A TH400 is about 10 lbs heavier and the 10 lbs is in the rotating weight. Mostly the planetary sets.


What Im getting at is with the th400 isnt good for gas milege,its good for performance.


Anyway this thread is getting off topic back to the original posters question.carry on
r_marczak_83 says that he will be dropping in a 454 which in that case a 4L80 much improved version of the th400 with an extra gear would work out better.
If he left the original 305 with a th400 it would eat up much of that engines HP in which case a stronger rebuilt 700r4 or nonelectric 4L60 would be better suited.

 

Isn't the 4L80 electric?

 

The 4l80E is electric

 

The th400 will produce a higher % of power lost between engine and tires because of its heavier rotating assembly. You think that 305 is a turd now? Stick a th400 behind it and really find out what a turd is. Now, you could change your differential to a lower gear ratio and find some more performance to make up for the loss. Your fuel mileage is going to suffer along with performance. Your going to create the opposite of a streetable off-road rig. Your fuel mileage and cruising ability will be gone. The engine is going to labor on the street. Then when you try to go off-road your not gonna have the power to really turn the tires.

IMO, stick a TH350 behind the 305 if you really don't care for the 700R4. Or get the big block in when you put the TH400 in. Just remember, big blocks don't like sustained high rpm's.

 

Two types of the 4L80 were produced nonelectric and then the e electric version.I had a 94 chevy van rare with 4.3 behind a 4L80.