XF Forum banner

1 - 9 of 9 Posts

·
Registered
Joined
·
54 Posts
Discussion Starter #1 (Edited)
On a recent motorway trip, I notice the car has a slight pull to the left.

I’ve always felt something isn’t quite right as the car does feel a bit ‘twitchy’ at times, but this was more noticeable on the motorway.

It’s a lot worse on kickdown - almost feels like torque steering. Coming off the throttle suddenly, it again feels like torque steering before straightening itself out (with my intervention of course).

A bit of history - the car was damaged on the left side and when I had the alignment done, although the guy couldn’t see anything physically wrong, he did say that he thought the upper arm on the rear might be bent and that the front castor arm was on full adjustment, so that may also be bent.

Could this be the cause or will it be something else?

Please help with any ideas before I take it to a garage so I have a rough idea of what I might be looking at.

Thanks in advance.
 

·
Registered
Joined
·
2,030 Posts
I can't help you much, as I am far from being a specialist on steering issues.

What I can tell you is as follows:
Even with the more powerful 3.0 engine, I have never experienced anything that I would describe as torque steer.
My car has never felt twitchy, as you describe it, and on motorways, the car is as straight as a die, with only the occasional severe camber requiring any sort of attention.

From what I have read, the castor arm adjustment appears to be critical to self centering of the wheels, so that looks like a good starting point.
 

·
Registered
Joined
·
66 Posts
Pulling to the left is one thing - as you have identified it's likely to be an alignment issue.
Certainly I have experienced this myself with the car not feeling planted - a visit to a local specialist with the 'proper' 4-wheel alignment gear (Hunter) and a few relatively minor tweaks and all was well.

However, on a rear wheel drive you should not get pulling left (or right) when putting power on or off. I would be concerned something is flexing that shouldn't be and, from what you describe, if it's happening under power I would be concerned that one (or both) rear wheels is moving significantly on power on / off giving you an element of rear wheel steering (that shouldn't be happening!). Other possible causes could be completely different grip between the rear tyres or a differential issue. However, given the car has been in an accident' I would be concentrating on getting all the control arms and bushing and their mountings thoroughly checked. From what you describe (re elements being at the limit of adjustment) something is certainly bent - could be a suspension arm or the chassis.
 

·
Registered
Joined
·
54 Posts
Discussion Starter #4
Thank you for the replies and apologies for not updating this thread sooner.

I had the car in for a service and MOT earlier in the week and asked them to pay particular attention to the suspension - they couldn't see/ find anything untoward.

I might have overexaggerated the 'torque-steering feel' and perhaps I am overcompensating for the car pulling to the left which is probably more noticeable and more sudden under acceleration. Something still isn't quite right and, as you say XFNI, the car doesn't feel planted. It was a Hawk-Eye machine they used for alignment but I'm going to get it done again from somewhere else just to make sure. The only suspension components I replaced myself were the rear track rod and the drop link (track rod was done before the alignment). I'm not sure if these are torqued up properly as I couldnt get my torque wrench on them properly so maybe the flex is here?

What are the chances it could be a driveshaft issue (as this was mentioned as a possible cause by the garage)?
 

·
Registered
Joined
·
66 Posts
Going back to a clean sheet.....
Torque steer is caused by unequal traction between the driven wheels. It is prevalent in FWD cars because the (normal) transverse engine layout means the gearbox / differential is on one side of the car so the drive shafts are of unequal length. Hence, under hard acceleration, more power / torque is delivered to one wheel (with the short drive shaft) and hence the car pulls to that side.
Fundamentally this is not an issue for a rear wheel drive since the differential is in the middle of the car, the driveshafts are of equal length and hence power transmission to both wheels is the same = no torque steer.

