Thread: Halfshaft clutches - please can someone explain

the way Im reading it is that its a torque limiting device so that in the event of massive overload it just slips. Sort of like a clutch but different.

theres a few versions of it most a varient in one way or another of a sprag (like the one that mounts the stator in a TC) clutch or a viscus friction pack (like the one in a viscus fan or the viscus slip limiter in a rangie).

Not sure Id want them in the halfshaft assembley as most basic versions only have a limited number of "slips" before they start to deteriorate. they then either become free wheeling (like the sprag in an overworked TC) or lock solid( like the ones in the rangie slip limiter)

I can understand why they want them, in theory, it would give you the ultimately reliable halfsaft.

Thanks Dave, my next question ... how common would it be for a broken half shaft in conjunction with a front locker, to cause that sort of dramatic "mishap", for want of a better word? Would it be a one off type of event, or more common. And why would it lose control to such an extent if it had a rear locker engaged, unless the rear wheels were off the ground at the time?

(Not that I'm paranoid you understand!)

Something like Ashcroft's Cush Drive?

Ashcroft Transmissions

Think someone mentioned them a week or so ago.

Cheers
Simon

no, not like that. they provide a dampning, and reduce shock loading which is a very good thing but at the end of the day they will still provide a positive drive so if you lock a wheel solid and then jam 40000000000000000 nm of torque onto it it will still snap something.

the clutch would provide a release at X nm of torque and just keep spinning and generally make a lot of heat in the mean time.

Those crush drives are what I would be fitting if it was me.


the reason why it would have speared off will be at least 3 fold

1. Driver error, he should have ridden the brakes and left the front diff open. A standard procedure for going down hill under engine braking, you need to be able to steer and the locked rear will keep the back going slower than the front (till all traction is lost on the rear anyway)
2. Driver error, if he knew he had the problem and took no other precautions to prevent the vehicle from running away from him and loosing control, if he didnt know because hed been driving around all day locked up at what point did he ever do a check and, if he had just gotten into the vehicle why didnt he test everythings functionality first?
3. Driver error with a broken vehicle he was going to attempt an obstacle, if hed asked himself the 3 golden questions he should have gotten a no at question 2 or 3. (negating that question 1 is generally irrelevent in a comp)
4. the vehicle would have lost traction at some point on the rear axle (it would have been trying to overtake the front and get down the hill first) and the only retardation to this would have been the single front wheel with engine braking applied this would have turned the vehicle cross slope and caused it to roll.
5. being in a comp odds are it had an auto (or if a manual he may have been riding the clutch) , he may have not gotten the TC fluid coupled correctly prior to descending(or fully released the clutch and then when it hooked up it would have caused a sudden unexpected retardation which would have a, slid the vehicle to the side with the least braking effort b, yanked the steering wheel around uncontrolabley all of which would have made the vehicle try to cross slope at a fair clip.

I assume they mean GKN overload clutches or similar...

To help preserve the shafts and to avoid time consuming front shaft replacement the front axle has GKN Driveline Overload protection hubs. These work through a set of pre-torqued discs that allow slippage when high sheer loads begin but pull back the drive when the stress has dissipated. There were developed for use by the Army with their Wolf Defenders in front line action.

Originally Posted by isuzurover

I assume they mean GKN overload clutches or similar...

Yeah they are talking about GKN overload Hubs.

I had them on my winch challenge 90

They we designed a a sort of cental fugal clutch . So when the wheels spun in the air when they came down (which is the quickest way to break a half shaft ) they disengaged the front shafts and rengaged when the load was safe to
Look at the pics and you can see them on the front hubs





This is the set up i had on the front of my 90 , Standard shafts and Arb locker with Kam 4.7 ring and pinion . I could use standard shafts as i had the GKN overload hubs as you can see here on the left



Me and my brother both had them on our winch challenge 90's . I remeber Marcel ( from here) came to see me and my brother when i was in the uk and we went off roading . where my brotehr showed him what they could do . He put both front and rear lockers in on his 4.2 V8 90 and the put it on full lock and floored hit and did loads of donuts around and around . Much to Marcels surprise

yes more like them (Id imagine)....

and sorry panda...

that kind of mishap would be more frequent than you'd think under those conditions.

Thanks Dave ... dont' think that's what I wanted to hear though ...

Might have to do a bit more investigating ... mind you, the SIII has had a front locker for well over 10 years, & (touch wood), never had any problems with anything breaking. Maybe I'm just lucky!

Originally Posted by Blknight.aus

yes more like them (Id imagine)....

and sorry panda...

that kind of mishap would be more frequent than you'd think under those conditions.