Location of my problem FINALLY identified.
AFTER I replaced everything from the end of the steering column to the input shaft with no improvement.
Here's what I did to solve the sporadic and intermittent heat related binding.
I drove the car until up to temperature and then drove at 40-45 mph until the binding began. Drove home and measured the temperature (laser thermometer) of the bushing at the end of the steering column (125° F), the the casting in the area of the input shaft and driver side rack bearing (150° F).
Then I followed S. Reynolds suggestion.
Got the wheels off the ground with everything cool and used a heat gun to apply heat to each of those areas, got the temps up to the readings I found and,....nothing. No binding. SO,...I do the same to the passenger side casting area where the internal )plastic?) bushing is located, and at 125° F, I get the binding that I would only experience when driving relatively slow.
I pulled the boot off the end of the rack and pinion and can see the white (bushing or seal) recessed in 2". Shaft appears dry. Applied some high temp
synthetic caliper slide grease. Seemed to be better, but things were already cooling down. Will test on the road.
Talking to Flaming River Tech. was not very helpful. They claim no knowledge of this ever seeing this problem. They do not provide and drawing of the internal components or construction or parts lists. Will not tell you how to disassemble and replace a bushing.
BUT, they will do a complete rebuild for $150-200.
Wondering of the shaft is oversized or the bushing is under sized. No help from Flaming River in that area.
By the way, this problem occured from the time I got the car on the road 10 years ago and the rack & pinion was new out of the box from the factory.
Thanks to everyone for their 2 cents of advice and suggestions.
Follow up Comment: had the opportunity to drive in the fall on a warm day and the symptom returned when driving slow(35-45mph) on a warm day (upper 70's).
Convinced that heat build up on the passenger side of rack causes internal bushing to bind due to expansion of bushing and or cast alum. housing. Put car away for winter, wheels off, up on stands, boot pulled back, grease cleaned out (that I had added and seemed to help a bit). Cannot see any retaining clip. can see what appears to be a grease seal. Assuming that a bushing resided behind that.
Options: remove entire rack and pinion and have Flaming River rebuild, hoping that they can correct. Or look into ducting fresh air onto the casting to help kep it cooler. Shielding the casting from the radiator would require a shroud from bottom of radiator, up about 6" to above the casting on the rack. Possible to do both. All options extremely UGLY.
Inclined to have rack rebuilt and tell them to open up the tolerance on that bushing.
Appreciate any comments, thoughts, or suggestions.