Posi not working all the time
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Launching!
Joined: Mar 2004
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Posi not working all the time I have a 99 with the Zexel Torsen posi and it used to work great all the time. Now it seems like there is a 50/50 chance that both tires will spin. 
Around corners, it will sometimes spin both and go sideways like it used to, and other times just spin the inside tire all around the corner. Power braking in place even spins only one half the time. For about 2 years now it has been doing the typical Zexel clunk around corners and the "box of rocks" while coasting under 25 MPH. However, when I had the fluid changed it all looked really good inside with no metal shavings. The fluid has been chnaged twice in 68K miles, the last time was at 50K. I have read a few posts about this, so has anyone figured out what these things are doing? Any help or advice is appreciated.
Around corners, it will sometimes spin both and go sideways like it used to, and other times just spin the inside tire all around the corner. Power braking in place even spins only one half the time. For about 2 years now it has been doing the typical Zexel clunk around corners and the "box of rocks" while coasting under 25 MPH. However, when I had the fluid changed it all looked really good inside with no metal shavings. The fluid has been chnaged twice in 68K miles, the last time was at 50K. I have read a few posts about this, so has anyone figured out what these things are doing? Any help or advice is appreciated. A lot of it depends on the specific load the rear was seeing before going into a turn and what the condition of the road surface is. Pretty much like any other "open" rear-end in that once one wheel starts spinning, it's pretty hard to stop until you do something about the load (ie., throttle, turn-in, etc.). It just doesn't act like a clutch-type posi.
Here's a link to a pdf I came across a while back. You may find it interesting. I don't think your rear is broken unless you get a whole lot of noise under load conditions (like the Invex gears are broken). You can call up Torsen (now, Toyoda Torsen) and talk to the tech people there. They are very approachable and very helpful.
Here's a link to a pdf I came across a while back. You may find it interesting. I don't think your rear is broken unless you get a whole lot of noise under load conditions (like the Invex gears are broken). You can call up Torsen (now, Toyoda Torsen) and talk to the tech people there. They are very approachable and very helpful.
Last edited by Fran D; Oct 13, 2005 at 09:46 AM.
Thread Starter
Launching!
Joined: Mar 2004
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I took it someplace to have the fluid changed and the diff inspected. They are a very reputable tranny shop. I gave them Mobil 1 synthetic gear oil and the bottle of GM additive. I assume they used it, but the first time it was changed was by the dealer, and it clunked before I took it to the tranny place. So, that's probably not it. I think there is a lot of play in it. When I put the car in reverse it clunks pretty hard when the tranny engages.
Originally Posted by SilverV6Camaro
...When I put the car in reverse it clunks pretty hard when the tranny engages.
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Torsen will only bias torque about 2:1 (2.2:1?). That
means if the difference between your tires' adhesion,
spinning vs sticking, is more than that then the second
tire will not come loose. As rubber ages its stickiness
reduces and the static/sliding friction difference is
anyone's guess.
A higher-bias version will spin both, I can tell you.
This is not necessarily better for acceleration or
stability but it does make for a more entertaining
show.
There is some anecdotal stuff about heavier, non-
synthetic gear lube increasing the Torsen torque
split and synthetic, thin & slippery stuff decreasing
it. But nothing I consider authoritative.
means if the difference between your tires' adhesion,
spinning vs sticking, is more than that then the second
tire will not come loose. As rubber ages its stickiness
reduces and the static/sliding friction difference is
anyone's guess.
A higher-bias version will spin both, I can tell you.
This is not necessarily better for acceleration or
stability but it does make for a more entertaining
show.
There is some anecdotal stuff about heavier, non-
synthetic gear lube increasing the Torsen torque
split and synthetic, thin & slippery stuff decreasing
it. But nothing I consider authoritative.
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Launching!
Joined: Mar 2004
Posts: 213
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U-joints are tight, I can't get them to wiggle or anything. I heard that about the Torsens, the 2:1 torque ratio, but I swear as the the car has racked up more miles this has gotten worse. All I can think of is that the gears that operate the Torsen develop some play, and don't engage as often as they used to. I guess th bottom line is that it isn't broken, but if I want to have better posi traction I need to replace the posi unit. I would rather break it first, but seeing as mine is a V6, I doubt it'll ever bust.
if the back tires are off the ground and you spin one is their a lot of pausie before the other spins? thats what my old rear was doing and the diff was almost shot on it. it would only do a 1 tire peel makeing right hand turns but never kluncked. it did whine really bad tho (axle was bent)
Thread Starter
Launching!
Joined: Mar 2004
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I have to try that again, but the last time I did that they spun in opposite directions (which is normal for a Torsen, like an open diff) with just a little play and clunk sounds when switching directions. I could also turn the driveshaft with the car in neutral and hear a clunk in the rear with some play in between directions.
Originally Posted by SilverV6Camaro
I have to try that again, but the last time I did that they spun in opposite directions (which is normal for a Torsen, like an open diff) with just a little play and clunk sounds when switching directions. I could also turn the driveshaft with the car in neutral and hear a clunk in the rear with some play in between directions.
You may want to check the backlash to see if it has openend up. After 70K miles and constant hammering on the pinion, I found that mine had opened up to ~0.017"!
It had pounded the crush sleeve down an extra 0.010". However, with an M6, I couldn't hear any discernable "clunking." I know it doesn't solve your posi issue, but it may have something to do with your "clunking." Thread Starter
Launching!
Joined: Mar 2004
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You could be right about that. My old Cutlass had an open diff, and by 90K that thing clunked like crazy! You could turn the driveshaft either direction quite a bit before it would catch in the rear.
On the Camaro when the diff was inspected they did mention that there was some play, but they claimed that it was because of the "cheap" torsen posi unit. They said the gears loosen over time, I suppose that means the smaller 4 gears that make the torsen unit work, which means when getting on and off the power they clunk when they engage and disengage. They told me the only fix was to replace it with an Auburn or Eaton clutch style posi. However, they said it probably won't break, it'll just be noisy. Now that was a year ago, and at that time the posi seemed to always work. Now I am getting the on and off one wheel peel which is why I am questioning how well the torsen is holding up. It could be backlash though.
On the Camaro when the diff was inspected they did mention that there was some play, but they claimed that it was because of the "cheap" torsen posi unit. They said the gears loosen over time, I suppose that means the smaller 4 gears that make the torsen unit work, which means when getting on and off the power they clunk when they engage and disengage. They told me the only fix was to replace it with an Auburn or Eaton clutch style posi. However, they said it probably won't break, it'll just be noisy. Now that was a year ago, and at that time the posi seemed to always work. Now I am getting the on and off one wheel peel which is why I am questioning how well the torsen is holding up. It could be backlash though.
