Upgrade Auto Trans in '77
Thread Starter
Instructor
Joined: May 2006
Posts: 206
Likes: 0
From: Barrie Ontario
Upgrade Auto Trans in '77
Is there a trans switch or upgrade that can be made from a 3 speed auto 350 to a 4 speed auto to reduce the high rpm? I'm not considering changing to manual at this time or is it worth the effort.
Thanks for your help
Domer.
Thanks for your help
Domer.
Melting Slicks
Joined: Jul 2004
Posts: 2,577
Likes: 2
From: Long Island New York
From what I've read here on previous threads about this subject, the 700R4 requires some mods to the crossmember and a few other things in order to install it, and the 2ooR4 is pretty much a bolt-in and go type of swap. Maybe some other members who have already done the swap will chime in with some info. I'm still running the T350 in mine but will eventually go with a 200R4 more than likely unless there are other significant advantages of the 700R4.
Thread Starter
Instructor
Joined: May 2006
Posts: 206
Likes: 0
From: Barrie Ontario
Thanks for the comments. It looks like the answer is the 2004R for ease of installation and operation. I'm still going to check out the 700R4 just to make sure the 2004R is the right application for the $$.
Domer
Domer
Racer
Joined: Jul 2004
Posts: 323
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From: Abilene Tx
I just installed a 2004R in my 76. It is a level 2 from BowTie Overdrives (BTO). They are great to work with. It went in over a weekend. I replaced a TH350. The crossmember went back with no change and so did the driveshaft. I used my original dipstick and dust cover because they fit better than what came with the 2004R. Anyway, it went in pretty easy and I have put a few miles on it and love it. I have the 3.08 rearend and it sure makes it long legged. Havent checked the gas mileage yet, but will next week when I take it on a 1000 mile trip. Good luck.....you will like whichever of the OD trannies!!! 
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Pro
Joined: May 2002
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The 700 is generally better with high rear gears due to it's 3.06 first gear (3.08 or higher/lower numerically), while the 200 is better with lower rear gears/higher numerically like 3.55's and up due to it's 2.74 first gear.
Either works well, though the 700 needs a couple of new holes drilled in the crossmember (use the 700 tailhousing that has the mount in the same place as the TH400, it's from the S10 and other GM applications), and the driveshaft shortened and balanced.
I DIY'd mine about 15 years ago before there were kits, and my 700R4 is still going strong behind a warm 406ci in my 71 Coupe with 3.08 rear gears.
Doug
Either works well, though the 700 needs a couple of new holes drilled in the crossmember (use the 700 tailhousing that has the mount in the same place as the TH400, it's from the S10 and other GM applications), and the driveshaft shortened and balanced.
I DIY'd mine about 15 years ago before there were kits, and my 700R4 is still going strong behind a warm 406ci in my 71 Coupe with 3.08 rear gears.
Doug
Originally Posted by Domer
Thanks for the comments. It looks like the answer is the 2004R for ease of installation and operation. I'm still going to check out the 700R4 just to make sure the 2004R is the right application for the $$.
Domer
Domer
Thread Starter
Instructor
Joined: May 2006
Posts: 206
Likes: 0
From: Barrie Ontario
I'm glad that you are satisfied with the upgrade, looks like this is the one to do for ease of installation! Hope you trip goes well and you get great mileage from the new transmission. It'll be interesting to see what difference you have. If you have time, let me know of your results.
Domer
Domer