If your RWD Jag car is pulling to one side and this is only happening under acceleration then there has to be a fault as it's not a characteristic of the car.
So, you need to so a bit of research and eliminate potential causes - i.e. what's causing different traction on the driven wheels or is the suspension flexing under load so introducing a steering element.
- Given the car has been in an accident, my first suspect (as earlier) would be alignment. A dedicated 4-wheel alignment check should show this up - i.e. a system that checks each wheel independently to a datum. The standard 2-wheel check really only ensures each axle has the correct toe - i.e. the relationship between each rear wheel (or front wheel) to the other is correct, but it doesn't check accurately that the front and real axels are pointing along the same plane. This is the Thrust Angle and it should be shown on the print-out from a 4-wheel alignment check. See here https://www.knowyourparts.com/technical-resources/suspension/understanding-thrust-angle/
- Check is the tyres are the same on each axle (not so important front to back, but should be same side to side) and they are correctly inflated etc. If one tyre is gripping more then this will cause torque steer. You should try swapping the wheels side to side to see if any difference - if car pulls the opposite way when you swap them over you've found the culprit!
- Check there isn't a brake binding. If one wheel has a braking applied it will cause the car to pull to that side.
- You mentioned a driveshaft could be the cause - yes I suppose it could although more likely to be an issue with a universal joint or the differential as it's unlikely that a driveshaft has failed (and that would be fairly obvious!).
- All of the above are related to different traction being applied to one wheel (or one wheel not transmitting the same traction to the road). The other cause would be the wheels moving about in a lateral plane - i.e. twisting out of alignment so giving a steering effect. As discussed previously this could be worn bushings or ball joints. If a component is bent this is more likely to show up as a misalignment. However, if the (static) alignment has been adjusted to compensate for a bent component (or bent chassis) then this could cause a steering effect. As the wheels move up and down on the suspension the toe angle will change slightly. So, if part of the suspension or chassis is bent, even if it is adjusted to be the correct length, the pivot point will be slightly different on the bent side and hence that wheel will move slightly differently to the opposite side. Hence, since the car will squat slightly under acceleration, you can get a steering effect. Given your car has been in an accident and you said that some of the suspension adjustments were on the limit, this could be a possible cause.

Only thing else I can suggest is to try and establish when the 'torque steer' you are experiencing manifests itself.
- On a flat straight road (e.g. motorway) does the car steer straight. If you accelerate does it pull to one side.
- On an undulating road does the car move about - i.e. as the suspension moves up and down is this impacting on the steering (so called bump steer).
Depending on when it's happening will help identify the root case.
 

·
Registered
Joined
·
54 Posts
Discussion Starter #6
Don’t know if I’ve mentioned this before, but the back end seems to twitch when the car is changing up through the gears.

On a side note, the front end of the car seems a bit ‘skippy’ when doing a 3-point turn - even more so in the wet.

I’m going to have the alignment redone/ rechecked as it doesn’t seem right to me.
 

·
Registered
Joined
·
54 Posts
Discussion Starter #7
Car Pulling To The Left - UPDATE

Had the car in at a specialist today.

On the rear, the track rod wasn’t tight and therefore had play in it. That’s now been sorted. Also, the rear shock absorber bushes had lots of play in them. These have also been replaced. The rear of the car is now nice and tight.

On the front, the lower arm bushes also need doing. These will get done soon and then a full 4-wheel alignment.

Not sure if this will sort out the problems I was experiencing but it certainly wouldn’t have helped so it’s a step in the right direction.

On my way back, the rear was definitely behaving itself more than before, so a result!
 

·
Registered
Joined
·
6,985 Posts
I hope you don't have bushes under your XF, but, yes, worn bushings can cause the sorts of lurching/pulls under accelerations.

Under sudden acceleration, the engine and drive line components are trying to twist the car. If there is play in the suspension (bushings or otherwise) the car can pull to one side and generally feel very sloppy and require constant attention at the steering wheel (it can be fatiguing to drive such a car for long).

I think you have a good chance of solving your issues with the actions taken/being taken. Good luck.
 

·
Registered
Joined
·
13 Posts
Your lower arm bushes as well as the front castor arm needing to be on full adjustment is certainly something that would cause the pull to the left. I would also suggest that you look at the front struts themselves.

Also, check your tyre pressures. Are both front tyres at the same pressure???
 
1 - 9 of 9 Posts
Top