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.
Dog Biscuit said:
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/
Thank you very much for help.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
This is the geo result before after changing left rear wheel to right, and before switching to michelin :
REAR /
LEFT CAMBER : -1.51
RIGHT CAMBER : -1.47
LEFT TOE OUT : 0.12
RIGHT TOE OUT : 0.16
THRUST ANGLE : 0.03
FRONT /
LEFT CAMBER : -0.53
RIGHT CAMBER : -0.49
LEFT TOE IN : -0.05
RIGHT TOE IN : -0.04
It didn't move since 10 month (marked with pencil on bolt alignement)
- It can't be differential bushes : it doesn't have one, there are only transmission bushes hydramount on left and right. Differential is bolted to the transmission and the whole thing sits in the rear subframe.
As you can see here
[url]
images.pistonheads.com/783013/202607145243623[/url]
I doubt it could be this honestly. From the informations i got here and there on web + chat gpt asked, best probability is bushes somewhere and then suspension.
I checked the rear toe link bar again, I try to put pressure on with a lever arm it but I think wasn't able to put enough force on it. Bushes looks ok from both sides and they can pivot on their axes normally.
All triangles and toe arm have been checked by mechanics by the past . That is why I'm left without answers for now. Maybe they just checked it badly without enough force to see the problem on one of the triangles / toe arm bushes.
I live in France, so too far from gravity center...
Gooly said:
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.
Wow... you are giving me so much hope there.Thank you for passing by.
I assume you are talking about this element :
Gooly said:
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.
Is your car left hand drive and right hand drive ?Gooly said:
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.
Is your car left hand drive and right hand drive ?V12BEN said:
Gooly said:
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.
Wow... you are giving me so much hope there.Thank you for passing by.
I assume you are talking about this element :
V12BEN said:
Dog Biscuit said:
Fluid bushes can be deceiving and hard to really be sure about without some prober leverage
How could be leverage those without disassemble all the rear of the car ?You mean the blue ones in pic right ?
What about taking it to centre gravity?
eta just checked the pic - the circled ones are just vibration/rubber bushes
Edited by Dog Biscuit on Tuesday 14th July 21:22
V12BEN said:
Is your car left hand drive and right hand drive ?
My car is right hand drive. Mine failed on the hub side - you can lever the arm off the whole bush on mine! I have ordered two new toe links (one for each side). It appears to be the arm you have pictured. They are £500 a piece lol - painful. When I spoke to specialists none of them said it would be this. I was quite pushy in saying it was to do with toe control. One thing I did was get my friend to visually check the wheel under acceleration. I had him stand on the pavement while I got the car to a normal speed and then accelerated hard past him to trigger the issue. He said he could see the wheel toeing out under load which made me strongly believe it was the toe arm.
The way the bush has failed looks very normal for any car of this age. It would be my first assumption for this kind of issue.
Also I should note that after this issue developed I took it to a geo place. They checked everything and aligned the car and found no issue. The issue persisted and it was only after this that I did a thorough lever check and found the issue. The alignment place is very good - the issue is it is difficult to spot wear on this bush on the ramps.
I am saying this to basically say that don't trust a garage who has just put the car up on the ramps and inspected it. You need to assume it is this arm and thoroughly test it. I don't think there is any other part of the Vantage's rear suspension or drivetrain that can cause this issue.
As you can see, we were able to push the arm down revealing the bush (silver ring) such is the extent of the wear. This is probably quite an extreme example. This is on a 106k V8 Vantage 4.3 which is running coilovers. This is no.15 on this diagram: https://www.astonstore.co.uk/product-category/comp...
I am getting new arms fitted and the car re-aligned. I'll let you know how it is after. I hope you find the issue - please keep us updated.
Edited by Gooly on Tuesday 14th July 23:37
Dog Biscuit said:
Im not too sure tbh
What about taking it to centre gravity?
eta just checked the pic - the circled ones are just vibration/rubber bushes
No, no these are hydramount transmission bushes not rubber What about taking it to centre gravity?
eta just checked the pic - the circled ones are just vibration/rubber bushes
Edited by Dog Biscuit on Tuesday 14th July 21:22
https://www.scuderiacarparts.com/part/189978/aston...
I didn't see leak on both , from what I could "see"...
Gooly said:
My car is right hand drive. Mine failed on the hub side - you can lever the arm off the whole bush on mine! I have ordered two new toe links (one for each side). It appears to be the arm you have pictured. They are £500 a piece lol - painful.
When I spoke to specialists none of them said it would be this. I was quite pushy in saying it was to do with toe control. One thing I did was get my friend to visually check the wheel under acceleration. I had him stand on the pavement while I got the car to a normal speed and then accelerated hard past him to trigger the issue. He said he could see the wheel toeing out under load which made me strongly believe it was the toe arm.
The way the bush has failed looks very normal for any car of this age. It would be my first assumption for this kind of issue.
Also I should note that after this issue developed I took it to a geo place. They checked everything and aligned the car and found no issue. The issue persisted and it was only after this that I did a thorough lever check and found the issue. The alignment place is very good - the issue is it is difficult to spot wear on this bush on the ramps.
I am saying this to basically say that don't trust a garage who has just put the car up on the ramps and inspected it. You need to assume it is this arm and thoroughly test it. I don't think there is any other part of the Vantage's rear suspension or drivetrain that can cause this issue.
As you can see, we were able to push the arm down revealing the bush (silver ring) such is the extent of the wear. This is probably quite an extreme example. This is on a 106k V8 Vantage 4.3 which is running coilovers. This is no.15 on this diagram: https://www.astonstore.co.uk/product-category/comp...
I am getting new arms fitted and the car re-aligned. I'll let you know how it is after. I hope you find the issue - please keep us updated.
So you said it was passenger side arm right ?When I spoke to specialists none of them said it would be this. I was quite pushy in saying it was to do with toe control. One thing I did was get my friend to visually check the wheel under acceleration. I had him stand on the pavement while I got the car to a normal speed and then accelerated hard past him to trigger the issue. He said he could see the wheel toeing out under load which made me strongly believe it was the toe arm.
The way the bush has failed looks very normal for any car of this age. It would be my first assumption for this kind of issue.
Also I should note that after this issue developed I took it to a geo place. They checked everything and aligned the car and found no issue. The issue persisted and it was only after this that I did a thorough lever check and found the issue. The alignment place is very good - the issue is it is difficult to spot wear on this bush on the ramps.
I am saying this to basically say that don't trust a garage who has just put the car up on the ramps and inspected it. You need to assume it is this arm and thoroughly test it. I don't think there is any other part of the Vantage's rear suspension or drivetrain that can cause this issue.
As you can see, we were able to push the arm down revealing the bush (silver ring) such is the extent of the wear. This is probably quite an extreme example. This is on a 106k V8 Vantage 4.3 which is running coilovers. This is no.15 on this diagram: https://www.astonstore.co.uk/product-category/comp...
I am getting new arms fitted and the car re-aligned. I'll let you know how it is after. I hope you find the issue - please keep us updated.
Edited by Gooly on Tuesday 14th July 23:37
So your right hand drive was pulling left because of the left rear toe arm ?
Then it should be same left for me.
I guess the rear left tyres has its toe opened more on throttle. From above you could see the tyre pointed outward not to the center of the car right ?
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