Driveline Vibration

rheat · 08-25-2009, 07:09 PM

My 2006 Mustang GT has developed a vibration which occurs between 60 and 70mph, mainly noticeable during decellaration. Prior to this I've had the gears swapped out to 373s. There is no gear whine and I took the car back to the shop that did the work to have it checked out. They said everything was fine and maybe one of my tires was out of balance. So I've rebalanced and rotated the tires and still have the same vibration at the same speeds. Any suggestions?

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Blair · 08-25-2009, 07:37 PM

Do you hear it more or feel it more? By hear it does it sound like a lot of bass (think 15" subwoofer" or is it a vibe that makes you feel sick and shakes your mirrors?

If its the bass it is your driveshaft. The driveshaft is balanced as a unit with the pinion flange, so I have been told. If you bolt the parts back together out of alignment then you get a vibration that sounds like a bass drone or rumble. You hear it more than feel it.

If it is pure vibration it is probably the wheel/tire balance.

I know this because my prior mustang an 08 GT had a driveline vibration that 30 days in the shop could not fix.

rheat · 08-25-2009, 09:16 PM

I think I hear it more than feel it. And its only around 60 to 70 mph. I've pushed in the clutch around the same time and it did not fade very much. I questioned the shop that did the gear change whether or not they installed the drive shaft back in the same position. Their answer, obviously, was yes. But I think I might try repositioning the drive shaft and see if that takes care of it. Before the gear change everything was fine. In fact I was more worried about gear whine but that has not happened. I'm really fustrated because I finally got the money together, and the wifes persmission to do the gear change and buy a supercharger and now I got this issue.

rjg426 · 09-27-2009, 08:29 PM

Sorry about the late reply, I haven't been active on here much and was searching for this exact problem, as this is exactly what happened to me. I had 3.73s installed a few years ago, and had a considerable driveline vibration mainly at about 63 MPH. I didn't have any problem before the gear swap. The shop told me they usually install an aluminum driveshaft to correct the problem, but I couldn't afford that. So I followed the method in the factory service manual and tried to balance the driveline by trial and error with a large worm-gear hose clamp on the driveshaft. Sounds crazy but it helped alot.

Since then, this past spring, I decided to spring for an alum DS. Well, I got the vibration back, but not as bad as the OE steel driveshaft without the hose clamp (I suspect not as bad because the alum is alot lighter than the steel and has less of an effect). I tried indexing the alum shaft every position but it made no difference (telling me that the shaft is well-balanced, as it is supposed to be).

So my conclusion is that the pinion must be slightly off causing the problem. When I get a chance, I'm going to use the dial indicator on the pinion yoke area as I turn it, because I suspect it's off a little. Then I guess I'll try to trial-and-error balance it like I did with the steel one (only problem is the 4-inch alum DS probably doesn't have the clearance for a hose clamp).

Sorry for rambling, just wanted to put some info out there on the same problem.

Riptide · 09-27-2009, 10:58 PM

My installer told me the same thing. Aluminum drive shaft to fix it after the gear install.

jahudso2 · 09-28-2009, 09:27 AM

I have the same loud droning vibration after my 3.73 install at ~65 mph. What is this worm gear procedure?

Blair · 09-28-2009, 12:16 PM

You take two hose clamps that are large enough to fit around the driveshaft and you attach them to the end of the driveshaft closest to the differential, but before the cv joint that attached to the differential. You orient the screw/worm gear sections of the hose clamps opposite each other 180 degrees apart. The screw parts act as counter weights to offset any imbalance in the driveshaft. Sometimes this works to get rid of vibrations and a little bit of the noise. It didn't work on my old car though.

rjg426 · 09-28-2009, 12:27 PM

Quote:

Originally Posted by Riptide

My installer told me the same thing. Aluminum drive shaft to fix it after the gear install.

The problem I have with this is that the DS was fine before the gear install, so the pinion must be a little off. I tried indexing the DS and it didn't help. Then when I installed the alum DS, it was much better but not totally gone. The alum is so much lighter that it has much less of an effect on the slight imbalance of the pinion.

rjg426 · 09-28-2009, 12:55 PM

Quote:

Originally Posted by Blair

You take two hose clamps that are large enough to fit around the driveshaft and you attach them to the end of the driveshaft closest to the differential, but before the cv joint that attached to the differential. You orient the screw/worm gear sections of the hose clamps opposite each other 180 degrees apart. The screw parts act as counter weights to offset any imbalance in the driveshaft. Sometimes this works to get rid of vibrations and a little bit of the noise. It didn't work on my old car though.

Thanks Blair, I was finding the procedure in the factory service manual and scanning it to a PDF, but the file's too large to attach. Anyway, if I may add more info, I'll just paste the pertinent part here. I did this with the stock DS but the aluminum one might not have the clearance for a clamp around it.

Basically, you lift the rear and put the axle on STURDY jack stands and run the car up to the vibrating speed. I put traction control off and I leave the tires on (I know they're balanced and not the culprit). Then you attach a clamp at the differential end of the driveshaft and run the car again to see if the vibration is less. It's trial and error. Here is the manual procedure:

205-00-12 Driveline System - General Information 205-00-12
8. Mark the rear of the driveshaft into 4
approximately equal sectors and number the
marks 1 through 4. Install a hose clamp on the
driveshaft with its head at position No. 1.
Check for vibration at road speed. Recheck with the
clamp at each of the other positions to find the
position that shows minimum vibration. If 2
adjacent positions show equal improvement, position
the clamp head between them.
9. If the vibration persists, add a second clamp at
the same position and recheck for vibration.
If no improvement is noted, rotate the clamps in
opposite directions, equal distances from the best
position determined in Step 8. Separate the clamp
heads about 13 mm (1/2 in) and recheck for
vibration at the road speed.

Repeat the process with increasing separation until
the best combination is found or the vibration is
reduced to an acceptable level.

Blair · 09-28-2009, 07:29 PM

That is the procedure I was taught too. But the guy who told me how to do it was a ford tech and he told me to just start out with two band clamps from the beginning because he was never able to get a vibration reduced with only one. He said if it is a small imbalance it can be remedied by rotating the clamps 90 degrees at a time until the vibes are reduced. He also told me that if the only way to reduce it is to put both clamps on one side opposite the imbalance, then you just need to replace the driveshaft since the difference in weight is too great.