driveline Vibration....driving me nuts

[mike lane lawn care]

hey guys. got a question i can't figure out. my truck has a very distinct vibration that feels like it's coming from the mid section of the drive line, about half way through the truck. but, it only occurs at 1250-1350 RPM. whenever the engine hits that range, it vibrates, whether accelerating, decelerating, or coasting, if the engine falls into that range, it vibrates. and i can't figure it out.

Help.....Please!!!!!!

[jaybird24]

Check the u-joints, had this a few times and thats what I always found. Fix it and viola.

[pclawncare]

I dont know about this specific truck and if it has one but does it have a carrier bearing? It might be going bad

[fiveoboy01]

U-joint going bad or a midship bearing if you've got one, looking at both of those vehicles in your sig I doubt they even have a midship bearing.

A u-joint going out will display all the symptoms you've mentioned. Get under the vehicle and push on the driveshaft at the u-joint, also grab the driveshaft and try to twist it. If the u-joint is loose, you'll see/feel the play.

[mike lane lawn care]

k, thanks guys, i'll give it a try. i just replaced the U-joints not 10k ago, but i have been driving in hard conditions and in mud and deep water.

[mag360]

u-joints you will notice at a certain speed---not at a particular rpm.

[hockeypro1411]

as i can see u drive a gm truck. same problem on a brand new sierra we just picked up, and the same story on my friends 06 silverado 1500hd. at around 30-35, and 40-45 mph there will be a "rumble". since everyone i know with a gm truck has had this from the get go i assume its normal

[mike lane lawn care]

this is different from that, that is at a speed in MPH, the one i'm having is a speed in RPM. and to my knowledge that rumble at 45, is the transmission going into overdrive to lower the RPM to increase fuel economy. but it makes the engine lug.

[mike lane lawn care]

In the process of replacing my e-brake assembly, i checked they U joints, and they are worn pretty good. so i'll try that and hope to hell it works. only other thing i can think of would be driveshaft balance.

[DiyDave]

How to describe this here? U joints are crosses or look like a plus sign, so picture this... +----X---+. Suppose that the first + is your first joint, the X is the second joint, the second + is the next joint, etc. all joints in a shaft need to be aligned so that when the shaft bends, like when you are hitting a bump etc the drive line is parallel at all of the joints. Sometimes when the joints are assembled after a repair, if you don't note how it was originally assembled, you can mis align the joints on the sliding portions of the shaft. In the example above, the X joint is rotated 45 degrees to the other 2. When dissassembling, take a paint marker, and put a dot of paint at each point to be dissassembled, and putting it back together is loads easier. Also check to see that the sliding areas of the shaft are not dry, they need some lube to slide easily.

[mag360]

If you are 100% certain that it fluctuates with rpm at any speed then your only options are from the front of the motor back to the torque converter (maybe exhaust touching frame somewhere too).
Good luck with it and here's to a cheap fix :drinkup:

[totallawncare25]

Get Rid Of A Gm And Get A Ford That Will Fix It..

[TandM]

Then all you will be doing is fixing more stuff if you buy a piece of junk like that!

[totallawncare25]

Ford makes the best heavy duty pickups out there, THey wouldnt still be the #1 selling truck for over 30 years running

[Petr51488]

Ford makes the best heavy duty pickups out there, THey wouldnt still be the #1 selling truck for over 30 years running

Oh god, here goes another ford vs. chevy allready. Give it a rest. He has a 1/2 ton truck and beats the hell out of it. Things will break, and will have to be replaced.

[mike lane lawn care]

Oh god, here goes another ford vs. chevy allready. Give it a rest. He has a 1/2 ton truck and beats the hell out of it. Things will break, and will have to be replaced.

to quote my mechanic "you beat that thing like a redheaded stepchild"