Drivetrain Vibrations

[bschooled]

Ever since I had my TC replaced, I have noticed a slight vibration in the drivetrain. It occurs especially between the speeds of 40-50 MPH, usually when letting off throttle and RPM's drop but TC is still engaged. It also is making a sort of howling/groaning noise definitely coming from the rear of the car. Above this speed the noise and vibrations seem to disappear ... except if I accelerate heavily at a high speed then the vibration, but not at a low speed.

From everything I have read on the forums it could be a couple things. The rear differential ... god I hope not. Or the center support bearing for the driveshaft.

Just looking for suggestions and to see if anyone else has had this problem.

 

[JoshMcMadMac]

If you have an eight-bolt torque converter, it needs to be properly aligned to the adapter plate. If this was not done, it could be the source of your issue. Also, if the transmission was not aligned when bolted back in that as well could be a problem.

 

[bschooled]

Those are good points. I probably should take it into a real drivetrain shop and get them to look it over. I definitely notice the noise in the center of the car, its not so much at the rear, you can feel it vibrate through the transmission hump especially in the rear seat.

I wonder if they didn't index the driveshaft when they dropped the transmission.

 

[JoshMcMadMac]

Those are good points. I probably should take it into a real drivetrain shop and get them to look it over. I definitely notice the noise in the center of the car, its not so much at the rear, you can feel it vibrate through the transmission hump especially in the rear seat.

I wonder if they didn't index the driveshaft when they dropped the transmission.

The driveshaft should not need to be indexed; it does not have universal joints like a lot of vehicles do.

Are you in Hancock, MD?

 

[joegr]

The driveshaft should not need to be indexed; it does not have universal joints like a lot of vehicles do.

Are you in Hancock, MD?

It does have one U-joint, and some indexing is involved.

CAUTION: All driveshaft assemblies are balanced. If undercoating the vehicle, protect the driveshaft to prevent overspray of any undercoating material.

The driveshaft is a 2-piece design. A single center U-joint and a slip yoke connect the driveshaft assemblies. The front and rear shafts are separable at the slip yoke. It is imperative to index-mark the assemblies before separation to prevent an imbalance condition. The driveshaft uses flex couplings at each end of the shaft that take the place of traditional U-joints. The driveshaft has alignment bushings at each end of the shaft. These bushings align the driveshaft with the pilot stems on the transmission output shaft and the axle drive pinion stem. Only remove the flex couplings from the driveshaft if it is necessary to install new flex couplings/alignment bushings. Always install a new alignment bushing and flex coupling as a pair.

The driveshaft has traditional balance weights attached (spot-welded) by the manufacturer. The final driveshaft balance occurs, with the complete drivetrain assembly at vehicle assembly, by attaching weighted color-coded nuts to the axle flex coupling bolts. For this reason, the rear flex coupling bolts are longer than the front transmission flex coupling bolts. Always install the driveshaft flex coupling bolts with the head of the bolt seated against the flange, and the nuts seated against the flex coupling.

 

[bschooled]

So what you are saying is only the middle joint needs indexing?

The only end they should have disconnected when replacing the Torque Converter is the output end on the transmission.

I have heard of the center support bearing going? I am assuming this is what the driveshaft sits in, in the driveshaft tunnel?

But I wouldn't know how to check that, and the part doesn't seem to be anywhere.

 

[Kumba]

Welcome to my hell.

My car has a 75-mph vibration that I am 99% positive is driveshaft related. Still fighting with the dealership to use my warranty on it. Instead, I will probably just put up with it for now and throw the stock driveshaft through their window after I do the 8.8" upgrade with the carbon fiber shaft.

 

[JoshMcMadMac]

It does have one U-joint, and some indexing is involved.

CAUTION: All driveshaft assemblies are balanced. If undercoating the vehicle, protect the driveshaft to prevent overspray of any undercoating material.

The driveshaft is a 2-piece design. A single center U-joint and a slip yoke connect the driveshaft assemblies. The front and rear shafts are separable at the slip yoke. It is imperative to index-mark the assemblies before separation to prevent an imbalance condition. The driveshaft uses flex couplings at each end of the shaft that take the place of traditional U-joints. The driveshaft has alignment bushings at each end of the shaft. These bushings align the driveshaft with the pilot stems on the transmission output shaft and the axle drive pinion stem. Only remove the flex couplings from the driveshaft if it is necessary to install new flex couplings/alignment bushings. Always install a new alignment bushing and flex coupling as a pair.

The driveshaft has traditional balance weights attached (spot-welded) by the manufacturer. The final driveshaft balance occurs, with the complete drivetrain assembly at vehicle assembly, by attaching weighted color-coded nuts to the axle flex coupling bolts. For this reason, the rear flex coupling bolts are longer than the front transmission flex coupling bolts. Always install the driveshaft flex coupling bolts with the head of the bolt seated against the flange, and the nuts seated against the flex coupling.

So what you are saying is only the middle joint needs indexing?

The only end they should have disconnected when replacing the Torque Converter is the output end on the transmission.

I have heard of the center support bearing going? I am assuming this is what the driveshaft sits in, in the driveshaft tunnel?

But I wouldn't know how to check that, and the part doesn't seem to be anywhere.

Joe is going a bit too technical for this issue. As is always the case, everything he posted is spot-on true. However, for practical application the center section of the driveshaft can be neglected as there is no reason anyone would be messing with it (and not know any better). For your problem, there is no universal joint to be concerned with and no indexing to be concerned with.

 

[regiment1]

Welcome to my hell.

My car has a 75-mph vibration that I am 99% positive is driveshaft related. Still fighting with the dealership to use my warranty on it. Instead, I will probably just put up with it for now and throw the stock driveshaft through their window after I do the 8.8" upgrade with the carbon fiber shaft.

Does your vibration go away after a while, or is it always there at that speed?

 

[Kumba]

Does your vibration go away after a while, or is it always there at that speed?

If I hit 80+ it's gone. If I stay under 70 it's gone. But that ramp to 75 between those two speeds it gets gradually worse until I hit 75. Then the whole car has a nice vibration to it. It pretty much stays there. If you are on a long road-trip you get used to it after an hour or so and don't notice it till you stop and get out of the car for a bit.