vibration at high speed - where to go from here
 

My car, LS1 fbody with TH400/Midwest Chassis 9" rearend drives great under 75mph, but I'm getting a vibration at 75 and over. The vibration goes in and out if that makes sense, you'll feel it for about 2 seconds, goes away for a second, feel it again for 2 seconds, goes away for a second, and it just keep doing that over and over.

The wheels and tires are being balanced as I type this. If that checks out, what's the next step? Should I get my driveshaft balanced? I could have sworn Midwest Chassis balances these at high speed.

I'm going to drive the car from here to California in the next few weeks; in west Texas the speed limit bumps up to 80 and I'm looking forward to that so I know it'll suck to have the car uncomfortable at that speed.

I'm in the Houston Area; anyone recommend Northwest Drivetrain? Not sure if they're a sponsor here.

Has anyone had this issue before? Thanks for any help

hit a curb?

have your driveshaft and axle shafts checked and make sure the wheels are hub-centric, if not get the rings that you would need.

Never hit a curb. Called Midwest and they told me if I got the driveshaft from them, it doesn't matter which way the u-joints go into the pinion yoke, and that their Strange ds's do get balanced at high speed.

The wheel is a stock wheel; I don't think I need the hub ring but I'll double check; i appreciate the response man.

Wheel and tire balance is a good start. Check the alignment to make sure everything is within spec, especially the thrust angle. Then check the drive shaft pinion angle and adjust if necessary. If that doesn't resolve it, check driveshaft balance and joints. I'd give Midwest a call. I'm sure they would be a great resource for tracking down driveline issues.

Thanks. I'm heading up to the wheel/tire shop in about an hour to see what the results are.

I had Icon here in Stafford set the pinion angle to Midwest's specs. Well they say they did anyway. lol

I'll keep you guys updated.

have the wheels road force balanced, oem rims are usually good at balancing out correctly and you won't need a hub-centric ring. could be that your tires have a heavy spot.

Pinion angle
Shocks
Transmission mount

I know what kind of vibration you are talking about, it sounds like a driveshaft or wheel/tire. Have both checked. Checking the drive shaft wont hurt, yes it should be balanced properly, but not all new parts are always perfect, every once in a while things happen.

driveshaft!

in my th400 I had a small crack in my flywheel and the vibration was like that also.

may want to check your flywheel

Rotate your drivesaft 180 deg and when you are at it inspect the u joint for wear

if the wheels check out, id then be looking at pinion angle and driveshaft balancing.

ive heard nothing but great things about northwest drivetrain from multiple sources

Good luck with that...it took me a long time to figure out what was wrong with mine. In my case, it was the tranny.

What was it? Did you find out the exact cause? Or did it just go away after a rebuild or replacement?

Tranny went out....I had it completely rebuilt, vibration went away. It suxs....I had just about everything replaced.

update
 

Had the wheels and tires balanced today at a shop that can balance them while they're on the car (Sal's Auto Sport on 290)...

Three of the wheels and tires checked out with a good balance, but the front passenger side wheel/tire was so bad it caused the HOOD of the car to vibrate!!

After they were done we went for a test drive; I drove. Car drove very smoothly at 80mph, so I think the problem is solved!!

I appreciate all the responses and advice; this was really driving me crazy.

was the tire seperated?

Oh you got lucky. Good to hear it is fixed.

Separated from the wheel you mean? Not sure, good question.

Hell yeah man. Bout time for me to get a little lucky after all the crap I've had to deal with with both my LS cars. lol

[QUOTE=demonpixel;14490636]Separated from the wheel you mean? Not sure, good question.


no sometimes the steel belts inside of the tire seperate which causes the tire to have like a big lump in it which would cause the car to shake like hell, but not all sepo's are bad some are minor like your case where it only shakes at a certain speed and some are so bad it makes the steering wheel move left to right when driving in a parking lot.