lol

 

Anyone have an answer? If there is any slip from the front (left and rt average) to bacK?

 

Yes, tire circumference difference is said to be bad for the ACD because then you are basically "dragging" the ACD at all times since the computer will detect differing rotational speeds of the two sides outputs.

Terry S

 

Thanks, one more stupid question, what about non ACD, is there any front to back slip? If so is it damaging?

I did a test a while ago with tire pressures by marking tires at 6:00 both front and back then I let them rotate 10 rotations. A change in 5psi from the sweet spot resulted in one tire being in 6:00 and another at 9:00 when I stopped.

 

Any AWD vehicle with a center limited slip will wear it out faster if there is a difference in rotational speeds between the front and rear sets of tires.

It's the same as with any limited slip differential. If it's constantly engaged then it's going to wear out faster.

Terry S

 

Did you do your test with the car on the ground?

The VCU (viscous coupling unit) on the non-ACD cars can be thought of as silly putty. Like silly putty, if you push on it slowly or pull it slowly (or have a slow speed differential between the front and rear tires), it is soft and very elastic. If you take the silly putty and hit it with your fist or try to pull it apart quickly (or have a high speed differential in wheel speeds), it acts more like a solid.

I think that a small differential in front and rear wheel speeds, such as from having one end inflated higher than the other, is not going to spin the VCU fast enough to create much heat or cause any problems.

 

The non ACD unit has some play ...... I had a spool in my DSM ..... that didn't have any play at all. I would drag a tire on every tight turn.

 

Here is what I did:

1. Stopped car on a level road with steering straight
2. Placed a mark on each wheel at 6:00 (closest point to ground) with a sharpie
3. With steering straight, traveled forward while observing the mark on tire (hang out of door) and counted 10 complete revolutions and stopped when mark is 6:00 again
4. Compared left rear (6:00) to left forward (9:00) with both pressures at 30psi (on the other side, (right) similar, but not exactly same, differences between them occurred)
5. After putting 32psi in front and 30psi in rear and a little more precice air feathering did all four tires land on same spot after 10 rotations

Conclusion: Due to the greater weight load on front tires, the overall circumference decreased from it squishing

 

Does acd works when decelerating?

 

Ok so let me see if I am tracking here
Open= wheel speed vary, torque split constant
Closed= wheels speeds same, torque split varying

And the torque you are referring to isn’t the actually toque delivered by the engine. It is the toque (twist) that the shaft experiences when you try to turn it. For example in the ice/pavement example for the closed the ice has less friction to resist the wheel turning therefore there is less twist(torque) on the shaft than the pavement side since they are both spinning at the same speed. And in the open example the wheels are allowed to spin at varying speeds to keep the torque (twist) the same on both axles.

So in the case of the ACD in a turn it varies the locking action between the front and rear tires between open in closed. Since in a turn the front tires have a longer distance to travel there is going to be a torque (twist) differential between the shaft feeding the front wheels and the shaft feeding the rear wheels but they will be spinning at the same speed if the ACD is closed. But if the center differential is open the front and rear wheels are allowed to spin at different speeds to keep the twist (torque) on the shafts the same.

In summary: The ACD’s main function is to manage the speed differential between the front and rear tires and how long it lets that differential persist is what the different modes change.

Does this sound correct?

 

Holy ****, nice man, thank you!

 

I have a question...


so why would you want your center diff to lossen up at a slower rater when on wet/gravel and snow compared to dry "drippy" roads?

I thought the looser a dif the more traction on a conner? or not?

 

thanks for the info

 

So what about torque biasing differentials? If you have one front and rear how would it interact with the ACD or the older viscous style?

 

just one question, what do you think has gone wrong if i have hooked up the unit to run the acd pump to bleed the unit and nothing happens? as in no fluid running