I need some help, guys. I just installed a new power steering gearbox and rag-joint in my 68 (J-code, power steering) and while I’m thrilled to have eliminated 99% of the slop from my steering, the repair mysteriously wiped out the caster effect, i.e., my steering wheel no longer wants to center itself after a turn-- it only returns about 2/3 of the way and I have to manually turn the wheel the rest of the way.
Thinking that the gearbox lash was perhaps a bit too tight, I tried temporarily backing off the adjuster a bit, but that only added some play to the steering and didn’t seem to help the caster issue. Next, I added a degree or so more of positive caster to both front wheels and that seemed to help slightly, but not enough to center the steering wheel completely. The strut rods are now at the end of their adjustment so I’d have to start shimming the upper control arms to see if even more caster would fix the problem. It seems I shouldn’t have to do that. The car tracks straight and doesn’t wander so the alignment seems good. Would increasing toe-in help? Should I loosen the lash in the gearbox even more?
Alignment specs are really important, especially if you’re running power steering. It’s hard to get enough caster with stock parts to have good RTC. It would not be unreasonable to go with something like 5 degrees, if you could get it. Caster increases steering effort, but it also adds camber when cornering, so it helps keep your tires planted and tread flat to the road. It also helps with high speed stability. For manual steering, 3 or so degrees should be fine, unless you’re Popeye.
Adding toe-out will just make your car indecisive and wandery feeling, as well as causing unwanted treadwear. It will not want to turn, but that’s not the same as good RTC. Too much toe in should be avoided altogether, as it creates serious instability issues. The idea is to have a tiny bit of toe-in (1/8" on each side, 1/4" total), so when you’re driving down the road, the slight drag of the tires takes up slack in the moving parts, allowing both tires to be straight and parallel to the road.
And as for camber, generally, for these cars, nearly ‘straight up and down’ is best. Tipping the tops in a tiny amount can help with cornering, but don’t get too dramatic or you will just end up causing uneven tire wear with little benefit.
I was only able to squeeze an extra 1/2 degree of caster out of the strut rods before running out of adjustment, and like I said, that did help a little bit, so if things don’t loosen up after my trip, I think I’ll go ahead and try shimming the upper control arms.
By “borgeson” do you mean the all-in-one power steering type? If so, that’s not what I have. Mine is the stock-type replacement- looks identical to the old one.
If your idler arm is old needs changing. The bushings ‘winding’ up in the idler arm on a turn help force the wheel back to center. The new box is tighter and possibly can’t be pushed back.
Well, that’s something I hadn’t considered. I do remember replacing the idler arm but that was probably over ten years ago Man I’m getting old. I’m not sure how I’d go about testing it, though, short of simply replacing it with a new one.
I crawled under the passenger side tonight and sure enough, the idler arm is toast—the whole thing is loose. I’ll replace it tomorrow and see if that solves the centering issue. Even if it doesn’t, it still needs to be replaced.
Drove 600 miles today (Wisconsin to Kansas) and I’m convinced the idler arm is the problem- the tightness of the new gearbox made me think all of the play was gone, but once I hit the interstate, I realized some of it is still there.
I changed out the idler arm last night and drove the car about 20 miles this morning. Can’t say I notice much improvement even though the old idler arm was visibly loose. There is still have some play in the system and the return-to-center issue is still there as well. Rats.
I think the remaining slop is a weak power steering pump. Even with the engine running, I can see that the ball stud on the control valve still has free play before the wheels actually start to turn, just like when the engine is off. My understanding is that once the system has pressure, that play should disappear. I just ordered a remanufactured pump so we’ll see what that does after it’s installed.
I think the remaining slop is a weak power steering pump. Even with the engine running, I can see that the ball stud on the control valve still has free play before the valve itself starts to move, just like when the engine is off. My understanding is that once the system has pressure, that play should disappear. I just ordered a remanufactured pump so we’ll see what that does after it’s installed.
The PS unit is an early example of ‘force feedback’ (though they didn’t even have that term back then). You will always see the control valve move when you turn the wheel, but when the system’s “on”, it should try to recenter itself by moving the hydraulic piston, shoving the rack ‘away’ from the direction the valve is being pushed. It doesn’t magically ‘tighten up’ or something. You shouldn’t feel it as slop when you’re driving though, despite the visible play, because the hydraulic system takes care of it. If the tires are providing enough resistance, you can usually wiggle the valve somewhat, because until there is sufficient hydraulic pressure to actually turn the wheels… well, you get the picture.
Modern grippy radial tires tend to make return-to-center worse at very low speeds, along with increasing steering effort, but on the road they shouldn’t cause much trouble.
Have you done the Shelby/Arning drop? That might help you get a little more caster in, which will help. Keep in mind, with the original bias-ply tires, these cars didn’t need or want a lot of caster. However, radials require about 3-3.5 degrees with manual steering, and power steering does better with another 2 degrees, if you can get it.
Caster increases steering effort, but improves return-to-center, adds high speed stability, and adds camber when cornering, aiding in grip.
Man I’m getting old. I’m not sure how I’d go about testing it, though, short of simply replacing it with a new one.