My wife Linda does all of the driving of our '93 Breakaway, and she is convinced that when downshifting the transmission has noticably incresed the sound and ruffness as the gears change. We checked the level of the fluid and it was fine. Does anyone have any suggestions? Does this portend any future problems? Are there any tests that I can perform?

Some of the items you should check are...
1) The height control valve for your airbags. See if the linkage is attached and at a 45 degree angle.
2) Grease the drivetrain and check the u-joints.
3) Check the fluid levels in the rears.
4) Check your wheels, If the wheels are loosening up you'll get a vibration.
5) If someone EVER had the driveshaft out check the alignment or timing of the driveshaft. If the yokes on any given shaft is not on the same plain then it's out of time/phase.
6) Check to see if a large rock is wedged between your dualies.
7) Check the driveshaft for any signs of it being struck and or missing weights.
8) Check to see if any of the pinion nuts are loosening up at the trans and rears.
9) Check the motor to transmission bolts on the bell housing. The Bellhousing bolts could be coming loose.
10) Check motor and transmission mounts. While downshifting you motor torques in the other direction so It could be lifting up or bottoming out and vibrating on something other then a mount.
11) Look at your tires and rims for signs of damage.

Do not assume it's the transmission. I have seen people loose wheels because they figured the slight vibration was a u-joint. I've seen driveshafts go thru airbags because of a missing pinion nut or bad u-joint. I've seen wheels fly off as a set because the end nuts on the axle tube came loose. I've seen Rear ends burn up from no lubrication. I can go on and on.

Vibration conditions while downshifting could be just about anything so check everything. All of the above mention items are good places to start. I'm only mentioning the stuff that you should check that requires no money outlay on your part.

Of course the transmission or rear end could be failing or in need of a fluid and filter change but don't bet on it. Check out these other items first before taking it to a truck garage. Good luck and let us know what you found.

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http://www.truckroadservice.com/

[This message has been edited by Bill (edited December 05, 2005).]

Don

Bill is dead on with his suggestions. The main point here is to check it out, don't wait. Even if you don't do it yourself, get it to a good shop and have it looked over. A $100.00 inspection could save you thousands it there is a problem.

Bill G