Rear end setup. Not easy is it?

I work on a lot of different gearboxes and have repaired/overhauled several different types rear axles, including banjos, all with opposing tapered roller bearings. The break away torque is always a fair bit more to get it rolling. Rolling torque is what you are after. If you have new bearings there then I'd say you have it going your way. Used bearings have to be set to the low side of specs but most folks don't go that route for automotive stuff. Setting them up with a preload ensures they won't get loose or shaky after a good bit of wear takes place. Timkens can take a lot. The rolling preload torque is different for all the different diameter sizes of bearings. The bigger the bearings the more preload you have to have. I've always set up the pinion by itself using a light oil for this purpose then I do the final reassembly after all the checks and adjustments. I wouldn't exceed 14 In/Lbs for a bearing set that size. I have a dial type torque wrench I use to do the checks. A long as you have a good preload, which it sound like you do, then it should work just fine. If it's a bit on the loose side, then it will just run cooler.
 
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Well Mart, I just don't know what to say.:eek:
All that top notch advice and now this.:) (not really meaning to poke you in the eye:)) The stuff below is for those that don't know, from someone who has never done one of these diffs: (I have done the truck 3 ton (full floating hub) axle)
Factory pinion preload is applicable to new bearings done with only the pinion in there.
If you are using old bearings you would aim for a slightly lower preload.(keep in mind that the preload is there to keep the pinion and carrier in their respective planes and place, under maximum load)
Static friction is different from moving friction. You have to first overcome the static to get it moving and then take your measurement. Ford made a preload gauge that hooks on the pinion spline or keyway. They are a little rare and expensive. The method I mentioned in a previous post works well.
When doing a diff without the special gear you are going to spend a fair bit of time doing it to get it right.
You need to get the pinion preload sorted along with the pinion height. You also need to set your carrier preload and then the meshing of the gears. This is based on a tooth mark which is taken when assembled at which time the mark dictates what you have to adjust (not possible in a Timken- covered later) Talking hypoid gears here, the old addage is: Toe or heel move the wheel, Face or flank move the crank. In otherwords if it aint right, you have to pull the crown wheel with the carrier out of the housing and generally shim or de shim the pinion, assemble it back up, reset the back lash and check it again. It is a bit of an art.
Anyhow Henry Ford tried to make things a little easier for us and (I think) he made things so that with no shims and the pinion preload done properly (With new bearings- (probably Timken? Did timken make the Ford bearings?)), that the pinion height is correct. On the big diff at least, he machined the housings so that with new side bearings and the correct thickness gasket (parts system only does a ).010"), the carrier preload, and backlash were automatically correct. Is that how it works with these car diffs?
 
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I was unlucky time wise on mine but not due to messing around on it , I was held up with wrong and bad parts sent so it took weeks and weeks longer . I was VERY lucky however because Lawrie was in town an kindly came past and showed me a few short cuts and how to "feel" for certain things. I have an engineers vice so I can spin the diff any which way, again a big help.. I was able to get all the shims right the first time ; )
 

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Bluebell...these early Ford banjo differential gears are spiral bevel gears, but not actually considered to be hypoid type gears. Googling those two types of gears will explain the differences.
 
Hope you don't think I'm flogging a dead horse by keep on replying to my own thread. I thought about it a bit and decided to redo the pinion measurement with just the pinion. With the axle mounted vertically I unbolted the left (uppermost) bell and held it and the diff carrier up, clear of the pinion. I reattached the small torque wrench and the lowest setting I could maintain turning action after the initial startup was under 10 lbs in. I then reattached the bell and measured again with the pinion turning the ring gear and diff carrier. I got a reading of roughly 15 lbs in.

This is where I am looking for some advice. Now, a pinion with used bearings on it's own, after the initial startup, is roughly 8 lbs in enough? It doesn't sound like much, but it is a lot tighter than when I felt it before dismantling. (Didn't have a way of measuring it then).

Lets say the pinion is ok. It takes roughly another 7 lbs in to turn the diff carrier. There is no binding between the pinion and ring gear, there is a small amount of backlash. Now that is a 3.78 ratio, so by my reckoning, the load to turn the diff carrier must be about 26 lbs in.

Now, even with one new bearing, that sounds a little high to me. I'm thinking I need to pull it down again and add another thou or two to the gasket pack. I don't know if the thinking is correct or way off, but something is stopping me from feeling like this job is complete.

I think I may pull it right down again and measure the diff carrier preload direct. It's a hobby, right? This is fun, right?

Any input??

Mart.
 
On a worn bearing set, you would just take all the perceptible shake out and then just add enough so you can still rotate it without too much drag. It sounds like you are pretty much there. If you tighten too much, it may just cause premature bearing break down. Most of the bearings are already bedded in so definitely be cautious. Part of the process on the new bearings is setting them up for break in. They wear down all the high spots & even the surfaces out with each other after they have been in service for a while.

The old shop manuals just tell you to set new ones up stiff then after the bells are back together you should be able to rotate them by hand but just barely. This doesn't give a mechanic a lot to go on so I feel your pain.

If they end up loose, you will hear it. It will start giving you the groan. Then you just need to know if it groans under power or if it groans when you let off of it. If it runs quiet, then you know your good to go.
 
Sounds good to me the way it is. Remember the carrier bearing have a preload as well. So your talking the pinion preload, the carrier bearings preload and the drag of the ring & pinion together, axles, etc.
 
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