measuring final dirve preload (yet again) - BMW Luxury Touring Community
 
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post #1 of 4 Old Jul 19th, 2012, 7:43 pm Thread Starter
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measuring final dirve preload (yet again)

Just discovered enough glitter in my 1150RT's final drive oil to decorate a Christmas tree-
All the Beemer internet sites seem to point here, the home of the Final Guru, the voice of Experience, aka CharlieVT -

I've studied your video (many thanks) & read such other postings as I can find & would like your (and anyone else's) opinion of the solder-crush method of measuring the bearing-housing gap as opposed to the pry-the-gear method shown in the video. I can see several advantages to the crush technique (more even force distribution with less chance of distortion, less time sensitivity before the cover cools & grabs the bearing, no need for rigid measuring setups, maybe more).

In the collective wisdom of the group, are there good reasons to favor one gap measurement technique over another?

My other concern is whether or not one can do an adequate cleaning of a final with a disintegrating bearing without a full teardown - seems like particles will have been deposited throughout any lubricated area -like the input shaft bearing - and of course those pesky particles go in a lot easier than they go out.

Is there any way to determine (beyond making sure no roughness is detected) that a sufficiency of particulates have been exorcised from the inner recesses of the assembly,
and that no further damage has been done?

Thanks to all; it's always a pleasure to find a knowledgeable group which is willing to share it's accumulated experience.

- ldw
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post #2 of 4 Old Jul 19th, 2012, 9:07 pm
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Re: measuring final dirve preload (yet again)

If you do use solder, use three very short pieces of the tinyest and softest stuff you can find. The solder will otherwise support a substantial preload by itself as it is being crushed. You'll need a good micrometer too.

You might also check w 3 pieces of Plasti-gage (available from an auto supply store) but as I recall that can only handle clearances of maybe 0.1 to 0.2 mm or so.

A lot of the mojo magic that CharlieVT applies has to do with heating things to get the necessary axial freedom for the outer race OD for clearance measurements.

You do want to rinse things out thoroughly.
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post #3 of 4 Old Jul 20th, 2012, 1:41 pm
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Re: measuring final dirve preload (yet again)

Quote:
Originally Posted by niel_petersen
If you do use solder, use three very short pieces of the tinyest and softest stuff you can find. The solder will otherwise support a substantial preload by itself as it is being crushed. You'll need a good micrometer too.

You might also check w 3 pieces of Plasti-gage (available from an auto supply store) but as I recall that can only handle clearances of maybe 0.1 to 0.2 mm or so.

A lot of the mojo magic that CharlieVT applies has to do with heating things to get the necessary axial freedom for the outer race OD for clearance measurements.

You do want to rinse things out thoroughly.

Use Plastigage instead of solder. When I used to build drag engines, I used it to verify actual bearing clearances. Pretty accurate when used as directed.

Plastigauge PL-X is for measurements of 0.018mm - 0.045mm

Plastigauge PL-A is for measurements of 0.001" - 0.007" (0.025mm-0.175mm)

http://www.plastigaugeusa.com/

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Last edited by LJSMITH1; Jul 20th, 2012 at 1:49 pm.
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post #4 of 4 Old Jul 21st, 2012, 5:45 am
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Re: measuring final dirve preload (yet again)

Many posts exist in the archives here which answer the questions raised.

In summary: Plasti-Gauge is not suitable in this application; read pasts post for a discussion of why.

Other "crush" methods using solder or epoxy have been discussed, proposed, or tried. Dan Martin is the only person I know of who has written about his results using epoxy. To my knowledge, no one has provided data comparing one of these methods to another known method that would demonstrate consistent results on multiple final drives. Because of a lack of data I would not recommend using any of these methods.

I have compared results using the dial indicator method first described by DMAN to results using the method described in the BMW Service Manual. Both these methods are somewhat technique sensitive but will provide consistent results in experienced hands. The DMAN dial indicator method is a little more forgiving and is probably a better method for someone who is planning on doing just one drive. However, the DMAN method can be misleading, and the process of measuring should be repeated several times to ensure that consistent results are obtained.

On cleaning the pinion shaft assembly: Disassembly of the pinion shaft is not for the faint of heart. Special tools, high torque values, ability to heat the whole drive housing are required. Unless there is reason to disassemble the input pinion assembly (e.g. "creeping needle bearing race) I recommend against disassembly.
Using a parts washer with clean solvent, flush the pinion shaft assembly area while rotating the shaft as thoroughly as possible. In my experience, not a lot of metal gets into this area. After running the rebuilt final drive a few hundred miles, I recommend changing the lube again to flush out any residual solvent; rarely has residual metal been seen or reported.

Last edited by CharlieVT; Jul 21st, 2012 at 5:54 am.
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