Car veers to right at 8000 rpm

[steve74]

I picked up my Mk2 GT3 yesterday and had a lovely 450 miles drive!

Anyway, on a dry stretch of empty road, there was no traffic so I accelerated to 8000 rpm in second as it seemed ideal to hear the engine. As I went to change to third and applied the clutch, the car veered to the right suddenly. Now this wasnt a problem as I'd chosen a completely empty 3 lane road and barely exceeded the speed limit.

My question is would this be normal for a GT3? My guess is that I came off the gas too soon, but I was in a straight line? The car is from a Porsche dealer so I presume would have had an alignment check... I'm thinking that maybe the camber on the road affected the car and when I took my foor of the gas at maximum rpm, the weight distribution shifted causing the issue? Or is there something wrong with the alignment?

Anyway, suffice to say, I havn't exceeded 4500 rpm since!

[1999Porsche911]

I picked up my Mk2 GT3 yesterday and had a lovely 450 miles drive!

Anyway, on a dry stretch of empty road, there was no traffic so I accelerated to 8000 rpm in second as it seemed ideal to hear the engine. As I went to change to third and applied the clutch, the car veered to the right suddenly. Now this wasnt a problem as I'd chosen a completely empty 3 lane road and barely exceeded the speed limit.

My question is would this be normal for a GT3? My guess is that I came off the gas too soon, but I was in a straight line? The car is from a Porsche dealer so I presume would have had an alignment check... I'm thinking that maybe the camber on the road affected the car and when I took my foor of the gas at maximum rpm, the weight distribution shifted causing the issue? Or is there something wrong with the alignment?

Anyway, suffice to say, I havn't exceeded 4500 rpm since!

Check the air pressure in the right back rear tire. When letting up on the gas, low pressure in a rear tire will pull the car to the side of the low pressure tire. If tire pressure is the problem, the car should pull to the low side whenever you let you on the gas at any moderate or higher engine speed.

Edited December 13, 2006 by 1999Porsche911

[steve74]

I picked up my Mk2 GT3 yesterday and had a lovely 450 miles drive!

Anyway, on a dry stretch of empty road, there was no traffic so I accelerated to 8000 rpm in second as it seemed ideal to hear the engine. As I went to change to third and applied the clutch, the car veered to the right suddenly. Now this wasnt a problem as I'd chosen a completely empty 3 lane road and barely exceeded the speed limit.

My question is would this be normal for a GT3? My guess is that I came off the gas too soon, but I was in a straight line? The car is from a Porsche dealer so I presume would have had an alignment check... I'm thinking that maybe the camber on the road affected the car and when I took my foor of the gas at maximum rpm, the weight distribution shifted causing the issue? Or is there something wrong with the alignment?

Anyway, suffice to say, I havn't exceeded 4500 rpm since!

Check the air pressure in the right back rear tire. When letting up on the gas, low pressure in a rear tire will pull the car to the side of the low pressure tire. If tire pressure is the problem, the car should pull to the low side whenever you let you on the gas at any moderate or higher engine speed.

Will check this evening!

It was quite a violent movement - a complete involuntary lane change!!

I spoke with the dealer and they say that the alignment was checked before sale (111 point check by Porsche). Dealer suggested trying it again on a different stretch of road!

Edited December 13, 2006 by steve74

[steve74]

Ok, I've checked the tyre pressure - 36f, 40r both axles even!

Rollbar setting maybe?

[RayGT3]

Maybe those crappy sloppy motor mounts in the car acting up. These things can cause all sorts of strange problems.

[1999Porsche911]

Ok, I've checked the tyre pressure - 36f, 40r both axles even!

Rollbar setting maybe?

Does it do it if you simply throw the clutch pedal to the floor, or only when decreasing speed in gear and clutch engaged?

[steve74]

Ok, I've checked the tyre pressure - 36f, 40r both axles even!

Rollbar setting maybe?

