Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) diff noise

Grant my 4/4 (2011) has had the diff “moded” to 4.1:1 & it does just that. The noise is more of a gear ringing noise. I was warned prior to fitment that they could be noisy due manufacturing tolerance. No limited slip involved. I assume yours has not been modified but maybe the same problem. I sound insulated the rear woody bits to help deaden the noise.

Dave, a 2009 4/4 has the Salisbury axle in combination with the Ford gearbox?

I agree, I was copilot in several 4.1 final drive cars. They all howl and chirp. But still, a 4.1 final drive is very sporty in a 4/4.

The axles have all been BTR since the late 1990's....

Simon, if this is so, why was it relatively easy to change the final drive on the older 4/4 Sports to 4.1 by fitting a new bevel gear and ring gear, and why did both Williams a few years ago and Techniques as well tell me this was not possible on my 2014 4/4? Do you have a solution? I would love nothing more than to drive my 4/4 more dynamically. Now I have 160 km/h in 5th gear at 4000rpm and at 6500 rpm I would theoretically go 264 km/h. My third gear goes up to 165 km/h which is complete nonsense. In hairpin bends, even second gear is way too long and I have to shift into first gear. If you have a solution, a bottle of good wine or whiskey comes on top:)

Anyone know how you tell which axle you have fitted?
As I said elsewhere, I thought my 2011 car had a BTR axle which Techniques converted to 4.1:1
However, from Heinz info mine must be a salisbury.

Because BTR changed the size of the crownwheel and pinion. They went from an 8” diameter to 8.8” or similar, The diff carrier (the pigs head) in the middle of the axle is also physically larger and heavier
Morgan didn’t want to invest in new CWP sets with different ratios
BTR also no longer make the axle so spares will dry up in a few years

Simon, thank you for that eloquent explanation. Assuming I could find an older BTR axle, two questions. A) Would I need a different propshaft? B) Was the older BTR axle slightly less wide? Visually, it looks like the rear and rear wings are slightly wider than earlier 4/4 Sports models?

Hi guys,thanks for all the input.This is where I am at the moment.I have had it confirmed that my 4/4 sport was converted to competition spec by Revolutions up in Perth who converted it to go racing.It has throttle bodies,LSD,roll bar,AVO,s,panhard rod,etc,etc.After listening to all your comments and talking to Revolutions my next course of action is to replace the medium priced diff oil I purchased(with friction modifier)for some very expensive(£215 for 2.5 litres)diff oil+friction modifier,as advised in gomog.I will give this a go and report back to you with the result.Revolutions have said that if this does not cure the "ringing howl"I can take it back to them for investigation.

Grant, the way you describe your car with all the tuning it could be possible that it already has a final ratio of 4.1? And these differentials have always whined significantly. So if it's even louder now, a good oil might actually remedy it as you suggest.