Crown Wheel Bearing - Wisdom Required

[Twotter]

Had the final drive apart last night to replace output seal when in a moment of genius I managed to knock the crown wheel over from where I had 'safely' placed it and knocked the cage off the taper roller bearing on the top = bearing bits all over the place

I've cleaned everything up, reassembled it and got all the bearing bits the right way up (they look slightly conical so the slimmer end is at the top and the fatter end, with the dark 'dot' on the bottom, is at the bottom) and refitted it to the crown wheel. The bearing turns easily and the cage doesn't come off when I give it a pull.

So, now I'm looking for a bit of wisdom from the collective - use the existing bearing or go and get a new one ???

 

[Packer]

Two points:-

1) Is it all spotlessly clean and free of grit/dust. If so can you put manual pressure on the outer cage and turn it without feeling any variation in resistance or any lumpiness. If so it may be OK.

2) Get the bearing number and find out the cost of a replacement, maybe from an independant bearing supplier. Then decide if the risk of having to break it all down for a second time is greater than the cost of a new bearing?

If it was mine (40,000 miles) and the bearing was up to about £25 I'd replace it any way. More than that I'd be inclined to take a risk. Yehhh, I know I'm a cheapskate

 

[ianboydsnr]

I would change it, unless it was new and I was sure that it was clean and back together complete, as its a known weak spot

 

[Ragnar]

If you felt you had to ask the question, the answer you're looking for is get a new one

 

[davegs]

Rear bevel bearing

Get a new one any way, give you peice of mind and it will las a very long(?)
time. Motobins have these and their not expensive.
Dave gs.

 

[ebbo]

I'll go against the grain and say 'if that bearing is good, reuse it', I would.

My reasoning being that that bearing was 'in theory' shimmed to to fit that bevel box, most people who 'have to' change that bearing take a chance and don't re shim (which is what I would also do).

Thats my two penny-worth

 

[Steptoe]

Change it - I can show you pictures of what damage that taper bearing does when it fails.

It destroys the final drive unit, the housing, the whole lot is likely to be toast.

If the large bearing fails, it very very rarely causes any internal damage. But if the small taper fails

You may get away with it. But............

 

[Steptoe]

[URL="http://www.ukgser.com/forums/showthread.php?t=85786&highlight=rear+bevel"]HERE[/URL] found the old post , scary

 

[Twotter]

Thanks gents - new part ordered from Motorworks

 

[MIKE R]

When my 'large' bearing showed signs of wear I went to Roy Gardner (excellent independent) and he changed the 'small' bearing as a matter of course. It's not very expensive (about £25 I think) and whilst your in there..... in my case paying for labour....might as well do a complete job.

So IMHO change it.

Mike

 

[Arbreacames]

Has anybody been able to do a proper shimming "at home"? The gap is supposed to be determined from the difference of two measurements. The required 0.05-0.1 mm tolerance seems impossibly accurate without the factory tools.
I am wondering if the preload gap could also be measured with a thickness gauge as shown in the picture. To test the concept after a crown bearing replacement, I reassembled the FD and measured the "loaded" gap. Then I untorqued the bolts and measured the "unloaded" gap. The difference between the two measurements would be the required preload. Can anybody chime in on what you think of this approach to measure the preload?

 

[MikeP]

Has anybody been able to do a proper shimming "at home"? The gap is supposed to be determined from the difference of two measurements. The required 0.05-0.1 mm tolerance seems impossibly accurate without the factory tools.
I am wondering if the preload gap could also be measured with a thickness gauge as shown in the picture. To test the concept after a crown bearing replacement, I reassembled the FD and measured the "loaded" gap. Then I untorqued the bolts and measured the "unloaded" gap. The difference between the two measurements would be the required preload. Can anybody chime in on what you think of this approach to measure the preload?

But there's an 'O'-ring between the two halves of the housing and the eight nuts that hold the two halves together are torqued-up.

Surely the gap between the two housing halves is irrelevant?

 

[Arbreacames]

In the "untorqued-but-finger-tight" state, the housing cover is in contact with the bearing. In the "torqued" state, the cover is pressing into the bearing. Unless there are deformations that I am not accounting for, the difference in the two gaps should be the amount of pre-load that should be in the range 0.05-0.1 mm. Mine came out to be in the middle of this spec range.
I wish I had done the measurement after my previous bearing replacement because that bearing only lasted 12,000 miles and I can only wonder if it had the right pre-load.

 

[davegs]

Bearings.

These new bearings are of a high prescison manufacture and should not
re-shimming, the original was done to accomodate gear / casting tollerances
and so should not be affected by a replacment bearinfg (new0.
dave ds./