Finished up the T56, tonight.
Driveshaft length is a bit short: I received the Steeda 11/16" spacer. It should have been 0.6875", but measured 0.669". On a straight edge, it looked like the yoke extended out beyond the output shaft housing by ~1 3/16 - 1 1/4". Ideally, I wanted .75" - 1", but according to the other rules of thumb, the amount of yoke-to-output-shaft spline engagement will be fine. I'll keep my eye out for a 44.5" driveshaft, which, without the spacer, would be just about perfect. But, I suspect, this will be good enough. While, I have a 44.5" FMS driveshaft on my garage floor, the vibrations it caused eliminates it from ever going back into a car.
*edit:* I'm editing this for my own future reference. After a lot of subsequent work on the D/S to reduce vibrations, I realized that I'd been measuring wrong. I used the point on the yoke that begins to expand away from a 'flat' cylinder as the baseline for measurement. I should have bottomed out the yoke in the transmission, because the yoke will not fully go into the trans. It was difficult to get a perfect measurement with the tools I had available to me at the time, but I believe the distance I'd been measuring as a baseline was 1/2 - 5/8" with the yoke bottomed out in the trans. Therefore, given the measurements above, it would put the actual yoke extension at between minimum 0.5625" (9/16") - 0.75" maximum. This may be worth addressing later with more precision as .5625" may present some risk of impact to the output shaft. This also means that a 44.5" driveshaft would not work. Another option to consider may be a better yoke. I believe the yoke on my buddy's D/S went all the way in, despite being perceivable the same length. In any case, for the time being, I'm choosing to take the risk.
Vibration very minor and/or eliminated:
I checked the pinion and engine-trans angles. The pinion was nose up ~2*, while the engine-trans was nose up ~2.3*. I left it alone. On the test drive, it no longer had the vibration that the old driveshaft caused. The D/S spacer probably helped in this department too, by moving the forward U-joint closer to the output shaft and reducing any wobbling that the previous limited spline engagement length may have caused. While there is still a minor tremor above 75 mph, it feels like it's the rear tire and not the drive line. More driving will help me figure that out. I suspect it may be my old Nittos. I plan to swap the winters back on at some point to test that theory. It's possible the new-to-me-but-used driveshaft or its yokes may be to blame, but my gut tells me that they aren't.
Driving Impressions & Gear comparison:
I could tell a MASSIVE difference with that 2.66 1st gear. I gave it a sporty-ish launch, and it bogged like it never has with the older 3.35 1st gear. I revved to 3k and came out of the clutch aggressively, was not at WOT and it bogged down pretty far. With the 3.35 1st in the T5, anything above ~1,500 RPM would have easily spun the tires. The T5's 1st gear yielded ~26% more torque than the T56.
It didn't like 6th below ~50 mph (~1,300 RPM), where the engine has some pulsation.
For comparison's sake, 1st gear will run just about 10mph more (44 vs. 34 mph) to the limiter. I'm honestly not a fan of how much harder it's going to be to launch the car, now, but I am a fan of how much more useable 1st will be in normal street driving. In 6th gear at 80, I'm taching 2,150 RPM on the 275/40/17 Nittos, whereas with the T5, I was right at 2,900 RPM. That's a HUGE difference to NVH, and I'm sure MPG, that will make things nicer on a longer trip!
Up next :
- On Friday, I'm looking forward to seeing the impact to the fuel economy in the car.
- The MM caster/
camber plates came in. I'm going to get 'em in, and have the caster set so that hopefully the steering will return to center on its own.
- I intend to roll the driver's fender because on sporty-ish cornering, I can hear what I believe is some part of the tire repetitively hitting the fender lip.
- Concerned about rear-end whine, a bit.
- Car's ready for nitrous, now... This is a long-term aspiration. Hopefully some progress here in the Summer.