RALPH, LIKE I SAID...and Monte who's opinion about pinion should be agreed.

Slap the driveshaft in, check the angle against the diff yoke. Make sure you have at least 3 and go cat go. Bet it works better at 5

As for pinon having no effect in traction/hit with leafs or ladders, that's keyboard cowboy crap. It does help, and that's from actually adding pinion till it bites in SEVERAL cars, not watching engineering videos, and imagining what it must be like to go racing.

Like Monte said chassis cars are another deal entirely. I have an RJ car that only has 1.5 pinion, but the driveline is straight at the pinion. My ladder car has 6.