"It suprises me that GTM failed to catch this."


Ah!!! Short shifter was never mentioned!!!

Archimedes was right!!

Rotate the shaft 90 degrees, drive it, 180 degrees, drive it, 270 degrees, drive it again.

Log the amount of NVH in all 4 positions, let us know what you find.

 

Regardless of having a short shifter or not, there shouldnt be any increase in NVH. At least thats what I was told.

I'll try rotating the shaft 90, 180, 270 today and see what happens. What exactly would this do? Can I just remove the 4 bolts at the rear and rotate the shaft or do I need to slide out the shaft/yoke completely from the transmission and rotate it?

 

Anytime you stiffen anything in the drivetrain or suspension it will add some NVH. Depending on what you do it may not be enough to notice any difference or it may be a lot. Your short shifter added some. Mine (TWM) added so much that I took it off and sold it. It was too much for me, not for others. Adding the more rigid shaft (1 piece) vs the OEM 2 pc will add some. In my case (different shaft material and manufacturer), I didn't notice it but it is there.

 

I rotated the shaft 90 and it significantly reduced NVH! I went back under the car to rotate another 90 to see if it would get any better but of course I rotated it the wrong way and now its back to its original position and the NVH is back. I have to go to work now so ill be rotating it 180 from its current position tonight.

 

Booyah!!!

 

You can leave the yoke in the tranny, what you are doing is balance matching it to the differential pinion and yoke.

Use a grease pencil to mark the shaft to the diff.
Mark 4 spots by the bolts, 1, 2, 3, and 4 to keep track.
Find the spot with the least NVH.

 

Well i took some time trying to find the best spot. It was tough because I lost track at first where I started and didn't want to do it all over again - its a simple job but tedious. NVH seems to have decresed a bit but it's still there, just not as harsh as before. I'll assume its just the TWM shifter now.

Lets say I never did this and the balance between the shaft and pinion yoke were off. Whats the worst that could happen in the long run?

 

Nothing will break. It'll just be a less civilized drive form the extra NVH.

 

You will get more NVH due to the fact its a manual, everything is coupled mechanically. A 7AT would be somewhat isolated due tot he fluid coupling in the torque converter.

Now, at this point, is it NOISE, VIBRATION, or HARSHNESS you feel?


BTW, Im still having issues balancing my ceiling fan, if its any consolation!!

 

It's a little bit of all 3.

I'm not hearing any noise from the shifter, just from the aluminum driveshaft (like someone is rubbing another hollow metal pipe along the driveshaft's surface. I can really hear it between buildings with the windows down. It also seems like I can hear the transmission and gear changes more after installing the driveshaft.

The only vibration I have is from the shifter. Nothing else through the cabin, steering wheel, or pedals that I can tell. I'll examine this more as I get some more miles with the driveshaft installed.

"Harsh" is subjective. Nothing "harsh" to me except maybe the shifter at WOT. Honestly though, it's not that bad now. When I first installed the driveshaft, at WOT, the shifter vibration was a bit overwhelming and the vibrations transferred up my right arm enough to make me let go of it.

 

Sounds like you solved the vibration issues.
Im betting its the short shifter, Betty had the same issues, as he dumped his.

 

I just installed my GTM driveshaft today. I don't have any noticeable increase in NVH.

 

Do you have a short shifter? Auto or manual? I still have vibs from the shifter only due to the TWM Shift kit. Otherwise, no problems whatsoever with the DS.

 

No, I've got a 7AT. What is your impression of the performance gain?

 

Noticeable but not drastic. However, my perceived gains probably would have been greater if I hadn't put on 20's a couple days before. Moderate-WOT accelerating from a dig is where I think most people would really notice any change.

Bottom line: I'd buy this again.