SleeperZ Posted September 18, 2001 Share Posted September 18, 2001 Wooooo.... Drove the Z with the 3.90 installed today. What a difference compared to the 3.54!!! Keeps the turbo in the power band, very lively off the line (T5 ZX tranny), I love it. It's also nice to have no more gear whine I've seen discussion that the lower ratios may be faster as they help the turbo make boost -- I've seen no evidence of that -- I get full boost in 2nd gear, just like the 3.54, and it pulls harder. So for anyone that was wondering, 3.90 is amazing behind the T5. I installed the urethane mustache bar bushings, no problems, thanks to all the advice about burning out the old rubber - if I'd tried to take out the bushing shell I'd have been po'd at a tremendous waste of time. The diff bolted right in, and I got a white tranny gear for the speedo - I was surprised it fit the T5. So bring on the 5.0s! Quote Link to comment Share on other sites More sharing options...
pparaska Posted September 18, 2001 Share Posted September 18, 2001 Congrats! Sounds like you're having a blast! Let us know about kills and time slips... Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted September 20, 2001 Author Share Posted September 20, 2001 Hmmm, OK. The 3.90 is a serious demon now, got a 6.9 second 0-60 on the street with G-tech, and that's with bad tires and a 2.7 60'. Problem is, I have a vibration, or growl, in the rear now, with new diff and new urethane bushings in the mustache bar. It makes noise over 80mph, and it sounds like what folks talk about being a problem in the V8 swaps. All I changed was the R200 3.54 with an R200 3.90, the mustache bar bushings (used the thick washers on top and bottom), and I swapped some halfshafts because my old ones had grease fittings in the "stretch" part of the u-joint instead of the compression part. The halfshafts seemed to have good joints, and I just greased them up good. What do you think? Is my diff mis-aligned from the urethane bushings? Or do I have potentially bad halfshafts, and I should focus on replacing those? Any guidance? Quote Link to comment Share on other sites More sharing options...
pparaska Posted September 20, 2001 Share Posted September 20, 2001 I've not investigated the stock u-joint angles with the L6 and stock tranny in place, so I don't know. Buy an angle finder and measure it up. I don't think you can hurt much by putting the urethane ones in. How is the driveshaft? Bent or bad U-joints? Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted September 20, 2001 Author Share Posted September 20, 2001 My driveshaft is custom made with replaceable solid spicer joints. It was very smooth before with the 3.54. I re-used the stock front diff mount, as it was still solid, and I secured the nose with a plastic-coated piece of 3/16" cable. But the mounting in the rear has changed to the urethane mustache bushings. I guess I can try to measure the distance from the bar to the body at the loops - I have no capability to measure the u-joint angles with any accuracy. I was just wondering if anyone else had this problem with stock stuff...? Maybe it's just a halfshaft (although I've had those go bad on me, and they clunk, not hum). Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted September 20, 2001 Share Posted September 20, 2001 Umm, where did the 3.9 rear come from? Perhaps it's got a bad gear setup? [ September 20, 2001: Message edited by: BLKMGK ] Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted September 20, 2001 Author Share Posted September 20, 2001 I got the 3.90 from an '81ZX 5-speed. I also got one from an '84 200SX turbo, and compared the two. The one from the SX was baked inside, and had as much backlash as my old 3.54, so I was pretty sure I had another whiner. The ZX had very little backlash, was very clean inside and had no metal in the plug. Both 3.90s came from the local pick-n-pull. I drove the car again today, and the vibration is hardly noticeable...I think I will drive it some more, just check all the driveshaft and halfshaft bolts, and see what gives out on me. Thanks for all the ideas and advice. Quote Link to comment Share on other sites More sharing options...
Evan Purple240zt Posted September 21, 2001 Share Posted September 21, 2001 Hey dude, i noticed a difference with my urathane bushings too. They tend to transfer more noise and vibration. That COULD be what your noticing. Evan PS.. mine doesnt vibrate, make sure your halfshafts and drive shaft arent coming loose! Mine LOVE to do that. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted September 30, 2001 Author Share Posted September 30, 2001 Okie - I think I have found the source of the vibration... I checked the angle of the tailshaft yoke and the diff yoke the best I could. I used a tape measure and compared the length between the joints at the top and the bottom of the driveshaft. Nuts-on. Hehe, what the heck is it??? Pushed up on the ujoint at the diff...click, click. I have a bad u-joint on my driveshaft. I have no idea why I didn't notice before, but there it is. Maybe the new urethane diff mounts allowed me to hear it now, the rubber ones masked it. I should be able to get it repaired before Test and Tune at the strip on Wednesday evening. I will post a timeslip, good or bad. Wish me luck!!! Quote Link to comment Share on other sites More sharing options...
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