Thread: Advice on shuddering/vibration @ 45 mph

I've been trying to figure out what could be causing my 97 GT, with 132,000 miles on it, to shudder/vibrate when I hit about 45 mph. It feels like the whole car is shaking and it's driving me nuts. It's only just cropped up in the last couple of months.

I first thought it was wheel/tire related. To that end, I've replaced, tires, LCAs wheel bearings, rotors. That's just this year. Last year it was struts, tie rod ends.

After a little research, I'm thinking it may be some transmission problem but, the car shifts fine. I'm planning on changing the fluid/filter this weekend though. The problem occurs on all road conditions. It just starts at 45 and can be a quite severe bouncing/shaking but then goes away when I hit 50 mph.

If anyone has any ideas as to what the problem may be, or how to diagnose it, please chime in.

I'm more inclined to think it's something to do with the tires really. I'm going to get them re-balanced Friday. I made a quick check or two driving home today and it's gotta be something there. The transmission didn't seem to have any effect on the vibration I was getting today.

That's what I'm thinking. does anyone know how to test if the half shafts need replacing? At the moment, they look good (boot wise) and they don't make any noises.

Meanwhile, it's off to the tire place again tomorrow for another re balance.

Originally Posted by Swash

Could be tires - could be input shaft - could be warped/bent rim - could be could be could be.

First thing to look for when you think a halfshaft might be a problem - grease. Check inside the wheel wells for any grease on the control arm - and on the sway bar - it tends to accumulate on the outermost sway bar bushing. Half shafts tend to "let you know" when they are going out - you will either have a noticeable noise when turning corners, or even when just cruising down the highway. In corners, you'll hear a sort of "wharble" - sounds like something is out of round, and is often accompanied by tire squealing - on the highway it will sound like a growling noise - almost like excessive road noise. You may want to check the tie rods as well - jack the car up, grab the tire and 3 and 9 o'clock and try to move it left to right, do the same at 12 and 6 o'clock. If it moves much at all - that could be your culprit- and yes it can/will cause vibrations.

If you check those and all is well - or don't have any of those other symptoms...get the tires/wheels balanced - make sure to have them tell you what corrections they made and where. If that still doesn't fix it - I would recommend pulling the driver's side halfshaft and checking the input shaft on the transmission - if it starts puking fluid as soon as you pull the halfshaft off - and the input shaft is loose - there is your problem...and I'm sorry. At that point - call Trannyman.

-Swash

I've checked the half shaft boots and they are clean. I can't tell if they are loose or anything. Like I said, they don't make any noise so I think they may be ok. I had the tires rebalanced today and it helped a lot. Although, there is still some vibration. The guy said he matched up the high spots on the rim with the tires and checked to see if my lateral runout on the rims was ok. All checked out.

I'm still pretty much stumped really. I could go for one more balance but I'm pretty skeptical if it will solve the problem. Maybe a half shaft replacement is in order. Or, I was thinking maybe it might be the rear rotors. I replaced the front two but the rears haven't been messed with. I've run out of money to mess with it really but at this point all that's left that hasn't been replaced are the half shafts and rear rotors.

Thanks for all the feedback everyone.

yea even if the tire/wheel is perfectly balanced...a bent rim will still cause a vibration as this was a problem on my vette and i tried tires and balancing and alignments...but it was a bent rim

The rims checked out fine for straightness. I'm still kind of leaning toward the rotors on the rear. I don't see how they could be that much of an issue but I'm getting really tired of going back and forth to the tire place.

Oh, and if anyone else needs any tips on car repair and diagnosis, I found this site ( Auto Repair Articles ) that has some good articles on all kinds of stuff.

i got the same problem but it goes away when i accelerate and gets worse when i brake

You can always swap rims and tires front to back so you can see if a rim is the issue. The position the vibration is coming from will let you know weather tires and rims are the issue.

does the steering wheel look like it shakes side to side, if it does its deffinitly not a bent rim, i had the same problem with my car ended up needing new bearings, tierods, and cv Axel.