hypoid ???

i have been a mechanic my entire life. most of my education has been learned from the school of hard knocks, though i have been to many new model updates and several specialty tech (one item) schools. i have set up at least a half dozen ring and pinion gears / rear axle rebuilds, all of which were sucessful. but on just completeing one for myself (and trying to teach my kids how to do this) i came across a question, that i did not have an answer for. kids seem to be great at doing that. i know it is important to have enough preload on the pinion bearings. but why? and why so much? the specs for my truck call for 15-20 inch pounds of drag. which seems to be a lot to me.

Obviously the bearings must engage the race sufficiently to handle the load and eliminate any play which would affect backlash and tooth contact. There has to be some tightening spec to achieve this and all pinion and side bearings in the diff require some pre-load. Also after break in and some use they will loosen up so with no pre-load you would now have poorly fitted bearings.

thanks maxwedge. i had not even thought about things loosening up after break in. i got it all the way together, and took the first 1/4 mile test drive. i have a few issue i have to take care of. one of them, is i tried bleeding the brakes by myself, which is not good enough to drive safely. i did not figure it would work, but trying to get help is hard right now, so it was worth a shot. the other is now, the locker rear end acts like it is permanently locked. trying to make a turn on pavement results in the inner wheel sliding and the rear end kind of hopping to get caught back up. i did not disassemble any of the inner workings during the service(Eaton G-80 Gov-Loc) it should not act like a locker all of the time. while i did not tear down any of the inner workings of the "locker" differential or clutch packs. but they did get washed repeatedly in kerosene to get everything clean. i am hoping the first drive where things get warm to operating temperature, will re lubricate all of the friction discs and plates. and that things will work normally again. other than dealing with shimming things to get the gear pattern right, nothing gave me any trouble during assembly. its the only thing i can think of.

Drive in tight figure eight turns in a parking lot somewhere, if the locking diff doesn't release it is bad, and they have been known to do this,

well, i started it up this morning, and ran it on jack stands. i used a propane torch to help thin the oil out by warming it up. the right rear axle is locked all of the time. it never releases. the drivers side, will momentarily release, until the play in the system is taken up. then it locks solid as well. i opened up the pan, to take a look, the last thing i need is to explode parts. i have not yet figured out why this is happening. i did remember that i tried to take the shafts out that make the system operate. i was going to take the clutch pack apart, to see if anything needed replacing. i had forgotten i had tried to do that until i was thinking about it last night (around midnight). when the shafts did not want to come out after a few swats with a hammer and punch, i stopped. both shafts still turn (i just checked), so i do not think i caused a problem there. all 3 counter weights operate freely. but as soon as either axle is turned, the clutch packs actuate, without either of the counterweights turning at all. this does not seem right from the video i watched on youtube. a real manual would be nice. the Haynes manual does not even address this at all.

The locking diff is governor actuated by a 100rpm difference in rear wheel speed left to right. They are not repairable.