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MG MGB Technical - Banjo Axle Whine

Since I don't anyone with an early car that uses a banjo axle I would like to know how loud these axles are supposed to sound. I took a ride to Connecticut to a MG car show and I couldn't believe how loud the rear sounded. Not bearing noise but a whine. I have a 66 Datsun Roadster using the same type of rear axle/diff and it's quiet but I don't know about MGBs. I heard they were fairly load which is why the factory went to the tube axle design.

Can anyone tell me what to look for when I dismantle the diff? I have another diff I can throw in which I cleaned and had looked at by someone who knows more than me and they said the wear pattern looks fine.

Could low oil cause the whining? My diff was pretty low on oil when I bought the car last year and I immediately filled it up. I then realized my rear pinion seal is leaking :)
Mike Magee

Could low oil cause the whining? My diff was pretty low on oil when I bought the car last year and I immediately filled it up. I then realized my rear pinion seal is leaking :) ]]]]]

You may have answered yer own quwstion.

Did you or do you ever ever check the rear end oil? Is the housing coated with oil?
glg

And if it was run too low for too long, it will have done damage that is not reversible. But, if kept full, it may well run for many noisy years.
FRM
http://www.usachoice.net/gofanu
FR Millmore

Mike the banjo axle is an MGA leftover. Mine always makes a whine when under load. When coasting it's dead quiet. I've read that because the MGA was more of an open air car the noise was much less apparent. The B's subsequent quiteness was a factor in replacing with the Salisbury axle. Try 80W140 Hypoid. Quieted mine down quite a bit.
Paul Hanley

Ok question... how would one differentiate differential noise from gearbox noise? My car is pretty quiet other than the usual rattles, but when I downshift (I know, not healthy) there is lots of whine, kind of like a turbine winding down. I've been asked if that was the supercharger making that noise. I wish!!!
Steve Simmons

Rear axle noise, while varying with load, will be at constant frequency for a given speed. Gearbox noise will vary in frequency by what gear you are in. A noisy gearbox, if it hasn't been out of oil, likely means that the laygear bearings are going away, which lets the gear teeth run out of proper mating contact. If you replace bearings soon, you may save it, though it could still be noisier than it would have been had it not been run this way. If you don't fix it, it will proceed to scatter itself into several, or many, more pieces than it should be!
FRM
http://www.usachoice.net/gofanu
FR Millmore

Hmmm... good thoughts. I guess my rear end and tranny are both quiet then. However it sounds like it's the transmission making so much noise when decelerating against the engine. Is that anything to worry about? It sounds smooth, but there is a whine. It's an early unit, 3-sync non-od with 9,000 miles on it.

(sorry to sidetrack the thread!)
Steve Simmons

My diff only makes noise 'on the throttle' not when coasting. I was told by a mechanic at our monthly meeting last night that my gears are probably shot. Good thing I have another diff to put in. I can't wait to rip it all apart and have a look-see at the condition of the gears.

Thanks for all the advice and help :)
Mike MaGee

Mike--"on the throttle" is when it's supposed to whine--it's normal.
Paul Hanley

One reason for the change to the tube type"Salisbury axle was the introduction of the MGB GT . The Banjo unit would have just been too noisy in the closed car. I have been told by racers that they prefer to run on the banjo , perhaps because it reduces unsprung weight?
S Best

Mr. Gofanu, your email address is bouncing back. Did you get my reply?
Steve Simmons

S Best,
The banjo is lighter, a plus for racing, and you can change gear ratios in under 1/2 hour.
Leland Bradley

TY Leland .
S Best

Steve,
No I didn't get your reply. A little disturbing, and possibly explaining why I am not getting replies from some who I expected. But, I do get messages from some. Are you sure that you aren't getting a space in there somehow?

gofanu@usachoice.net

FRM
http://www.usachoice.net/gofanu
FR Millmore

I replied to your email directly. I sent another reply tonight. Hopefully you receive it.
Steve Simmons

I had a bit of a whine in the 3.9 banjo I put in my Magnette - annoying because it peaked at right around 55-60 mph. ' Cant remember the source of this suggestion, but it worked. Drain the rear end and fill it with kerosene. Drive the car around the block once or twice - no more. Drain the kerosene and fill with 80-140 SYNTHETIC hypoid gear oil. This made a very big difference for me.

