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

[Hen]

Background:
My sprinter has been running fine recently. No (well no more than usual) issues. I pulled out the T18 T-series diff and install a MS112 Crown diff. Everything seems to function fine, except that when I get on the gas hard the car wants to pull right. And under severe engine braking the car wants to head left. When coasting it doesn't pull. Braking seems to have no effect.

That's the issue. Does anyone have any suggestions what may be causing this?

More details:
- The AE86 mounts were welded onto the diff by me, then straightened by a diff shop.
- Centre is a brand new LSD (I've run it in too), built by a shop into a 4.1 centre (old T series was 3.9).
- Wheel alignment is spot on. 00deg 01' thrust angle, bugger all rear toe. Entire front is fine.
- The diff centre is not quite horizontal, it's a little nose up. Could this cause the problem?

Thanks
Hen

[brett_celicacoupe]

i had this issue when a nolathane bush was on the way out. by the end there was about 10mm of movement in the bush


so my suggestion is to check your bushes, unless you have rose joints?

edit:

put the handbrake on really tight and ease the clutch out in 1st and reverse. get a mate to safely look underneath while your doing this and you may see the weak point in the setup.

is the diff dead centre? can you measure the clearance between the wheel archs and wheesl on both sides?

[oldcorollas]

sounds like the drivers side of diff is moving forward on accel and moving backwards under decel, giving you right/left turning?

or something to that effect...

[Matt-AE86]

I was going to say trailing arm bushes. Replace and see if it makes a difference. (It's good to replace them anyway, you will like it much more than standard 25year old ones

[TurboRA28]

On this topic, I find aftermarket rear trailing arm bushes on the Celica only last 6 months or so before there is 5mm of so of slop in each one.
Anyone else have this problem?

[GA61XX]

You say the hangers have been welded on....
Q:- what type of jig was used..??
Q:- Did it hold the brakets in place or did you just line them up...??

Many diff specilest's can weld, But are not jig builders....

If hangers were just lined up then may be out of line.. & you may need adjustable rear control arms, as diff may be twisting under load...

The jig i've just made for MX13 to RA40/60, took me 2 1/2 days to build, & hold's the hangers in 100% same place as the stock RA diff's..
( i'm a professional toolmaker / jig builder, by trade. )
It's a bastard to assemble the parts in the jig, But will only go in the one place.. so you can't get it wrong...
Jig holds diff tight, & have not needed to straighten after welding..
The 1st diff is now in a mates car & no prob's... So i'm doing the next now.. i've got 4 of these things to do...

So in short the hangers may look right, But may be out of line.. Start again....

cheers

PS. i may look at building other jig's.. But need to find more MX13 diff's, & need the demand for the diff's... because if i was to charge to build a jig, it would be $900.oo + ...

[brett_celicacoupe]

Anyone else have this problem?

i did

[Hack]

I too thirdly think that it sounds like a stuffed bush. Tho, if you have only just put the arms back in, you should have been able to see if they had slop...

Hack

[IN 05 NT]

sound like a very simillar issue to mates car, had a locked diff in a r31. new nolathane bushes fitted when the diff was locked,

as the bushes slowly wore out due to the locker, if you gave it a hit in 1st, then went to throw it into 2nd, it would shimmy between gears (rear end would shift over)

blake

[Hen]

Good point on the bushes. While I had it all apart nothing seemed amiss, though I didn't purposely check all that. They are poly that I fitted ~4 years ago, and they have had a hard life.

The diff jig held all the mounts in place. I checked it with the stock diff first and it seemed spot on. It should be dead centre, I measured off the diff flanges to the outer mounts to make sure it was centred before I welded it.

Thanks for the advice, I will update with any further news once I have an opportunity to get under it.

Hen

[GA61XX]

If hangers are central, thats good... But what about the rotation of the hanger...???

If when hanger's were welded on & rotation is out car will pull to one side.. this is where you need adjustable upper control arms...

This is why my jig took 2 1/2 days to build.. it holds the hangers by the bolt hole for the control arms.. (not just a line up of hanger) hence the hanger is in the same place as RA60's.. with no rotation...

cheers

[Hen]

I just checked the bushes and they look exactly as they did when first fitted. They all seem fine.

I'll try adjusting the rotation of the diff (pinion angle) by extending the lower control arms and see if anything changes.

Hen

[Hack]

I wonder if swapping the upper & lower control arms as they are would cause the car to reverse its behavior???

Hack

[oldcorollas]

maybe it's the size of the driver... adding more inertia to the drivers side

[Hen]

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