How many pound-foot (or Newtonmeter) torque will you tighten the nut that holds the pinion to the cardan axle?
For what it's worth, John Regan recommends 70 foot-pounds for the drive shaft nut after installing his pinion bearing conversion kit. Not sure what the original spec was; don't think they used torque wrenches when assembling at the factory back in the day.
OK - I gave it 50 foot-pounds - hope that is enough to prevent it from moving on the conus and breaking the key and not enough to break the pinion. So far a few miles have not given any problems and the rear has same amount of noise I think as before.
A grade 5 5/8" bolt calls for 150 ft. lbs. I would say that this is closer to the right torque for a Model T pinion nut.
70 ft lbs should be fine. The narrow nut does not have as many threads as a 5 5/8 bolt. If you over tighten it the threads will strip. If you under tighten it, you could have a loose pinion gear and mess up the slot in the shaft, or break the key. Or you could have a gear wobble and break teeth.
During the 2008 tour in Richmond, I lost drive on the last day as I drove into the RV park. When I arrived home I stripped the rear axle and the nut was loose and the key broken. Experts told me I had not tightened it enough. As I remember I used 50 lb/ft.
So on replacement I used 70 lb/ft and then moved to the next castle to line up the hole. Just as a matter of interest, I checked the torque, it was 105 lb/ft. Still runs and has not come loose.
I would recommend 70 lb/ft as a minimum.
In one of the books I have read a suggestion to rap it with a brass drift and hammer to make sure it's seated, then check the torque again. Go around the face as close to the nut as you can keeping the drift flush to the face.
I just now finished my axle rebuild using the Fun Projects roller pinion bearing assembly. I torqued the pinion nut to 70 ft lbs. I then removed the nut to make sure the pinion was stuck on the shaft which it was. This did not occur until it was near 70 ft lbs. 50 ft lbs is not enough!!! I finished by moving higher in torque in 2 lb increments to line up the cotter pin hole. The hole did not show up until I reached 96 ft lbs. You must do 70 plus the cotter or you will regret it, I can tell. My axle assembly seems perfect and will be going in the car tomorrow.
I would wager that the T pinion nut is more like a grade 8 nut. It is important that the pinion drive on the taper and not from the key. I have never stripped out a nut tightening it to 150 ft. lbs., but I have seen pinion gears split open from driving on the key. More than once.
Couple things. First one is the new nuts the vendors -- or most of them sell -- are grade 5 at best. I've stripped a couple of them. Use an original Ford one.
2. Make sure you are using a correct key. The standard Woodruff key and some replacement keys do not have the correct height. Too tall will hold the gear slightly off the taper.
I stand the driveshaft on end, take big 3/4 drive socket and a bfh and smack the gear several times to seat it. Then I put the driveshaft in a vise, backup with a pipe wrench on the shaft and hang all 275 of me on the end of a 15 inch wrench. I smack the wrench with the bfh while I'm hanging on the wrench bouncing up and down. I dunno what torque torque that is.
I've never torqued one. I just tighten it as tight as I can, and line up the cotter pin hole! Stan is correct on the woodruff key. Try to use an original.
I do pretty close to what Stan Howe says, except I have an old cracked rear drive shaft race that just fits over the drive shaft with out touching the threads. I hit the end of the race and then tighten the pinion gear. I do this several times. that way I do not damage the THREADS ON THE DRIVE SHAFT.
SIDE BAR: One time many years ago I was in Central City, Colorado in a speedster. I began hearing noises. I didn't know what it was. You have to understand the entire town of Central City sits on a very steep hill. Just as we were leaving the City Parking Lot I suddenly was in NEUTRAL. I knew the emergency brake was near worthless because I needed to shorten the rods but had not got around to it. I told the wife to hold on as we were going to go for a ride. We ended up down in the town of Black Hawk. I saw an empty parking lot that was slightly up hill and pulled in and finally got the speedster stopped.
Believe me it was a relief and after that I used the method above to set all my pinion gears and made sure that I have a good emergency brake.