1975 Chevy Bel Air Transmission

Tiny
EYESTRAIN
  • MEMBER
  • 1975 CHEVROLET BEL AIR
Transmission problem
1975 Chevy Bel Air V8 Two Wheel Drive Automatic N/A miles

Transmission won't engage when sitting for a week or two. Transmission has 3000 miles on it new fluid and filter. What is wrong with it?
It does shift normally when it does engage.
Do I need a new transmission or do I need to rebuild again?
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Saturday, April 3rd, 2010 AT 7:00 AM

6 Replies

Tiny
HMAC300
  • EXPERT
It gets to who rebuilt it? If you did yourself and it takes a week to not engage, did you replace all the seals, including the rings? Did you pressure check it when it was done to see if a seal didn't roll or get cut? Is it full of fluid? Or what type is it a THM 400 or 350. Afilter could have slipped out of the pickup tube which happens alot and causes them to not engage. Or is there a check ball missing in the valve body or the gasket has/was torn when installed. Regardless the pan has to come off and see if anything falls with it.
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Thursday, April 8th, 2010 AT 5:31 PM
Tiny
EYESTRAIN
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Well let's see. The previous owner rebuilt the transmission and it has about 3000 miles on it so I have no idea about the quality of the rebuild or pressure, I do know he was driving it regular. He says he did a total rebuild FWIW, It is full of oil according to the stick it may be 1 quart over. It is a TCI turbo 350 with a 9" tail shaft about a 1975 model. I did have the pan off and yes the filter was in the bottom of the pan along with the 2 screws and a fair amount of graphite looking material not alot though. I put on a new pan and filter on attached the screws and torqued as required. I did not see any bearings, balls or large stuff in the bottom of the pan. The transmission fluid looks normal with no burnt smell. I did put 8 quarts of new fluid in it when I dropped the pan. It is hooked to a 454 in a 57 Chevy and I believe it may have had a hard life in the car. I hope this additional information helps. All of this has happened after I put the new filter on, but could have been going on before I bought the car. The dip stick was leaking so I put on a Lokar dipstick that has a good seal where it goes into the transmission. I not a retired mechanic but have almost 40 years of mechanical experience. I just don't know automatics like I do 4 speeds. Thanks g.
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Friday, April 9th, 2010 AT 7:58 PM
Tiny
HMAC300
  • EXPERT
Please don't get that I was trying to be smart as I wasn't. But it sounds like there is air getting entered or you have a vlavle sticking or a broken spring in one of the valves. It could be a torque converter problem as well. Best bet would be to take it to a trans pro and have him take a look because he can hook up presure guages or may know what the problem is right off the bat. One thing though a 350 trans shold not be used behind a 454 due to them having weak planetary reaction carriers. The graphoite you foind was probably due to first time assembly and with the filter being found in the pan it may have damaged the seals already. One thing was there a gasket between teh filter and valve body? There should be as that may be giving you the air. If you pull the pan again just add what you need not change all the oil as it sounds as if it is ok. Also as you now say the previous guy did it he may not have changed all the seal rings which are steel or there is wear between some of the rings and bushings where they seal and when it warms up it works, but cold it won't. If you do go with another trans either go with a THM 400 or a 4L60E, that is an electronic trans with overdrive for better fuel mileage. It wil need a stand alone computer though. But both of those are for 454's
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Saturday, April 10th, 2010 AT 7:46 AM
Tiny
EYESTRAIN
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Thanks for the info....No there was not a gasket between the filter and the valve body, it was just held in place by 2 machine screws. SHould there be a small gasket there, It looks like the one in the oictue so I guess that is the gasket.? I feel the same way you do the damage has already been done without the filter in place, and for how long is wasn't no one knows. I think I'll take your advise and have the pressure checked at a transmission shop. It is really a PITA to change out an automatic unless you have a good jack and an extra person to help. I did notice some felt stuff in the pan, I failed to mention it. I'm going to try to attach a picture for you to see.


http://www.2carpros.com/forum/automotive_pictures/511310_Car_pictures_2122010_007_1.jpg

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Saturday, April 10th, 2010 AT 8:00 AM
Tiny
HMAC300
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If you have some what you call felt it may be clutch pak material. But ya have apro look at this. What happens when a novice builds stuff like this they aren't real careful putting seals in and sometimes they roll instead of going in correctly, which allows slippage due to the clutch piston not being able to apply the clutch pak like it should. Plus they may not have changed the steel rings which I had stated in the last email and there are 3 or 4 on the back end of the oil pump assy which is for the torque converter and a couple on the input shaft. If these leak then it gives you problems. Plus if the filter was in the pan it's possible that junk got into the valve body or govenor, although there should be a screen to protect the govenor. On the filter it looks like it might be pieces of clutch material. At least from the picture. Remember it is hard to give a proper diagnosis on the computer here without seeing this. Good luck with it.
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Saturday, April 10th, 2010 AT 10:54 AM
Tiny
EYESTRAIN
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Thanks you very much for your technical information.
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Saturday, April 10th, 2010 AT 12:15 PM

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