Tranny to go with 400

[Dirka]

Rebuilding a 400 motor, and curious if the auto TH-350 in the truck is ok to use with the new motor.  The current tranny had be rebuilt with new torque converter according to person I purchased the truck from. I'm not doing anything super crazy to the motor but I'm hoping to be around 400+hp and 500+torque, (when compared to similar price rebuilds I've researched) and I believe it has NP205. Is this too much for the current setup? I'm not going to do any hardcore mudding, or lifting the truck or anything like that. Thanks!

[Captkaos]

The 205 won't be a problem for any power level.  The TH350 could be fine if it was built correctly.

[Irish_Alley]

yes the th350 would be good but you are left with a 1:1 ratio. from what i understand a th400 is stronger but again you are left with a 1:1.

[bake74]

      Here is a great article from Hot Rod Magazine on how to beef up the TH350 for street or strip.
      The shop in Van Nuys California that the article mentions is know for building the 700R4 trans for racing, but he started out building the TH350.

[Dirka]

What is this 1:1 ratio referring to Irish?

[bake74]

What is this 1:1 ratio referring to Irish?

     It is basically the ratio of the top gear in a transmission.  1:1 means that the transmission is turning the same speed as the engine in this gear.  The 700R4 4th gear is an overdrive transission, hence it's 0.696:1 gear.
     Here is the Wikipedia Encyclopedia link for GM Turbo-Hydramatic transmissions that will give you the ratios of the different transmissions.

[Irish_Alley]

1:1 like stated isnt od. you will get better millage with a od unit like 700r4