RHD 1968 240 with automatic Borg Warner 35

Just been completing restoration of steering bushes and resetting the automatic links to get the arrow in correct place for the gears. During the process had the car up on 4 jack stands and when starting the car for gear shift changes noticed that the rear speed wheel spin rates were completely different.
Looked about the same in Reverse gear, stopped in Neutral and Park. However in D1,D2 and L the N/S rear wheel spinning at massive rate and O/S rear wheel hardly turning at all. I understand the purpose of the differential is to allow the wheels to turn at different rates for cornering and camber etc but never expected one wheel travelling so fast at idle and the other one hardly turning. Is this within the "normal" expectations of the differential or does it imply significant brake binding on the O/S or a problem with the differential? Is the differential just choosing the least resistance on the N/S and sending all power to that wheel? The rear wheels turn manually in Neutral without and audible binding?

Appreciate your advice and opinions.

Frank

 

Though I've had my car running axle stands, I've not paid attention to the rear wheels - more worried about it falling off the stands and taking the back wall out of the garage. Getting back on topic, I'd guess that if there's slightly more friction at the slow wheel than in the diff and the fast wheel, you'll get what you are seeing. Since things are equal in reverse, it might be worth checking for a dragging brake, particularly hand brake. It might also be interesting to see what happens if you add a little friction to the faster moving wheel (perhaps by tightening the handbrake caliper or something safe) to see if it reverses the effect, but be very careful.

 

Thank you Peter. I did start the engine running with a degree of trepidation. However at idle with turning back to see the o/s wheel turning very slowly and the car rock steady it seemed ok. It was more by chance that I went round the back and saw the n/s wheel spinning at quite a substantial rate that I was a bit uncertain!
That was the time that I checked all of the rear wheel movement in the different gears.
Have set the links for the auto box so might just leave this alone. If it goes flying forward it won’t hit the garage wall it will go right into the back of an AM DB7!

 

I wouldn't worry about it, Frank, if you've done the basic checks, as all vehicles with a differential are like that. It's most likely that it's just a rear brake dragging from lack of recent use and all will be fine on the road. My '66 S Type is very reluctant to turn a wheel if only one is up off the floor but both will spin happily by hand if I have both rears up on jacks.

I know my car likely doesn't have the same diff as yours but if any car will push to and fro on a level surface by hand then there's nothing much amiss.

Ray

 

Thanks Ray.

The car has done 5 miles since restoration and apart from the steering wheel wobble that I had it seemed to drive ok. It passed a pre-test MOT and the brakes were “very good and equal “ so I was surprised by finding this different wheel spin.
Will check out the rear brakes whilst it’s up on stands but as you say I will just ignore it for now.
Thanks for your help and steering column went pretty straightforward. Frank

 

It would only take a small amount of drag over one wheel to cause this. The drag could be caused by (as said) a brake binding or the hand brake not equally set up on one side. Then again it could be a wheel bearing that is worn but not enough to hear or feel or on the other hand it could be one wheel bearing has been stuffed with more grease than the other side. Lastly it could be the Diff bearing slightly worn or more tightly packed. I would not worry about it until you can feel the drag when turning the wheel by hand or you start hearing something.

 

I wouldn't worry about it, but I would touch the wheels and brake discs after a run to see if one is much warmer than the other. The Dunlop brake design was brilliant for it's time and still provides more than adequate stopping. However, the pistons tend to stick in their cylinders and can bind against a disc. If it's too severe for too long, the disc can crack and it's a bit of a PIA to swap.

 

Thank you everybody, great to get a unanimous “don’t worry”. Also unusual to be given advice not to do anything. I will of course review all the brake fittings and try to check whether there is any undue binding of handbrake.
After that at 73 I might be able to do my first donut! As long as it’s a planned one I will be happy.
It does make sense that it would only take a minor difference in friction in one side to get one wheel going and presumably after that the motion on that one wheel would perpetuate that motion so it would get faster and faster. I’m not a real physicist though! I am however very grateful for everyone’s input.

 

Frank, I've never done a donut in the Mk2. However, when I was much younger and it was my daily driver, driving to work in the snow, I wondered how it would respond to a little right boot. Suddenly, it was very much Roger Clarke and RS Escort going round the corner sideways spraying snow into the air. Fortunately, the car sorted itself out. Mk2s can go very well but it can be a delicate balance and involve more tail out than is really a good idea on the public highway.

 

Ha: I was a regular attender (visitor not driver) at the RAC Grizedale Forrest stages in my earlier days. Loved it, maybe that’s where some of the passion comes from? Most of the drivers only knew how to go sideways or so it seemed. Sadly my MK2 ambitions will be a Sunday driver hopefully keeping all 4 wheels on the ground and going in a straight line. Roger Clarke, Colin McCrae, fabulous drivers of their day. Thanks for jogging the memory. Frank

 

... which has brought back a memory of mine. It must have been around 1980. A friend and I went to see an RAC stage in Oulton Park. 'See' - we didn't see anything but headlamps flashing by as it was pitch dark. Still it was memorable for a few things. BL had decided to rally the TR8. The V8 engines made a terrific, rich burble. Nothing else sounded like them. In the dark I stepped in to 6ft deep hole and magically vanished for a minute - fortunately I was totally unhurt. And finally, when it came to leaving, my Mk2 had no clutch as the slave cylinder had failed. It turned out that the car happily could drive off in first gear on the starter, even on uphill slopes, and with a touch of throttle, the engine came to life. And the ancient Moss box didn't seem to notice the absence of a clutch for gear changes. Got us home quite easily. Nothing would ever stop that car. Happy days.

 

Hi Peter
clearly similar interests at that time. Lived in Cumbria, Gosforth in the 70’s hence Grizedale Forest and early career working in Manchester so would go to Oulton Park for their fixtures.
Ive got a photograph somewhere of the cars with headlights and half a dozen spots exactly as you describe.
As you say happy days.