SennAP1

I have done research on this subject in S2KI forums on different threads.
I have a rear drive-train vibration that comes on over 40 mph and it is mainly felt under acceleration and more so with acceleration out of fast corners.
This subject seems to be resolved for everyone by switching the CV cups from left to right, but instead of doing this i purchased new half shafts left and right, and the vibration remains if not worse.
I justt had the wheels and tires balance too with no change. Rear tires are Toyo and they are new.

The AP1 rear has:
BLOX axle spacers installed from previous owner.
The car is lowered with Tein springs.
Has LSD clutch pack differential.

Should i take the axle spacers off?
Could this be a bearing as sometimes i hear a high pitched wine under load?
I read everywhere this vibration under load most likely is the CV's pitting but it's doing the same thing with NEW half shafts so what is going on?
Please help, this community has been awesome in helping me investigate other issues, i have never needed to post until now.

Thanks

s2000Junky

Are the half shafts oem? Many have reported this issue with inexpensive off the shelf parts store options.

Could also be a diff or even trans issue.

You can try removing the half shaft spacers to at least get that out of the way as process of elimination. Hopefully the guy who owned the car before you had enough sense to buy the two piece kind so you don't have to go pulling your shaft again.

SennAP1

No the half shafts are NOT OEM they are DSS made in china.
I have a feeling i just threw some time and money out the window.
There's nothing quite as expensive as a cheap replacment....

My diff was making chatter sounds and i added some friction modifier to the diff and it quieted down in the tight turns, it was running smooth but now that's back too...
The vibration is back and the chatter from the diff.

The spacers are 2 piece so i can try taking those off in a couple days and then see if it makes a difference.
I wonder if the bolts attaching the half shafts have gone bad maybe?

I noticed when my friend and i were installing the axle, that the driver side pillow ball bushing looked ripped.
We have access to my buddys shop and lift every other sunday.

I also heard about differential mounts possibly being a factor

s2000Junky

Sounds like you may have a couple different issues effecting vibration. Do you still have your old oem shafts? If so swap the cups right to left an reinstall them, then return the new ones. try the spacer removal, but id be somewhat surprised if that did anything for you. No the bolts dont wear out, but possible they could get lose, make sure they are good and tight.

SennAP1

No the axles were aftermarket before this change. I'm going to try taking off the spacers first and install a new pillow mount.

this is all a big bummer throwing money at a phantom.

I apreciate your help

s2000Junky

No problem, i help when i can. Ive been there many times over the years with this car so I know how you feel. Just be systematic about it, think it through carefully and you/we will figure it out, and you will be the wiser for it. There is only a set number of things it can be that will cause this vibration symptom.

hecash

I had a similar issue but it was not restricted to speed. The car shuddered under any very hard acceleration. That turned out to be a bad rear joint (at the rear assembly) on my propeller shaft. A lightly used propeller shaft cured the problem.

SennAP1

Thanks for your input hecash.
I'm kind of leaning towards something in the propeller shaft because of the characteristics of the vibration. The vibrational feedback feels close to the gear shifter inside the car.
Like you said it has nothing to really do with speed it's more hard acceleration, and mainly climbing from lower rpm in tall gears 4th through 6th do you feel it most pronounced.
Plus nothing changed when i changed both axles; In fact the vibration lending itself to being more noticable more than likely due to the cheap design of the solid steel DSS axle half shafts.

My AP1 is nothing crazy it probably pushes 260 hp at the wheel. It has a LSD with 4.44 gears.

How susceptible are prop shafts to getting damaged in our cars? This is something i have not found.

s2000Junky

Not very in my experience. I personally put 220k miles on an original set which saw a lot of abuse in a boosted car for half of that mileage at least. The trick like any part is they are a wearable part, but you can prolong their life interval by swapping cups back and forth when the cups wear and vibration starts to set in under acceleration, after that when they start to vibrate again you can put in spacers and milk them another 50-60k. So 3 different configs you can do before you toss them. Like I said after 220k i finally threw in the towel and bought new cups and put them on the old axles. Yet to actually break an axle.

And hey stay away from those cheap aftermarket axle/shaft options...

Car Analogy

Get some used axles, they will be better than the new parts store axles you have. Once those used oem axles wear out, have them rebuilt with new cv joints. Don't buy aftermarket axles.