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Fitting a quaife LSD to 9k - issues!

3490 Views 13 Replies 5 Participants Last post by  faero, 
F
So - my gearbox builder is having a little issue here:

Diff is from my broken '96 box. It's going into a '97 9k box.

Original diff removed from '97 box. Speedo drive is fine.

Final drive shells and inners fitted from my '96 box (they are mint/quite new)

Speed drive is not meshing correctly on the quaife - When you try to turn the diff the speedo drive is binding. Message is it's not 'sitting down' correctly but hard to say until I see it. (later this week)

Put back the standard diff and it's fine.

So - Is this a shimming issue under the diff? Is there a difference between the way you fit the quaife to standard diff and handle the shims? (there should not be as far as I know.

I have read Nick's excellent gearbox chat on GS but this is a specific odd issue imho.

Any ideas welcome!
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F
OK - ditch that idea - the shims are only on the driveshaft side.

So - back to drawing board - what could cause the speedo drive to 'not mesh' correctly.
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christian900se
I would give Nick a call personally, he knows all about it and maybe can point you in the right direction?
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F
yeah - I'll maybe do that. He does have a business to run so direct calls like that are usually a last resort...
I pick up the box tomorrow so I should be able to see the issue better then.
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F
So - I got the bits today:

Original Diff (black ring and speedo pinion). 1997 9k Box: Drop the diff in. Speedo drive spins fine.

Drop in the LSD and I can see that the speedo pinion is actually hitting the edge of the LSD closest to the speedo crown ring.

It's as if the LSD is sitting just a touch too low. The 9k LSD has slightly exposed internals as the casing is cut away - and the only reason I can see is to clear the speedo pinion so it's damn close.

Sitting standard and Quaife LSD side by side, speedo ring on the bottom side, the LSD speedo drive is about 1-2mm lower.

Baffled! Will try and get some pics later.

LSD: QDH6S
Box: FM54 003
Serial: 873314 2942 A-01
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christian900se
Is there a way to potentially shim the differential so that it sits slightly higher? I wish I could help you more.
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F
Christian - you are spot on. A Shim under the diff bearing outer shell would almost certainly fix the issue.

Problem is - I should not need to - the shims go on the other side and I worry if shimming this side will mess up the space for shims on the 'shimming side'

Once I get some pics I'll do the rounds with all the gearbox guys I can think of - This is specific to 9k's with LSDs...
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saabkid37
what i can gather here is that the diff does not seem to be sitting far enough down in the bell housing correct?

to me it seems you need to re measure for shimming, as it just has too thick a shim. no two cases will require the same shims, and neither will two different diffs, at least thats what occurs in my other non saab car world.

but i do not know what assortment of shims are available saab wise.
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F
So - I'd say it's sitting about 1-2mm too far into the bellhousing from a speedo ring perspective. A touch too low.

The point is there 'should' never be any shims on the bell housing side. They are all on the outboard driveshaft side when you shim up after you've built up the box....

hmmmm


good thoughts though - keep 'em coming as I'm stumped!
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G
How do the final drive gears align? Do they need the shim?
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F
I havent tried building that far - I'll do that and see how well it matches up.

I did another test and raised the height of the outer bearing shell by 0.8mm. Thats enought to resolve the speedo issue.

Checked and rechecked that the inner and outer shells are the matching pair (both Timkins)

I've just been going along the lines that 'it should not need a shim on that side'... but maybe it's been required before.
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F
5
Here are some pics to help explain what on earth I'm on about here.... I raised the diff up 0.8mm as an experiment and the issue is resolved but I am not happy that I need to do this.

I will build up the final drive but I can see it will be quite hard to check if it's within tolerance or not (final drive to pinion) as I can't really see where they mate up.

I lifted the outer diff bearing shell up 0.8mm (checked with feelers) in the casing and the speed drive clears OK - as per pics.

I'd be happy to shim properly if I fully understood why and the full consequences but it just should not be needed. Some oddball case I've got? Who knows !

So - here's the list:

Quaife on the left Standard on the Right. Both speedo rings seem to be at same height but it's quite hard to tell. ( I measured but need a better method as need to be <1mm accuracy)


This is where they go: See speedo pinion and bearing outer bearing shell


Now - I nudged up the outer bearing shell by 0.8mm as shown here:


And the result is that for LSD the pinion JUST clears - you can see how close it must be even without this 'problem' - the body of the LSD overhangs. Right bu66er to get that pic!


And here's a the standard Diff ; bags of clearance regardless really as the body is way smaller
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M
Grinding shoulder slightly in case..........
usually you need to grind some material off the shoulder of the cases in the 9000 boxes. The area is on the right in your second picture, it touoches the diff and keeps it from sitting properly in the lower case.

Are you sure the lower bearing is pressed on fully?

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F
Thanks MTAero - nice to hear to specifics on the 9k. Where did that picture come from - I've never seen an official looking LSD guide.

For me - it's not hitting the bellhousing shoulder but I will check how close it is just in case.

My LSD is actually sitting too low (not too high) in the bellhousing thus the collision with the speedo drive..... If the bearing was not pressed fully home then it would get even lower and be even worse.
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