speedjw

I have an 89 GTU, that has developed a bad vibration. I can feel it throughout the entire car, not just through steering wheel, not just through shifter.

It seems to be dependent on wheel speed only. It does not make a difference if I have clutch in or out, if I have it in any certain gear, or what rpm I am at.

My first indication was wheel bearings. But when I swerve side to side, I get no increase or decrease in vibration. I then jacked car up, wheels spin freely, without any grabbing in the bearings.

So, I then thought it was the differential or the driveshaft. The driveshaft was supposedly replaced 6 months before I got the car, I have had the car almost a year.

Also, I had never checked the fluid level in the diff (as everything else on the car had adequate fluid level, and open diffs are usually low maintenance). Ok, so I'm stupid. But, when I checked the fluid level in the diff (about 3 weeks ago, after vibration had started). I only got out maybe 1/2 a quart if I'm lucky, and its supposed to hold 1.5 quarts.

So, I pulled the diff., cracked the case, and checked it out. The teeth are little worn, but no worse than I would expect for 169,000 miles. The diff spins freely, the input shaft bearings dont seem to feel too bad.

Ok, so I'm stuck. Is there something I am overlooking here. Has anyone experienced this? Could it be a bad driveshaft?

I mean, once I put the clutch in, and change gears, the only things that I can't change are the output shaft from transmission, driveshaft, or diff. I wouldn't think the halfshafts could create this much vibration, there is no ticking when halfshafts are strongly loaded either, so CV's seem to be good.

ANY HELP IS STRONGLY APPRECIATED!!!

Felix Wankel

Was the replacement shaft new or used?

Aaron Cake

iTrader: (1)

Sounds like a bad U-joint on the driveshaft. Remove it and inspect.

Ranzo

are your tires and wheels balanced? maybe some of the weight came off.

If if was a U joint it would be RPM Related. a wheel bearing would usually not cause a vibration as you described.

Start simple and go from there.

Ziggy682

I would think a U joint would be speed dependent, not RPM dependent.

Thaniel

U-joints, everything from the mainshaft in the trans on back for that matter, spins at the same speed as the wheels.

I would think wheels, tires or driveshaft would be good places to start.

Samps

The wheels are spinning at a ratio of either 3.9:1; 4.1:1; or 4.3:1; with the drive shaft. Think "ring and pinion." There is no point at which the drive shaft and the wheels are spinning at the same speed.

As for the vibration; did you check your differential mount? How about your tranny mounts? Maybe even your motor mounts? And at that milage there are probably some really worn bushings all over the car.

blu_gxl

well you can balance your tires (good place to start). also you can check for drive shaft balance issues by useing 2 clamp and screw type hose connectors just connect them in series and at the bottom both screws down then move them away from each other slowly and see if the vibration goes away. if it does go away then you need to rebalance the drive shaft. if that's not it i'd check your crush sleve on the pinion gear. also diff mounts are good to check. once you check that let us know the out come.

james

Ranzo

OK my brain fart about the drive shaft. What I was thinking that normally if you clutched the car the vibration would probably change due to change in tension on the driveline.

Anyway check wheels and all the above mentioned items im sure you will find it

speedjw

Thanks a lot, I went ahead and pulled the bottom end out of the car. Sure enough the front U-Joint is bad. I mean, I can't even flip it over by hand.

So, I'll have her replaced and back on the road again in no time.

Thanks again...

Thaniel

Yes. your right. Glad to see someone is paying attention.

I ment to say, they always spin togther, can't spin the drive shaft without spinning atleast one rear wheel ( drive shaft and axles do spin at different RPM).

That's what I get for eating lunch, Talking on the phone and posting messages.

Green

driveshaft.. had same problem... bearings on a ujoint totally gone
can't believe I drove on it for like 2 months... lucky it didn't snap..
get a used driveshaft to replace.. or get a driveshaft with removeable ujoints.. don't purchase a new stock driveshaft with unchangeable ujoints.. yuck

'Vert in Vegas

If it is the driveshaft, it will change the vibration characteristics by going "power on - power off"
with the throttle.

mr_vaughn

iTrader: (1)

I went to get my tyres rotated and my alingment done today.

I installed a rear adjustable camber link to replace the sub link bar.See picture (item II)

This helped me adjust my negative camber on my 7.
Shortening this bar decrease the negative camber.
But the diff. mount was broken.(item I)
So when i acceclerate the diff get pushed down on to the sub frame at the bottom of the diff and then a sound like you decribed happens.
this is only when i acceclerate because the rear end get pushed down by the power applied.

my mount is cracked and broken i will be getting it fixed tomorrow.

Barwick

balance those wheels.

Or if it ONLY happens at a very specific speed, you might have a broken belt in one of your tires (happened on my Accord.. it would vibrate pretty bad at EXACTLY 60 mph, then go away above or below 60).

Also check the U-Joints, and again check the wheel bearings to make sure there's no play (not just spins freely, but if it wobbles more than it should)

mr_vaughn

iTrader: (1)

They also did the wheel balance when changing the tyres on mine

Poindexter10thae

iTrader: (2)

This comes from experience:

Check the front U-joint on the driveshaft(the one that slides on the spline in the tranny) I have had REALLY bad experiences with that particular piece. get under the car and move the driveshaft(the shaft, not the yoke) in the direction of the U-Joint(side to side) If there is ANY play at all it is your U-joint. Lucky for us mazda made it so that the U-joints are not replaceable. Go to a reputable drivetrain shop and have it machined to accept replaceable(more durable as well) U-joints.

I felt a vibration at certain speeds and rpms and when I had the clutch disengaged and was just coasting. One night I was driving and the driveshaft broke(at the U-joint), when it broke it hit the gearbox on the tranny, effectively ripping it from the tranny housing, breaking the bolts(and tranny housing in places). The vibration has happened 2 more times since then, I replace the driveshaft both times quickly, but have been getting used, high mileage driveshafts cheap, so it just postpones the problem, I am having a T2 Driveshaft fitted with the N/A plate(to bolt up to the N/A Diff) and have it machined to use Chevy truck replaceable U-Joints.

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