How tight should the fit of the pinion key in the slot in the drive shaft be? I can press mine in with my hand and can pull it back out with my fingers. Mine appears to be new and has the Ford script stamped on it on one of the flats that fit into the ujoint.
All the discussion about who has good replacement driveshafts and whos not to buy really makes me reluctant to buy a new one.
If there's no lateral movement of the key, as Glen says in the book, it should be OK. If the rest of the shaft passes inspection as described in the book, you can use it. If not, you can buy a new one from John Regan with confidence. He's a stickler for making things correctly. I would also skip the original style of pinion bearing and use the Regan version.
With used parts, that is likely. With new, have to use brass mallet and lightly tap the key in place.
But in reality, the taper fit of the pinion gear on the taper of the drive shaft is what 'locks' the gear on. The key is safety. Like a cotter.
On used parts, you must inspect carefully. Especially the end of the drive shaft, lots of torque put there from going and stopping over the years. See this one, was great in all respects, 'til I spied this tiny crack!
Had to junk this shaft.
I use new drive shafts, new axle shafts and new ring and pinion whenever doing a rear end. Don't trust old used parts for these items, even if Ford, as they have an unknown, but assuredly harsh life in that old T!
When you get the gear on, before you tighten the nut, the gear should not move concentric with the shaft. If it is snug enough not to move, tighten the nut very tight and you should be good. However, if the gear will rotate on the shaft, you will have a problem because there is concentric pressure between forward and braking and also between forward and reverse.
Tommy, you can rest easy purchasing a new driveshaft if it is one of the new Fun Projects driveshafts. I believe Lang's sells them now. All tolerances are perfect as per Ford specs. I talked to John R personally over the phone after having questions about some of the other drive shafts being offered. I had absolutely no problem with the Fun Projects driveshaft. Some of the newer ones being offered at the time (last August)were undersized on the pinion end and oversize on the universal end so as not to allow the universal-joint to slip on without modification.