Driveline Elasticity

So ever since I got my '08 spec.B I have had an excessive amount of elasticity in the drive train. Although this bouncing can be felt through clutch engagement it happens while in gear as well. After reading through several posts nobody seems to have a clear answer. Some point at the clutch, others to the transmissions, some call out the bearings in the drive shaft, some mention the transmission, engine, or diff mounts, etc. After some further reading I came to the following comment:

 

It's a very confusing problem, that's for sure. I also see your logic in not throwing money into it until you know the problem for sure. It may not be a bad idea to borrow someone's GoPro camera and attach it underneath the car to go for a drive. You can then blip the throttle and find out what's moving so much. I may even do this.

from page 5 of http://legacygt.com/forums/showthread.php/jerky-5-speed-manual-189786p5.html?highlight=driveline+slop

 

I don't have a GoPro but I do have an old camera and a $20 suction cup mount. I went over to an empty parking lot this morning and captured these:

 

Rear diff from behind

[ame=http://www.youtube.com/watch?v=PrJdUSjOaxA]Spec B Driveline Elasticity Debug (1 of 3) - YouTube[/ame]

 

Rear diff from passenger side

http://www.youtube.com/watch?v=sIh3PcjCYcg

 

Transmission (sort of) from driver side

[ame=http://www.youtube.com/watch?v=f604lsN_Mvw]Spec B Driveline Elasticity Debug (3 of 3) - YouTube[/ame]

 

The second video is particularly interesting. From my research I was betting on the rear diff mounts being bad. From the video they hold on alright, but the front of the rear diff has quite a bit of movement.

 

Has anyone else ever videoed this? Has anyone ever replaced these bushings? Did it fix the problem?

I like your systematic approach.

 

Despite the myriad possibilities out there, I would recommend changing to a Group N transmission mount. Made all the difference in my car, and worst case, if it isn't the source of your problem, you still have all the other benefits of the stiffer mount.

I did a Spec B 6 speed swap in my 05 wagon. I found that the transmission and subsequently the whole driveline moved a great deal under load, especially in reverse. I replaced the transmission mount with an STI 6 speed mount and all my driveline issues were resolved. The factory rubber in the Spec B mount is NOT solid all the way across the mount. On the other hand, the STI 6 speed mount is a solid piece of rubber between both mounting pieces (metal) which made a significant difference in driveline movement for me. If I were you, I would start with the transmission mount first and see if that resolves your issues. Just my 2 cents.