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MG Midget and Sprite Technical - Pinion seal

The oil drip from the differential seal on my 1971 midget is getting worse. I am planning a cross-country trip and worry about having to top it off along the way.

Is it possible to remove the end yoke and seal without removing the carrier assembly? I do not have the vice and shop equipment to remove the nut without the weight of the car to provide the grip. My thought was to disconnect the driveshaft, remove the nut with an impact wrench, replace the seal and replace the nut using the full force of the impact wrench.

Any suggestions to avoid a late hour tear-down would be appreciated.
Glenn Mallory

I wouldn't be using an impact wrench, as it may damage the gears.

Also, if you were to 'use the full force of the impact wrench' when tightening, what sort of preload would you have on the bearing?
Dave O'Neill 2

Yes, impact cannot be good for the gears. There is enough of that around anyway without adding more.

If the gears and shims are not disassembled, is preload an issue? If I can get remove the nut and end yoke and have access to the seal, it should be possible to retorque the nut to 140 Ft. Lbs. per specification. I don't have a torque wrench hefty enough for that.
Glenn Mallory

This subject has been covered on the BBS in the past and will be in the archives. The 140ft lbs torque is required to crush a new spacer to give the correct pre-load but you still need to check the much lower torque required to turn the pinion shaft to indicate that the pre-load is correct. I helped my neighbour rebuild a Morgan final drive and it took him a while to get his head around the difference. The torque to crush the spacer is like 140 ft lbs but that required to turn the pinion at correct pre-load is in the low inch lbs IIRC. Often people mark the pinion shaft and nut and once the seal is replaced just put it back in the same position which should at least give you the same pre-load as you had when removing the pinion nut. Re-torquing to 140ft lbs with an old spacer is likely to over do the pre-load and result in rapid bearing failure/wear.
David Billington

I did mine using the mark it and tighten back up to the marks method as David mentioned. Worked for me. I've still got the bar I made to hold the pinion while I undid/tightened it somewhere in the garage.
john payne

Norman's article:
http://www.mgexp.com/article/mg-midget-differential-rebuild.html

THe nut is bloody tight. Get a long breaker bar. Or a scaffold tube.
I believe it is possible to replace the collapsible sleeve without a major stripdown.
I managed to check the preload by hanging the appropriate weight on a string wound around the input shaft and doing a quick "moments" calculation.
Something rings a bell in the back of my mind about reseating the new seal. I think you need to keep the outer face flush with the edge of the housing. If you seat it too far in the lip can drop off the lead-in taper on the boss that it seals against.
Graeme W

140lb-ft relates to the solid spacer and shims set of the earlier diffs. Though coincidentally the torwue to crush the spacer is similar but not always the same, it's a case of it is what it takes. If the spacer hasn't crushed at 140, you need to use sufficiently more to do so or the bearings will be slack. Or the other way, if the spacer crushes at 110, then 140 will kill the bearings.
Generally, the spacer seems to need more torque to crush it when unmolested (new) but once it has started it can reduce a bit. The key thing with the collapsible spacer as others have commented is to do it up enough to get ther correct pre-load torque.

Paul Walbran

>>Re-torquing to 140ft lbs with an old spacer is likely to over do the pre-load and result in rapid bearing failure/wear.<<

Thanks David. I read in Haynes only this afternoon that the torque value for the nut is 140lb/ft after renewing the seal.

You have just saved my bearings. Cheers.
Greybeard

I think that you may be overcomplicating this!! I undid mine with a long bar, changed the seal, tightened it up with a breaker bar and a solid heave and never had any more problems! Marking the pinion and nut sounds sensible to me.
Robin Cohen

This thread was discussed between 27/10/2015 and 30/10/2015

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.