Just my .02 cents, triggered by the mention of speed, speedos, and shafts...Sorry guys.
In both of my dynos, I observed a speedo error. 40 MPH on the dial was 38.8 at the wheels, and I believe this speedo error multiplies itself as both numbers grow, because at my top (3rd gear,OD off) speed of 120 MPH at the rear wheels (with a 4:10 gear) my speedo reads about 132MPH. This occurred with my Reinhart chip on, and off. Why am I specific on this?
I'm specific because at 120 MPH (in 3rd gear, OD off) my driveshaft is rotating at 6000 RPM, and not showing any drive line vibration. So, in my case, the only benefit of an drive shaft replacement, is only emotional insurance that I may have fixed a problem that wasn't really a problem yet.
Once you break 100 MPH under any cir***stances, you will know what drive line vibration is, and you will learn about it before it becomes critical, unless you totally are brain dead and a** numb in the driver's seat. If drive shaft vibration is something you feel you need to repair, for real reasons like blurry mirrors, tickling in the feet, or, hands, through gas pedal, steering wheel, or, shift stick, and it's NOT a tire balance gone south, or, a s**t road you experiment on, then you should consider skipping the suggested FMC/MMX upgrade over Reinhart's drive shaft kit.
Yeah, it's expensive, but it's also a tested and guaranteed fix for rotational speeds over 6000 RPM. It's not just a drive shaft, it comes with a matched yoke and U-joints, all balanced and tested together, as a ready to install kit. Again, you may not need this, but if you do, get the best, yes? IMHO.
BTW, if you ever pull your factory shaft for any reason, remember to index it first, and to put it back exactly how it came out. The factory production line installs matched shaft/flange sets, but they are not specifically pre-tested with other parts, only grouped into most likely best matches. Re-install that out of index, and you may come to create your own imbalance problem.
Whoa, that's a buck twenty-five, eh? Cha-ching...
Beemer...Welcome, congrats on your new wheels, and a tip of my hat over your 633Csi project.
I was going to ask you if you came over here from CVN alone, but I see by other threads, you have not.
welcome all.
