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Old 08-06-2007, 03:55 PM
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th-400 help

I have a few questions for the th-400 experts.

I have a customers 400 here that has issues. It's been to about every shop around and has never worked right. The initial problem with the trans was that it would stack shifts. Then it stopped shifting into high gear, and around the same time it would drop out of gear going around corners.

It is a 40's willys with a 450 inch blown pontiac engine. I did not have the chance to check the line pressure before he took it out. I did get it apart and found the front band and drum burnt, the intermediate clutch pack burnt black. There is some light chatter burning on the direct pack and the foward clutch looks like new. the trans has about 500 miles on it total.

I did check the intermediate case plug and it's in and sealed. The intermediate air checked good and the seals are not torn. The 1-2 accumulator valve is not stuck.The rear accumulator is also ok.

Any ideas????

I am also wondering if any body has the B&M part number for the separator plate for the pre 87 kits..I called B&M and they were there usual helpful selves. I gave the guy the part number and he told me it was for a 707 trans???

Keith

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Old 08-06-2007, 08:45 PM
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you have pressure problems...

check for wear in the case at the center support. Lug area, sealing area from support to case.

Check the rear band servo area & accumulator for wear , ring grooves or lips in the bores.

Check the pump for wear... flatness of stator support, gear clearance at .0015 to .002 .
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Old 08-06-2007, 09:25 PM
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Has anyone checked the vacuum signal at the modulator?

This rings like a gong in my head... high vacuum signal when driving (low line pressure), customer HATES the shift feel, timing, etc and uses the shifter to control shift sequence (burnt band, int. pack), pretty soon forward takes too much abuse and slips...

Has this dipstick and tube been checked for accuracy? The full mark must be at or slightly above the pan gasket level (max 1/8" above). I can verify B&M seperator plates.... Check your PM
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Old 08-06-2007, 09:46 PM
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good point chazmac .... I wonder where the vacuum feed line is plugged into??
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Old 08-07-2007, 07:57 AM
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400

If this is trapped vacuum, using a vacuum gauge will be necessary to qualify this problem.

Last year we did a 425, in a motor home. It came back with reverse slips concern. With a vacuum gauge we could see, under a load, the engine would not drop vacuum.

A piece of carbon was floating around in the vacuum line.

No vacuum drop= no line rise.
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Old 08-07-2007, 11:13 AM
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trans

Thanks for the help...I got the Pm chazmac.

It's funny that the vacuum question came up. I was always under the impression the blower engines had vacuum signal problems under load???? ..I kind of over looked it because of all the rest of the shops looking at it but now i am thinking thats the issue and they all missed it???? Including me...

I did not get a chance to put a vacuum gage on it but i can tell you that it's hooked onto the back of the second carb ( the one closest to the fire wall)

keith
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Old 08-07-2007, 07:59 PM
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back when I ran some blown motors on the street.... I ran vacuum feed from between the carbs & the blower with a 6-71 blower setup.

My t-400's worked fine like that
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