7 replies to this topic

[Tim]

Has anyone ever had their 99 torsen LSD stop sending power out to one wheel while on the dyno pack? When our car would hit around 3000 rpm all the power would go to the right wheel and not the left. Do I need another new diff, or is there a reason. Thanks

[Justin Baltrucki]

Torsens are torque biasing with typically a bias ratio so they can only transfer a multiple of the available torque at the lowest grip weel. For example on an AWD car with a center torsen if you sit the rear tires on ice, and the front on pavement the power available to the front wheels is only say 2 to 4X (depending on bias ratio) the available grip to the rear wheels. And 4X zero = zero so the front wheels don't get squat. This is similar on RWD car that might lift an inside wheel in the air around a corner. With a torsen the diff goes nuts and you get no power to the outside wheel and you just spin the inside airborne wheel like crazy. I suspect this is what you are seeing in action

[Bench Racer]

If you have a 99 FSM is there a process for checking the Torsen?

I copied this below from a Honda S2000 thread.


Well, the manual lists a short test. And I quote...

1. Set the parking brake, and block the rear wheels.

2. Raise the rear of the vehicle, and make sure it is securley supported.

3. With the ignition turned to Lock (0), shift the transmission into 1st gear, and release the parking brake.

4. Rotate either rear wheel by hand, and check that the other wheel rotates in the opposite direction. Check both wheels.

5. If the opposite rear wheel does not rotate, or if you cannot spin the rear wheels at all, the limited slip differential is faulty and should be replaced.

[FTodaro]

Have you pulled the drain plug to see if you have debries in the oil?. Its almost, unheard of for a torsen to fail in a Miata since we are not pushing that much HP through them but by the nature of the beast I am not sure you issue is not with the dyno. you might ask if other cars do the same?

I am not sure about your test, I know you use somthing close to that test for a diff with a clutch pack and testing the pre-load but I do not think the tires turning in the opposit direction or not, proves much, but I could be wrong.

[Bench Racer]

I am not sure about your test, I know you use somthing close to that test for a diff with a clutch pack and testing the pre-load but I do not think the tires turning in the opposit direction or not, proves much, but I could be wrong.

No one was offering support so I went looking. I searched this site & found nothing. The info is copied from a Honda site where someone had issues with a Torsen.

[Tim]

Has any one tried that s2000 test? We just replaced all the fluids and every thing looked ok. The dyno shop has done hundreds of Mazda's for some pretty top notch guys.He has only seen this happen one time before. We did the rest of the dyno on a drum, and everything seemed fine. But with a 6000 lb drum, who knows. I will try the wheel spin test tomorrow and report back. Diff is pretty new, one race season, so I hope it doesn't need to be replaced.

[Ron Alan]

Torsens are torque biasing with typically a bias ratio so they can only transfer a multiple of the available torque at the lowest grip weel. For example on an AWD car with a center torsen if you sit the rear tires on ice, and the front on pavement the power available to the front wheels is only say 2 to 4X (depending on bias ratio) the available grip to the rear wheels. And 4X zero = zero so the front wheels don't get squat. This is similar on RWD car that might lift an inside wheel in the air around a corner. With a torsen the diff goes nuts and you get no power to the outside wheel and you just spin the inside airborne wheel like crazy. I suspect this is what you are seeing in action

No expert here...but spinning a inside wheel(right hand turns only)was what we always experienced with the open diff. Since installing the torsen...same corners...no issue with a corner(of car) going light and getting wheel spin. I suspect there is a little...but hardly detectable by sound in video. Also, looking at drawings of a torsen1 or torsen 2, they are all gears. I would think if something was wrong/broke you would have a lot of metal in your fluid(chunks)and major noise...just my Maybe someone who has seen a broken torsen can chime in on their experience??

[SaulSpeedwell]

Has anyone ever had their 99 torsen LSD stop sending power out to one wheel while on the dyno pack? When our car would hit around 3000 rpm all the power would go to the right wheel and not the left. Do I need another new diff, or is there a reason. Thanks

Left brake dragging.