Car pulls to one side mystery issue - SOLVED - I am a nong.

[roadsailing]

stupid question, are the tyres on each side the same profile?

is the diff perpendicular to the car? (ie panhard rod the correct length and diff mount in the same position as the T series one)

also got a question for you, PM to be sent shortly

[GA61XX]

Upper and lower control arms are extremely different lengths, so that's not an option.

I'll get my girlfriend to take it for a drive and see if she finds the same problem, or only experiences a 60/90th of the problem.

On a serious note, I dropped the nose of the pinion a little and it seemed like the problem became less pronounced, though I'm not sure if it's real or placebo.

Hen

So you have adjustable control arms..???
You may need to adjust one side more than the other.. as your hanger may have a twist in them.. eg. rotation is out...
try adjust one side only & see if it is better or more stuffed..

cheers

[Hack]

Upper and lower control arms are extremely different lengths, so that's not an option.

Hen

Uh, whoops, yeah, I ment both left hand side control arms with the right hand side...

Hack

[Hen]

The diff is not sitting at the wrong angle across the back of the car. I got an alignment and the thrust angle, rear toe and all other measures were spot on. Yet the problem still appeared.

Plus I've been under there a number of times and measured from the diff tube to a mount on the chassis and the measurement is the same both sides (ok +/- 1mm, but that's well within the margin of error measuring with a tape measure).

No, I don't have adjustable arms, however I am adjusting the position of the mount holes on the diff. When everything is spot on and working nicely I will weld it in place.

Yes, identical tyres on each side too.

Hen

[Toyo Truck]

Hen,

I have had alot of experience with pinion angles due to my lux being lifted and
lowered about 100 times.

What sort of setup is it? 3-link? 4-link? 5-link?
You need the pinion to be at the exact same, or as close as possible to the angle of
the gearbox at rest on a flat surface.

This way you will minimise driveline wobble at speed due to mismatched uni joints.

Another way you can check the setup is to lift the car on a hoist, let the suspension
fall to full down-travel, then measure everything, as the bushes will be supporting ALL
the weight and any wrong mounts, lengths will be apparent if the diff leans to one side,
is looser on 1 side than the other, or moves more than the other, with more/less effort.
(get under it with a long bar and move the diff around to test this)

Failing that, cut em off, start again. This is really the only way if more than 1 mount is
stuffed.

Good luck with it man

Cheers,
Bart

[Drifty Midship]

Yeah may sound dumb but I experience this with a tight LSD if my tyres are worn differently on either side or even if the pressures are slightly different.

[Hen]

Trucker - thanks for the advice, I hope not to have to redo all the mounts, The F series is damn heavy and I've put it in and pulled it out too many times already.

I'll take another look at tyre wear, profile and pressure. If it's that simple I'll kick myself for not doing that first.

Hen

[Hen]

OK, the official count is in.... and the results are.... I'm a dickhead.

Was home for lunch today and checked the tyres. 195/55 on the passenger, 195/50 on the driver's side. That'd cause it.

The tyres came off a friends daily driver. He must have run different profiles front and back. You wouldn't believe how pissed off with myself I am.

Thanks for all the advice though.
Hen

[cri_ag]

good to see it was a simple fix, have you realy given it hell yet? you stated your pinion was pointing a little towards the floor. ive just (like in the last week) got my sprinter going with a ms112 in the rear and my diff was pointing up a little as well, resulted in massive axle tramp and the diff actually hitting the floor, and my car is not low by any means.

Solution for me was linden's (roadrunner) adjustable lower arms, increasing the length and thus changing the pinion angle. All sweet now.

[Hen]

I have barely driven the diff. And most of that has been breaking it in and test drives around the block. It has been given some stick a time or two (to check the LSD works), and have had no issues with axle tramp or the like. But the rear tyres are pretty old and hard.

I'd considered adjustable arms, though I'd prefer to get the diff spot on with stock.

Hen

[roadsailing]

told you to check the tyres! must not have seen the post among all the extremely technical ones.

[LeeRoy]

Well on the plus side, since you have now checked everything, you can take some relief in knowing that the car is ok.

[Toyo Truck]

YAY for Hen!

[Hen]

Well on the plus side, since you have now checked everything, you can take some relief in knowing that the car is ok.

That is a far better way of looking at it than my current mindset. I feel I had a perfectly good diff and then went and screwed with it for a total of zero gain.

But in any case I think it needs a serious flogging to further "test" it... at Calder on Feb 9th.

Hen