I'm not very familiar with auto's but am leaning towards a TH400 because it seems to be capable of handling a lot of torque when modded, is light and plentiful. It's for a 427 turbo engine in a retro installation. I know a TH350 fits my chassis. Does anybody know if the TH400 is of similar width to the TH350 in the centre section and is it a stronger box then later GM offerings? 4L80's seem really heavy. Thanks.

 

Street car or race only car?

If race only, then TH400 is a mistake. Aftermarket powerglide transmissions are a far better choice for anything less than 3500 pounds in a drag race only car.

If you are going to drive it every day, then the 4L80E is a much better choice than a TH400. OD and lockup converter make a much better street transmission.

 

Thank you TT. It's a road car (Triumph TR7-v8) but very little road use maybe 1000 mls pa maximum. I want to drag race it to get use out of it but retain road car options. The T56 only just squeezes in the tunnel so I need something no bigger then that. I know the 350 fits hence my considering the 400. The 'built' 4L80E I saw the other day looks good but was expensive. I've no idea if the 400 is the stronger box and am aiming for 1000 hp or thereabouts.

 

if your looking cheap and dont mind winding the motor while street driving it th400 with a trans break

 

The trans brake is the bit that excites me