I have a shimmy or shake at about 50 mph and up. I am not entirely convinced that the tires are not at fault, but would also appreciate other ideas. I replaced the shocks last year with Monroe Reflexes and installed air bags earlier this year. Seems that I didn't notice the shake untill about 2 months ago.

Thanks for the help!

Try getting your tires Road force balanced...I had the same thing and it fixed it...

could be your pitman/idler arms failing. Budy of mine with a 2001 and 265's had to have them replaced. His TBars were slightly raised. Also check your aligmnet

Do you have the 2-piece steel driveshaft?

Do you have the 2-piece steel driveshaft?

yep! I have a rusty 2 piece steel drive shaft.

Also, I have had Sears (bought from them) balance the tires many times, but it doesn't seem to help. I do know that an independent shop found radial drift in the right rear tire. This tire also has 3 large weights on one side.

P.S. The air bags are on rear, not the "lowering" kind. ;)

I though mine was tire related as well because of the oversized tires I have. I also had the infamous 'shudder' while towing my 5th wheel. Not towing I had the shake from about 30-40 and from 65-75. I replaced my crappy 2-piece shaft per a GM TSB, with a one-piece aluminum. The shaking and shudder went away.

Regular balancing is not the same thing (or even close to) road force balancing...

I had the same problem. Turns out two of my BFG's were out of round...One rim needed 7.25 oz of weight. Noticed that when I went to rotate the tires. Never felt the shimmy until I rotated the tires... Anyway went back to Discount Tire for the second time and told 'em it still wasn't right. That is when they found two tires out of round. Wish they had a road force machine though... Soo the truck got new shoes this afternoon. Only got 19k out of 'em, they were at 9/16" tread depth...

I had the same problem. Turns out two of my BFG's were out of round...One rim needed 7.25 oz of weight. Noticed that when I went to rotate the tires. Never felt the shimmy until I rotated the tires... Anyway went back to Discount Tire for the second time and told 'em it still wasn't right. That is when they found two tires out of round. Wish they had a road force machine though... Soo the truck got new shoes this afternoon. Only got 19k out of 'em, they were at 9/16" tread depth...

Same for me this weekend. Sears insisted that the tires were ok. So, saturday morning I had an independent tire shop balance the tires for me. All four were out of round and had 1/2" of side to side movement (rims were perfect!). The independent shop gave me an invoice stating that all four tires were out of round and recommended immediate replacement. I spent the rest of the afternoon (5 hours) fighting sears and finally got a reasonable deal out of sears. I now have four new Michelien 265/75r16E XC LT4's on the truck. Not an aggressive off road tread, but hopefully a longer tire life. The General's were at 10/64 (new 17/64) after 27k miles. They wore well, just all were out of round. :eek:

I though mine was tire related as well because of the oversized tires I have. I also had the infamous 'shudder' while towing my 5th wheel. Not towing I had the shake from about 30-40 and from 65-75. I replaced my crappy 2-piece shaft per a GM TSB, with a one-piece aluminum. The shaking and shudder went away.


ABQFirefighter - do you know what the TSB # was for this?

Bulletin No.: 01-04-17-001B
Date: March, 2002
TECHNICAL
Subject:
Launch Shudder On Acceleration
(Install New One-Piece Propeller Shaft)
Models:
1999-2002 Chevrolet and GMC K2500/3500
Extended Cab Long Box and Crew
Cab Short Box Pickup Models
With Automatic Transmission
This bulletin is being revised to add model information, remove procedure steps and change parts information. Please discard Corporate Bulletin Number 01-04-17-001A (Section 04 - Driveline Axle).
Condition
Some customers may comment on a vibration during acceleration from 0-40 km/h (0-25 mph). This may also be referred to as launch shudder. This condition may be more noticeable when the vehicle is carrying cargo or is used for towing.
Correction
A new propeller shaft is available for service to correct this condition. This new propeller shaft is a one-piece design and will replace the current two-piece design.
Install a new one-piece propeller shaft on affected vehicles. Refer to the service procedure and the pans information listed below. Match the affected vehicle with the appropriate propeller shaft. Refer to the usage information below. This fix does not apply to the Chassis/Crew Cab Models (K35943).

Also:

Bulletin No.: 01-04-17-001A
Date: June, 2001
TECHNICAL
Subject:
Launch Shudder On Acceleration
(Install New One-Piece Propeller Shaft)

Models:
1999-2001 Chevrolet and GMC K2500/3500 Extended and Crew Cab Long Box Pickup Models With Automatic Transmission

This bulletin is being revised to remove an illustration. Please discard Corporate Bulletin Number 01-04-17-001 (Section 04 - Driveline/Axle).
Condition
Some customers may comment on a vibration during acceleration from 0-40 km/h (0-25 mph). This may also be referred to as launch shudder. This condition may be more noticeable when the vehicle is carrying cargo or is used for towing.
Correction
A new propeller shaft is available for service to correct this condition. This new propeller shaft is a one-piece design and will replace the current two-piece design. Install a new one-piece propeller shaft on affected vehicles. Refer to the service procedure and the parts information listed below. Match the affected vehicle with the appropriate propeller shaft. Refer to the usage information below. This fix does not apply to the Chassis/Crew Cab Models (K35943).


You'll see an A & B, different chassis/cab combos.

Same for me this weekend. Sears insisted that the tires were ok. So, saturday morning I had an independent tire shop balance the tires for me. All four were out of round and had 1/2" of side to side movement (rims were perfect!). The independent shop gave me an invoice stating that all four tires were out of round and recommended immediate replacement. I spent the rest of the afternoon (5 hours) fighting sears and finally got a reasonable deal out of sears. I now have four new Michelien 265/75r16E XC LT4's on the truck. Not an aggressive off road tread, but hopefully a longer tire life. The General's were at 10/64 (new 17/64) after 27k miles. They wore well, just all were out of round. :eek:

hehehe. Didn't notice my misprint at first. My tires were at 9/64...not 9/16.. :D my bad. Glad it worked out for you as well!
Bob