Baffling suspension issue
Hi guys. It's been a while since I've posed but I still follow threads. I have a problem that is baffling us. This is a bit long so please bear with me.
Car is a 69 with a ZZ430 (350), TKO 600, Baer 13" Track discs on all 4. I've gone through a few suspension changes over the years and am pretty familiar with how things work. Current front setup is Ride Tech upper and lower control arms and coilovers, L&H Customs tall spindles and steering arms (no longer in business, I think). Lee Engineering steering box. Hotchkis lowering springs rear. Wheels are 8 x 17 Billet Specialties with 235/50x17 Bridgestone Potenza S-04 Pole Position tires all around. Nice sticky tire.
This setup has been on the car for several years now with no issues. Handles well, pretty neutral. Sits pretty low so I have to be real careful on speed bumps. My headers show flat spots from that.
My issue: a few weeks ago I put the car on my rack and changed the oil and lubed the fittings. All normal. But when I lowered the. car back down and took it for a drive, the toe-in had changed drastically. There was so much toe-in that the tires squealed and smoked going in a straight line! I measured the tire temps with a pyrometer and the outside edge of the fronts were over 180F anfter a short drive. I could smell the rubber burning. Also the car sat a bit higher in the front (maybe 1/2 inch). I put it back up onto track and tried to find something that moved. Nada, nothing. Put a 3 foot pry bar on everything to try and find some movement. Nothing. Tightened everything I could find but nothing was loose. I re-adjusted the toe-in just to see what would happen. The adjustment needed to go from severe toe-in to somewhat straight is less that a turn on the sleeves so it doesn't take much. I lowered the car back down and drove it. All is well again. Drives great. Oh boy! Car is still about 1/4 inch higher that before 9measuring from grade to the front fender lips) but still ok.I scratch my head and leave it alone and just drive it. Still can't figure out how raising the car on the lift would affect anything. It's been on that lift dozens of times.
Driving it around all seemed normal again until yesterday. I pulled out of our local grocery store parking lot turned left with light acceleration. I felt the car kinda twitch a bit and it felt like the front end lifted a bit. The toe-in changed back to severe toe-in, the tires are stealing again and the self-centering for the steering went away. I
drove it home and in the garage the toe-in was quite visible and the ride height increase was evident. (1/2 inch at the fender lips). So I put it back on the rack again. This time I loosened everything up. Lowered the spring adjusters so the springs were loose and re-centered them. I retightened everything again and reset the toe-in. Again it is now driving great. But what is changing? I don't have confidence to take it anywhere and I drive this car to load distance events.
I've bought new tie rod ends and new idler arm just out of frustration. The existing ones are only 7-8 years old but I'm out of ideas of what to change. When it changes it is not subtle. It is either good or very bad; no in between. The fact that the ride height increases when this happens is a clue, but not sure of what. I have looked closely at the springs pockets, frame welds, and anything else that is connected.
I've got the new parts so I'll be putting them in this week but I have zero confidence that that will change what's happening.
Thanks for taking the time!!
69 Coupe; ZZ430; TKO600; 3.55 posi; 13" Baer 4 wheel discs; 17" Billet Specialties wheels; Hotchkis/Koni rear; Ride Tech front; Classic AutoAir AC and power windows cuz I'm old and lazy!