Vibration (not shimmy) source?

[Not-Choppa]

Hi, I have a '93 Maverick/GQ patrol - (the best 4WD that Ford never made)




The Basics

4.2D naturally aspirated
Manual box
Wagon
Coil Springs
Disks all around
Approx 2" suspension lift
No body lift
30" diam tyres on 16" Rims
No uneven tyre wear or scalloping etc.
Symptoms

I have a high frequency vibration at approx 90 - 100 Kmh
Up to 85/90 Kmh - No vibration
Steering wheel doesn't shake.
Feels like the source of the vibration is not from the wheels, but middle to rear of vehicle.
Vibration frequency is too high to be tyre issues.
It feels much faster than the rotation speed of the wheels.
It almost feels "notchy" like gear teeth. But there is no unusual noise from diffs or gearbox.


Attempts made to fix

Front wheel bearings replaced around a year ago, when I replace the front diff centre. There was a wheel stud that had somehow become lodged between the teeth of the crown wheel and pinion of the front diff prior to my purchase of the vehicle. I have pics.
All wheels balanced
Tailshaft removed, unis replaced, tailshaft balanced, tailshaft installed with slip-yoke to front as advised by Driveline due to rub marks from crossmember when it faced the standard way.
Transfer case replaced because of rear output shaft bearing showing a little play and weeping of oil.
(Interestingly - the speedo is now very optimistic. GPS speed of 100 Kmh - Speedo shows 115 Kmh.)


Questions

Is it possible the transfer case has reduction gears or something in High range? - or is it just a different speed sensor in the xfer case. She does seem to be accelerating a little quicker.

Can anyone venture a guess as to the likely source of the vibration?
Cheers, Ross

Gday Ross welcome aboard ive moved your thread to the intro section gotta friendly mob here fulla great info and advice

[johno90]

First thing i would have looked at would have been your mounts. other then that handbrake drum, bushes!!!! everywhere, how certain are you that its from the middle? wheel alignment, King pins, ball joints. There were also 2 different types of transfer case for gq both look exactly the same so there could be you speed difference. Doesnt have to vibrate the steering to be a steering part either!

[Robo]

Have you tried turning the tail shaft back around to compare.
re-check unis feel smooth still, they can vib a bit.
when you swapped tail shaft around they can be reassembled out of line and this also can cause a vibration.

sometime the tail shaft angle can be to much for the unis to handle whilst turning and they vibrate as a result.
usually over 2" lift for said angle, but ya never know.

I some times get a vibration that sounds a bit like what you describe, but it is on a certain bit of RD only.
small ripples in the asphalt I recon, never happens anywhere else though.

speedo problem, transfer cases can have different drive gear tooth count, might be your problem.
there's a thread on here about, talking on this subject, different drive gears incl part numbers.

[Dhuck]

Welcome to the forum mate.

[Maxhead]

G'Day and welcome to the forum mate

[Not-Choppa]

First thing i would have looked at would have been your mounts. other then that handbrake drum, bushes!!!! everywhere, how certain are you that its from the middle? wheel alignment, King pins, ball joints. There were also 2 different types of transfer case for gq both look exactly the same so there could be you speed difference. Doesn't have to vibrate the steering to be a steering part either!

Ok - thanks for the heads up. Next thing I will check is mounts everywhere for play/wear.

Then I will take it for front end checkup.

Not certain of where the vibration is coming from - just a hunch/hearing thing. Could easily be wrong.

What are the differences between the two different transfer cases?


Have you tried turning the tail shaft back around to compare.
re-check unis feel smooth still, they can vib a bit.
when you swapped tail shaft around they can be reassembled out of line and this also can cause a vibration.

sometime the tail shaft angle can be to much for the unis to handle whilst turning and they vibrate as a result.
usually over 2" lift for said angle, but ya never know.

I some times get a vibration that sounds a bit like what you describe, but it is on a certain bit of RD only.
small ripples in the asphalt I recon, never happens anywhere else though.

speedo problem, transfer cases can have different drive gear tooth count, might be your problem.
there's a thread on here about, talking on this subject, different drive gears incl part numbers.

Tailshaft was only rebalanced and new unis fitted just before easter.

With the tailshaft angle - is the solution to fit off-centre bushes (not sure what they're called) to adjust angle of rear diff, and to also slightly lower gearbox? (can the gearbox be lowered effectively by putting spacers between gearbox crossmember and chassis?)

With fixing speedo problem - is the solution just a matter of swapping the drive gear from the old xfer case into the new one? - Can it be done whilst on the vehicle?


Welcome to the forum mate.

Thanks.


G'Day and welcome to the forum mate

Cheers.


Thanks for all the suggestions guys. I'm a newbie to forbies, but reasonably comfortable with a spanner. I don't mind having a go at the less complex stuff, but will chicken out if it looks beyond my limited capabilities. I'm also a bit of a tightwad and don't like to spend money if I can do the work myself. I would have replaced the rear unis myself, but since I couldn't balance the tailshaft - I let driveline do both jobs.

One other thing I have noticed - I don't know if it could be related is a little clutch shudder on take-off. There is no slipping of the clutch that I can detect at any speeds.

My wallet hopes the answer isn't something expensive.

Thanks again for the help, Ross.

[Silver]

G'day Ross, might be worth copying your question to General Mechanical as not everyone looks at the intros

[Robo]

Sometimes new parts can be no good straight out of the box.
not having a go at anybody, these things happen.
just an idea for ya to check up

[powkers]

I think the reason is crosspiece of the propelling shaft.

[Lieney]

See if you can isloate the vibration.
Does vibration change with RPM?
Does it change depending on the gear you are in?
Is it different with clutch in or out?
Check your wheel nuts and balance.