Stuck in the Mud

[Trevor]

I am posting here among friends because we share the same type of transmission with a centre LSD and you, unlike me, have experience in snow.

Last night my wife and I attended a country dance, which was great. I parked off the road on grass and my back wheels were on some soft stuff. (Do I need to confirm, driving the SVX? ) On return and trying to get under way there was wheel spin and applying the normal technique of not too many revs, which could dig wheels in, I got nowhere. I engaged the "manual" option, which starts the car in second and is stated as being provided for these conditions, but still to no avail.

I had been limiting RPM to say 2500 but after some thought I increased things to say 4,000 and this resulted in traction. I have not investigated fully as to why all wheels did not at first engage, and at this stage I am left with :-

Transmission line pressure called for more revs, but not likely.

TCU Expected more revs or an increased throttle opening.

Buzzing the wheels a bit resulted in digging down to something firmer.

To be honest I was disappointed with the cars performance and would like comments from you up there who have snow experience.

N.B. The down under king of the transmission world is not welcome within this thread, as I have absolutely no respect for his opinion, much less any aledged facts put forward.

[ItsPeteReally]

Originally Posted by Trevor

I
Last night my wife and I attended a country dance, which was great. I parked off the road on grass and my back wheels were on some soft stuff. (Do I need to confirm, driving the SVX? ) On return and trying to get under way there was wheel spin and applying the normal technique of not too many revs, which could dig wheels in, I got nowhere. I engaged the "manual" option, which starts the car in second and is stated as being provided for these conditions, but still to no avail.

I had been limiting RPM to say 2500 but after some thought I increased things to say 4,000 and this resulted in traction. I have not investigated fully as to why all wheels did not at first engage, and at this stage I am left with :-

Mud is funny stuff, and momentum is all important. When you are stationary, you don't have any!

I'll accept that we will have to rely on your impression that the transmission took a considerable time to lock up and asking the good lady wife to wade through the mud to verify which wheels were spinning was probably inadvisable

In my experience it does take a little time for the transmission to lock up, maybe half a second or so after the wheels start to spin. This is not unreasonable, considering that a solenoid has to operate, fluid has to flow and build up pressure, and other arcane mechanical gubbins has to leap into action - perhaps for the first time in many months (or in your case possibly years).

My guess, and it is only a guess, that nothing's broke and that whatever was previously sticky, gummed up, or stiff, has now magically got better after that little bit of gentle exercise.

There's only one way to be sure though! Which way to the nearest muddy field?

[b3lha]

You know more about this than I do Trevor.

Perhaps you have a solenoid problem and your front wheels are not being driven. Have you tried inserting the diff lock fuse and seeing if it makes any difference?

As I understand it, the rear diff has a viscous coupling which requires a substantial speed difference between the two rear wheels before it binds them together. Possibly one rear wheel was spinning and the other was stationary. When you increased the RPM, the extra spin locked up the rear diff and got you moving?

Phil.

[Trevor]

Originally Posted by b3lha

You know more about this than I do Trevor.

Perhaps you have a solenoid problem and your front wheels are not being driven. Have you tried inserting the diff lock fuse and seeing if it makes any difference?

As I understand it, the rear diff has a viscous coupling which requires a substantial speed difference between the two rear wheels before it binds them together. Possibly one rear wheel was spinning and the other was stationary. When you increased the RPM, the extra spin locked up the rear diff and got you moving?

Phil.

Thanks Phil,

I don't think I have a fault as a problem and am confident I have normal AWD. It would appear that revs are required on several counts before all comes into play.

I had not thought of one back wheel spinning due to the LSD not locking up, in view of our featured AWD. It was the rears which were on soft stuff and I am sure you have the answer.

P.S. Please do not mention solenoids.

[svxistentialist]

Originally Posted by Trevor

Thanks Phil,

I don't think I have a fault as a problem and am confident I have normal AWD. It would appear that revs are required on several counts before all comes into play.

I had not thought of one back wheel spinning due to the LSD not locking up, in view of our featured AWD. It was the rears which were on soft stuff and I am sure you have the answer.

P.S. Please do not mention solenoids.

I think Pete's point about moving from standstill says a lot. Shifting all the car's weight take a lot of torque. As our road tyres have zero grip in slippy conditions, they can spin freely in low grip situations. Perhaps the percentage weight of the LSD is set low, so as not to jerk around the luxury ride.

I figure if you were wearing traction lug tyres like a jeep, she would just pull out of the muck without a chirp.

The other point is like what Phill said; if I was in a situation like you describe, as soon as I realised one wheel was spinning, I would pull the diff fuse to give it a better chance of rocking it's way out of bother.

Joe

[Trevor]

Originally Posted by svxistentialist

I think Pete's point about moving from standstill says a lot. Shifting all the car's weight take a lot of torque. As our road tyres have zero grip in slippy conditions, they can spin freely in low grip situations. Perhaps the percentage weight of the LSD is set low, so as not to jerk around the luxury ride.

I figure if you were wearing traction lug tyres like a jeep, she would just pull out of the muck without a chirp.

The other point is like what Phill said; if I was in a situation like you describe, as soon as I realised one wheel was spinning, I would pull the diff fuse to give it a better chance of rocking it's way out of bother.

Joe

Hi Joe,

I had no trouble getting traction as soon as I used RPM, my point was one of interest as to the exact reasons why. I won my car club's mud trial many years ago, in/on an AC sports car with a Ford V8 engine transplant, I had at the time.

What are you suggesting with - "I would pull the diff fuse to give it a better chance of rocking it's way out of bother."

Inserting a fuse would lock up the centre controlled LSD on my JDM car, but would have no affect on the rear LSD?

Cheers, Trevor.