Hey guys,

Just thought I would pick some brains about a problem I am having with my tornado ute, there is a vibration coming from under the ute and as the vibration comes on the revs drop by about 250rpm. It's not a constant thing it is only really cruising around 1500 Rpms if the car is under load it doesn't happen, it's only intermittent and last maybe at most a second but it comes on and off at regular intervals. I have noticed that the middle muffler has been hit by something and the rear muffler seems to be bent aswell, I am wondering if this could cause a restriction and could be causing the problem. I have notice it seems to be running a little warm (about half way between quater and half and slowly rises if I am waiting in traffic to just below half) aswell which is making me lean towards the exhaust restriction any advice would be handy I am Having the back half of the exhaust change for a 2 and a half inch system soon to see if will help but like I said any advice would be much appreciated

Bent tail shaft maybe!
Bad harmonic balancer!

MITCHY

Tail shaft had balanced up perfectly I gave it to ford about a month ago and they couldn't find a thing, but even the tail shaft shouldn't affect the revs

Just an update, I have have the muffler change out just for a xforce cat back system, the noise is still there mainly up until it reaches operating temperature......if anyone has any ideas please let me know

A restriction in the exhaust would be felt across the rev range rather than a specific point. Intermitent vibration, that occurs at cruising speed around 1500 rpm but not under load... hmmm. Toughy. What driveline does it have (auto or manual)?

Is it possibly in the differential? ie worn bushes, or perhaps too much backlash. Perhaps even the clutch (if manual) isn't grabing properly... a lot of variables there.

It is an auto, it's just odd how it's seems to affect the revs.

the way you describe it hapening while cruising at low revs, and not under load makes me feel like going with something in the differential. Could be miles off though since it's just a stab based on the selected info.

I once had a Laser that after an engine reco developed an alarming vibration under deceleration or at low throttle cruising. That turned out to be the flywheel undoing itself since the guy who transplanted the motor didn't used the right thread lock on the bolts holding it in. It was hanging on by the skin of its thread according to the mechanic who fixed it Doubt that that is the problem here though, just sharing a stroy since I have nothing else lol.

What you expalined was what a uni joint does when on it's way out..
As the load keeps uni together taking up the slack..
Do the new drive trains have CV's ??
Could be alot of things..
Harmonic balancer, engine or gear box mount..
Bushes in suspension, diff etc..
An unbalanced tyre or uneven out of round tyre..

Thanks for your help guys, still hasn't been sorted out it isn't getting worse but it's not going away either. I just find it odd how the revs drop at the same time. I have a feeling it's either the revs dropping which is causing the vibration....when it happens and I put the foot a bit it just stops which makes me think it may be fuel system related. All I no is what ford have said that the 2 back tyres are scollaped and there has been a new hub put on the front right