i just did my clutch and tranny swap... well, the tranny grinds if you shift into 4th hard, and it grinds some times on hard down shifting into 3rd, and doesnt like to downshift into 2nd unless you rev match.
it also likes to pop out of 3rd if you pull on the shifter any when off the gas.

its miles better than my old tranny and i dont want to do another tranny swap, it was a bitch and i need the car on the road.

so how much of a difference would redline make? im running super cheap fluid, plus the trammy sat a while with no fluid, might it smooth out after a few hundred miles?

 

Use royal purple, it's better than red line. It will help with some mild gear grinding... but from what your describing you need a transmission rebuild. My advice is try the stuff and see what it does before you rebuild the trany.

 

Redline does not help grinding. If you take advantage of Redline's ability to help you shift faster, you might find that you're able to make it grind more. Royal Purple should help a little. So can Neo or Mobil 1. I'd go RP or Neo. And always rev match even on the gears that aren't toasted yet, so you can go easy on the synchros and squeeze a bit more life out of those gears.

If your cheap fluid is GL-5 or if it contains sulphur or smells of eggs, then change it out ASAP. It'll eat through your synchros about twice as fast. Worn out synchros are what force you to rev match. Most cheap oils are GL-4, though, and not all GL-5 has sulphur.

EDIT: (for below) If your tranny oil is liquid gold, then you could sell it to buy a new tranny :P. Nothing will fix the tranny, the above will just soften the problem a little and help you squeeze out a bit more life as you run the tranny into the ground.

 

If your tranny is fubard liquid gold wouldn't fix it.