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