Difference with type f versus dexron III

[OneLethal87GN]

I want to change my fluid out from dexron III to type f and was wondering what difference it would make. I've heard that the type f will firm up the shifts a little, but how much is a little? I have a rebuilt tranny with a heavy duty 2nd band and Bruce's shift kit. It shifts nicely from first to second and a little firm in the other gears. Will the type f fluid add even more firmness? I'm not expecting a huge difference or anything. I just need all the help I can get because it is the tranny out of my 85 GN that's in my 87 GN. One last thing... my car has a problem going into 4th gear. I have to let off the gas for it to shift into 4th. Either that or I have to get the rpms way up there for it to shift itself. I was told that the valve body had a little to do with it and I needed an 86-87 valve body put in my 85 tranny. True?

 

[turbo nasty]

Type F made my TCC start to chatter. Changed back to Dex 3 no more chatter. Did not shift any different, either.

I asked Art Carr himself and he said that it was not needed until 500 hp or so.