MGB Register Forum

So, I had a clunk and figured it was the shims in the sun/planet gears so I swapped them. Made absolutely no difference. So then I got some moss +40thou washers and tried again. Exactly the same. I need to measure the free play on the diff flange. It was about 8mm before I put in the bigger shims. Pretty sure it's less now. The prop seems fine. I've checked the tightness of every nut and bolt.What else should I be looking at? Thanks

Stu

Do you mean the cup shaped bronze washers? I changed mine and it did make a difference without a complete cure.
I did try +60 size and they were definitely too tight.

On the positive side, these axles/diffs can clunk for ever and just keep going, so unless you get really serious noises it could just be left alone.

Ian F

Is it a Salisbury axle?

Ian F wrote: Wed Jul 17, 2024 8:49 am Do you mean the cup shaped bronze washers? I changed mine and it did make a difference without a complete cure.
I did try +60 size and they were definitely too tight.

On the positive side, these axles/diffs can clunk for ever and just keep going, so unless you get really serious noises it could just be left alone.

Ian F

Hi Ian

I replaced both the cup washers and the thrust washers. The latter being 40 though oversized. The free play on the axle flange is now down to about 3mm from 8mm with new standard sized phenolic washers so I'm pretty happy with that and thinking that the clunk must be coming from the prop so I'll take that off today to check. There's definitely a little play on the rear joint so need to check the front and sliding joint when off the car and decide whether to get a new one or just replace the joints.

Vic Butler wrote: Wed Jul 17, 2024 10:28 pm Is it a Salisbury axle?

Yes, Salisbury axle on a late model Roadster

I did use oversize cup washers as well, I think they might have been +20 or +40. They certainly tightened things up nicely. The +60 were definitely too tight.

Ian F

Ian F wrote: Thu Jul 18, 2024 10:18 am I did use oversize cup washers as well, I think they might have been +20 or +40. They certainly tightened things up nicely. The +60 were definitely too tight.
Ian F

Thanks - where did you get them? Just realised I have been using non hypoid oil in the diff so I wonder if that has caused issues - I don't remember it clunking when I fist got it on the road.

Searched through all my old invoices but couldn't find where I bought them.
Could have been MGOC or MGBhive. If you call around someone should be able to help.
You must use hypoid oil!!

Ian F

With a Salisbury axle the pinion is lower down at about 5 o'clock clock position and therefore slides against the crown wheel as well as driving it. The old axle diff had the pinion at 3 o'clock and there was a straight mesh with no sliding motion.
The Salisbury axle is a lot stronger than the earlier one and it was used because the drive line is lower. It's also a lot more complicated and even replacing the pinion oil seal isn't straightforward.
As Ian said, hypoid oil must be used because of the friction generated in the sliding movement of crown wheel and pinion.

Thanks. Could well be that my stupid mistake of not using hypoid for 500-1000 miles has worn the crown wheel and pinion. Bugger. Got some of the correct hypoid arriving today but maybe too late.