New car to me, and just figuring out how it all works. Today I noticed that when I step on the gas going straight, the car pulls to the left. When I let off the gas, it straightens back out (shifting to the right).

Any ideas? It is subtle, but enough to notice.

 

My guess is it's something in the rear suspension. It could be as simple as one of the rear tires is underinflated. It could also be a bad bushing in a rear trailing arm, allowing that side to toe in and/or out under acceleration.

 

This could be many things and in my years working in an Alignment/Brake/Tire Shop we called it Torque Pull. You could have a Brake hanging up on one side, Low Tire Pressure in the front or rear on one side, Front End or Rear End out of alignment. I used to have to test drive cars to figure it out.

The Rear Differential in the Corvette is a Limited Slip Positraction Differential and might be as simple as sucking out the old fluid and installing new fluids. Under power both wheels will engage a Clutch in the Rear Diff and cause it to go into Posi Traction mode. If one side is slipping more then the other it could pull the car to right or left.

Or as the other dude says could be a bad bushing in the Trailing Arms or rear suspension causing the Rear End to torque in a direction than cause a pulling problem.

I would crawl up under the rear of the car with a pry bar and flash light looking for spent component bushings. Pull on stuff to see if it moves. These cars are old and need repairs if the previous owner did not repair them. Not uncommon. I spent about $1800 having my front end rebuilt and it pulls right all the time because I did not have the money at the time to fix the rear suspension also. My rear suspension now needs rebuilding and it is a project for next year because I could not supply the parts for a rear rebuild. I intend on tearing out my rear suspension myself and installing all new parts to save money on labor. Front suspension I did not have the tools for or equipment to repair is so I had a shop do it. Rear end I am not afraid to tear down.

 

Several threads in here about this... Mine was fixed when we put new trailing arm bushings in ....

 

 

My guess from experience is its your power steering control valve. Its suppose to balance the left/right. If one or the other seal goes it will pull left or right with the pressure caused by acceleration. Are you leaking any power steering fluid? Are you low on power steering fluid?

 

Its the part in this video

 

The valve usually won't cause this problem under acceleration only. When the valve is out of center or going bad, it will cause the car to act pull all the time.

Just like above, in most case when we have a car in our shop with this problem, there is an issue in the rear suspension... Rear trailing arm front bushing, rear wheel bearing, and even a failing trailing arm (there is a crazy story that goes with the failing trailing arm).

 

Eliminate the easy things first.

Make sure both rear tires have equal tread (make sure they're the same model tire, too) and that they're equally inflated.

Exactly what you describe occurred on an S2000 I had and all it turned out to be was the right rear tire loosing air.

 

Okay thanks everyone! Plenty of things to check, and will start with tire pressure when it stops raining tomorrow. I'll keep you posted...

 

It is something with the trailing arms. I had an alignment and the rear would move around when I accelerated and braked. They left ONLY about 1/8" of shims out and left the bolt loose! Lou.

 

That was a very informative video. I wish they had shown the piston move back and forth with adjustment screw. That would have been a very help visual.

 

This is your problem.....ususally 7-8 lbs of air difference will do this...or 2 different tire types...or two different tire sizes.

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The posi units are sensitive to these differences....back in the 70's, I took my vette to a highly rated hard to get an appmt with mechanic who worked out of his house...he was the ex Chevy dealer vette specialist, he was so good, the chevy dealer begged him to work on their vettes at his house after he quit, I told him my rear end had something broke and the car jumped a full lane giving driving it hard and jumped back when you let offf the gas....he finally came out into his driveway and looked under the car and said...I am only going to tell you once again....go make the amount of air in both rear tires the same. I thought he was way over rated by telling me that garbage...I went and checked and sure enough....8 lbs or so off. Fixed the problem and it went straight as an arrow.

I now go to visit and take this mechanic food at least 5 times a week...he is 86 now and without his help for the last 20 years building 3 streetrods from the ground up, it would have been impossible without his knowledge and actual help for free usually. He and I rebuilt my distributor just this week for my 49 Fleetline.

When my rear spindle bearing went bad while I was in college and had no money, he drilled the rear housing where the bearing lives, tapped it, put in a grease fitting, greased it all for $5.00 a side at the time....I have greased them 2 times since then and thats it.

 

That pretty much tells me you have good torque, dont be overly concerned about it.

 

Tire pressure was the same on all four tires, so it's not that. It's pretty scary as it swerves left on the gas and then back right when I let off the gas.

Going to check trailing arm next...

Also, noticed something I had not heard before. On the left side of the driver's side footwell, there is a hissing sound. I opened the hood, and it is definitely on the driver's side below the brake master cylinder but I can't figure out what it is. It continues when I shut the engine off, for about 10 seconds. Any ideas?

 

Snake!!!!

 

Again....it sounds like a tire problem.

Are the tires identical brand?

Are the tires the exact same size?

Do the they have the same tread depth?

I would move the front tires to the rear and see what happens...I almost guarantee that if you were running non radials and switched the rear tires...it would jump to the right.

I did also end up putting posi additive from the GM dealer...it works great and it definity helps any cracking/popping in the rear end from the posi parts not on the same page.

On the noise...sounds like the booster, if you have one, is leaking down....do a brake booster check.

 

I'm note sure if that's were the vacuum lines run on yours but it could be a vacuum leak. Do you headlights go up and down?

 

His 71 metal vacuum tank could have a rust hole in it. Lou.

 

I'll be surprised if the pulling issue isn't related to worn/broken/missing rear suspension components. My money is on the T/A bushings and or shims, but failed strut rod bushings or loose camber bolts will make the rear track funky too.

Does the car ever swerve going over a good-size bump?