How much ET loss going from a TH350 to TH400?

[johnnycarlo]

I'm thinking of swapping in a TH400 that I've had laying around, it has a shift kit and is fresh built. I'm running a TH350 right now and it has a good 7 years on it behind several small blocks and now my budget 454. How much much will I slow down with the TH400 as I have read they eat more HP and a little steeper first gear? My car runs 11.9s consistantly with a best of 11.77. On spray it has a best of 10.99 the gears are 3.55s and it has a 3500 stall and 26" ET street radial tires. I'm just curious if anyone has done this swap and what their ETs reflected after. I really don't want to go slower, but I'm worried the ol TH350 is going to give out on me one of these passes. Thanks for any info you guys may have for me.
John

 

[eharley_1]

I done the same thing last year with my bu, Everyone was telling me not to do it and it would slow me down,well i did it anyway and i never lost any et. I footbraked the th350 and i did put a t-brake in the th400 but even with footbraking the th400 my et was the same as the th350.

 

[johnnycarlo]

I done the same thing last year with my bu, Everyone was telling me not to do it and it would slow me down,well i did it anyway and i never lost any et. I footbraked the th350 and i did put a t-brake in the th400 but even with footbraking the th400 my et was the same as the th350.

That is great to hear.Nobody wants to spend 3-4 hours working on their car to make it slower......

 

[79Lemans]

I don't think you will slow down either.One thing if i remember right,i did weigh my TH400 and was 30,35lbs heavier then the TH350.

 

[85monte_ss]

th400 take more hp to turn and th350 can handle up to 1000 hp i woudld stick to 350

 

[10secBu]

I too went from a th350 to a th400 and the car did not slow down one bit.

I myself don't care much for the th350, would most likely never run one again.

Th35's are hard on bushings as they lack the center support like a th400 has which holds up the middle between the input & output shafts. Also, no way a th350 will handle 1000HP in stock form. It would take a serious amount of aftermarket parts to hold up to that much power. All a th400 needs to handle that power is an aftermarket sprag & race, and good clutches & steels and attention to detail with assembly. No aftermarket drums, input/output shafts, etc needed for the th400.