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Turbo 350 build question

I would like to get my turbo 350 rebuilt but would like my 3rd gear much taller(drop 500 rpm or more). is that possible? is there a good trany builder in Manitoba? must be good for 800hp.  


Canadian Poncho Superstar!

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I'm not a transmission expert, but I suspect the only choice for 3rd gear is a 1:1 ratio the tranny came with.  Plus with 800 hp I'm not sure I'd be going with a Turbo 350.

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A good friend ran CASCAR back in the 90's, he told me all his race cars had THM 350's. He also dissuaded me from changing my trans to a THM 400, his opinion is that once the THM 350 needs a rebuild he'll build it properly to deal with my 454. So far after 5 years the 454 hasn't broken the THM 350 yet.


On top of that I did a quick search on Team Chevelle Forum, lots of support for using THM 350's over there. Here's a good quote:

th, 04, 12:03 PM
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My son has been running a turbo 350 behind a 540 cu. in. Big Block in a Chevelle that has somewhere in the neighborhood of 775-800 H.P. and has even sprayed it some although i wouldn't recommened it. The car usually runs high nines and the only problem he has had is one broken sprague. This trans was beefed up by ATI and has a real good converter also by ATI. Best E.T. is 9.42 and the best speed is 147.61 MPH on a little juice.
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Poncho Master!

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T350 is NOT an overdrive trans, 3rd gear is direct drive, i.e. 1:1 and you cannot change it. Just like Muncie 4-speed or Powerglide, top gear is direct drive and you cannot change it.

If you want a taller highway gear, you either must add an OD unit behind the trans, or change to an OD automatic like the 700r4 or the 200r4. It is easy to find info on the internet about those - as near as I can gather, the 200r4 is the way to go, same length as T350 so can keep driveshaft, can be beefed to handle 800HP, 3rd gear is 1:1 but 4th gear is overdrive so you can cruise on highway at lower rpm.



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