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Discussion Starter #1
I am replacing the drive shaft seal on the rear end. I had shaft off, nut off slide the plate that the drive train bolts to off. All was going fine. Emptyed the gear oil out. Wanted to clean the rear end so I slide the plate back onto the shaft comong out of the rear end....did not put the nut back on (possible bad move) and rolled it out of my garage backward 20 feet. All still fine. Jacked up rear end with jack on bottom of rear end (was this bad?) cleaned rear end. Jacked up rear end to take off blocks, lower jack....starter to roll it forward into garage. It moved about 10 feet and felt like some one put it in gear, locked up.

I jacked it back up....the wheels will spin but I can not turn the shaft plate.

What in the world did I just do?
 

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Discussion Starter #2
Additional information......looks like the pinion shaft has slide back into the assembly about 1/4 inch. Is this fixable by taking the lower cover off and moving it forward? Could it be that simple. Anyone ever been inside one that could shade a bit of light on this?
 

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If I understand you correctly, here's what happened. You have simply disenguaged the pinion gear from the ring gear. When you rolled the car backwards, the pinion was pushed forward - out. no problem. When you rolled the car forward, it pulled the pinion in and jammed it into the ring gear, locking everything up. STOP now, do not apply any force, or you will damage the ring gear, or pinion or pinion bearings. To correct the problem, reinstall the pinion nut, and tighten (not all the way) firmly enough so as the car (on its wheels, not in the air) can be rocked, gently, backwards. Both rear wheels must be turning the same direction (backwards) at the same rate. With luck, you will hear a clunk as the pinion once again enguages with the ring gear. Then tighten the pinion nut further and check to see if it is now free.
I have been using the differential bottom as a jacking point for 45 years with a soft wood block. No problem. However, IF you had the old seal out when you washed the rear end, you have most likely introduced some moisture into the case. You should probably replace the gear oil at least twice after driving it until the diferential is hot, maybe 50 - 100 miles the first time, and then again at about 500 miles. The moisture usually cooks out and vents the half shaft breathers, but if not, it can eat up the bearings.
Look for a foamy or milky color to the otherwise clear yellow spirex as an indication of moisture. Be SURE to use the pinion flange holding fixture when re torquing the pinion nut. Incorrest preload (torque) on the pinion can cause all manner of nastiness. Gordon Raymond
 

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oops, i did this very thing on an early model mustang and both the ring gear and the pinion gear were chipped, unusable and junk... Follow the advice above, hopefully this won't be the case for you. Let us know.
 

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With an old differential, chances are that the pinion bearings are worn quite a bit. Don't be surprised if when you torque the pinion nut to spec, it will make the preload way too tight. This happened to me and I had to back off on the torque a lot in order to get an acceptable preload.
 

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Discussion Starter #6
Gordon

What you suggest is what my thoughts were on a fix. If I take off the bottom cover can I see the position of the pinion in relatioinship to the ring gear. I might be able to tell if I chiped anything. I was pushing pretty slow and not much force (wishful thinking maybe).

Roadtrip

My 88 has low miles so hopefully what you mentioned will not be the case. Explain preload to me. I this the resistance on spin of the pinion shaft?
 

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The pinion runs on a tapered roller bearing. Tapered roller bearings must have preload to live. Too much preload will cause binding in the bearing and premature wear, excess heat, and could possibly take out the bearing in less than 100 miles. If you have too little preload, the bearing will have too much slack and the pinion will jump around on the ring gear probably chipping both gears. Preload is the amount of pressure that the tapered bearing exerts on the outer race.
 

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Dis-Rail-E Gears

alfa88grad said:
I assume preload is controlled by the torque on the pinion nut. Is this right? If so how is it measured?

My photo attached shows the hole in the bottom casting through which you should be able to make an inspection of pinion gear. Because the gear on the pinion has such a pronounced taper, I doubt if it backed up much or if you chipped it -although, the gear set are quite hard. The pinion and carrier preload and backlash is accomplished with a sophisticated set of ALFA Special Tools. You won't be able to do that, and you don't want to anyway. I think you should torque up the differential nut to about 65 foot/pounds, flush the inside well with kerosene, and put some grease back in. If you stain the kerosene with a coffe filter and find metal particles, flush it again. Hopefully, you won't. Incidently, the factory spec for torque is 58-100 foot/pounds. :(
 

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Excellent!;) Bud knows! You can see from his photos why one does not want to experiment with pre load unless one has the tools! You can also see from his photos the difficulty in "seeing" the position of the pinion with the bottom removed. When the pinion is "lost" unless force or a lot of vehicle rocking has happened, the ring and pinion most often remain intact, no chipping. Removal of the bottom cover will aid in washing things out with kero and a turkey baster or whatever, and watching for chips in the flushed residue. Bud's 65 Ft/Lbs is the number I use without owning the tools. :D Gordon Raymond
 

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alfa88grad said:
I assume preload is controlled by the torque on the pinion nut. Is this right?
No. The pinion bearing preload, and pinion depth, are adjusted with shims at the front and rear pinion bearings. The pinion nut just holds everything together although the preload can not be measured unless the nut is installed and torqued.
 

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Discussion Starter #12
Thanks for all the tips.....pictures help. I heading out now to try and get the pinion gear back in place. I will keep you informed.
 

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I hooked the rear of the car to a come along and gentle tugged it backwards. With slight pressure the pinion gear popped back into place. I will fush, filter and look for chips.
 

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Great!:D Hopefully, you won't find any chips. Your situation is one I have helped others with, and the clunk, as the pinion was shoved forward, was rewarding.:cool: If there are chips, they are usually aparent as they are considerably larger than the fine metal "dust" that collects on magnetic drain plugs. Good job. Don't forget the 65 + Lbs torque on the pinion flange nut to set the pre load. Gordon Raymond
 
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