Gibbo_UK

HI there

Been to the allignment shop today and all is good.

Things were badly out as you guys predicted!

Car now has 1.6 degrees negative camber
6.5 degrees positive caster
Very very slight positive toe in

The handling of the car is superb, there is definetely improve front-end grip and feel. Turn-in is still crisp. Steering is also a little heavier which is very welcomed with improved feel and precision.

I am running 3 turns from firm in the rear with the Tokicos and 4 turns from firm in the front, ride is controlled but firm. Car is confidence inspiring.


I now have two problems, one is something car had before I fitted the new kit and one seems to be a new devolopment.

1. First problem is a rattle/vibration/resonance at 2900-3050rpm. Today the guys at the shop had a listen and first thing they said it was not the engine so good news. They checked header bolts, made sure the exhaust was tight etc. etc. but the car still does it, this developed about 2 months ago and it might be a coincidence but around same time clutch started slipping. So could the clutch possibly cause this as it is slipping a little but surprised it could maybe cause this. My only other thought is its maybe possibly the cats or one of them but giving them a wack reveals no rattles. What do you guys think?

2. My other problem developed after fitting new bits and is in the form of a vibration in the rear of the car, its only at very high speeds of past 90mph and normally upon de-acceleration the rear-end of the car seems to vibrate and resonate, this is not the clutch and pressing clutch in makes no difference, accelerating more helps a bit but its really noticably on de-acceleration and its speed related not revs related as only speeds past or close to 100mph I notice it. Could this be down to the new rear shocks, is it normal when they are set to stiff and is there any cures?

Apart from that car is handling awsome and I know a thing or two what makes a good handling car after having owned M3 CSL, Skyline R34 GTR, Honda S2000 etc. and am very impressed with the Mustang, I just now need to sort these little niggles.

SoundGuyDave

Outstanding!! Glad to hear it. The package that you have on the car should be pretty stellar, and it's good to hear that you got it all sorted.


This one is nearly impossible to diagnose without being right there and hearing it, but you may want to check your front exhaust hangers, where they connect to the trans mount. IIRC there was a TSB that essentially eliminated them, and the 08+ cars don't have them fitted from the factory, and I believe the symptom was a rattle...

This may sound like an odd question, but where on your body can you feel the vibration? First step that I would take would be to pull the rear wheels and reinstall them, using the following procedure:

Hang the wheel on the studs, and with just a socket but no ratchet, hand tighten the lugnut closest to the top of the car. Next, do the same with the lug closest to the 7:00 position, while wiggling the wheel. Re-tighten the top lugnut. Next, do the lug closest to the 5:00 position, still wiggling, and then re-tighten the first two. Next run on the other two lug nuts, and then torque them in a star pattern first to 30 lb-ft of torque, then to 60 lb-ft, then finally to 100 lb-ft. This will take any centering error out of the wheel, just in case there was some slack. If you just gun the lugs on, you can actually mount the wheel slightly off-center, with vibration as the result.

If that doesn't do the trick, have the two rear wheels re-balanced, and see for certain that they are in spec. If there's still no joy, get a mate to drive alongside of you and see if there is any visible vertical wheel motion under high-speed decel. 20" wheels and tires are very heavy, and a little imbalance can be magnified at speed. It would be rare, but it's possible that is your culprit. Under acceleration, the rear tires are loaded more heavily (increased spring pressure) so they would be forced into contact with the ground. Under steady-state cruise, there may be enough pressure to overcome a slight imbalance, so the tires still stay planted. Under decel, though, the rear becomes unloaded, and you may wind up with some wheel tramping as a result. The solution, if that is indeed the problem, and it can't be fixed by more conventional means, would be to stiffen the rear shocks up just a touch more, slowing the damping rate, and transmitting the cyclic load to the chassis, rather than the spring. Rare, but possible.

Anybody else have any ideas?

Gibbo_UK

Hi m8

They mentioned what might have been this TSB or maybe something similar and what they did was to put to jubilee clips not sure if thats what you guys call them but they put them around the exhaust hang mounts and tightened them, but its made no difference but would that be what your referring too or is there another TSB?

The actual noise sounds like the dash is rattling/vibrating and the guy from the shop said it was like an exhaust resionance and as such suggested it might be baffles in cat degrading but thinks that is unlikely as they showed no symptons of rattle when giving them a wack. He also said as the clutch is slipping it is possible that maybe one or more springs in the clutch are broken and as such could be causing this.

I wont be replacing the clutch for a while but when I do will let you know if that makes any difference.

I do have some straight through pipes in the garage to DE-CAT the car so might put those in to just rule out the CAT's but one question if I remove my cats do I need a new tune for my car?

Lastly I shall try what you suggest as to the vibration coming from the rear on de-acceleration as it is only at high speed and putting clutch in makes no difference so its definetely the rear of the car and all thats been changed in the rear is the shocks.

I shall remove a wheel a time from the rear and do as you say and set the shocks to their stiffest setting and see how that is.

Once the clutch is done and these rattles/vibrations are gone the car will be perfect and just as I want it. My only next upgrades will be 18" light wheels and possibly set of AP 6 pot brake kit.

SoundGuyDave

I think you mentioned that you had headers in another post, and if so, your tuner probably turned off the rear O2 sensors, which is the only thing that will come into play when dumping the cats. Even without a tune, swapping to an off-road pipe for testing purposes will only set a code for catalyst efficiency, but there would be no drivability issues. I would give it a try, just to rule out the exhaust.

Just a reminder: when trouble-shooting, do one thing at a time. First, re-hang the rims in the rear, and test-drive. THEN go to the shock damping. If you do both at once, you'll never know what the problem was, and what cured it. The shock adjustment is a band-aid, not a solution, but it is diagnostically interesting.

Gibbo_UK

Hi there

Not had chance yet to try resolving the vibration from the rear but did think that when the rear shocks were installed the suspension was not loaded, would that have caused any issues?

Should the suspension have been loaded?

The bolts at the bottom were tightened without suspension loaded.

However the top bolts were tightented with the suspension loaded.

SoundGuyDave

No issue... the bottom shock bolts can be tightened without loading.

presto

Look under your car on the transmission cross member. if there are exhaust hangers attaching there, that could be the cause of the instrument panel vibration. I had the same issue and took a sawzall to the solid hangers on the pipes and then with the car on a lift i removed the hangers on the crossmember. i have attached the TSB for you here.
Jubilee Clamps = worm gear clamps over here

RRRoamer

Can anyone tell me why this TSB says to cut the mount off the cross member but NOT to cut the hanger off the exhaust system??? You would think that removing the rod would be the quickest way to get the vibration away from the bottom of the car...

presto

I don't know either, I removed both, and gained 37 rwhp

SoundGuyDave

LOL!! I like it!

I can only guess, but a lot of the TSBs are field-expedient fixes, and if it was later determined that there was a long-term problem with the fix, it would be a LOT cheaper to replace the two isolators, than it would be to replace the mid-pipe with four catalysts on it...