fluid out of dipstick

Does it puke fluid only when shifting from 2nd to drive, or all the time?
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Old Oct 8th, 06, 3:15 AM
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Default Re: TH 400 leaking fluid out of dipstick

If you decide to rebuild think about getting an overdrive my 400 is fine and I still want one.
My truck has a 3.92:1 with overdrive, it will pull my tractor out of mud and still get 2200 rpm at around 60 mph at 21 mpg running a 360.
I know you would rather fix this one but just in case.
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Old Oct 8th, 06, 12:37 PM
lester lester is offline
 
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Default Re: TH 400 leaking fluid out of dipstick

Doesn't puke out all the time - seems to when getting back home and in reverse - at least that's when I notice it. No that it was slipping it did it when I put in drive and was waiting for it to engage.
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Old Oct 8th, 06, 1:36 PM
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Default Re: TH 400 leaking fluid out of dipstick

Shouldn't the fluid level at the pan with the motor running?
Wont the fluid drain back into the pan with the motor off giving you a false reading?
I say that cause ya check your fluid with the motor running and in park normally, don't ya?
Also don't you have the highest line pressure when in revers?
May be something there?
T.C.
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Old Oct 8th, 06, 1:46 PM
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Default Re: TH 400 leaking fluid out of dipstick

I'm not a trans expert have rebuilt a few though but I have a feeling you may be getting fluid back from the converter too fast creating fluid pressure in the pan instead of the converter.
Maybe a trans mechanic will notice this and weigh in.
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Old Oct 30th, 06, 11:53 PM
lester lester is offline
 
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Default Re: TH 400 leaking fluid out of dipstick

Still haven't figured this out...just getting back on the task now. It wasn't the fluid level. I still am hoping vent tube even though I stuck a wire in there. It is very hard to get at so I'm not sure if it went all the way in. Can air be blown into this vent tube without damaging anything?
Also going to replace vacuum Modulator which someone said could be the problem. (vacuum to the modulator was fine)
Lastly - I disconnect cooler lines at the radiator and blew air through rad - all was fine there - could the problem be the lines are switched at the trans end? I belive the pressure line from trans goes to bottom of the radiator and return to trans is the top correct? Would this make any difference?
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Old Nov 1st, 06, 8:32 PM
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Default Re: TH 400 leaking fluid out of dipstick

Update
Just fired up my 69 after being in restore for a year and yep spit out the stick.
I got to looking at my setup I have an external filter before going into the extra cooler started thinking the filters may have gummed up sitting so long so I bypassed it and wala it worked stopped spitting up from the stick hope this helps.
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