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4SPEED427


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Big block with TH350 automatic?
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In an effort to not derail another thread (because I am often accused of being the king of derailments (and I admit to being bad for that) ), I want to ask a question here.

Does anyone own or know of an original 454 powered 1973-1976 Chevy/GMC 1/2, 3/4 or 1 Ton with it's factory installed automatic transmission still in it? If so, is it a TH350 or a TH400?

Interesting debate on the other thread. Ray posted a web page that says a 454 came with a TH350 in those years, I say never.

Prove one of us wrong!

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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles 

1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)
4SPEED427


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RE: Big block with TH350 automatic???
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And it just occurred to me for certain that at least one 74 had a TH400. A few years ago, I bought a 74 454 2wd long box from one of my co-workers. His dad bought the truck brand new at our dealership. I parted it out and it was most certainly a TH400 in that truck.

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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles 

1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)
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StriperSS


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I tried to find my sales brochures for those years, but wasn't able to. Carl, if you have the parts books for those trucks, there will be clues that should tell you. Ie, trans mounts, cross members, trans cooling lines, by engine, trans designations.

John



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StriperSS


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I'm going to say Turbo 400's were the one, especially in a truck application.



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4SPEED427


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StriperSS wrote:

I tried to find my sales brochures for those years, but wasn't able to. Carl, if you have the parts books for those trucks, there will be clues that should tell you. Ie, trans mounts, cross members, trans cooling lines, by engine, trans designations.

John




That's a good point. There would be no TH400 listed for those years if a 454 didn't have it I would think. It would make no sense to have a TH350 behind a 454 but yet offer a TH400 behind a small block or 6 cylinder. I'll check those books.

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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles 

1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)
73SC


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[Chart showing transmissions used in 1973 - 1987 Chevy trucks. Includes gear ratios.]

 

1973 Chevy Trucks.jpg

 



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Ray White, Toronto ON

1973 LeMans 454 "Astro-Jet"

Built March 9, 1973 - Oshawa ON

1993 Corvette Convertible LT 1

Built January 10, 1993 - Bowling Green Kentucky 

 
4SPEED427


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454 th.jpg

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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles 

1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)
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1975 75 454 th.jpg

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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles 

1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)
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1974

74 454 th.jpg

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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles 

1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)
427carl


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I had a 1974 Nova SS hatchback with a 350 2bbl and 400 turbo 



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4SPEED427


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M49 is not a TH350 as it says there. M49 was a Turbo Hydramatic option code, be it a TH350 or TH400 that was installed. Apparently starting in 74 it was broken out correctly according to transmission installed. http://67-72chevytrucks.com/vboard/showthread.php?t=554460 m49.jpg

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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles 

1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)
StriperSS


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I parted out a 71 GMC with a 402 and it had a turbo 400 back in about 85.
Alco parted out a 71 Belair with a 350 2 bbl, turbo 400. I can't see them putting a turbo 350 behind a big block in a truck, knowing how trucks got used.

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Elroy


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RE: Big block with TH350 automatic?
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I have never seen a TH350 behind a big block from the factory. I have a 77 TH400 out of a wrecked 454 3/4 ton. It has the HD case and the bolt on rear yoke. Wanna buy it , 100 $ takes it !

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67Poncho


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Talked to a buddy of mine that had an original '79 heavy 1/2 with a 454... THM400 is what it had.... and I say had as it was toasted...



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In 1967-68, the only Turbohydramatic offered in light duty trucks was the TH400, even with a 250 six! They did build them.

I have a picture in a 1974 brochure of a pickup chassis with a 350, fully dressed including the infamous saddle fuel tank. It seems to me the small blocks came that year with a TH350 with a long tailhousing. Check out the GM Heritage site in the U.S. where you can download the SAE specs in .PDF form. They go into great detail on all specs and will tell you all. The TH350 had a 2.52:1 1st while the TH400 had a 2.48:1 1st.


Don't get too excited when you see M40 vs. M38 on some car spec sheets; M40 was often used generically to refer to a 3-speed automatic, even when the specs called for an M38 TH350.



I can't check my reference material right now because I am in India as we speak.



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67 Chevelle Malibu Sport Coupe, Oshawa-built 250 PG never disturbed.

In garage, 296 cid inline six & TH350...

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no TH350 behind a big block but you could get a glide behind it. sad



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GLHS60


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CdnGMfan wrote:

In 1967-68, the only Turbohydramatic offered in light duty trucks was the TH400, even with a 250 six! They did build them.



 Makes sense as the T-350 wasn't introduced until the 1969 model year.

 

Thanks

Randy



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