well i have my 66 with 4.5 mideyes on the rear, performance lowering springs on front w/uca drop and roller perches. my car has a good alignment and tracks great.
My question is:

when i accelerate hard the a$$ end sags and the front lifts, but when i let off the front end drops back down and the car pulls quickly to the left. it straightens out right away but the initial veer to the left can get a little scary when im hard on it. It didnt do this with the stock rear end but now with the trackloc it does it.
Would traction bars help? or, is it a front end issue?

 

Yes, Traction Masters (don't get the cheaper fakes) will improve, and perhaps eliminate, this problem.

 

That's curious and may be resolved by traction masters as mentioned by 2+2GT (beautiful undercarriage by the way, I saved that pic in case I ever install traction masters/ caltracs). I wonder if it's the driven wheel giving resistance from the tracloc which would be engaged only on the right rear tire on deceleration?

I'd also find a hill and do a down hill coast in neutral with hands off wheel to see if the car pulls left at ll on it's own - sticking LF brake or alignment issue.
Jon

 

Have you already measured bump steer?

 

I'd scour the front end, when the weight comes down something could be flexing, possibly a cracked shock tower.

 

Not my undercarriage, mine is all the same parts as the one in the photo, but not clean.

If you have Traction-Lok, it's a torque-sensitive wet-clutch that effects each wheel equally. The suspension, however, does not react equally to the torque.

The way the prop shaft torques the rear axle, and the way the spring wraps from the torque, tries to lift the right rear wheel. Doesn't, of course, but what happens is the body squats down on the right rear corner. The Traction Masters prevent spring wrap, by forming a box with the spring. The Caltrac only works one way, which is supposed to be an improvement. At twice the price, it'll take some convincing for me.



. .

 

The pulling to the left he is describing happens during breaking. These trac bars will help during acceleration but not during breaking. The shelby drop makes bump steer a little bit worse. Also your caster could be off from the alignment shop. Its really difficult to get caster right without adjustable strut bars. Also check to make sure both your stock strut bars are tightened down.

 

When you aligned the car after the drop and component replacements did you use the shelby specs or the stock specs? You can't use the stock specs with the drop and radial tires - it will tend to over-steer on decelleration. The caster has to be increased and the camber has to be decreased to make up for the tires and the camber changes due to the drop.

 

it is aligned to the shelby specs. i took them from a thread on here i believe. I took it to the best shop in town. Network Alignment on the west side of phoenix is noted for their work on customs and street cars. they are the best of the best and they showed me the specs as they aligned it. really good guys.

FYI, braking is great. No pulling at all. very little bump steer if any. our roads out here are pretty nice so they ride and tracking is nice.

The problem is only when letting off the throttle from a hard acceleration. I am running the explorer rear end so the axle tubs are 3.25" Im not sure i can use the Traction Masters in their original form. i will need to alter the bolt pattern to match my spring plates.

I may order some in the next week or so. i have notice that it has gotten worse as i use the car more. I think it may be due to the rear springs settling and softening a bit.

I will also inspect the fron end and the shock towers tomorrow.

thanks guys

 

Check for worn or broken bushings or shocks. Something is not right.

What shocks are you using? Are you sure all the springs are the same? If that's only happening under decel in gear then it's a load transfer issue.

Another source could be the trac-lok. Is it set up correctly and using the proper friction modifiers? It could be heavily biasing 1 axle under decel and engine braking is going almost entirely to 1 rear wheel.

In either case it's a sign that something is wrong.