Paul Valente
Automotive Engineer
Preloaded Helicals
Right, you are governed by the worse wheel so if you get zero torque to the worse wheel (like if it comes off the ground) you get zero times the bias ratio to the other wheel (e.g. 0 x 2.0)...which is still zero. Once the diff breaks-away and you get a spin-out, it is hard to stop it and start over again (momentum, mu static > mu dynamic, etc.)
Plate-type diffs are more responsive to pre-loads and can support a lot of torque just due to the pre-load spring. There are pre-loaded helicals (like the Quaife as you know) but they are less effective though the pre-load does dampen lash. You can see the disc spring-pack in the middle of the assmebly shown in the inset picture. Pushing two steel side gears against a steel case has much less effect than pushing against a clutch pack:
As far as Quaife the company goes; Tractech was selling Dana 30 sized helicals (about the size of a front wheel drive diff only a little bigger), made in Warren, Michigan, at a union shop (Teamsters) for about $400 retail. Quaifs were about $1200 at the time. Not saying that the Quaife is a bad diff or anything, Steve. Just that they are expensive. Maybe we could start our own company to compete with them? :hmm:
This is because the Torsen type diffs open up if one wheel looses its resistance. This is because (as I am sure you know) the helical planetary gears require some torque loading to provide enough thrust action to generate the required friction to transfer drive to the other wheel.
The Torsen in the Supra opened up regularly relegating it to open diff status. And once you have one wheel spinning, you have to get completely out of the throttle before it will lock up.
I assume this is the reason that TRD offered a standard clutch type diff for the Supra. I switched to that unit and was much happier.
Right, you are governed by the worse wheel so if you get zero torque to the worse wheel (like if it comes off the ground) you get zero times the bias ratio to the other wheel (e.g. 0 x 2.0)...which is still zero. Once the diff breaks-away and you get a spin-out, it is hard to stop it and start over again (momentum, mu static > mu dynamic, etc.)
Plate-type diffs are more responsive to pre-loads and can support a lot of torque just due to the pre-load spring. There are pre-loaded helicals (like the Quaife as you know) but they are less effective though the pre-load does dampen lash. You can see the disc spring-pack in the middle of the assmebly shown in the inset picture. Pushing two steel side gears against a steel case has much less effect than pushing against a clutch pack:
As far as Quaife the company goes; Tractech was selling Dana 30 sized helicals (about the size of a front wheel drive diff only a little bigger), made in Warren, Michigan, at a union shop (Teamsters) for about $400 retail. Quaifs were about $1200 at the time. Not saying that the Quaife is a bad diff or anything, Steve. Just that they are expensive. Maybe we could start our own company to compete with them? :hmm: