'68 300

Ok I'm having an issue. I had the rear diff apart and cleaned it up. I put it back together exactly like it was (made marks, took pics, and did all the backlash requirements etc.) When I go to put the 240 ft/lbs torque on the pinion flange nut, it pretty much stops the pinion from turning at all, like it tightened down and won't move. Do I need a new belleville washer? Other sites say you can reuse it. What am I doing wrong?
 
Ok I'm having an issue. I had the rear diff apart and cleaned it up. I put it back together exactly like it was (made marks, took pics, and did all the backlash requirements etc.) When I go to put the 240 ft/lbs torque on the pinion flange nut, it pretty much stops the pinion from turning at all, like it tightened down and won't move. Do I need a new belleville washer? Other sites say you can reuse it. What am I doing wrong?

Sounds like you have a 489 case with a crush sleeve. If so, you've got a problem.

Check the side of the diff housing for the casting number. If it ends in 489, head over to YouTube and find some videos on crush sleeves.

Jeff
 
The standoff valve (triangle shaped one) is not needed. It was to allow pressure to get shoes out to the drum in rear while holding pressure off of front calipers. This was done at low pressure/low traction conditions. It has no effect on normal to panic braking. Omit it except 1000 point resto car.
The offset block with flat cap on the one side is factory proportioning valve. Little to no difference across car lines so effectiveness is suspect and better replaced by adjustable one, which you should make the effort to set by panic stopping the car a few times, wet,open parking lot works best for this.
240 ft/lbs. is way too much torque on pinion nut. Low 100s to maybe 150. You may have crushed the crush sleeve too far.
 
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I wasn't able to get the full 240 on it. Not even close to be honest. I guess I should mention that the whole axle is out on stands. I stopped tightening when it stopped moving. The number on the case is 2070742.
 
I only tried to go to 240 because thats what the manual says. But I don't need to?
 
Also, with it all together, when I spin the pinion the axles (wheels) turn, but if I spin the axles the pinion doesn't. Shoulda never touched it.
 
I'm really sorry about all these posts guys, just trying to make sense of all this. So, ill try to explain what I got. With the pinion held in place(hand holding it), both axles spin in same direction( either forwards or backwards). With the pinion free, if I spin either axle the pinion turns and the opposite axle starts to turn backwards(but only just a little bit). Im just stuck on the fact that when the pinion is held in place, the wheels turn. I mean if the car is in Park , won't it just roll away?
 
When the tires are on the ground, one axle can't roll the opposite direction of the other, therefore the car won't roll away when in park. What you describe sounds normal for an open rear. It wouldn't be ok if it were a Sure Grip.

As far as the pinion locking up when you try to tighten it. Is it possible that you lost one or more of the shims that go between the pinion and front pinion bearing? Or could you have put them back in the wrong spot?

How far apart did you take things to do the cleaning?

Jeff
 
I did not remove the shims. I only took apart the adjusters, bearings and races.i kept all the races in the case in place (I knew I wasn't going to replace anything, yet). Thats it, cleaned up as few individual parts as I could. Replaced the seal and gasket. The crush washer before the pinion nut was totally flat. I didn't know it was a belleville.
 
Ok, then we'll have to continue tomorrow, as I won't be around the computer for the rest of the evening.

Jeff
 
If you were to remove the ring gear/diff case assembly, then try to tighten the pinion nut up to 240 ft/lbs, you are saying that the pinion would lock up and not turn?

Jeff
 
Nope, im saying that after its all back together, it all seems perfectly fine ( turns, no abnormal noise, good backlash, etc). As soon as I put on the crush washer and nut and tighten em down, they're fine until it hits a certain spot, then seems to tighten the pinion gear so that it locks up. Like its tightening the flange against the case, seizing it all up.
 
Did you touch the adjusters for the side bearings at any point, or was the pinion nut and flange the only part that you removed?
 
Yep, took it all out of the case. Cleaned, replaced in what I am almost sure was the same way. Made sure all parts stayed on the same side, marked em where they were and rematched it all up. Did not remove pinion races or shims
 
I think you're going to have to pull the diff case and ring gear out, then tighten up the pinion nut and see what happens. That's the correct way to do it. You're supposed to get the pinion all set up before moving on to putting the ring gear back in.

Those side adjusters are finicky. One slot makes a huge difference, and I'm not sure if you can know for certain that everything is back exactly where it was going by the marks you made.

That beveled washer isn't a big deal. It was basically flat on the rear that I just did a few weeks ago. Just hit the nut with a heavy dose of blue loctite before putting it on.

Do you have some kind of holding fixture for the flange while you are tightening the nut? It won't be easy to get to 240 with things moving around on you. Many people (including pros) use an impact gun on the pinion nut, but I don't think that's a good idea.
 
Something else to check.

The metal splash shield on the pinion flange is just pressed on and can move. Make sure it hasn't slid down closer to the spline end.
 
Thanks very much for the information/videos. When I get a chance to get back at it (working heavy overtime) I'll try all those things. Thanks again.
 
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