I don't completely understand the purpose of the kick down lever in the auto trans - but I know I am currently using a 5.0 lever in my 904. Engine is a SB stroker making maybe 420HP?

My question is - do I need the 5.0 lever and is there a down side to using it instead of the 4.2?

Its kitted with steel planetaries and Kevlar bands...and a Trans Go shift kit.

Try to keep it simple fellas as I'm Grade 101 in transmassion stuff.....

Just make sure the 5.0 is well adjusted as it can hang up slightly on release. the 5.0 applies the most pressure to stop the drum to shift into second.
But it is a leaver and has to travel twice as far as a stock 2.7 to apply so if it is adjusted loose it has to travel a mile to apply. nice and snug then just a 1 1/4 to 1 1/2 back off.

I personally don't like the 5.0 in a torqueflite 727 race transmission with a good manual valve body. But they can be used successfully in a 904, especially with a factory valve body and shift kit (if the kit is designed to use that lever ratio).

So, simply, if the kit calls for a 5.0 lever (904), use it. The 4.2 would be good also.

The higher lever ratio (5.0), puts more holding power on the front band (2nd gear). The side effect of that added ratio is that the band applies slower since the servo has to move farther to apply it the same distance. And that slower change to the band is also seen when releasing during the 2-3 shift, and that is the common problem (potential), with band overlap if the front clutch (3rd gear) applies faster than the front band releases. So shift timing is effected by changing the lever ratio. Shift timing is also changed by the valve body modifications.

I've never used one on a 904 based tranny, but on a 727, the 2-3 shift feels like your tapping the brake when it shifts from the band not releasing fast enough. The 4.2 works perfect.

The 904 can use the 5.0 lever. the surface area on the high gear drum is so much smaller then a 727, it needs the extra clamping force for holding power.

As for the release, as I remember the 2nd gear servo availilbe volume is much smaller then the 727, which means the same sized flow orfice will fill the hole faster (turn the band off quicker).

In the end it really doesn't matter much, as long as the direct clutch apply circuit in the valve body is timed to the 2nd gear band release. It's more in the valve body then anything...

Also, I agree 727's feel like they hang up at low speed shifts, but even with the playback tach/driveshaft recorder, I've never seen any evidence of it actually hanging up at full throttle. I mean remember, even if the band was off, the drum still has to accelerate from a dead stop anyway, so it will always feel a little harsh from the basic system design.

A local guy built my 727 years ago and swore by the 5.0 lever but when Pro Trans freshoned it up they put in the 4.2 so,

OK - thanks all for the replies.

Guess I'll stick with it and make sure its adjusted regularly by someone who knows what they are doing.