Replacing 850 mk3 Primary Cover

Hi, my Primary Cover is very poor on its bottom face, especially almost no surface around the middle bottom hole, to seal against the inner cover. The casting is pretty poor and it has started to split at the bottom hole. I had success last summer, using grease on the gasket, but it is leaking again, worse than ever.

A bit reluctantly, I've decided I will hit the credit card and replace it. Couple of areas for any advice, please:
- Strangely, on my current cover, the 2 dowels are fixed in the cover, not the inner case. The dowels are not available from AN. If I grip them in a mole wrench and twist/pull, will they come out without heat etc?
- the gear lever cross shaft goes through a Bush and oil seal as it exits the cover. I can't see anything in the service manual, are these easy to remove and install. Should I buy both new? Any tips on fitting?
- does anyone have any recent experience on the quality of the casting on primary covers available from Andover Norton?

Thanks

The pre-MKIII covers I've bought from AN were excellent - haven't bought MKIII covers. The dowels will come out with heat but grip as lightly as possible - scratching them makes them difficult to re-use. I use needle-nose pliers perpendicular to the dowel so I'm only touching one spot.

The cross over shaft doesn't exit the outer case, no? It's the gear lever?? (Apologies if that appears pedantic!).
IIRC the seal and bush can both be pushed or drifted out, though reusing any seal would be a gamble?

Mart UK said:

my Primary Cover is very poor on its bottom face, especially almost no surface around the middle bottom hole, to seal against the inner cover.

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That doesn't sound right as the inner case is narrow in that area but not the cover.

Mart UK said:

Strangely, on my current cover, the 2 dowels are fixed in the cover, not the inner case.

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The dowels should be sliding fit in both so just remained in the outer cover probably stuck with sealant.

As EstuaryBoy said there are two bushes in the outer cover, the cross-shaft has a blind bush.

Mart UK said:

Should I buy both new?

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I'd have said yes before I saw the price!
The cross-shaft bush you may have to buy.

Mart UK said:

- does anyone have any recent experience on the quality of the casting on primary covers available from Andover Norton?

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Hi Mart,
I remember AN (or more precisely, Joe Seifert) wrote about the difficulty getting the Mk3 primary covers right. NV had made many changes to the drawings back in the day, some of which never made it to the molds. When ordering the outer cover, please ask if the new cover is guaranteed to fit your old inner cover. You may end up having to order the inner and outer cover (I hope not!).

If dovels don't release, try to heat the cover. Grip dovels using strips of soft copper between plier's jaws, this will increase transferred torque as well as avoid chafing them.

- Knut

Before ordering, I didn't get how the bushes for the gearshifter and seal worked, so removed the cover. There was a piece of wire sticking out of the drain hole on the inside. It looks like a failing helicoil. I trimmed it and put a new gasket on the drain plug, with wellseal on each surface and the final couple of threads of the plug. I regreased the cover and put it back on. Took it for a ride to get it warmed through. No sign off any leaks. So, I think it was all coming from the drain plug and running along the bottom joint.

I'll research how to remove a helicoil. By any chance, does anyone know the likely size of the one that's in there? I assume they didn't come helicoiled from the factory? Or, instead of a new thread repair / helicoil, has anyone just drilled and tapped, to take a larger plug?

Mart UK said:

By any chance, does anyone know the likely size of the one that's in there?

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The drain plug is 1/4 UNF.