Rear Differential Information
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Rear Differential Information
I had a 2004 GT back when they were new, and a 2007 after that. Sadly I haven't had an RX8 wince 2009.
But I was thinking about them today. What did these cars have for rear differentials? Was it an open diff, or some kind of limited slip? If it was limited slip, what kind of limited slip?
I don't remember which, but one of those cars had this problem where the diff would seem to lock up after 45m+ of highway driving. So when you'd get off the highway and took a corner, there would be a lot of grinding for a while before it would go away.
I had it looked at at the dealer a bunch of times but they were never able to reproduce it, which makes sense since if wouldn't do it if you want for a 10 minute drive up the highway. It had to be 45 minutes or more.
Eventually I gave up since it was a lease anyway so it wasn't my problem. But I still think about it once in a while and wonder what was actually going on with that. Even if it was a clutch based limited slip system, you wouldn't think driving on the highway would be the least likely thing to upset it.
But I was thinking about them today. What did these cars have for rear differentials? Was it an open diff, or some kind of limited slip? If it was limited slip, what kind of limited slip?
I don't remember which, but one of those cars had this problem where the diff would seem to lock up after 45m+ of highway driving. So when you'd get off the highway and took a corner, there would be a lot of grinding for a while before it would go away.
I had it looked at at the dealer a bunch of times but they were never able to reproduce it, which makes sense since if wouldn't do it if you want for a 10 minute drive up the highway. It had to be 45 minutes or more.
Eventually I gave up since it was a lease anyway so it wasn't my problem. But I still think about it once in a while and wonder what was actually going on with that. Even if it was a clutch based limited slip system, you wouldn't think driving on the highway would be the least likely thing to upset it.
The RX8 uses a Tochigi Fuji "Super LSD." It's technically a Torsen, but only in the most general sense. It uses the spreading force generated by the spider gears when there is a speed differential between the rear wheel to engage a cone clutch to limit the slip. It can apply a slight bias to the wheel with better traction, but not much.
They are not a great LSD and are prone to failure of the cone clutch which turns it into an open diff. I'd wager that the majority of RX8s have had the cone clutch fail.
For your issue, it might have been caused by a tire size difference between the rear wheel. Even a small mismatch in size (for example; a new tire on one side and a worn tire on the other, two different brands of tire or sizes, a manufacturing flaw, or an underinflated or overinflated tire) can cause the spider gears to rotate which would slightly engage the cone clutch. Over enough time, the friction builds up heat and and might have caused the clutch to stick until it broke free or cooled off.
They are not a great LSD and are prone to failure of the cone clutch which turns it into an open diff. I'd wager that the majority of RX8s have had the cone clutch fail.
For your issue, it might have been caused by a tire size difference between the rear wheel. Even a small mismatch in size (for example; a new tire on one side and a worn tire on the other, two different brands of tire or sizes, a manufacturing flaw, or an underinflated or overinflated tire) can cause the spider gears to rotate which would slightly engage the cone clutch. Over enough time, the friction builds up heat and and might have caused the clutch to stick until it broke free or cooled off.
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the_marky
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Dec 7, 2009 04:39 AM