Rebuilding the rear end

[F100builder]

No problem. It covers both open and locker differential rebuilds, the torque specs and preloads for new vs. used bearings, and even shows how to get the axle bearings off and problem areas to carefully inspect. Good stuff.

[Darrman]

Well, I finally got the axle apart today, what a stinkin mess, . Love that old gear oil smell.
Anyways, turns out one of the wheel bearings is toast, falling apart and sqeals when turned. The other side has been replaced at some point, but I am going to change both, along with the seals.
As for the gears, they are tight and smooth as glass to turn. I looked them over good and see no wear at all. So I am just going to replace the pinion seal and stuff it back in, after a good cleaning.
I finished stripping the housing and cleaned the inside out real good, got all the old oil and sludge out.
I did not find any shavings, or signs of wear anywhere except for the bearing.
I picked up the new parts this afternoon, and will go get em pressed on Monday.
By the way, I cannot find the gasket that goes to the pinion housing. I found the one for the main housing, but nothing for the other. I will make one with gasket maker, but does anybody know the name for this gasket, or who sells one?

[F100builder]

There is no gasket for this. The pinion housing should have an o-ring to seal it that will recess down into the main case. DO NOT USE A GASKET!!! The pinion is shimmed which allows you to center your gear mesh from pinion gear to ring gear. You need to be careful not to damage these shims and should reuse them to set your lash. I STILL do not recommend replacing your pinion seal without replacing your crush sleeve and pinion nut and resetting your bearing preload!

[Darrman]

Thanks for the heads up, I picked up some crush sleeves today.
Where are the shims at, I took the pinion apart today and dont see any kind of shim, except for where the pinion housing bolt to the gear housing.
I did order a o-ring today also.

[F100builder]

That should be it. It looks like a thin metal gasket. There is typically more than one but there may be just one. I've never seen 'none' before. The torque should be 8-14 INCH-lbs. for used bearings and 16-29 INCH-lbs. for new bearings. For example, when the pinion nut is tightened down with USED bearings, your torque wrench should 'click' when set at 8-14 inch-lbs. but actually TURN the pinion (while the pinion housing is in a vise) when set above 14 inch-lbs. and NOT 'click'. If it clicks at say, 20 inch-lbs before it turns the pinion, your preload is too tight and you will need to start over with a new crush sleeve. It's really not too difficult but once you get the nut pretty snug, you take 'baby steps' until you're between 8 and 14 inch-lbs. (assuming you're reusing your bearings). Hope this is clear enough. It's kinda hard to explain.

[Darrman]

Well, everything is ready to go back together, got the new wheel bearings pressed yesterday, new seals are already installed, and managed to free up the vent finally.
All that I need is to set the torque on the pinion, but I dont have a inch pound wrench, so I will have to wait to run to Sears so I can get a Craftsman (all my other torque wrenchses are Craftsman).

One question, how do you usually reinstall the splined yoke back on the pinion? I am thinking to heat it up so it will just drop back on, instead of knocking it back on or something.
Thanks!

[Darrman]

I am looking at torque wrenches, and all that I see start at 25-30 inch pounds. How do I set a torque that low?

[James72]

When setting any bearing it's a rolling torque so useing a klick type torque wrench is difficult, I recomend a dial type. It may take over 50 in/lbs to get it rolling and have 20 in/lbs rolling, so if you set it to 20 to get it moving you may only end up with 5 rolling. Also be sure to put some gear oil on the bearings before you start. You also should rotate the pinion a bunch of times then check it again too. As for diff gears a quick way to tell if they are failing is to take a little oring pick and see if you can catch any pockets on the face of any of the teeth, if you can they will fail soon. When I rebuild diffs I can spend hours inspecting all the gears, so be sure to take a good look. The same goes for bearings, you have to know what you looking for when inspecting them, what may look fine on a quick look, could be a few miles from disaster to the trained eye. I would also recomend reading a failure analysis book if you have any doughts or if you're curious, it's an interesting read.


James

[Darrman]

Hmm, I am not sure what you mean by a rolling torque. How would you be able to get reading while its turning?
Thanks!

[James72]

You put your torque wrench on the yolk nut and turn the pinion at a steady slow rate and read the dial to see how many inch lbs it takes to keep it rolling, like I said, it will take more to get it moving but the reading you care about is the rolling one. This is also done with out you axle shafts in or diff carrier. I know your not pulling your diff to set your pinion, so I would go to the high side of the torque range to offset the resistance of the carrier and you should be fine, but do have your axles pulled cause those bearings and brake drag can really add up.


James

[averagef250]

Never ever use a click type torque wrench to attempt to measure bearing preload. Click types are not made for this type of work at all. The are made for static torque, not dynamic loads like preload readings.

You need a dial type or a bent beam type like James suggests. Clickers will not work at all for this. You're better off just guessing than using a clicker. The size of torque wrench you need to to measure light duty differential bearing preload is about the smallest lever type torque wrench you can buy. Mine is only about 10" long and goes from 0-60 inch/lbs.

If you measure the preload before, replace the seal and tighten the pinion nut to duplicate the same or slightly more preload you do NOT need to replace the crush sleeve.

[Darrman]

Well, it looks like I have a problem. I put the brake backs and shafts back in today, after finally painting the whole thing.
The one axle went in without a problem, but then the other has some issues. With the axle fully seated, the bearing is sticking out a 1/8 inch, and on closer inspection the the plate that holds the bearing in is bent at all four corners, meaning that this has been a problem all along. I only hand tightened the nuts, so I did not bend them.
The shafts do not match each other on the ends, so I am guessing that this one has been replaced, and it may be too long? The axle has become hard to turn as well, requiring both hands.
Any ideas on what to do? The plate is probably toast, either way the bearing would have to be pressed back off to fix it.

[James72]

Just a thought, maybe they are in the wrong sides? I don't know about these trucks but some have slightly different length axles from side to side. Worth a try anyway.


James

[Darrman]

Yup, that was it. Seems the P.O did the same thing and tightened it down, bending the plate. I swapped sides and fixed it right up. The axle turns real easy now.

[James72]

Good to hear