Pecuiliar vibration

[vex]

has cropped up in the last two days. I've been trying to isolate it, but it very hard to tell where the vibrations are based off of. I do not really feel it until I get above 40MPH and it seems to be oscillatory in nature. This leads me to believe that it's speed based and so a thrown weight, or something to do with the suspension and not the engine forward.

This seems to be confirmed when I free rev in neutral. I don't feel any increase in vibration similar to when I'm traveling at speed.

I am however still a little concerned with it as I don't feel any vibration under 40 at all. Vibrations also don't appear if I accelerate quickly to 40+. Which leads me to think that it's in the transmission/differential area.

Is there any other tests I can preform in the meantime to narrow the possibilities down?

[RETed]

If you're trying to isolate it to a certain tire, rotate your tires front-to-back.


-Ted

[vex]

Originally Posted by RETed

If you're trying to isolate it to a certain tire, rotate your tires front-to-back.


-Ted

Easier said than done. Front tires and rear tires are not interchangeable.

[RETed]

Got a spare?
Change them out one by one after taking test drives in between?


-Ted

[vex]

Originally Posted by RETed

Got a spare?
Change them out one by one after taking test drives in between?


-Ted

Darn you Ted. You keep giving me good ideas on things I can't do!

I'm trying to isolate it a little more than either the tires/suspension and more along the lines of isolating it by function: Engine, Transmission, Differential, tires/suspension.

I don't get vibration, or at least the vibration subsides a little when I engine brake and speed is above 40. I feel the vibration comes around from the rear up through the chasis eventually feeling it in the steering wheel. At 40+ I start feeling it in the seat.

I have a few things to check, and will hopefully have the car up in the air this weekend to double check the bottom of it.

[classicauto]

Wheel bearings likely.

How old are the tires/rims? I would jack up the car, check all the wheel bearings and if they're tight have the wheels balanced - then go from there.

[RotaryDiagnostics]

Put the car on stands and run through the gears while watching the drive shaft. Could be a damaged/out of balance drive shaft or worn "U" joints.

[TitaniumTT]

You might even be able to see the u-joints. But the @ speed test is a good call

I had a similar vibration recently as well. It popped up on the first test drive. I could've sworn it was the wheel bearings as they had been fucked with by the previous owner that I got the 5 lug swap parts car from. So I swapped the wheel bearings. Vibration persisted. I blamed my friend for giving me a bad TII driveshaft. So we swapped that out. Still there, now I'm pissed to the point of seeing red. I had swapped in the Torsen and set the backlash myself so I knew that was good. I rebuilt the axles so those should've been fine, so in a fit of rage we swapped my rear end out. Vibration gone. The vibe must be in the pinion area. Seemed OK when I checked it out, the spermburper that sold it to me said it was in great shape, I guess I can't complain too much becuase I got an entire TII rear end, subrame, arms and a few spare axles for $200.

Anyway, check the driveshaft, axles and wheel bearings. Worst case it's in the diff. Mine is going to KDR to be repaired/setup next week.

[WE3RX7]

^ Diddo, I say driveshaft or dif itself... have you playing with your new found power too much lately??

[vex]

I don't think so... No hard launches, not in the boost all that often or for very long as I don't have a system in place to tune for positive pressure. It's definitely from the transmission out as I still get vibration when off power and rolling. I also find that the vibrations subside a little bit when I get the car warmed up.

I'll be checking the drive shaft today. I know the diff was slightly worn when I installed it... It may infact be time for a rebuild of it. Though I can't say for certain. If I had my bore scope here, I'd drain the fluid and check out the inards for wear. From what I can tell the bearings still seem fairly firm with no play.

Oh yeah. Funny story yesterday. I was doing some trouble shooting yesterday and put her in boost (Vibrations seem to subside to nill if I get weight off the front--yet to check the front bearings as I haven't had time). Heard the blow off valve for the first time and thought it was the greatest sound in the world. So I put her under boost again in hopes of hearing it... all i hear after about 2 seconds in boost is "Pssssssssssssssssssssssssssssshhhhhhhhhhhhhhhhhhh hhhhhhhhhhhhhhhhhhhh." The car then stutters to off. I popped my first coupling! Actually my idle control recirculation line popped off.

[TitaniumTT]

Lifting the front usually makes the vibration worse if the problem is in the front end somewhere

[vex]

http://www.fostertire.com/tcm_vbrt.htm

Some helpful information. Seems likely that I may have some tires out of balance.

Anytime the seats and floor of your car vibrate when you are traveling over 35 miles per hour have the transmission mounts, front drive axle shafts and drive shaft checked. This can even be caused by a faulty vibration damper. If nothing can be found that would cause the vibrations check to see if the exhaust system is making contact with the chassis. Also, check for broken or loose clamps. When your car vibrates only when you are traveling at high speeds this is usually a sign that your tires are out of balance. Although some amount of vibration is normal in the dash and especially on transverse engine front drive cars, if the vibration becomes a rattle you will need to check your panels and brackets. Press your hand over the area on the dash where the noise is coming from. If the noise is eliminated or reduced you will need to tighten the retaining screws. If this still doesn't stop the noise, loosen the panel and slip a sheet of rubber under the panel before tightening the screws. Wind noises can usually be traced to bad weather stripping. Tape the window shut and if the noise stops, have the weather stripping replaced. If the noise does not stop check the grille to see if you have a broken section. You can test this by taping the section and driving the car. If the noise stops you will need to have the grille or grille section replaced. Do not leave the tape on the grille since this could cause your car to over heat. A whine under the body of your car could indicate that the rear axle or front drive final drive unit is faulty. Have them checked and serviced by a professional mechanic.

http://www.allsands.com/potluck3/tro...ing_udr_gn.htm

[rx4ur7]

Do you feel it in the steering wheel or your butt? If steering wheel it will be in the front. In you butt, engine back.

U joints possible but usually they will show through out the range. Check for bad tire, shifted belt. Bearings usually do not cause vibration unless they have really gone bad and you will hear them then. Check half shafts and installation.

Rear bearings and rear you can get a good idea of any bearings by listening to them with your stethoscope. Long screw driver will work, as will a length of fuel line.

[vex]

Originally Posted by rx4ur7

Do you feel it in the steering wheel or your butt? If steering wheel it will be in the front. In you butt, engine back.

U joints possible but usually they will show through out the range. Check for bad tire, shifted belt. Bearings usually do not cause vibration unless they have really gone bad and you will hear them then. Check half shafts and installation.

Rear bearings and rear you can get a good idea of any bearings by listening to them with your stethoscope. Long screw driver will work, as will a length of fuel line.

That's the thing... I feel it in both. It's literally shaking the entire chassis--pretty sure it's from the rear though.

[lcrotaryracer]

I have the same vibraton. it started light then made the car shake so bad where i dont drive it any more.