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Gearbox front cover shims

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catlotion Avatar
catlotion Toby M
Leeds, West Yorkshire, UK   GBR
Another post about this I'm afraid. I've searched long and hard but struggling to understand.

I've removed old MGA cover to swap for MGB one and the only two shims that came out sat inside the recess in the cover plate whereas new ones I've purchased are larger and would sit outside this recess (new shim shown on first photo). Which are correct?



Edited 1 time(s). Last edit at 2019-03-07 04:31 PM by catlotion.

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Blueosprey90 Avatar
Blueosprey90 Jeff Sienkiewicz
New Milford, CT, USA   USA
The shims I used had an outside diameter just under 3" and an inside diameter just under 2.5". The width was perhaps a little over .25" .

I did this twice. Initially, I made my own shims, but then the second time I bought some from Moss - USA. Part 461-280 was for the .002" thick shims. Ultimately I reused the ones I made as they provided a better thickness.

So I would say inside where the old shims sat.

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catlotion Avatar
catlotion Toby M
Leeds, West Yorkshire, UK   GBR
Thanks. Sounds like the same as what was in there then. I was confused as guy at Moss said that the bigger ones are correct...

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Blueosprey90 Avatar
Blueosprey90 Jeff Sienkiewicz
New Milford, CT, USA   USA
I think those large shims will also conflict with the gasket that is supposed to be behind that front plate.

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dickmoritz Avatar
dickmoritz Platinum Member Dick Moritz
Philly 'burbs, PA, USA   USA
The shims go where the old ones were. Their role is to abut the outer race of the first motion shaft bearing to keep it from spinning in the main gearbox case. The spec is 0.000 to 0.002, meaning that, once the cover is tightened, there should be zero clearance or up to two thousandths clearance. This will secure the bearing in the case.

The process for selecting shims is a bit fiddly, but worth the effort. You need to measure how far the outer race protrudes from the main case, the depth in the front cover from the gasket surface to the area where the original shims sat, and the thickness of the gasket that seals the front cover to the gearbox main case. Do a little arithmetic and you'll know what thickness shim(s) is/are needed to achieve the proper fit...

Dick



Errabundi Saepe, Semper Certi
(Often wrong, but always certain)



Edited 1 time(s). Last edit at 2019-03-08 10:38 AM by dickmoritz.

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Gary E Avatar
Gary E Silver Member Gary Edwards
Kernersville, NC, USA   USA
Large shims are not correct. The shim is a bearing shim and needs to be the same size as the bearing.

Dick types faster and give a better explanation.



Gary

Hammer: Originally employed as a weapon of war, the hammer nowadays is used as a kind of divining rod to locate expensive car parts not far from the object we are trying to hit.



Edited 1 time(s). Last edit at 2019-03-08 10:07 AM by Gary E.

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barneymg Avatar
barneymg Barney Gaylord
(Somewhere in USA), Pick one (or more), USA   USA
1958 MG MGA "MGA With An Attitude"
I think the spec is 0.000 to 0.002 clearance (not interference). If the shims make interference fit, the gasket may not seal. Shims are to reduce end float of the bearing outer race to near zero. This is important to reduce wear in the housing when the bearing may move slightly. If the bearing could move more it would also increase backlash in the drive train due to the helical gears.



Barney Gaylord - 1958 MGA with an attitude - http://MGAguru.com - barneymg@mgaguru.com
(Please email me direct, do not leave a PM on the public server).

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dickmoritz Avatar
dickmoritz Platinum Member Dick Moritz
Philly 'burbs, PA, USA   USA
As usual Barney is correct, and I have edited my post accordingly. Not sure what I was thinking, but glad he was around to correct me...

I gotta switch to decaf....

Dick



Errabundi Saepe, Semper Certi
(Often wrong, but always certain)

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