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MG TD TF 1500 - TD Gearbox main shaft problems

We are rebuilding my mate’s TD gearbox and came across the following problem. As you can see, from the attached photo, the spigot on the main shaft is badly scored and pitted. There were noises from the box but no shifting problems so we think the main problem lay elsewhere with the laygear.
We were discussing the option of a repair rather than a replacement. NTG does have them second hand which might very well be the only feasible option. My other make is scouring Beaulieu Autojumble.
As the spigot runs in the 18 needle rollers 3x28mm, we were discussing having the shaft ground down and the metal built up. A local company who does this type of work advised against it due to the point loading of the needles and say the built up metal would break up which I could well imagine. We were then thinking of grinding the spigot to take a phosphor bronze (Oilite) bearing bush which is easily made up and we have all the tooling required. This would of course spread the load over a far greater surface area.
Do you think this would be doable or have you ever heard of such a repair being successful?
We were also discussing fitting oversize needles as opposed to a phosphor bronze bearing.
Have you any other suggestions? What do you think?
Thanks in advance

Declan


Declan Burns

Bushing not good due to load/ big rpm difference. I would guess it has taken 60+ years and thousands of miles to wear like this? How much will the car be driven in the future? Unless it will be driven thousands of miles a year, you could just polish the bad area a bit, and just replace the rollers. Or fabricate a short spacer, shorten the rollers so they are all on a good surface. Perfect and ideal- no, but would last for many years and likely miles. If the damage extends below the surface and/or the steel is soft there for some reason, turning and using larger rollers may not be ideal either. George
George Butz

Declan
The Ford Courier gearboxs here suffer the same problem and although new mainshafts are available there is an engine reco joint here that repairs them
They grind the shaft down and press a hard sleeve on it and then regrind to original size--perfect repair and they last better than the original
They get the hard sleeve from the local bearing shop, I think it's the centre out of a little roller bearing
It'll pay to have a good look at the matching end of the input shaft to make sure it hasn't suffered the same wear

A tip here----When you reassemble the box don't pack this bearing with grease-
Sometimes the grease can create a dam and stop the lube oil getting in, Best to use vaseline (petrolium jelly) as this will melt away as soon as it gets warm

willy
William Revit

Declan,

Another option is to use oversize rollers. I recently I spoke to a person who has worked on T types for over 60 years, he told me that you used to be able to get them.

You will need to grind the shaft, this may be a problem as you could grind through the case hardening, but this will also be true for any sleeve which you will use.
Just an idea.

I was at Beaulieu this weekend, found some good stuff.

John


J Scragg

Declan
Oilite bushings are not capable of withstanding the radial loads and surface speeds for that application. It looks like you have spalling of the shaft which may have already destroyed the case hardening locally. Oversized needles still need the hard race which would be removed in order to repair the spalled surface. Also oversized needles can sometimes overcrowd themselves on the same diameter which can cause wear/cage problems rapidly. Using a pressed-on case hardened bushing may work if the wall thickness is sufficient to accommodate the surface stress depth of the rollers under load.
Mike
TD15250
Mike I

I have several, what appear to be NOS, TD/TF mainshafts for sale. Send me an email if you are interested.
Hugh Pite
H.D. Pite

Thanks for all the good suggestions-much appreciated.
Against all my expectations the lads did find a good shaft at the Autojumble in Beaulieu UK over the weekend-There was a chap selling TD gearbox bits and pieces and he had 3 shafts!
I could hardly believe it only cost £30 ! Sliding hubs for £5!
It is an early shaft so we will do the eroding for the tacho drive. We have an eroding machine.
Luckily the first motion shaft showed up not to be damaged.

Regards
Declan
Declan Burns

Declan,

Does your mainshaft have the indent for the third and fourth sliding hub? if not it may be worthwile to machine one at the same time as the keyway. The sliding hub should have also one through hole to match this ident.

John



J Scragg

John,
No idea as I haven't seen it yet. I will ask my mate to compare both shafts in this respect.
Thanks for the tip.

Regards
Declan
Declan Burns

John,
The indent is not there.
We will have to erode it.

Regards
Declan
Declan Burns

This thread was discussed between 04/09/2017 and 08/09/2017

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