After the rear diff u-joint detonated, I replaced all u-joints, center bearing, rear pinion flange, and diff oil seal. I was trying to adhere to the "count the revolutions off" of the rear flange nut when putting back on the new flange, but of course when I couldn't hit the 17 counts (could only make it to 16.5), I assumed something was wrong. It's been pointed out to me that the thread counting only applies to re-installing the original and not a new yoke..........having said all that, I now have a whine only during de-accel in the rear end. It sounds exactly like a mud tire sound, but I haven't changed tires, and again this is only during de-accel...............therefore,

1) Just exactly what makes that whine? I know sound usually comes from friction, so is there something chewing inside the diff?
2) Is this a "STOP THE TRUCK AND DON'T MOVE" issue until I get it resolved?
3) Is there an absolutle value that is to be obtained when setting the pre-load on the flange nut, or are you supposed to only go to the value it was before the nut was removed? If this value is not known, then what?
4) I felt of the diff casing up by the bearing to see if I had over-tightened the flange nut causing the whine to be from the bearing, but it's not hot, and after all, aren't you supposed to use 300-400 lbs to crush the washer, which is way more torque than I was applying to the nut?
5) I intend to take it to a tranny shop for setting of the pre-load only.......what should be a reasonble cost for someone to do this? I figure if it needs to be over $100, then I'll just mess w/ it more myself......

Thanks for any input you might have,
Rod

 

Stop driving. You're pinion bearing doesn't have enough preload, meaning you didn't get the nut tight enough. You are supposed to tighten it until there is a spec amount of rotating force which you measure with an in-lb dial torque wrench. Counting revolutions is never an acceptable method to me, even with the original parts going back together. To set it up properly now you need to pull the carrier and measure the preload, then tighten until it is within spec for a new bearing or used bearing (whichever you used), then reinstall the carrier. For it to be done correctly, expect anywhere from $150-300 if no new parts are required. Chances are they'll put in a new pinion bearing since yours may be scored up from being loose.

 

ah, OK - thank you VERY much for your reply......

I was afraid I had OVER-tightened it since I was hitting ~180 ft/lbs on my torque wrench, which wasn't making sense since there's that 300-400 lbs for the crush washer. It sure seemed like I was hitting a brick wall while tighteneing it.....pert near snapped a (cheap) 14" breaker bar trying to tighten the nut.

 

You probably came up against the crush sleeve, but didn't crush it any more. When I did mine, it took a 3/4" drive breaker bar and a 3ft cheater with my 210lbs on it to crush the crush sleeve.

 

Just how many teeth could you knock out w/ a slip of that?!

So if I was hitting the crush washer, wouldn't that be where the preload should be?........but then again, if that's the case, then why the whine..

 

Well, lets start over just to be sure we covered everything. You lost your rear u-joint and it wiped out the flange, correct? So you replaced the flange, did you replace the pinion bearings? If you replaced the pinion bearings, then you should use a new crush sleeve because the bearings could be slightly different.

 

good point......sorry for the gaps in information! BTW - this is a late year '99 F250, and stock as stock can get.

ok, I started noticing a good vibration after about a 1200 mile trip. It was most noticeable between ~30 to 60 mph. I hadn't at all noticed the prob during the trip, but w/n a couple days of being back, it was very evident. I assumed it could be a tire out of balance, so I had the tires rotated/balanced. I ran it a few days like this (maybe 80 miles total), I then hooked up a 16' enclosed trailer and made it about 8 miles before the vibration turned into an earthquake. I was able to limp it home @ no more than 10mph -- any faster and the shaking would displace my teeth. When home, I noticed the rear u-joint had one cap completely gone off the stud, and it was free to move a good 20 degrees in the yoke. The Yoke wasn't actually completely destroyed, but there was a deep groove in it where the missing cap had once sat as well as the cap stop tab was completely gone. The end of the driveshaft was fine.

I replaced all 3 u-joints and the center support bearing from the transfer case back. I as well got a new yoke and nut but did not get a new pinion bearing since the destruction of the yoke wasn't quite as bad as I might have led on.

After cleaning up the outer pinion bearing and replacing the oil seal, I started pressing on the new yoke via the new nut. It seemed like a forced fit the whole travel of the pinion nut, I'm assuming from the new loctite on the new nut. After hitting ~16.5 turns of the 17 I thought I should go, it seemed like I, as you stated, hit the crush sleeve. I was using a small breaker bar and being also 220lbs, I was nearly snapping the breaker bar. I backed the nut back off, cleaned up the threads, applied new loctite, and tightened the nut back down. I was just thinking perhaps I had lost count (yeah, I know ........ getting lost counting to 17 is probably an indicator I shouldn't have started this on my own in the first place!......), so I threaded the nut back down and again hit the brick wall. I borrowed a buddies 2' SnapOn breaker and put some pain on it. I knew I didn't want to flat out pull as hard as possible as to not crush the sleeve any further.........I then used my 1/2 torque wrench and set it to 180lbs. I was hitting the clicker on the torque wrench at definitely a lighter torque than what I was applying to the nut previously. I assumed from that point on it must be tight enough. It was right after this that someone pointed out that the new yoke could definitely be a different dimension and therefore a different depth for the nut rotation count. When test driving the truck, I then started noticing the slight whine when de-accelerating. The sound was most prevalent around the 50 down to 20 mph range. There was no feel of vibration, just the sound. And again, it sounded just like a big mud tire might sound, but again only during de-accel. When any load was put back on via the accelerator, the sound completely silenced.

One other thing, after I had tightened the yoke nut, I felt for any movement of the pinion, and there was no in/out or up/down movement. I also felt of the case right around the pinion bearing after drivng a few miles and it was barely warm..........

Probably a bit more of the whole story than needed, but I think I've included every detail I can remember. The u-joints are Spicer and the new yoke is Ford OEM......

 

Well, whine on deceleration is a sign that the pinion does not have enough preload. There is the off chance that the carrier bearing could have started making noise at at the same time, but I would bet its the pinion. What needs to be done is the carrier pulled and the pinion preload checked to see if its in the range of a used bearing and tightened if need be. If you don't have the tools to do this (good dial in-lbs torque wrench), I would recommend you take it to a shop that is experienced with differentials work. I've only done this once before, but disconnecting the driveline, removing carrier, and checking preload would only take me a few hours, so it shouldn't be too costly at a shop with experienced mechanics. BTW, all my knowledge on this subject I got from reading the Differentials book from Randy's Ring and Pinion before I changed gears in my '03. It was a great source of knowledge and my gears turned out great. If you want to tackle more differential issues in the future I'd recommend you pick it up. Best $22 I've ever spent.

 

I will certainly pick up the book! Thanks for the referral and all your feedback!