swapping 400 trans from a 350 trans 1971 c20 question

[zacharywest34]

So ive never swapped a trans before but everything ive read about swapping in a 400 from a 350 trans is that the 400 is shorter so i will need to move the trans crossmember? Also im guessing i have to get a slip yoke for the 400 as well, but for the driveshaft it will obviously be too short what have you guys done with yours? just buy a new one or take it to a driveshaft shop? Anything else i should know, everything helps.
Thanks

[hugger6933]

yes on everything . Slip Yoke, yes you need a new one. Driveshaft yes you need a new one. Yes you will have to move the crossmember but the hole will be there.That isn't at all a bigge cause you have to take it out anyway and when putting it back it will go where you need it. Also your gonna need the TH400 kickdown switch it is electric.

[kwmech]

Turbo 400 is longer than a 350. Yes you will have to move the x-member back to the next set of bolt holes. 400s usually have a fixed yoke, so a drive shaft modification is necessary. Cooler lines are the same, speedo cable should be able to fit. Shift linkage will cross over.

[zacharywest34]

for the kickdown ive never ran one on the truck is it essential to have, what does it exactly do ive never understood those.

[Bigdav160]

It won't kick down to a lower gear when accelerating (like passing or going up a steep hill).

You could do it manually with the shift lever though.

[zacharywest34]

Ok that makes sense. would the flexplate work with the 400 that i used on the 350 i think that would be the only other thing

[AussieinNC]

Have you considered a 200R4 instead of the T400?

Same length as a T350...same yolk spline...no need for new tailshaft...

and You end up with overdrive....

Unless there is a monster engine in front of it, a well built 200R4 is a much better way to go, in my mind anyways...

[zacharywest34]

No never thought of it, ill look into that thank you all i want is a 4 speed or more trans that can handle 300 hp

[AussieinNC]

200R4 is the way to go then...just make sure its in good condition...

Google "200R4 performance rebuild"....

There is a good selection of parts available...

350 flex plate will work as well...

[zacharywest34]

ill look at that, i also forgot about the 700r4 anybody know how that install would go from a th350

[mjshealy]

I would honestly go with the 400 if you aren't highway driving, they're a lot tougher than a 200r... It all really depends on how you are going to use it. If you want some better gas mileage, do a lot of 55+ mph driving, and you have a light gas pedal foot, then I agree with Aussie. If you will be towing/hauling, heavy on the gas pedal, and just cruise... And don't have radical gears, I would go with the turbo 400. I'm biased though, I've never been able to blow up a turbo 400. WHICHEVER ROUTE YOU GO, I would rebuild the trans first if it's used, but as a minimum always replace the torque converter, input shaft seal, and flexplate. If you're on a budget B&M sells a 2000 torquemaster converter for around $200, I've had great luck with them. New iridited flexplates are pretty cheap too, through summit.

[zacharywest34]

Ya i normally just do around the town driving nothin on the highway really

[old51sedan]

Originally Posted by zacharywest34

No never thought of it, ill look into that thank you all i want is a 4 speed or more trans that can handle 300 hp

I totally agree on the 200-4R! I have one all ready to go into my truck as soon as the motor is done. All you need to do is move the trans mount back, trans is the same length, so drive shaft will bolt right in, yoke should be the same, you will need a TV cable and you should be ready to go with a 4th gear.