V12 V Behaviour / Pulling Left on gas
Discussion
Hi folks,
I've been looking around on web, YT.. Pistonheads might be the last hope.
My V12 Vantage Manual is pulling left hard on gas. Steering wheel at the center.
Here are the symptoms :
- 8 times out of 10 it will pull to the left when torque/power arrives (from 2nd to 4th gear, 1st gear is too short to really appreciate the behaviour and above 4th it kinda fades away). It feels like the rear right is pushing the car to the left . I have to steer a little bit to the right to correct it but feels weird / dangereous.
Sometimes , it doesn't do it.. especially after I've been flooring on purpose just before or just when the road has something "magic" on it.. I don't know what and why. That is for the 2 out of 10.
- 10 out of 10 it will be to the left side . When I lift it goes back to the right a little. Less franckly.
- When road surface is different from right to left side of it, it pulls even more, while Im just accelerating a little.
- On corners : when accelerating at 3500-4000 rpm, even smoothly, car looks like it wants to turn more on left corners. It looks like : oversteer on throttle in left corners and understeer on throttle in right corners.
- On rainy surface, it will always start sliding from the rear right more than rear left. I've tested to start from the opposite side of the road, with natural curb "forcing" the opposite reaction : left rear begin to slide and then it goes to right rear like it wanted to since the begining.
I've been changing tyres to michelin (front PS5 and rear PS4S) changed diff (DAE rebuild), and did geo .
- Rechecked pressure tyres : ok.
- Geometry checked; ok. Except right front caster is 0.5° more than left but seems ok. 0.03 ° thrust angle .
- Bushes seems ok too. Car has 20 000km and 15 Years now.
- I expected the diff to be the root cause at start. It broke some month ago and..... have been replaced. Still the same.
I'll really appreciate your help. Its been months since I can't figure out what to do.
I've been looking around on web, YT.. Pistonheads might be the last hope.
My V12 Vantage Manual is pulling left hard on gas. Steering wheel at the center.
Here are the symptoms :
- 8 times out of 10 it will pull to the left when torque/power arrives (from 2nd to 4th gear, 1st gear is too short to really appreciate the behaviour and above 4th it kinda fades away). It feels like the rear right is pushing the car to the left . I have to steer a little bit to the right to correct it but feels weird / dangereous.
Sometimes , it doesn't do it.. especially after I've been flooring on purpose just before or just when the road has something "magic" on it.. I don't know what and why. That is for the 2 out of 10.
- 10 out of 10 it will be to the left side . When I lift it goes back to the right a little. Less franckly.
- When road surface is different from right to left side of it, it pulls even more, while Im just accelerating a little.
- On corners : when accelerating at 3500-4000 rpm, even smoothly, car looks like it wants to turn more on left corners. It looks like : oversteer on throttle in left corners and understeer on throttle in right corners.
- On rainy surface, it will always start sliding from the rear right more than rear left. I've tested to start from the opposite side of the road, with natural curb "forcing" the opposite reaction : left rear begin to slide and then it goes to right rear like it wanted to since the begining.
I've been changing tyres to michelin (front PS5 and rear PS4S) changed diff (DAE rebuild), and did geo .
- Rechecked pressure tyres : ok.
- Geometry checked; ok. Except right front caster is 0.5° more than left but seems ok. 0.03 ° thrust angle .
- Bushes seems ok too. Car has 20 000km and 15 Years now.
- I expected the diff to be the root cause at start. It broke some month ago and..... have been replaced. Still the same.
I'll really appreciate your help. Its been months since I can't figure out what to do.
Edited by V12BEN on Wednesday 8th July 19:53
I wouldn t be satisfied with geometry is ok here, because static geometry can look fine while the rear axle is moving under torque.
From the symptoms, I d be looking very hard at dynamic rear steer rather than the diff itself. If the car always yaws left under power and then comes back slightly on lift-off, that suggests something in the rear suspension/subframe/diff mounting is deflecting and changing rear toe under load.
Priority checks for me would be:
Rear lower arm bushes / rear toe-control arm bushes. A visual check or levering by hand often won t show it; they need checking properly under load. On similar Vantage running gear, rear lower arm bushes have been known as a cause of this exact type of pull under acceleration. My mate had one
Rear toe links and eccentric adjusters. Make sure nothing is seized, slipping, bent, or incorrectly clamped. Paint-mark the adjusters and recheck after road testing.
Rear subframe/diff mounts. Since the diff has been out/rebuilt/replaced, I d want to confirm the diff and rear carrier are sitting correctly, mounts are not torn, and all bolts were torqued at the correct ride height where applicable.
Rear wheel bearings/hubs. Any small play can become a toe-change problem under power.
Bent rear arm/upright. Even a slightly bent component can align within spec statically but behave wrongly once loaded.
I d also want a proper four-wheel alignment printout showing individual rear toe, camber, thrust angle, caster, SAI/KPI if available, and ideally compare left/right wheelbase. Geo ok isn t enough with a fault like this.
The fact it is worse where the two sides of the road have different grip also fits: the car is already marginal/dynamically steering from the rear, then the road surface exaggerates it.
I d stop chasing the diff for now unless the LSD preload/ramp behaviour is obviously abnormal. The diff may have been suspected, but if it has been rebuilt/replaced and the symptom is unchanged, the next suspect is rear suspension compliance or mounting movement.
Depending on where yu are based, it's definitely worth visiting centre gravity
https://www.centergravity.co.uk/
From the symptoms, I d be looking very hard at dynamic rear steer rather than the diff itself. If the car always yaws left under power and then comes back slightly on lift-off, that suggests something in the rear suspension/subframe/diff mounting is deflecting and changing rear toe under load.
Priority checks for me would be:
Rear lower arm bushes / rear toe-control arm bushes. A visual check or levering by hand often won t show it; they need checking properly under load. On similar Vantage running gear, rear lower arm bushes have been known as a cause of this exact type of pull under acceleration. My mate had one
Rear toe links and eccentric adjusters. Make sure nothing is seized, slipping, bent, or incorrectly clamped. Paint-mark the adjusters and recheck after road testing.
Rear subframe/diff mounts. Since the diff has been out/rebuilt/replaced, I d want to confirm the diff and rear carrier are sitting correctly, mounts are not torn, and all bolts were torqued at the correct ride height where applicable.
Rear wheel bearings/hubs. Any small play can become a toe-change problem under power.
Bent rear arm/upright. Even a slightly bent component can align within spec statically but behave wrongly once loaded.
I d also want a proper four-wheel alignment printout showing individual rear toe, camber, thrust angle, caster, SAI/KPI if available, and ideally compare left/right wheelbase. Geo ok isn t enough with a fault like this.
The fact it is worse where the two sides of the road have different grip also fits: the car is already marginal/dynamically steering from the rear, then the road surface exaggerates it.
I d stop chasing the diff for now unless the LSD preload/ramp behaviour is obviously abnormal. The diff may have been suspected, but if it has been rebuilt/replaced and the symptom is unchanged, the next suspect is rear suspension compliance or mounting movement.
Depending on where yu are based, it's definitely worth visiting centre gravity
https://www.centergravity.co.uk/
Edited by Dog Biscuit on Thursday 9th July 06:16
Hi, my V8V developed this exact issue this weekend. Got it on the ramps and jammed a lever bar around and found the rear passenger side toe control arm bush had failed - not sure of the proper name but its the arm that mounts to the back of the hub which controls toe adjustment. Hope you manage to solve your issue.
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