Posted by Gary on Wednesday, October 31, 2001 at 1:44PM :
Driveline vibration or chatter in a divorced transfer-case drive line system (the transfer-case and transmission are not one integral unit) can be easily eliminated or moved to a less objectionable part of your regular driving speed range. The vibration or chatter is caused by the change in relationship of the front (transmission to transfer-case) drive shaft to the rear (transfer-case to rear-end) drive shaft each time the vehicles transfer-case has been operated in low range.
The following technique may be common knowledge to some owners of vehicles with the above mentioned driveline system, however I came by the information by the trial and error method on my own (then new) W100 Power Wagon back in 1968. Many trips to the Dodge dealership and several visits by the factory rep. failed to eliminate the “sometimes it vibrates on take off and sometimes it vibrates at various highway speeds complaint”. I asked the engineer at an original equipment driveline supplier about the pesky vibration, he said that it was the nature of the beast and that variable speed of origin was caused by the changing relationship of the primary and secondary drive shafts in the two-transmission system.
First block the wheels then pop the transfer-case and transmission into neutral. Dive under the vehicle and grab the short (transmission to transfer-case) drive shaft and rotate it till the universal joint yokes (ignore the one that goes to the front wheels) on both sides of the transfer-case match each others rotational position (if the flat surface of the rear yoke is facing straight down match the flat surface of the front yoke to it. Next put the transfer-case back in high range and drive the vehicle, be critical of only your normal driving speed range, if the vibration has been eliminated or moved out of your normal driving speed range you are done (the procedure will only have to be repeated after the transfer case has been in low range).
If the vibration is still present somewhere in your normal driving speed range you will need a bit of time and a safe, smooth, flat place that will let you repeatedly stop and then do runs through your normal driving speed range. Make your first run and note at what speed the vibration exists, stop, leave the transmission in gear or in the case of an automatic put the transmission in park, shut off the engine (keep your foot on the brake, try not to roll) and put the transfer-case in low range. You may have to release the brake to get the transfer-case to shift into low range this is OK as long as you do not roll. Next drive forward about one foot, stop repeat the above process to shift the transfer case back to high range and then do another run through your normal driving speed range, the vibration will be have been moved higher or lower in your normal driving speed range. Repeat the process until you have moved the vibration out of your normal driving speed range. You may have to compromise if you wind up with either a low-end vibration or a vibration somewhere else in you normal driving speed range. In other words if you can not eliminate the vibration entirely find the sweet spot for it, the place in your normal driving speed range where it aggravates you the least. After this has been accomplished, stop, leave the transfer-case in high range, shut off the engine, block the wheels, dive under the vehicle and paint a permanent mark on the exact bottom of both the short (transmission to transfer-case shaft) and the long (transfer-case to rear end shaft). After each time that your vehicle has been operated in low range, realign the two marks with each other. The above process will take you less than one hour to complete and produce a vehicle that is more of a pleasure to drive!-------Thanks Gary
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