z-ya Posted June 7, 2010 Share Posted June 7, 2010 I been trying to figure out a drivetrain vibration for a few weeks now, and I'm running out of ideas. Here are the details: - 1971 240Z - RB25DE and 5-speed - New balanced driveshaft - Poly diff mounts - Stock rubber tranny and engine mounts - Stock halfshafts - R200 mounted in stock location with 280Z Moustache bar and RT mount Behavior: - From about 45-65MPH you feel a vibration through the chassis - Seems like it is coming from the diff or halfshafts - No vibration in shifter - When engine is idling in neutral, vibration is still present (at speed) - Stock rubber control arm bushings - Eibach progressive springs What I have swapped (without any change in behavior): - Differential - Half shafts - Tires (front to back) - Brake drums What I have checked: - Rear wheels bearing (tight, no play) - Eyeballed stub axles to see if one might be bent. Seem to run true - Rear suspension (tight no play when wiggling wheel) - Rear toe is around zero (using my crude measuring method) - All half shafts U-joints tight. At this point I am leaning towards the poly diff mounts. I will try and swap the the stock front mount first. Is there a rubber version of the Chevy mount used with the RT mount? The car handles well and nothing feels loose back there, so I don't think it is suspension. Comments, suggestions, welcome. Pete Quote Link to comment Share on other sites More sharing options...
JMortensen Posted June 7, 2010 Share Posted June 7, 2010 Does the RT mount put the diff at the right angle with respect to the transmission? If I'm reading your post right you didn't check the angles there. That would be my first thing to look at. The poly bushing isn't going to CAUSE a vibration, although it will transfer more vibration to the chassis. If you have something going on with the driveline angles changing to rubber might help mask the problem but won't fix it. Quote Link to comment Share on other sites More sharing options...
z-ya Posted June 7, 2010 Author Share Posted June 7, 2010 Thanks Jon. I didn't check the drive shaft angle, but it looks to all line up pretty straight. There is little to no bend at the U-joints. I installed the RT mount the same way I installed 2 previously. Didn't have any issues with them. The other thing I checked is the transmission output bearing end play. It is tight. Little to no play. I would think that any issue with the driveshaft would cause vibration to come up through the shifter. At least this is what Gilbert's Driveline said. Unfortunately they didn't have the right couplings to balance the half shafts or I would have had them balance the halfshafts as well. Quote Link to comment Share on other sites More sharing options...
rags Posted June 7, 2010 Share Posted June 7, 2010 Pete, Sounds like my yellow car. I've swapped everything you have and threw in a new trans also. Same crap. I've also checked the driveline angles with laser pointers which seem to be dead on parallel. If you figure this out and it stops my vibration also, beer is on me! Joe Quote Link to comment Share on other sites More sharing options...
woldson Posted June 8, 2010 Share Posted June 8, 2010 I'm going to hit a KISS, moment. Tires and/or balancing of wheels. Possibly check tire aliment. Problems of that nature in the rear can seem quite different then the front. Quote Link to comment Share on other sites More sharing options...
z-ya Posted June 8, 2010 Author Share Posted June 8, 2010 (edited) Pete, Sounds like my yellow car. I've swapped everything you have and threw in a new trans also. Same crap. I've also checked the driveline angles with laser pointers which seem to be dead on parallel. If you figure this out and it stops my vibration also, beer is on me! Joe Shoot! Is yours a 71? Mine is a 25k VIN. The vibration is not horrible, but annoying... I've got a line on a place that can balance the wheels on the car. I figure this might help me pinpoint the problem. Woldson, I did rotate the tires from front to back with no change. There is no vibration through the steering wheel, so it's not coming from up front. The rear toe is close to zero. I am getting the alignment done next week. It has bad inner tie rods. I'll keep everyone informed. Pete Edited June 8, 2010 by z-ya Quote Link to comment Share on other sites More sharing options...
Zmanco Posted June 9, 2010 Share Posted June 9, 2010 Have you checked that the stub axles are still in one piece? I had a vibration that turned out to be from stub axle snapping where the splined section ends. I had driven like that for some time Quote Link to comment Share on other sites More sharing options...
woldson Posted June 9, 2010 Share Posted June 9, 2010 (edited) Sorry should have read more carefully. Without vibration in the shifter, I jumped to the most outer components. Edited June 9, 2010 by woldson Quote Link to comment Share on other sites More sharing options...
dizzle Posted June 11, 2010 Share Posted June 11, 2010 Mine is the same way, It is your pinion angle. http://www.carcraft.com/howto/91758/index.html This is a great article, I am in the process of rebuilding mine as well. Z's are very susceptible to pinion angle vibrations, due to the extremely short driveshaft. Quote Link to comment Share on other sites More sharing options...
z-ya Posted June 12, 2010 Author Share Posted June 12, 2010 (edited) Mine is the same way, It is your pinion angle. http://www.carcraft.com/howto/91758/index.html This is a great article, I am in the process of rebuilding mine as well. Z's are very susceptible to pinion angle vibrations, due to the extremely short driveshaft. Nope, driveshaft. Mine is pretty much a straight shot. I brought the driveshaft back to the place that made it and had them check the balance again. It was off, but not much according to the guy that does the balancing. So they both static and dynamically (spin) balanced it. No more vibration! So even though I couldn't feel it in the shifter, it was the driveshaft. Joe, dizzle, you might want to get your driveshaft balance checked again. Thanks for all the suggestions! Pete Edited June 12, 2010 by z-ya Quote Link to comment Share on other sites More sharing options...
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