TH400 rebuilt delayed shift into "d" - Hot Rod Forum : Hotrodders Bulletin Board
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Old 11-15-2004, 04:18 PM
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Angry TH400 rebuilt delayed shift into "d"

so i decided to rebuild my own th400 out of my 69 chevy pickup that was "completely rebuilt" by joe hillbilly i bought it from. the trans burnt up after towing a car on a trailer. i bought a manual from ATSG that was a great guide! but i found many mistakes upon dissassembly.... ok to the point everything seems to work fine but when you first shift into "D" there is a 1 to 2 second delay before it drops into gear .this only happens in "D".
now once engaged into drive i shift back and forth from drive to reverse back to drive and it instantly engages in drive but if you wait a little while before going back to drive the delay is back. what is causing this problem??
i called a trans shop and they said " uhh well it could be anything and named off every part in the trans in some kind of ploy to convince me to let them fix it. the trans is completely stock- tc, shift kit, and all. the rebuild kit was a master kit from autozone with brown alto clutches.
one other thing i believe i once read the you could modify your own shift plate by drilling certain holes out to get the same results as an aftermarket shift kit. is this fact or hillbilly myth?
any help will be greatly appreciated to get my klunker back up par so i can go to the track and shoot a rod through my hillybilly built 350.

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Old 11-15-2004, 09:00 PM
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Cool

it could be many things. cut lip seals , cut or broken sealing rings, something left out that is blowing off pressure.


i'd put a 0-300 psi gauge on it and see what the main line is doing while shifting to various gear positions
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Old 11-16-2004, 05:09 PM
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thanks for the advice ill give it a try and see
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Old 11-18-2004, 05:54 PM
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pressure test completed

well crosley i have completed the pressure test and here are the results along with the normal readings according to my book

BOOK ACTUAL
P, N brakes on at 1000rpm 55-70 psi 60 psi
D @ curb idle spec. 60-85 * (600rpm) 50
D brakes applied @ 1000 rpm 60-90 75
D"2" brakes applied @1000 rpm 135-160 150
R brakes applied @1000 rpm 95-150 120
D brakes applied @1000 rpm,
down shift solenoid on 91-110 * 85


the two marked with "*" are out of normal range (drive and drive with detent solenoid on) but if you notice in drive @1000rpm i am in the acceptable range. from what ive read in my trans book it could be an internal leak in the forward clutch. what is your (or anyone elses) professional opinion.
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Old 11-18-2004, 08:17 PM
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Cool

It appears you have a leak in the forward clutch from the low pressure in D at idle.

I imagine the pressure drops a good amount when the selector is placed into D , then the pressure comes back up to 50 slowly
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Old 11-19-2004, 02:38 PM
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well the pressure drops to about 45 but it comes up to 50 in less than a second. it looks like ill be droppin the trans and inspecting the forward clutch. ill let you know what i find in a few days.
thanks
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Old 12-11-2004, 04:31 PM
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finally im back! the seals in the forward clutch were fine but the spacing of the clutches was wrong so i corrected it. now has 5 each steels and lined plates. i had one steel that was thinner than the others in before. and i found the bronze thrust washer to be missing from under the clutch hub. so i yanked one out of my donor tranny (previous owners first rebuild attempt) and installed it.
i havent done the pressure test yet i ran out of time today but i did get in a good test drive and it feels fine throught the operating range under normal driving and floored up to 85mph. it also grabbs just fine when i stomped it around a corner and cut loose the rubber.i have noticed one thing though when i turn up my steep drive way and push the gas it does a little- skip and jerk, sorry the only way to put it into words. but my rearend is about to fall apart and may be causing that. ill do the pressure test again probably tomorrow and post those results. and then ive got to properly set my timing and tune the new carb.
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Old 12-14-2004, 09:39 PM
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the test is in and its good @75 psi in drive at idle. acceptable range was 60-85. now i can move on to fixing the junk i already know how to fix. thanks for your advice crosley.. im out,.
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