Need help in Nashville, Tn.

[Bob & Tracey]

Looking for a mechanic in Nashville, Tn. Our GMC 4104 is developing a bad vibration and I would like to have it checked out. Even though this vibration was minor the u-joints we checked and replaced about 600 mi. ago. That made things worse and it is becoming much more pronounced.

Thank you,
Bob

[luvrbus]

Could be some body when they replaced the U joints didn't get the drive shaft timed right it has 2 arrows to line up for the timing BTDT.B_K bailed me on that one   Check and be sure the damper on the front of the engine is not coming apart also.

Could be a lot things from the flywheel to the differential and parts in between the 2,sorry I don't know of anyone around Nashville other than the Eagles Nest that would help and they are always booked 

good luck   

[Bob & Tracey]

Thank you luvrbus, just talked to Mark at Eagles Nest and they are going to look at it on Tues.

[robertglines1]

B-K is west of there on I 40.   

[chessie4905]

   Did you properly index u-joints when re assembling drive shaft? They should be in line from end to end. Also, did you grease them after install? They supply almost no grease in new u-joints anymore.

[Jim Eh.]

What speed (range) does the vibration occur?

[luvrbus]

Glad he got you in Mark will take good care of you a sharp guy

[Bob & Tracey]

I should mention this bus has an 8V71 with the V730 transmission.

chessie4905, the drive shaft was newer taken apart, it was removed and installed in one piece. Yes it was greased.

krank, before the u-joints were replaced I only noticed it at about 65mph/2200rpm. Now I feel it is engine speed related starting about 1500rpm and progressively gets worse as rpms increase.

Thanks for the input,

[RJ]

Bob -

When they installed the 8V71/V-730 powerpack, did they also change out the rear axle?  That powertrain requires a 4106 or later rear axle due to the placement of the pumpkin related to the centerline of the vehicle.  One is off-set to the curb side, the other is off-set to the street side, but I can't remember which is which at the moment.  (But I think the '06 and later is to the street side.)  If it's still the original '04 axle, that might be the cause of your vibration, due to the drive shaft not being aligned properly.

Hopefully somebody with an original '04 and an original '06 will chime in with which side the axle pumpkin is located.

FWIW & HTH. . .

[Bob & Tracey]

RJ, yes the rear axle is from the same 4106 as the engine and transmission.

[TomC]

If the vibration is engine related, then you should get the same vibration if you pull the trans down to 2nd or 1st at the same rpm. If not-it's driveline. Good Luck, TomC

[jackhanow]

Busforsale.com is in goodletsville just north of Nashville right off the interstate they have a service bay. And if it's engine speed related, you should be able to feel the vibration by slowly increasing  the rpm. Unloaded, the vibration may be more subtle but should have the same frequency, the motor should be stable as well, watch for rocking at accelerating and decelerating . You can try loading the engine by power braking and having someone watch.
A quick way to rule out the engine.

[gus]

My 4104 w/671 engine did that, it was severely worn teeth and grooves at the drive shaft slip joint.

I finally discovered the problem when it made clicking sounds at very low speed in an RV park.

[Bob & Tracey]

The bad news is we need a differential. Anybody know where to find one for a 4106? I do not know the ratio but we turn about 2100rpm @ 60mph.

Thanks