So since I had a Strange rear (w/ new driveshaft) put in some years ago, I have had a decent rumble when coasting at highway speeds. This past weekend I finally installed the BMR adjustable torque arm to try to get that worked out. I got to find out first hand how confusing this pinion angle setting can be.

I used a drive-on lift that was pretty much level. With the BMR torque arm installed, I measure about 2 degrees for the driveshaft angled down toward the rear. I tried several pinion angle settings centered around 0 degrees thinking that the driveshaft was -2* so a 0 rear end angle should give the desired -2* total angle. The vibrations remain.

Now here is where I really got confused. We then used a long socket to measure the transmission tail shaft angle (at the u joint). It was 3.5 degrees down toward the rear. The drive shaft was only 2 degrees down toward the rear. Assuming the measurement was right, that seems to be the opposite of of what I have read. Every example I have seen shows the transmission tail shaft being close to level and the driveshaft angling more downward to meet up with the rear. In this measurement it would seem the driveshaft leveled out more than the tail shaft. Is that right?

Assuming that is right, I drew out the angles on paper, and it seems like to zero out the driveline angle I would need to point the rear pinion up at 3.5 degrees I think. This doesn't seem right though compared to what I have read.

Anyone have some advice? I started giving it a turn each day and trying it out hoping to find the correct setting. The car is basically stock other than the Strange S60 / Strange DS, and now BMR torque arm and polyball LCAs.

 

You're over complicating it. Forget the driveshaft angle all together. Take your measurement that you got from your transmission (3.5*) and subtract the desired 2* from it (3.5-2=1.5) so you should be looking for 1.5* at the rear end.

 

Stop measuring the driveshaft. Thats for WORKING ANGLE not pinion angle. They are two different measurements.

 

I am now at ~2 degrees pinion up on the angle, and the rumble is still there. I have been doing one turn at a time on the adjustment so I didn't overshoot it. Could there be something else causing a rumble when coasting at highway speeds? Something in the 12 bolt perhaps? I think if the driveshaft was out of balance, I would notice the vibe in both acceleration and coast.

 

Could be a bearing issue, or possibly u joint issue. These misc noises can be hard to track down.