Drive Shaft Vibration Problem

[Tranman324]

I have been getting a annoying vibration when I decelerate in 4th gear around 2K-2.5K RPM. It sounds like a bunch of bees are in my transmission when I let off the gas. It does it in 3rd too at about 2K, but not as loud as in 3rd.

I originally thought it was my stock drive shaft. I tried turning it 90, 180, and 270 degrees; no luck. I then had it rebalanced and the carrier bearing inspected. The bearing was good, but the balancing didn't fix the problem.

So I caved and bought this:
http://www.z1motorsports.com/240sx/prod ... ts_id=3876
THE PROBLEM IS STILL THERE. Now instead of the buzzing inside the cabin when I decelerate, that vibration resonates in the new steel drive shaft and makes hella noise outside of the car when I let off the gas. It sounds like something vibrating on a sheet of metal. No, nothing is hitting the drive shaft and nothing else is rattling under the car. There is also no play. I also tried the 90, 180, and 270 degreed positions again.

From what I've been gathering through researching about this problem, the SR is prone to deceleration vibrations and a sprung OEM clutch is made to damper this vibration to keep it from resonating through out the car. So OEM is the way to go to keep this from happening. With my Spec sprung clutch, these s*** heads sold me a clutch with springs that are either too soft or too stiff to dampen the vibration of my motor. This problem is supposedly more prevalent in tougher clutches like 6 puck clutches. Am I right?

So this is what I have that could be related to the problem:
- 93 S13 Hatch
- S13 Redtop SR
- Z1 Motorsports Stainless 1 piece Drive shaft
- Q45 Viscous LSD
- Spec Clutch (Forget what kind, I think the second step from their base model clutch)
- Koyo T/O bearing
- Nismo transmission Mount
- Aluminum Sub frame inserts

So the thing I will NOT do in the near future: Pull the transmission and replace the clutch in HOPES i find the a clutch with the right springs. EFF THAT MESS. I'm sure many people would sympathize with me.

Now my next idea to subdue the loud metal rattling from my drive shaft is to fill my drive shaft with "Great Stuff" foam or the like and have it rebalanced. Through A LOT of digging I found that this has been a fix to some GM cars and 4x4s. I know this won't fix the problem. My goal is to minimize the noise without dropping the transmission again. Anyone heard of this before? Any other thoughts? Please discuss.....

[racinjayson]

I have the exact same problem. I have: -1989 s13
-kA24E,Lightened crank,light rods,forged pistons,ported head-SS valves
-June Racing Flywheel 11lbs
-unorthodox racing crank pulley
-Single piece alu driveline
-S-15 stock helical LSD rear end
-Nissmo engine and transmission mounts
-polyurethane sub frame mounts
-Clutchmaster stage two duel friction clutch
So pretty much a lot of the same things you have with exactly the same result. I have tried different trans, differnet clutch, had the driveline rebalanced, nothing has worked. So, I know this is not helping your problem, but at least your know your not alone. The guy that rebalanced my driveline said there's a reason why nissan used a two piece driveline, but your problem was happening with that as well, so obviously that's not it. Anyway, I'll keep at it and if I come up with anything I'll post back.

[biggie]

Sure its not a heat shield or something?

[sx moneypit]

I too have the same problem.I think that a light weight flywheel does not have enough mass to dampen the vibrations that are inherent in a KA series engine.It seems like my problem came after i installed the light weight flywheel.

[racinjayson]

I didn't start having the problem until after I installed the one piece driveline, but the initial post said it started happening before the driveline swap and he has an sr swap. So it's not just the KA, also not a heat shield because it's way to heavy a vibration to be a light piece of tin.

[Tranman324]

Alright, here's video 1. Notice that once I hit the gas the vibration goes away. It also stops vibrating right at 2k rpm in 4th gear. I also tried to cruise in 3rd gear to let you guys hear that as well. I have the window up as well.



Here's video 2 with the windows down. This was just in 4th gear. Notice the same as video 1, noise goes away when I hit the gas. Both videos are taken with my foot OFF the clutch, decelerating using the motor.

[terry_240sx]

maybe the backlash in the diff is off.
just my .02 tho.

[sr20detman]

add me to the list . ive had this problem for awhile now also. been troubleshooting it non stop. most everything on my car has been replaced. i tried different axles, different diffs. 2 piece driveshaft, 2 different 1 piece balanced driveshafts.

the other day I put my car on the lift and drove it in 4th gear and let it decel. where i noticed the vibration was at the back of the transmission where the driveshaft enters. so im going to look into replacing a bearing in the trans there. but for someone who replaced trans and still has this issue. that sucks.

[Harrythook]

Ok here is a thought about driveline vibrations….
95 KADE 5 speed here, same vibration issue. Very annoying at highway speeds. Went down the path of driveshaft, clutch, exhaust, ect with no change. This vibration actually stopped me from the turbo install, was afraid there was something coming apart.
Back to basics, if it’s a vibration at speed (mph) and not at RPM we have to look at rotational mass. My vibration will not happen in 2nd gear at any rpm, only comes in around 60 mph. So we swapped out welded diff to known good VSLD, no change.
Our car is riding on crappy lowering springs, so I looked into ride height and driveshaft alignment. As a test I installed spring expanders ( they clip onto the coils) and did test drive. Vibration was almost 100% gone, but the car looked like a drag car all jacked up in back. Stock ride height in rear with the front end on the ground kind of thing.
So its (for us here) basically the opposite of what we used to do in the 70’s with the drag cars. We used to raise the height of the rear of the car, and in doing so we would have to adjust the pinion angle with wedges and install a “snubber” to keep it in the correct angle. By adjusting the rear ride height of the 240 I think we found the correct angles or alignment for the driveline, reducing any bind in the joints in the shaft.

I am working on shimming the subframe to get the correct line, the guy from Hunter alignment provided me some tram gauges to use on our laser rack to set this. Just gotta pry the keys out of the kids hands for a couple of days to get this right.

My 2 cents………….

[PapaSmurf2k3]

^Great thought process. I was going to suggest the same "need to determine if its RPM based or speed based" approach.
I would also think it would either be a bearing in the trans (given all the intel in this thread), or a binding condition like you said.