Allen
Allen Bachelder

Mike, If you have one, you should definately swap the diffs over. It does sound like the teeth are worn and putting oil in now is like closing the stable door after the horse has bolted. My old diff had just the same symptoms but didn't get worse. As they say, they go on for years.

It isn't a hard job though it can be unpleasant if the diff hasn't been off for forty years.

One thing to check is the breather on the top of the axle. If that is blocked, you will lose oil through one or more of the seals.

Mike

Mike Standring

Mike. I too thought the banjo axle was kinda loud. I had bad hubs (silly mistake before I knew better involving a chisel and the 8-point nuts...) and lost oil rather quickly (rear brakes lasted FOREVER ;)).
Coming down a hill at 75 mph, one day, the rear end decided it was done being mis-treated and locked up. That was rather suprising and startling for the other motorists on the freeway, too.
I had cooked that pup good.
Once the new parts were sourced, I had a local shop do the install (took the 3rd member to him) and it is amazingly quiet now... even with the quaife I had put in.

Do have it looked at.

Mike!
mike!

quick question about the diff oil change.... how often should the oil be changed??

I drive my 79 MGB about 1,000 + (-) miles a year, had the MGB now for 5 years (Never have changed it)... Keep checking every 6-8 months, level is always ok.

So I think I'll do it this weekend... take it out for a spin, then drain... and I quess from what I read should use 80W/140 Synthetic Hypoid oil right? and clean the breather too.

Or should I use a different weight oil?

Thanks for any help,
Don
Donald Wheeler

I was always told to use 90W Hypoid.

Mike (Nevada), have you heard of the Quaife units being loud? I always assumed they would be much more quiet than the stock unit.
Steve Simmons

Steve, I have about 68,000 miles on my 79 MGB... do you think the heavier weight is needed? Probably has 90W HYpoid in it now... just don't know for how long (at least 5 years that I've had it).

So that is why it is this weekends project... just checking to get advice before I change the oil.

Don
Donald Wheeler

Thanks for all the help and suggestions. I may try the 140 oil as I will be dismantling my car for a full restoration after the summer, specifically Watkins Glen and I really don't feel like doing any extra work before the disassembly.

I checked the other diff I have and it looks sweet inside and there appears to be no play, the teeth look good and the copper washers appear to be in great shape.
Mike MaGee

Adding the 80W-140 oil will help,and putting in about
1/2 a cup of Lucas Oil Products gear additive will help a bit more, BUT some of them will whine even after everything you do, and after taking it apart about three or four times to re-set and/or check the mesh, you learn to live with it..or end up with a shelf full of newly rebuilt center sections, all of which whine.
Waynw Hardy

What's so strange is that I have the exact same type of rear in my Datsun Roadster and it's as quiet as can be. I never hear it.

Since driving with the top down eliminates the problem I guess I'll have to keep my top down at all times :)

unlike BMW drivers!!!!
Mike MaGee

Mike, that's what I've been trying to tell you all along. You only hear the whine top up while giving it gas. The MGA was noisy no matter what and so owners didn't really hear it. Go to the 85W140 and put the top down!
Cheers
Paul Hanley

Mike,

How did you check you spare diff?

When I had a '66 car with a banjo axle I mounted the diff case on the bench cleaned up the gears etc with parafin and the put engineers blue on the teeth. After turning the input flange for a few minutes it was possible to see the contact area on the teeth. This enabled me to set the diff up with the ideal contact pattern on the teeth. (That is centred and half way down the tooth.) With the rechecking it took quite a while as I was on the a beginner at playing with cars.

This operation made the diff much quieter. An a less noise usually means less powerloss provided the thing is not too tight.

One last point. The teeth are case hardened. If the hardening has worn through you will be wasting your time.

David
David Witham

Steve:

No, I didn't hear that they were particularly loud but the rear-end noise is more of a lash/bearing issue than a spider carrier gear issue so it wouldn't make much difference in a straight line... just when cornering there is more thrust load so if anything is out of whack it will be extra loud when the unit is engaged.
I run 80/140 standard in mine but that is only because it still leaks and I don't want to spend the money on synthetic.
Before anyone gives me a hard time I KNOW this is not good and I promise to fix it real soon.
It should knock a second or more off my autocross lap times!

Mike!
mike!

This thread was discussed between 11/06/2004 and 22/06/2004

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