brucep

Also has a close ratio 4 with 3.70 positraction, Goodyear Integrity 205/70 tires, HD springs and new Delco shocks. I know the tire/spring/shock combo is weird. I'm in the process of fixing that, but in the mean time, when going throught the gears at full throttle, shifting at about 4500rpm, the car "feels" like it's fishtailing, even though I'm pretty sure it's not because the pavement is dry, and the tires make no noise.

I just replaced the trailing arm bushings and did an alignment. Could the tires be breaking loose or is there something else wrong/loose here? Based on a drive/lift inspection, my Corvette expert told me the only thing the car needed in the rear suspension to drive well was shocks, those trailing arm bushings and an alignment.


[Modified by brucep, 2:37 AM 4/23/2003]


[Modified by brucep, 2:38 AM 4/23/2003]

achapman

I had a 65 327/365 with a CR Muncie and 4:11..... it always fishtailed..... it might have been due to the way the clutches in the posi hooked up..... or the independent rear suspension...... or a combo of both.... it was predictable so I just chalked it up to "the norm".... :cool: :cheers:

MikeM

I doubt your back tires are breaking loose past 30 mph. I would look at equal tire pressure in the rear tires and toe-in settings, front and rear and especially the rear. You also could have some really loose rear wheel bearings that have not started to make noise yet.

Mike

Vetterodder

:iagree:
Before I rebuilt my trailing arms, bushings, and had it aligned, the rear of my `65 would try to steer the car under hard accelleration. Most of the problem was in sloppy bushings that allowed caster changes under torque but a slight variation in toe from one side to the other also contributed to the problem. Even with everything in good order, power delivery will still favor the right rear but if everything is right, that shouldn't be very noticeable at the power levels we're talking about here.

427435

The bushings in your front suspension could be causing the same problem also. My car changes direction getting on or off the throttle but it's still got the original 1967 bushings all the way around. Need to do some rebuilding as it's no longer much fun to drive. I'm still trying to decide on rubber vs poly replacements.

magicv8

IMO if your car changes lanes to the left when you power shift (as mine did) the problem can be solved by redirecting the rear wheels 1/8inch to the left. :crazy:

I replaced all the rear rubber in my car 14 years ago (trying to solve the problem) to no avail - then started fiddling with the alignment. It's counter intuative. The rear end precesses to the right under load, which points the front end left. If you preset the attack angle of the rear wheels to the left, the rear pushes the front straight under hard acceleration. ;)

I have been driving the car with the 1976 wheel alignment specs (plus that angle change added) for the last dozen years without losing control of where the rear goes - and I flog the car occasionally, and drive it a lot - in sun, rain, sleet, snow, and hail. Try it, you'll like it. :cool:

StrayDog

My 66 big/block , smokes um up & goes to the left..while smoking the tires...............2.6 sec , ...60 foot time :crazy: need drag radials for my birthday :steering: The Dog.

JohnZ

Strange throttle-on vs. throttle-off behavior (especially in a curve) is generally a result of strange things happening at the front of the trailing arms - poor toe-in setting (or different from side to side), toe-in shims missing, allowing the front of the trailing arm to move sideways on the pivot bolt, or trailing arm bushings shot or deteriorated. If all is well in that area, it should go straight when you nail it (ignoring wheelspin effects); if it doesn't, it's time to see what's wrong. :thumbs:

427Hotrod

I'm with the others. Barring something mechanically wrong, the most common issue is rear wheel toe-in.

Make sure EACH wheel is measured independently to the car centerline. It can never toe out. Stay with stock specs even with High HP deals. They work. Some alignment shops try to zero out rear toe to help tire wear some, but in reality it makes things squirrely due to wheels pointing wrong way under load.

And as mentioned, it is possible to have toe in correct,but still have the rear wheels pointing the wrong way. Sometimes alignment shops get a stack of shims on say maybe both sides on the right side of arms. Toe in will still show correct if measured to each other, but wheels are pointing to the left in this case.


A Vette set up right will go very straight!


JIM

Daffy2

Changing direction a bit when you get on/off the throttle is an indication that one side (or both) lost a shim at the front of the trailing arm. I threw a 1/8" shim from the right side with some wheel hop on a wet road and noticed it immediately. Spooky feeling, too. Replaced the shim and perfect again.

Daffy

Ironcross

The first thing and easiest to check is the tire pressure, make sure they are equal. :thumbs: