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Old 01-08-2007, 03:35 PM   #1
C203/4
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1972 c20 3/4 ton

can anyone tell me how to tell what kind of transmission is supposd to be in my truck? i know it is a short shaft, and has the square 350 pan on the one in it now, plus a drain plug, not original i am assuming, will not shift into third, and i want to replace with a th350 short shaft, but not sure if that is good enough, no towing, or hauling, just regular daily driver. anyone near Austin texas have a nice used one untill i can get mine rebuilt?
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Old 01-08-2007, 03:38 PM   #2
Longhorn Man
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Re: 1972 c20 3/4 ton

if it has a kick down cable, it's a short shaft TH350 (which DID come stock with a drain plug)
If there is no kickdown, it's a TH400.
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Old 01-08-2007, 11:49 PM   #3
Robert1970C20rstbukt
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Re: 1972 c20 3/4 ton

That's a TH350, the one in my '70 K20 Suburban is original and it has a drain plug also. I don't think there was a short tail TH400, at least I've never seen one. The 400 in my truck is a 1967 long tail.
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Old 01-08-2007, 11:56 PM   #4
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Re: 1972 c20 3/4 ton

That's the only problem,that it won't shift into 3d?
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Old 01-09-2007, 12:41 AM   #5
poorboy
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Re: 1972 c20 3/4 ton

A short tail t400 came in alot of pass cars. There are long tail 400's that came in some trucks and older wagons anf 400's that came in 3/4 and 1 tons with no slip yokes.
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Old 01-09-2007, 12:46 AM   #6
skchevota
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Re: 1972 c20 3/4 ton

My 70 originaly had a short tail 400.... But it had a big block too.
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Old 01-09-2007, 01:10 AM   #7
RVFR
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Re: 1972 c20 3/4 ton

pretty sure mine is a short TH400 but its connected to a BB in a longhorn
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Old 01-09-2007, 02:35 AM   #8
72armyswbtruck
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Re: 1972 c20 3/4 ton

Go with a cheap $400 dollar rebuilt transmission from autozone, that's what my 350 replacement cost me
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Old 01-09-2007, 08:49 AM   #9
WorkinLonghorn
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Re: 1972 c20 3/4 ton

Who says you need a bebuilt? Unstick the governor,check the modulator.Check vac line to modulator. All real easy stuff,maybe 1 hour max.-cougar
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Old 01-09-2007, 05:44 PM   #10
C203/4
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Re: 1972 c20 3/4 ton

yes the only problem....
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Old 01-09-2007, 08:07 PM   #11
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Re: 1972 c20 3/4 ton

Take the vac hose off at the modulator (on the trans). Any fluid? Then you need a new modulator. Uncrew it and screw in a new/used unit. Check the line for leaks.A vacuum leak on the modulator line will cause it to not shift up. Then if it still doesn't shift up take the round cover off the governor on the side of the trans.and free up the governor,cause they occasionally get stuck with grit. It will now shift up.
If not,post again.-cougar
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