How much play can the pinion have?

[Arith2]

Long story short, I am having issues setting the preload. There is some axial play, about .035" of in and out play, and obviously no turning torque. What amount of play is normal as mine was shot seemingly due to bad play in the pinion? This diff has been a frustration from the start and I am missing a deadline because of this nonsense.

[sapote]

There is some axial play, about .035" of in and out play,

The pinion after properly preload by the big nut should have zero plays, axially and radially.
Ideally the pinion preload value (turning torque) should be done without the ring gear installed, but most situations you have to deal with the installed ring in there. This means you need to know that the turning torque is only valid between a small turns before pinion teeth touch the ring teeth -- the backlash space. Assuming with a new crush sleeve, the nut should be slowly torqued down until the pinion requires about 113 in-oz (was 20 incorrectly) torque to turn within the backlash space.

Editted: 113 in-oz or 0.8 Nm turning torque, based on this at 26:30 minutes clips:

https://www.youtube.com/watch?v=F7QTGKCcWVU&t=156s

[Arith2]

The pinion after properly preload by the big nut should have zero plays, axially and radially.
Ideally the pinion preload value (turning torque) should be done without the ring gear installed, but most situations you have to deal with the installed ring in there. This means you need to know that the turning torque is only valid between a small turns before pinion teeth touch the ring teeth -- the backlash space. Assuming with a new crush sleeve, the nut should be slowly torqued down until the pinion requires about 113 in-oz (was 20 incorrectly) torque to turn within the backlash space.

Editted: 113 in-oz or 0.8 Nm turning torque, based on this at 26:30 minutes clips:

https://www.youtube.com/watch?v=F7QTGKCcWVU&t=156s

I appreciate the help. I really didn't think it should have any. This is my second full rebuild and my other was some truck diff in school. Before I took it out, it was a hotdog in a hallway. It makes me think someone was pooping around in there prior to me buying the car. These aren't Timken so I think I'll stick to that spec. Now I can actually finish this turd. I'll share anymore grievances. I'll show how I has to cut the races off.

I also found that this bearing requires a ridiculous amount of pressure to seat. I was at 10 tons before it dropped. All others were under 1000lbs. It looked seated however, it had .035" to go.

[bigjae46]

Really can’t measure pinion preload with the ring gear in unless you know the carrier preload. The only way you can measure carrier preload is with the pinion not installed.

Order of work goes:
1. Carrier preload (no pinion gear)
2. Backlash (pinion gear no play but no preload)
3. Gear pattern
4. Pinion preload (no ring gear/carrier)
5. Backlash and gear pattern as a final check

You should have no play in the input flange before you get to the point of having any preload. I just use a big impact and it can get the pinion nut well past the preload spec. I went 1 uga at a time after I took out the play.

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[sapote]

Really can’t measure pinion preload with the ring gear in unless you know the carrier preload.

It depends on how much backlash between pinion to ring. If there is 10 deg or more backlash on the pinion then this should be enough to detect the required turning torque 0.8Nm without turning the ring/carrier.

[bigjae46]

It depends on how much backlash between pinion to ring. If there is 10 deg or more backlash on the pinion then this should be enough to detect the required turning torque 0.8Nm without turning the ring/carrier.

If you have that much backlash then it’s way beyond BMW’s spec.

Should measure preload at the pinion gear before removing the nut if you’re just doing the pinion seal.


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[sapote]

I also found that this bearing requires a ridiculous amount of pressure to seat. I was at 10 tons before it dropped. All others were under 1000lbs. It looked seated however, it had .035" to go.

Is this the inner bearing which locked the pinion depth shim? The first pic shows the bearing was badly pitted, and if a new bearing is used then the pinion depth needs to be checked: using gear marking compound to set the correct pattern and adjust the shim if needed. If the bearing was heated to 100C and install on a cold pinion shaft then it should be less force needed to press it in.

Did you measure how much rotation of the pinion backlash before the ring/carrier rotated?

[Pavlo]

There needs to be zero play in everything aside for the ring gear backlash. The big pinion bearing is always the toughest to press, that is normal. On brand new bearings, I usually set them between 15-17 in-lbs preload. The seal is approximately 1 in-lbs of drag, out of several dozen of those that I've rebuilt that is what they always measure. I usually get the pinion to slight preload with the seal out, then take the flange off and install the seal, then do the final preload. 12-23 in-lbs is acceptable.

Used/bedded in bearings are completely different, do not use any of the given specs for the pinion or the carrier if you aren't replacing them.

If you are using the correct nut plate that prevents the pinion from loosening, I am fairly certain that one of the bearings or races wasn't pressed in all the way.