STEERING DRIFT ON LEVEL ROAD

If you are sure the rack internals are okay then work your way out from there. Next is check the tie rod ends....upper and lower ball joints...wheel bearings....If you are happy all is well check alignment and the obvious like tires and tire pressures if not already done.

It's pretty easy to jack the front of the car up and feel for play in the wheels, try in both horizontal and vertical planes.

Julian

Kitchenguy ... Julian pretty much covered it .. but I may also add that Caster also adds to high speed swaying and increased caster makes handling at high speed easier .. some thing not easily adjusted on a Pantera.

Ron

If everything up front checks out OK, you may want to check the rear suspension. These are IRS cars which we know require a 4-wheel alignment, and a bad bushing, failing component,etc can mimic front suspension issues. I found this out the hard way when years ago I rebuilt the front suspension on my '69 Corvette. The problem turned out to be the rear trailing arm bushing....argh!

I have a feeling that the issue here is lack of sufficient caster. These cars were originally designed for skinny tires. A 185 front, later changed to a c60.

Front caster is what gives high speed stability. The car is already maxed out for those little tires.

Every time that you increase the size of the tire contact cross patch, you need to increase the caster. The cars that have been converted to GT4 specs will show it most.

Many owners like Johnny Woods realized this and have modified the front suspension to gain more caster. There is a trade off to this though. The more caster you dial in the heavier the steering will become. On a car without power steering it will become an issue eventually.

Ever wonder how they can get the Indy cars to be so stable that they can kiss the wall at 250 and keep going? A lot of caster.

Thank you all for your suggestions, we will now explore further into this problem

One other thing to look into - my GT5-S had a loose steering rack, which exaggerated my tramlining problem, despite having offset bushings. This is what I found this summer:

Hi all,

Ever since I bought my GT5-S, it has tramlined fairly badly. The car has
been a handful to drive, particularly on bad roads. Under hard braking, the
car would dart from side to side - not pull to one particular side, but
would go left-right-left-right requiring constant correction.

Last year I installed offset bushings up front, which improved the situation
greatly, although not completely.

At Le Mans this year, Mike Drew pointed out that I had all kinds of play in
the steering system. The car has more or less always been like that, so I
had not particularly noticed. But he was right - there was all kinds of
play.

Taking advantage of a visit by Tomas Gunnarsson this week, we just came in
from looking at what was happening. Basically, one tire (passenger side) was
nice and tight, but on the driver's side, turning the wheel resulted in
up-and-down movement of the tie rod instead of side-to-side. There was lots
of play on this side tire, which allowed all kinds of weird toe in/toe out
settings, depending on the position of the wheel. Tomas was hoping that it
was just a adjustment issue - there are a series of shims that basically
adjust between binding the steering rack and allowing free play between the
rack and column.

Off came the cover and we found 4 shims inside - one thick and three of
various (thinner) thicknnesses. We reinstalled the cover with NO shims and
found that the steering rack now was binding, but there was zero play. A-ha!
To make a long story short, we experimented, adding shims until we got no
binding, then removing them until it bound, and adding one more to get
minimum clearance. My steering rack is now completely tight, with no play
whatsoever, perhaps for the first time in the history of the car!

What I found amazing was that this steering rack was assembled this way.
Tomas has two possible explanations - during assembly there was some dirt of
something in the assembly which meant that the rack was ok when bench
tested, but when installed and driven this dirt broke down and opened up all
kinds of clearance, allowing lots of play. Or, the rack was just badly
assembled from day one, installed, and nobody ever looked into it.

Note that early steering racks and late steering racks are apparently quite
different, but those of you with late model cars, if you have play in your
steering wheel the fix could be free and could be done in a couple of hours.


Anyway I'm a happy camper as I had been mentally preparing myself for buying
a new steering rack... we just came back from a short test drive and it
feels like a new car. The darting under heavy braking is gone, and the
steering is now rather direct, as it should be.

Your mileage may vary...

Charlie,

Thanks for the heads up, my GT5 tramlines terribly and pulls slightly under braking. I'm going to correct the caster by modifying the a-arms when I can get to it (focusing on and just done same on the '74 at present). The rack shims will be one more area to look at.

I recall David B had a similar issue with an elusive pulling under braking so I'm wondering whether there is a common thread here.