The Stovebolt Site Forums The Shop Area Engine Shop Tranny swap

Hey all!
I'm a new guy with a '67 C20 327/400TH (hope it's not too young) anyway, I'm thinking about swapping the TH400 for a TH700R4. Anybody with that experience? I just checked out your forum today and it looks like a fun/informative place.

Welcome aboard, CrashBob. I haven't done the swap, but do know some about it. The TH400 is about 4" longer, so the swap requires the cross-member to be moved and the driveshaft extended. For info on the trannys http://www.novak-adapt.com/knowledge/transmission_gateway.htm

If you don't get all your questions answered here, you might try the 67-72 board. http://67-72chevytrucks.com/vboard/
But there are some sharp people on this board.

From a cornfield in central Nebraska? I've probably driven by your place.

Thanks FredT
Who you workin on airframes for? I'm engineering for Hamilton Sundstrand(used to be Sundstrand Aerospace)in York. I went to the sites you suggested and think I can get some help there.

The 700 is a considerably lighter-duty box than the 400, but it's got overdrive and a lockup torque converter. There is a modern, overdrive-equipped model of the 400, don't remember the designation, but I think it's computer-controlled, and it's a tough swap to make. GM uses it in their motorhome chassis, behind the 454 engine.
Jerry

Jerry,

I believe the later transmission you're talking about is the 4L80E-and yes, it looks physically identical to the TH400. Until you see all the wires hooked up to it... :o

Actually, a 700R4 can be built pretty stout, or you could just buy a complete performance rebuilt one from B&M or other such suppliers. They also have available electronic control modules to allow these newer electronic transmissions to operate properly as a "stand alone" unit-i.e. not connected to an engine control ECM, allowing use with an older carburated engine.

Crash, if you're on a budget and not racing or doing any really heavy hauling, a rebuilt 700R4 with some tweaks and upgrades should work O.K. for you.

Welcome to The 'Bolt, BTW. This is a great place to find out lots of info on these old GM trucks, glad you found your way here.

Regards,
Wannabe