2k to 2.7k RPM vibration.

[EXPLDER]

I seem to be getting a strange subtle vibration that is RPM/load dependant. It only happens between 2,000 to 2,700 or so RPM's under load. Vehicle speed doesn't effect it at all, only RPM and under any kind of load. It doesn't seem to get any better or worse the more/less load there is, it just needs some kind of laod to be apparent. The vibration can be felt in the floor and gas pedal. I was thinking torque converter, but I just replaced it along with a rebuilt tranny, so thats not it. Its not the tranny mount, as this would have been pickup when the tranny was going in/out. Only thing I can think of is the harmonic balancer/ main pully, radiator fan, or perhaps engine mounts. I think i'm going to pull the fan off this weekend and go for a quick cruise to see if thats it. Yes I will watch temps, as long as I'm moving it should be ok. I looked at the fan, it seems to rotate fine and has no broken fins or missing pieces.

Any suggestions?? (I'm hopping its a simple problem that is common amonst 2nd gen owners, but a search yielded no one with the same symptoms).

Thanks, ~Mike...............

 

[EXPLDER]

nothing huh? Should this be posted/moved in another forum?

 

[MountaineerGreen]

You have an odd problem- did you crank you torsion bars? Have you checked your driveshafts?

 

[EXPLDER]

It's RPM based, not vehicle speed, so that eliminates the drive shaft and tranny bits. I can stick it in drive, and hold the brakes and not let the truck go anywere, as soon as it gets to 2~2.2k RPM you can feel the vibration. This problem developed a while ago and hasent gotten any better or worse, but it still bugs me. Every time without fail, get to 2~2.2K RPM all the way to about 2.7K RPM and the vibration is there. If I drive a litttle harder so the RPM's stay above the 2.7 threashhold, theres no vibration. Like I said, its RPM based and from 2K to 2.7K RPM's regardless of what the trucks doing. I was hoping when I replaced the torque converter it would have dissapeared, but it didn't. It must be engine related. My torsion bars get twisted this weekend, other wise truck has been stock since it rolled off the showroom floor way back in 96. I guess I'll start with the easy stuff like removing the fan and seeing if it goes away and take a close look at the engine mounts. Other then the main pully after that I don't know were else to look.

~Mike............

 

[Turdle]

That is right in the torque converter lock-unlock speed band--

Sounds like a torque converter problem--maybe flexplate??

 

[IZwack]

When was the last time the transmission fluid was flushed?

 

[EXPLDER]

That is right in the torque converter lock-unlock speed band--

Sounds like a torque converter problem--maybe flexplate??

Thats what I thought too, but I just had the entire tranny rebuilt and that encluded a new torque converter too. I didn't think about the flex plate, but I assume (which is a bad thing to do) that the guys that did the tranny work at least looked at the flex plate because I did mention the vibration and they said they noticed it too before any work was performed. I guess I'll eliminate all other possibilities first (engine mounts, radiator fan, and main pully/harmonic balancer) first before i get on the tranny guy.

Tranny has less then 1000 miles sinse rebuild, so it doesn't need flushing.

~Mike.........