Syncro

iTrader: (1)

I've got vibrations in my drivetrain. It happens at all speeds (even crawling it feels like my wheels are squares, but they are not flatspotted). It comes and goes a bit, but never fully goes away.

I've already replaced engine, tranny and diff mounts. The driveshaft is good.

I lifted the car into the air and had my mechanic stand below it while I gave it some gas. In 5th gear, car begins to shake so bad at 2k RPM I didin't dare rev it more than that.

He was able to push the axles up by quite alot with his bare hands. He and I think the differential is shot.

Can anyone shed some light on this issue? I've already checked for unbalanced tires.

classicauto

iTrader: (3)

Welp, could be numerous things....

-Driveshaft out of balance (u-joints might be tight, but I've seen slightly dented driveshafts make one HELL of a vibration due to poor balance)
-Axles worn
-Diff worn

When he has moving the rear axles, were the CV joints themselves where you saw the play? Or were the axle "cups" on the diff actually slopping up and down?

Syncro

iTrader: (1)

I bought a used driveshaft (it was not meant as a permanent solution) locally that was "good" expecting mine to have bad u-joints. When I looked under the car the driveshaft looked to be in pristine condition. No u-joing play that I could see or feel. Was in much better shape than the used one I was originally going to replace it with. I looked up the paperwork on the car and a new factory driveshaft was purchases at 220k miles. There were no obvious dents on it... but at 60mph even a small unbalance will create vibrations. I'm getting an uneven feeling at 5mph here. It's as if the road is not flat.

I'm not sure what you mean the CV axles, is that where it connect to the wheel?

The movement was mostly in the 'cup' coming out from the diff that the axles were bolted to. Mechanic said that seemed to be the source of the vibration (he wouldnt sit in the car while it was high up on the lift - wuss ).

Syncro

iTrader: (1)

I forgot to mention the car is... er, blue! Yeah!

(This is a cleverly hidden bump )

classicauto

iTrader: (3)

Well a little bit of in-out play on the diff is normal....but I'd check the specs on it.

I would actually still suspect the driveshaft. The u-joints should have smooth, free motion with NO sticky spots or free play. Even a sticky spot can make some vibration......

But really, if its so bad that at 5mph the cars is shaking itself apart, something is DRASTICALLY wrong. Perhaps drain the diff fluid and check for chunks of metal. Its hard to say exactly what to look for, but by the way you're describing a violent shake, something MAJOR has gone ka-put. Even a slightly bent driveshaft with worn u-joints wouldn't make any real detremental vibrations until at least 20-25mph....at least one that looks sound.

Syncro

iTrader: (1)

I think my next step is draining the fluid...

Subsribe to this thread plz, if you dont mind

tooslow7

i dont mean to thread jack but when i turn left my car makes a knocking sound..is this my drive axle???

ibekinq

now are you talking bout a fwd or a rwd?
if fwd yes
rwd i dont know could be wheel bearing or sumthin

ibekinq

is your car stock? and have the same motor and all as the original parts?
just asking cause the s4 and s5 have different shafts and will make your car shake

junito1

i dont think its the diveshaft. I still have the same exact problem on my 88 tII. I also changed my motor,tranny, 2 subframe, front diff mounts. I also have a BRAND NEW driveshaft from mazdatrix. I am still getting vibrations at 60 to 70 mph. ANd when im slowly rolling my rear wheels do feel flat spotted. SO driveshalft is not the answer. I also put fresh diff fluid. Problem still not resolved. ANd oh. when the car is cold(as in only been driving for 5 mins or so) to where the oils havent warmed up yet the car wont vibrate as much or at all when going 60- 70 mph. so any ideas on what it is?

Syncro

iTrader: (1)

I didin't know the S4 and S5 NA driveshafts were different...

I will have to look into this, thanks.

junito1

whats about the turbo models? I have an S4 tII with a S5 tII tranny and s4 driveshaft...

am i going to get vibrations too?

junito1

Bump

classicauto

iTrader: (3)

LOL, Snycro, this guy's doing your work for you!!

to junito1 - No, you won't get vibrations. Provided that you maintain your car and you replace anything thats wearing in it. Meaning take care of it and it will treat you well.

Any car thats approaching (or clearing) 20 years of age is goint to need some attention. There's no inherint issues with vibration in these cars, its simply a matter of things getting old.

Syncro - Any luck on your shake yet?

One thing I would certainly look into is your wheels and tires, make sure they're balanced right on the money....................and torqued properly!!!

Other then that I just want to hear what you've tried since your last update.

slpin

iTrader: (9)

sounds like your halfshafts = dead
i sell u!

Syncro

iTrader: (1)

At this point I'm willing to try anything. What makes you think my halfshafts are dead?

I plan to get the car back on a lift. I want to take a vid of the vibrations, as well as how much I can move the half-shafts up and down.

I'm also going to drain the diff fluid... hopefully nothing odd comes out

classicauto

iTrader: (3)

if you can move the rear axles up and down.......they're shot.

When you described the play before it sounded like a bit of in/out movement of the axle "cups" on the diff....which a bit is normal. But any up and down play on the axles = fubarred.

Syncro

iTrader: (1)

What am I replacing?

Diff?

slpin

iTrader: (9)

u shouldnt be able to move the half shaft up and down....
i sell u!!!

Syncro

iTrader: (1)

What needs to be replaced?

Diff or half shafts?

Do you guys need more info to be able to tell?

classicauto

iTrader: (3)

If the half-shafts have up and down play - they're fucked.

Replace them

Syncro

iTrader: (1)

I PM'ed Splin about the Half Shafts.

Any thoughts on the diff? The 'cups' on the diff where the half-shafts bolted to seemed to move up and down as well.

Terrh

iTrader: (7)

time to rebuild the diff.

Syncro

iTrader: (1)

The way I see it, I have three choices:

1) Buy used diff and swap
2) Rebuild it
3) Swap internals for a Miata Torsen (NO more rebuilds woo! )

How expensive are #2 and #3?

Option #1 seems to be such a half assed solution. Car will be tracked starting next SCCA season.

classicauto

iTrader: (3)

Well depends on what you find the parts for. BRAND NEW............you're looking at about a thousand dollars in parts.

If it were me? - used diff........./problems

But Terrh is right, if the cups also have up and down play.......thats bad and it is indeed rebuild time.