Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing 1975 Plus 8 Diff noise?

Hello All

Whenever, I am in a hard right turn, whether under power or idle there is a grinding/whining noise from what appears to be the rear left hand side.

I'm thinking it's the differential because although it is central, its located next to my left ear. To add to my difficulty, I have a noisy stainless steel exhaust system making noise discrimination challenging.

1) Anything else I can do to confirm this diagnosis?

2) I don't suppose anyone knows where the original differential was sourced from?

And

3) Is there a better replacement choice than the original?

Thanks

Niels

Yes 40 years of use seems a short life span for a diff!!!!!!!!!!!!!!!!!

Have you eliminated the wheel bearing as a source of the noise?

Morgan Plus 8s from 1975 to the early 1990s were fitted with a wide-track Salisbury 7HA with a limited slip differential (LSD).

It sounds potentially that the LSD's clutch plates are sticking/grabbing, possibly worn or even that the diffs planet gears are breaking up. The latter happens if heavy standing starts are used. Mine went in this fashion competing in an autotest on tarmac; since then I have restricted myself to autotests on grass. Too much power is applied at slow speeds when turning causes excess strain on the diff.

The 7HA axles could be a tad marginal used in Plus 8s but not desperately or notoriously so.

LSD oil must be used in this axle. Castrol Hypoid LS or Castrol's competition spec Product B373. Under no circumstances use an oil additive designed to reduce wear or reduce friction or noise.

Quaife used to, perhaps still do manufacture an LSD unit for the 7HA that does away with the clutch plates.

Billy Bellinger in the UK specialises in rebuilding Salisbury axles. I'm unsure of cars exported to Australia with 7HA axles. I believe early Reliant Scimiters were fitted with 7HAs.

I suggest that you try and get a better diagnosis from someone who understands diffs and LSDs before you start assuming the worst. A 'normal' garage won't be much help.

I trust that this helps.

Hi Niels. The Salisbury 7HA limited slip diff in the +8s are specific for Morgan +8s and now that parts particularly the hypoid gears are hard to come by. I checked mine and several of the sintered bronze clutch plats had fractured. they were easily replaced via BHM very quickly. I take it that the diff in question has been having regular oil changes with the correct LSD oil (as above from David) I would drain the oil (Certainly after checking the outside wheel bearings they can be forgotten to be greased occasionally ) and check colour and contents of the oil. There always seems to be a very slight bit of metal contamination if the diff gets a bit of a workout. Hopefully no big bits . The back of the diff housing can be easily removed to check further. Good luck
Doug
from deep deep down under.

Hi Niels.
The replacement axle is the BTR that is built in Australia and as you probably know also the BTR axle is in Ford and Holden product albeit with different ratios. There is a way if it comes to it to obtain a new BTR direct without having to obtain via the factory. Hopefully it won't come to that.
Doug
from deep deep down under.

Phew.. Speedy replies.. Many Thanks.

Now, my only experience with diff noise on other old bombs that Ive owned has been a constant whine - rather than a specific noise only when turning tightly in one direction. Is this an LSD trait? Note : noise is there regardless of power setting - the same under trailing throttle as it is under hard acceleration.. is this worthwhile info?

Hamwich... I cant be certain, but the car is always on a hoist in my garage and the wheels spin freely with zero noise, friction or any indication of bearing problems... Besides which, I would have expected a noisy bearing to fail within a few hundred miles.

Nevertheless, not ruling out this possibility.. will investigate further - mainly because I'm an optimist and a wheel bearing failure would be manna from heaven!

Cheshire David.. The car was originally exported to Dubai - so I guess its a Brit spec car.?? And then the original owner exported it to Oz.

I'll start looking for a LSD guru (Not Timothy Leary, to be sure... not often I get to use that line.) to diagnose it.

Mogdriver.. Good Advice!!..OK, I'll drain the oil and see if I can get an analysis and at the same time change it for the correct oil (assuming the present oil is suspect).

Doug.. how deep down under are you exactly?

And if I need a BTR diff - can you advise a good source?

ps.. after my original post, I went and checked GoMog.. and I'm now sitting in a warm bath with a bottle of gin and a razor blade while listening to a Leonard Cohen CD.


OK..on a more serious note - I'll do the oil change and analysis thing in 10 days and report back.Many thanks for replying with good advice everyone. Will report back with whatever I find.


Some background: I've had the car for 2 years but have not used it at all in that time as I have been out of the country. Long story. Hence my lack of experience. But I'm now back with a vengeance and plan on using this baby as a daily driver and long distance tourer. No point in having a garage queen is there?

In the interim if there are any other ideas, I'll be checking every day.

David mentioned Quaife - I think they still make a replacement as one was fitted by Tim Ayres (New Elms) only a few short years ago. Easy enough to check their web site...

If you have a hoist, I suggest removing the back plate and visually checking the gears.

Certainly check that the grease nipples at the outer ends of the axle have been used. The grease serves two purposes: to grease the wheel bearings but also to stop the oil seeping past the felt seal.

A word of warning about changing to a BTR axle - you may end up having to change the hubs, brake back plates, shoes and drums; this could escalate the cost considerably.

My recommendation is to do the visual check and, if there's nothing obvious, change the oil and grease the wheel bearings. There is a very remote possibility that the LSD plates have gummed up and are stuck with lack of use.

If that doesn't work, consider removing the axle and remove the diff (whoever does this job will need to spread the diff housing a tad as the diff is slightly larger than the hole in the housing) and despatch the diff unit to Billy Bellinger or Quafe for a rebuild. Reassemble in Oz but ensure that you've the parts required such as the collapsable nose spacer and sufficient shims to get the backlash correct.

I am afraid that a BTR diff won't fit a Salisbury axle . If you do need a new diff , possible your best route would be to source a complete BTR axle in Oz and fit it to the car. The other possible route would be a diff rebuild in Oz, but this will be very challenging without the parts and local skilled technicians who know this axle well.

You will need to make some changes to a complete axle . The handbrake cable arrangement is different, but what concerns me more is the width of the new axle going into an early car, (or is this a drop in?) but nothing too major that a local engineering shop couldn't help you with.