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jacobs53

Is The Crownwheel In A Ma Box Bolted To The Diff Unit?

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jacobs53

Well I just found out something shocking and quite worrying!

 

The rover R65 boxes which are used through-out the rover range metro to Mg ZR... all have the crownwheel bonded to the diff unit - No Bolts! I know that the R65 box is very similar internally to the MA box so does the MA box also have a bonded crownwheel?

 

Also why does the MA box usually fail?

 

cheers lee

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MartinM
...so does the MA box also have a bonded crownwheel?

I don't think they're bonded - they're just 'sweated' on i.e. an interference fit

 

Also why does the MA box usually fail?

Because the interference fit can come loose, slip and get looser and looser until you have no drive at all - as it did on mine on the Welsh Endurance Rally a few months ago :(

 

(and as happened to another guy I know on the Lombard Revival last week :D )

 

Mine is now securely welded on.....

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jacobs53

The rover ones are definitly bonded, maybe they are also interference fit. Easy solution though!

 

Might have to do this to my rover gearbox soon! its started to slip and judder!

 

lee

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Baz

Is this on the metro Lee? Sorry, just a further thought, was stripping a Metro diesel last night and was wondering what box it was as we know the engine is a PSA/shared unit so presumed the box would be an MA type, although the casing was of a different casting to the diesel 106 type boxes.

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Sam

The internals are the same afaik, the Quaife gearset I have is also listed for Metro boxes, if you're that way inclined....

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jacobs53

yeah the internals are the same, just the outside casing differs between models.

 

Where did you exactly weld the crownwheel onto the diff, had a quick look today but couldn't see where you'd have room to weld.

 

lee

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Gregg

MA crownwheels are an interference fit to the diff, not sure if it is bonded on but I think might be. MA's have a habit of chewing up the planet gears in the diff, they start by chipping the teeth and eventually blow up, often sending bits of planet gear through the casing into the bell housing! Quaife ATB is a neat solution to this, it is a press fit and uses two large-ish ball bearings to hold it in position which needs some machining to the diff.

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jacobs53

I just brought a mgzr gearbox which has covered 18,000 miles for 40.00. These have bolted diffs as standard so might be a good upgrade for a standard MA box.

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