trying to move the z around and it seems hard work pushing it, brakes are free, but it seems the diff is making hard to push. is it a limited diff or has the diff seized??

Its not in gear is it! I have done things that stupid :lol:

no gearbox, so I don't think so

Might be a welded diff. Mine was very hard to push & the back wheel kept skipping if I turned the car whilst pushing it.

Check the tyre pressures makes a world of difference, even if they look ok.

 

Jeff TT

Tyres were all freshly pumped up, will get it on the ramps tomorrow and detach the arms

I have known a cars diff to lock up.it would make it a pisser to move when turning.

I have known a cars diff to lock up.it would make it a pisser to move when turning.

 

Sounds like the problems I'm having

have you had the car jacked up and one of the back wheels turned while the other is on the floor? it is possible to wind the diff up and lock it. just like over winding a clock. ????

Got it the on ramps now, the wheels do move independently, but still needs force to do it. So now I'm just so no take the diff off. I have an NA one to go on anyway

Your not trying to push an auto in gear are you? I'm in hailsham on Wednesday night?

no gearbox, so I don't think so

 

^^^

Your not trying to push an auto in gear are you? I'm in hailsham on Wednesday night?

 

I'm about Wednesday, but the car is in Cambridge lol

Ahhhh, ok just thought you may have wanted a hand for a few hours.

Thanks for the offer!!

have you had the car jacked up and one of the back wheels turned while the other is on the floor? it is possible to wind the diff up and lock it. just like over winding a clock. ????

 

I really like that idea, but that's not how our diffs work. I don’t know about mechanial locking ones perhaps they do that sort of thing, but ours are viscous so all done with oil.

 

This is how I understand viscous diffs.

 

There is a box of thin discs in special diff oil. A bit like a spindle of cds that sort of size and about 6 discs. The plates are thin metal with holes in them like 5p sized holes. The oil has a property (to do with surface tension and shear viscosity) that when swirled up by the spinning of these discs (which are attached to the half shafts) basically does a cornflour and goes fairly solid. So no wheelspin diff is open, but if there is a lot of difference in the speed of these discs, the oil is agitated and it locks up.

 

Bit off topic but like the clockwork idea, I'll have to look up how mechanical locking ones work.

Edited May 25, 201411 yr by tomfromthenorth

This is how I understand viscous diffs.

 

There is a box of thin discs in special diff oil. A bit like a spindle of cds that sort of size and about 6 discs. The plates are thin metal with holes in them like 5p sized holes. The oil has a property (to do with surface tension and shear viscosity) that when swirled up by the spinning of these discs (which are attached to the half shafts) basically does a cornflour and goes fairly solid. So no wheelspin diff is open, lots of difference in these discs speeds agitates the oil and it locks up.

 

Bit off topic but like the clockwork idea, I'll have to look up how mechanical locking ones work.

 

Thats a really good common man's description Tom.:thumbup1:

There are a number of people on here who should read that carefully and then they will understand how their car drives .:yes:

They will also realise why changing the oil in a viscous diff does NOT alter its slip load at all cos the part you described is sealed and tucked away inside the crown wheel.

 

I already knew what you have said about how it works and I know how a plate diff works too BUT I await your description if you do one.

Haha right! Taking one apart would have been easier than reading pages and pages of text but now I have a good Idea I'll have a go.

 

A viscous lsd is simple, cheap and takes a lot to wear it out, but the drawback is the lock effect is softer to come on and not as strong as a mechanical one.

 

If you want a really tight diff or want it to lock under deceleration you need a mechanical one.

 

There are many types that do the same thing in different ways I imagine due to patent issues, quaife, zf, torsen etc.

 

So, a diff needs to detect rapid increases in wheel speed and upon detection lock both sides together, or, more accurately send torque to the not spinning side.

 

A mechanical diff often uses helical gears to 'detect' the torque. A helical gear will have a thrust force associated with it's rotation. Imagine you have an electric screw driver with a gnarly old wood screw on it. You hold this out like a wand and lay the screw on vinyl on a record player. You could use the electric screwdriver to rotate the record and record deck but the screw would be trying pull itself forward out of your hand because the thread would 'climb' on the vinyl. This is how a helical gear has a thrust associated with the input torque.

 

Now the screw is the helical gear and the vinyl is a circular crown gear, as torque increases the shaft with the helical gear will move forward a bit.

 

This moving forward a bit then either rams a little cone inside a big cone and locks the back end together (cone type) or is attached to a clutch pack (clutch type).

 

There are a couple of these things in a diff, it will look like a shaken up box of Knex inside! This effect obviously only works in acceleration, 1 way diff, or you can have springs pushing on the clutch/cones all the time then the helical gear thrust effect as well, this is a 1.5 way diff; this means off throttle its still a bit lsd. Or use full on white mans magic and a system of freewheels and **** knows what and you have one that does it under braking too 2 way diff.

 

About right pete?

About right pete?

 

Oh you are way ahead!!:yes:

I only know a little about the clutch pack plates as in old school salisbury diffs and similarly in the Kaz ones where you can add plates or reverse them to increase or decrease the torque figure that they "break" or "slip" at.

The Quaife and Torsen ones make my (small) brain hurt.:biggrin: