bigbreak_2000 Posted February 28, 2014 Share Posted February 28, 2014 Any suggestions of what to inspect/check that could cause this vibration?...car is 1981 280zx 2+2 NA. Under normal driving there is no vibration. Smooth at constant speed, shift up/down gears easily, no vibration on deccel, no vibration on smooth acceleration all way up to top end, etc however only bad judder/vibration when hard accelerating, in lower gears (2nd, 3rd) 4500 - 6500 rpms. Makes about 250whp. Recently installed quaife LSD, JWT flywheel, tokico lowering springs. Technician says both front and rear u joints on the driveshaft is stiff, will get a new driveshaft with beefier dana spicer 1802-5-1310x u joints. Just yesterday installed a new OE transmission mount but it made no difference. They looked over the engine mounts, suspension bushings and everything else seems ok. When they have the car back on the lift next week just want to make sure they don't overlook something else that would need tightening or replacing. Driveshaft replacement is not cheap and unnecessary if that's not going to resolve the problem. Quote Link to comment Share on other sites More sharing options...
duragg Posted February 28, 2014 Share Posted February 28, 2014 Once clutch in, vibes stop? Raise rpm with clutch in to 6000 and be sure it's not flywheel related? There is an app for smartphones that does vibration analysis. You can determine tire rpm and driveshaft rpm and try to isolate the frequency. What is your Diffy ratio? Quote Link to comment Share on other sites More sharing options...
bigbreak_2000 Posted February 28, 2014 Author Share Posted February 28, 2014 clutch in no vibration. the diff is the r200 with 3.9 ratio. Quote Link to comment Share on other sites More sharing options...
aarang Posted March 1, 2014 Share Posted March 1, 2014 I know they checked, but if you are still using the original R200 rear mount bushing and rear cross member bushings, you may be getting a lot of deflection under load changing the driveline angle enough to cause vibration. My car did the same thing with the stock N/A engine. I changed all the mounts and bushings with poly and new Nissan parts when I went turbo and the problem went away. Quote Link to comment Share on other sites More sharing options...
bigbreak_2000 Posted March 1, 2014 Author Share Posted March 1, 2014 Thanks for the replies. How many hours of labor would be involved in changing the rear mount bushing and cross member bushings? Assume that I have access to a technician that are skilled and familiar with working on the datsuns. Quote Link to comment Share on other sites More sharing options...
bigbreak_2000 Posted March 28, 2014 Author Share Posted March 28, 2014 I desperately need some help on this vibration issue. Car still has bad vibration under hard acceleration, and now hearing somewhat of a low humming sound coming from the right rear end at speed between 50-70mph....even after we've done all of the following: All nuts and bolts on suspension was checked, mechanics combed this car front to back and there is nothing on this car loose or show any abnormal wear or tear. Car was never in any kind of accident Replaced driveshaft with a new unit. The u joint on the original unit, at both ends of the shaft, locked slightly. The new unit was fully balanced and upgraded with higher strength splicer u joints Checked the crankshaft for play or looseness, no issues there Re checked the flywheel installation - it is a new JWT balanced flywheel. At same time inspected the clutch and pressure plate yoke and bearings on transmission side, relative new unit, no signs of anything loose or uneven wear. Bellhousing bolts was little loose on first inspection but those are tight now absolutely no noises from transmission and it shifts hold gears etc like a brand new unit Re checked alignment, Re balanced all 4 tires/tires, brand new wheels and tires, rotated and no issue Replaced both rear cross member insulators with Nissan OEM parts Replaced transmission mount and rear diff insulator with Nissan OEM parts, did notice that the diff insulator was previously installed incorrectly with the "U" upside down Engine mounts are good and tights Opened diff carrier (R200 longnose), visually inspect Qauife LSD (new) ..did notice some backlash and wear on the main gear but will pull unit out next week to have indept inspection and have backlash corrected. Removed and inspected both side shafts - straightness, bearings all seems good Wheel beatings checked, no play Swapped new tokico struts with new bilstein struts, did not reduce any vibration Checked exhaust brackets and experimented by removing solid mid mount to see if exhaust shaking could cause issue, but it was not it With the car jacked up in the air, rear suspension fully decompressed, visually it looks like the right rear wheel is at a very slight different angle than the left. Not sure this is an indication of anything. Suspecting next step is to disassemble the entire rear suspension, check that cross member arm bushings are not bad inside, control arm is not bent, check bearings holding stub axle and that the stub axles itself is not bent. Highly doubt because the car was never in any accident and the vibration was not there before we installed the LSD diff and lowered the car with tokico springs. I do remember hearing occasionally a squeaking noise from the right rear wheel at low speed but thought this was just the clip on the brake pad. Anyone here have suggestions on what else I need to look for that would cause the vibration? Quote Link to comment Share on other sites More sharing options...
NewZed Posted March 28, 2014 Share Posted March 28, 2014 Recently installed quaife LSD, JWT flywheel, tokico lowering springs. Did the car have the vibration before you installed all of the new stuff? If yes, then it's probably stuff that was already on the car. If no, then it's probably the new stuff. Quote Link to comment Share on other sites More sharing options...
bigbreak_2000 Posted April 23, 2014 Author Share Posted April 23, 2014 After slotting the rear diff mount, effectively moving the diff up by about 3/8 in, I'd say 90% of the vibration is now eliminated. I'm now convinced the tokico lowering springs caused the geometry of the rear suspension to change to the extend that alignment of the differential (with deflection under full power) was thrown off and thus resulted in a vibration. Keep in mind this is a 280zx 2+2. I find it strange that no one else reported similar issues with lowering springs on a 280zx. Originally when the springs were installed it lowered the car by no more than 1 inch, so not extreme. I could slot the diff mount further, perhaps another 1/4 in, in attempt to completely eliminate the vibration, or re-install the stock springs. Slotting may be a fix but not necessary curing the root cause of the issue. My question is still, have we perhaps overlooked something done wrong in the process of converting the R200 to a Qauife LSD unit? Quote Link to comment Share on other sites More sharing options...
MONGO510 Posted May 7, 2014 Share Posted May 7, 2014 I cant see where you have checked your pinion- trans, drive shaft angles. this could cause your problem. Quote Link to comment Share on other sites More sharing options...
bigbreak_2000 Posted June 27, 2014 Author Share Posted June 27, 2014 (edited) Finally got this figured out - the problem was angulation of the axles. Once I installed CV style axles made by wolf creek racing the vibration is entirely gone. Edited June 27, 2014 by bigbreak_2000 Quote Link to comment Share on other sites More sharing options...
Savage42 Posted June 27, 2014 Share Posted June 27, 2014 Even without the issue, CVs are noticeably smoother than u-joints, even when new! Smooth is good! Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.