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MG MGB Technical - Pinion Set Up Banjo Axle

My rear differential is really singing.. at speed it whines but the moment I stop the drive shaft from rotating by pushing in the clutch or placing the gearbox in neutral it is very quiet. This leads me to surmise the pinion is the culprit as the axleshafts still turning are not creating the noise. Interestingly enough, this is a like new assembly. It is clearly not set up correct. I was of the belief that the assembly is setup outside of a specific car and would be good to go? When I placed this unit into service less than 300 miles ago it was flawless and quiet. What gives? Axle is mounted correct,full of fresh oil and correct propshaft? Perhaps the runout and lash is off now? Different shims? Any advice on what to look for. How do I determine if the singing has worn the crown and pinion too much? Thanks Ralph
R Stegs

Assuming you filled the differential with oil before driving the car you didn't do anything wrong. The banjo differentials are set up outside the car and should interchange between cars without making any adjustments. That said setting up gears isn't easy and requires the use of some special tools to get it right. My guess is they were not set up correctly.
Read this link for what is involved in setting up gears.
http://www.explorerforum.com/forums/showthread.php?t=144780
The specifications for the MG banjo lump would be different but the procedure is as shown in the article. I tried setting up a tube axle set of gears for a race car several years ago. In a 200 lap race the pinion teeth were sharp as a knife. I quickly learned I don't have the knowledge or skills to do gear setups. Remove the assembly and inspect it carefully. Any damage should be visible. Check around your area for a good racing team and find out who they get to do their gears.

Clifton
Clifton Gordon

Before tearing it apart check that the drive shaft flange to pinion nut is tight.
John H

I have the factory manual for setting a banjo axle. Its about 5 pages, uses a dial gauge and 3 special tools. I could scan it if you need it.
Stan Best

Did you use the correct oil?

Also, pushing the clutch in doesn't stop the driveshaft/propshaft from turning, but will remove the load.

Does it make the noise under all conditions...acceleration, over-run etc?
Dave O'Neill 2

When I bought my car I had a vibration in the exhaust that sounded EXACTLY like a noisy diff'. In fact I got a reduction in price because of it, so it fooled the car yard guy as well. So its worth a look, you never know your luck.
Peter

The noise is intense under load. If I throw the gearbox into neutral it stops. Loud pitched whine but no grinding or growling. If this differential made zero noise for a couple hundred miles, then it got increasingly loud rather quickly, I am guessing something is over stressing the correctly setup differential. By the way this was a factory NOS unit with no adjustment by me. Long stored but no rust and the bearings were good. The manual makes reference to a scribed number on the head of the pinion...mine had a zero and another of 3963. I assume the zero was the initial setup showing no plus or minus on the runout. At this point I am perplexed and sure do not want to try and throw money at this without sorting it out.
R Stegs

Stan,

The manual you talked about, is it section H of the MG factory workshop manual? If it is something else, like a manual fron the axle manufacturer, I would be interested in a scan copy.

davidwitham1961 at yahoo dot co dot uk

David
David Witham

You won't likely find anyone with setup jigs for these. But a good differential shop can use prussian blue and dial indicators to reset the gears and bearings. But, it will likely make some noise (from what I understand the banjo units were somewhat noisy even when new).

My guess is your bearings are failing or the preload is wrong. Fix it before you have to replace gears which may be impossible.

I replace bearings and reset the gears and preload on a 67 Mustang I owned. It howled like the devil before the rebuild. Afterwards not too bad a bit of noise on coast. I was happy considering I had to make shims etc.

Also, I'd switch to synthetic hypoid lube after the rebuild. It cut the noise on my 65 MGB differential quite a bit under load.
Robert McCoy

Nothing outside the diff itself will cause this condition.
The fact that it started out good means that something has changed.
Loose pinion nut causes loose pinion bearings = noise & wear.
Failed bearing - rust, dirt or wrong lubricant. Death.

Take it out and get someone who actually KNOWS what they are doing to examine it posthaste. Running it noisy will destroy the gears. The debris will destroy all bearings and gears. At this point, a good man can set it up by contact pattern, but it gets rapidly more difficult if the gears wear more.

FRM
FR Millmore

This thread was discussed between 31/07/2007 and 10/08/2007

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