Yesterday morning I decided to put in my detroit locker and rebuild my 9 inch rear. The results... Well lets just say it's a good thing I pulled it apart. I found the small pinion bearing in the case was destroyed and it had chewed up the pinion pilot. Nice. Pulled it all out and put in a set of 4.11's I had kicking around and assembled everything. So then comes the fun of setting the gears. Got it where I thought it should be and wouldn't you know I take it for a test drive and the damn truck is vibrating... Slack off on the gas and it gets worse. Ugh. Pulling the diff out is not something I wanna do again, that's for sure.
Although possible I would question whether anything inside the rearend would cause that kind of vibration.
I would be checking to make sure you got the u-joint properly installed in the rear yoke or maybe did the driveshaft got bent or dented while it was out?
Or maybe did you not tighten the pinion nut real good and tight as in 325-350 foot lbs?
Pinion nut 325-350 foot pounds, is too much. If it has been converted to a sleeve and shims 70-80 foot pounds is plenty on the pinion nut with some sort of locking compound. If it has the stock crush collar rotating torque is measured in inch pounds while setting the collar. When you are shimming to find pinion depth you can sneak feeler gages around the pinion housing in place of the shims. This will save you some time so you don't have to keep removing the pinion housing when you are changing shims.
I use an impact gun and an inch pound torque wrench when installing the pinion with a crush sleeve. Shoot for roughly 25 inch pounds to turn the pinion.
As far as I know the actual torque on the pinion nut to crush the sleeve is way up there. At least 250 ft lbs if you do it with a breaker bar etc. I dont bother anymore like I said just keep hammering it up with a 1/2 inch impact till it starts to drag. then check with the inch pound wrench.
Sounds to me like the pinion depth is to deep or to shallow allowing the gears to not mesh properly. How did you set the pinion depth?? did you use marking compound to track the gears in??
I probably screwed up the pinion depth. There was a bottle of rum involved when me and my buddy put it together. Oh well. Gonna be another 2 weeks till I can haul it apart. I've been watching youtube videos on rebuilding the axle and I think I know what I did wrong. Wost thing is I have to get it towed to my buddies garage now. $50 out the window. Oh well, betther than the price of runing a good set of gears.
How far did you drive it? Did you replace all bearings, Sounds like a Back lash problem, if thats off the whole thing is off! gear pattern, and pinion depth.
I replaced all the bearings. Had a full rebuild kit. I drove it about a kilometer, so give or take 1/2 - 2/3 of a mile. So hopefully no damage. It'll be another 5 or 6 days before I get to pull it apart.
When you replaced the bearings, did you also knock out the old races and install the new races with new bearings? If you didn't, you have scored races with new bearings, and it's like taking a shower, and putting on the same dirty underwear. LOL It sounds like you didn't get the pinion bearing pre-load right, and it's too loose. Did you check the backlash after tightening the pinion nut with the correct pre-load? That would have told you right there that something is off. Don't do the rum next time, until after the rebuild, and you will be okay. LOL If you use a crush sleeve, it does take alot to start the "crushing" of the sleeve, but stop when you start to feel some resistance, then start checking with the inch/lb torque wrench for "drag" or pre-load. On new bearings, you want to shoot for 16-29 in/lbs or if you use a solid spacer like I have, it gets torqued to 200 ft/lbs. I measured my old crushed sleeve, and set my solid spacer for the same thickness, and mine was within the spec of 16-29 inch/lbs, when torqued to 200 ft/lbs. I bought a video from this guy http://www.badshoeproductions.com/ and I have successfully done the Ford 8.8 and 9 a number of times. Good Luck!
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