Does it do it if you simply throw the clutch pedal to the floor, or only when decreasing speed in gear and clutch engaged?

Only when clutch to the floor while accelerating and max rev's. At the point of upward gear change in second!

[1999Porsche911]

Ok, I've checked the tyre pressure - 36f, 40r both axles even!

Rollbar setting maybe?

Does it do it if you simply throw the clutch pedal to the floor, or only when decreasing speed in gear and clutch engaged?

Only when clutch to the floor while accelerating and max rev's. At the point of upward gear change in second!

Lets me make sure I understand this. You can go to 8000 rpm in first gear and let up on the gas without pressing the clutch in and everything is fine. If you do the same thing, but press the clutch pedal in, the car will move to the right? That sure doesn't sound possible to me unless you have a real strange behavior with the LSD. It would make more sense if it pulled when decelerating whether the clutch was engaged or not.

A dragging brake would do it both ways. So would allignment or low tire pressure. Are you sure it doesn't do the same thing s you take the car to 8000 and simply let you foot off the gas pedal? If it only does it when the tranny is not engaged as you state, your car if free wheeling unless the LSD gets stuck to one side causing the drag of the right axle. I would suspect that a broken sway bar or other suspension componant would also show itself whether you were in gear or not. Does it do the same on your 2nd to 3rd gear shift?

How many miles on the car? Does the car want to pull slightly to the left when taking it to 8000 under full throttle in 1st gear?

[ymmv]

Rear toe is out of balance. The eccentrics are a weakness in the rear suspension design. It's not all that surprising, but sadly Porsche has carried this idea on to the 997. Rear camber might also have changed. Either track driving or bad roads can cause the rear toe to move out and this will create that tail shimmy on a shift.

Just to be complete, while it's rare, perhaps one of the rear tires is not in the same condition as the other. This tends to happen when there's a puncture and replacement late in the life of a set of tires -- the new tire will be "bigger" and have different heat and grip characteristics.

[Qualified Pole]

steve74,

I, too, am a new owner of a GT3 and had bad twitchiness and some exaggerated power off behavior, similar to --but not as severe as--to what you describe. I had the alignment re-checked by the dealer even though it was supposedly done in the CPO check (which I question since the car felt funny when I drove it off the lot). The rear toe was out of whack by a few minutes (!) and caused the weirdness, so I can imagine what a really tweaked toe out would do to handling.

clord gave me some suggestions for a street alignment in this post:

996 GT3 stumble or hesitation...

My car was not aligned to those specs but will be shortly, but just bringing the alignment within the loosey-goosey service manual specs has been an amazing improvement. On one of the other recent posts someone also mentioned that a bad alignment leads to bad tire wear which is unsolveable by realigning (thus new tires AND a good alignment are necessary). Good luck with the fix and please let us know what works.

Michael

[REDLINE WINS]

Make sure the tires all have the correct N rating as per Porsche for the GT3. If the N rating is correct then check the production of tires and see if they are within 1 or 2 months from each other. I have a client with the same issue, we checked everything and found all normal. Only after talking with Porsche Tech Line did we find the problem...right rear tire was made ten months later than all the rest. We replaced the tire, problem no longer present. Porsche claims this issue only effects the 996 GT3.

Robert

redlinewins.com

[Rob in VA]

I have noticed this behavior on my "new" to me '04 GT3. The dealer found out that the right rear strut was leaking. The car is still at the dealer, and it should be ready for pick up on Monday. Looking over all of the receipts from the previous owner, he changed the RR tire several times, and looking at the car, the RR needs replacing again. I ordered a new set of rear rubber (PS2s). The alignment will also be redone to more aggressive track settings.

[Rob in VA]

I got the car back today, and it's driving without any issues.

[spidermonkey]

I had the exact same symptom on my '04 GT3. It was the alignment that was the culprit. After aligning it to proper specs for camber and toe the symptom went away along with the twitchy handling. It's an absolute joy to drive now.