700r4 to TH400 two questions

[bryantreams]

Ok so I think my second gear band has completely gave up in my 700r4 and I was already wanting to go with a turbo 400 with full manual valve body. Rather than buy a used transmission in unknown condition I think I'm going to go with a new unit. I plan on swapping to a turbo 5.3 later this year and I need something to hold up to about 600 hp at the crank. The truck will see 99.9% street duty but may take it to the track once or twice (I'm not concerned with et's). So, onto the questions.

1. I think I have it narrowed down to a Rossler Terminator 1 after initially considering a TCI, B&M, or Hughes you can get from the popular mail order parts guys. Does anyone have a suggestion for a different route with a budget of $1500-1700 for the transmission?

2. I've tried searching and can't find any information on what I'll need to do for a crossmember. Can mine be modified to work with the th400 or should I fab a new one anyway since a lower ride height and dual exhaust is already an issue?

[martin_81]

a buddy of mines was running twin turbo 5.3 with a 2500 torque converter on a th400. 1st stage shift kit and that thing ran without a problem. more than possible to run a 5.3 with the th400.

[Slammed84]

I have a 400 in my 84, they're tough man. Not much needed to handle 600 hp. You could probably find a core and have a local guy build it for much cheaper. But its up to you.

As far as your crossmember goes, there are two different tailshafts on the 400, one is like four inches and I think the long one is like nine inches. Crossmember IMO really just depends on your exhaust setup.

You can fab one or use any really, just measure where it needs to be and drill new holes in the frame.

Mine is an actual 400 crossmember from a 70s 2500, which is cool because it has two humps in it for the exhaust pipes to run underneath it. Its flat unlike the 350 crossmember which is shaped kinda funky and kinda makes it harder to run exhaust on lowered trucks.

Hope this helps, look for a 70s 400 member and just redrill holes as needed. Also go for the trans mount with two bolts instead of the single hole in the middle.

[beamn7]

When I smoked my original 700 I tossed in a 400. Frame is pre-drilled already. Just moved crossmember back and lined it up. I used a truck trans which has the short tail shaft. Mine is two piece drive shaft so I just changed the front half with one that had a 400 and installed it on the original rear half. Worked great. Don't forget to install a vac line for the modulator and the kick down switch that mounts under the dash to I the accelerator pedal bracket. Bracket is already stamped to accept the switch. Just install and wire.
I've since built and installed a 700 to withstand what's under the hood and then some as I like the overdrive but you can't beat a 400.

[Slammed84]

Originally Posted by beamn7

When I smoked my original 700 I tossed in a 400. Frame is pre-drilled already. Just moved crossmember back and lined it up. I used a truck trans which has the short tail shaft. Mine is two piece drive shaft so I just changed the front half with one that had a 400 and installed it on the original rear half. Worked great. Don't forget to install a vac line for the modulator and the kick down switch that mounts under the dash to I the accelerator pedal bracket. Bracket is already stamped to accept the switch. Just install and wire.
I've since built and installed a 700 to withstand what's under the hood and then some as I like the overdrive but you can't beat a 400.

I forgot about the driveshaft issue. I robbed the one from the truck I got my 400 from along with the crossmember. I just had a local driveshaft shop cut the longbed shaft down to shortbed length. I had to drill new holes to mount the crossmember, I believe just the front holes lined up.

Another option for the kickdown switch is the B&M one that mounts on the throttle linkage. Pretty slick