OEM diff bush fitting - which way up?

mrscalex

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I was wrong-footed when I went to press this in and noticed the hole is not in the centre. There is a shorter and longer side as apparent from the photo. So which way up does it go?

IMG_6953.jpeg
 

Dakar Z3

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Looking at the bush stood upright, the solid rubber is to the left and right like a horizontal bar across the middle with the small slot at the bottom and the larger slot at the top.
i hope that makes sense
 

mrscalex

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Looking at the bush stood upright, the solid rubber is to the left and right like a horizontal bar across the middle with the small slot at the bottom and the larger slot at the top.
i hope that makes sense
Yeah thanks. It’s the orientation of the slots top to bottom that was confusing me. So small at the bottom. Like this then?

54F1A12F-8752-4BCE-A66D-59BE0D93BFE4.jpeg
 

mrscalex

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I also noticed it’s not circular but slightly oval. But presumably once the press starts its job the bush pulls in and conforms to the circular aperture of the cover?
 

Dakar Z3

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I also noticed it’s not circular but slightly oval. But presumably once the press starts its job the bush pulls in and conforms to the circular aperture of the cover?
There must be,
the steel outer band on the bush should be an interference fit in the diff bush housing, you would only get a change in shape if it were a split bush and had to be compressed before attempting to fit, eg 3 series E46 trailing arm bush,
 

mrscalex

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There must be,
the steel outer band on the bush should be an interference fit in the diff bush housing, you would only get a change in shape if it were a split bush and had to be compressed before attempting to fit, eg 3 series E46 trailing arm bush,
Thanks. Got pic and understood. The aperture is 84mm. The bush is 83x85mm. I’ve seen people comment before and quote these same dimensions but not sure I remember there was an answer. I know @Pingu came across this and made himself a compression tool from an exhaust clamp. But others appear to just push in with a vice or press.
 

t-tony

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Just lubricate the hole in the housing. It will go in.

Tony.
 

Dakar Z3

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A press would be your safest option to ensure the bush is being inserted in line to the hole in the diff mounting bracket,
good advice from t-tony, I have mine yet to do.
 

mrscalex

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A press would be your safest option to ensure the bush is being inserted in line to the hole in the diff mounting bracket,
good advice from t-tony, I have mine yet to do.
Yeah I have a 12 ton press. I’m just paranoid about busting the cover. Would be a very difficult thing to replace. No longer available as spare and secondhand would need to buy whole diff.

I could have made life easier with a poly bush. But I just didn’t want one of those.
 

Dakar Z3

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Yeah I have a 12 ton press. I’m just paranoid about busting the cover. Would be a very difficult thing to replace. No longer available as spare and secondhand would need to buy whole diff.

I could have made life easier with a poly bush. But I just didn’t want one of those.
I have a brand new poly bush but I’m not fitting it, I’m going the OE route like yourself.
 

t-tony

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Hi Tony,
does it press in easy enough with a vice?
Never done one in a vice, because you can end up being a bit short and then putting a tube on the vice handle, sometimes that doesn't end well.
I have an ex RAF Record 6" vice and I wouldn't use that when I have access to an Hydraulic press.


Yeah I have a 12 ton press. I’m just paranoid about busting the cover. Would be a very difficult thing to replace. No longer available as spare and secondhand would need to buy whole diff.

I could have made life easier with a poly bush. But I just didn’t want one of those.
As long as you keep everything flat and press at 90 deg. you won't harm the housing, and as I said use lubrication. If, it starts to cockle over to one side release the pressure and move the press to the other side and apply pressure till it levels out. Then press in the centre again. You just need practice Rob.

Tony.
 

mrscalex

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That was the question I had Rob. I came to the same conclusion as DakarZ3, that way when the diff weight is hanging on the bush the hole for the bolt becomes central.
Looking at other diffs they are mounted the same. Circle with 2 digit date at 12 o'clock with the triangle (arrow) pointing to the nearside when viewing diff cover from rear. Had a few bum steers elsewhere before looking into it for myself.
Good logic there thanks Adrian. I've done this little graphic to try and consolidate understanding. The plate shoulders are interesting too. I guess the wider ones go at the top so they pull in as the diff weights down.

Only other point is which way this face goes. I don't expect it matters. But if it did I think it might go the other way round (ie spun on north-south axis 180 deg) based on a 168 diff I've got sat here. So the BMW lettering (on the other side here) faces the rear of the car. Only thing that makes me wonder if it does matter is the arrow.

Diff bush orientation.jpg
 

mrscalex

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Apologies Adrian. You're right and I'm wrong. The arrow side faces the rear. Here's a photo of a new cover (no longer available) from the Turner Motorsport website.

We're looking at the outside of the cover. And I've rotated the image to make it more clear. You can just about see the arrow pointing to the left in the 9 o'clock position.

New OEM diff bush 2.jpg
 

mrscalex

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Any recommendations for a specific gasket sealer? Or will the paper gasket suffice?

Tried to read up on this but there's a 1001 different views out there.
 
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