With the engine OFF, you will have about 1/8 of an inch of movement left and right in the PSCV but little movement with the engine ON.
You might want to check the 'steering coupling' (rag joint) for slack. The top and bottom should move at the same time.
The pitman arm is under the steering box, while someone moves the steering wheel see if the pitman arm moves up and down before it goes left and right. There should not be any slack there.
You will have to confirm that the A-arm bushings, tie rod ends idler arm and ball joints are all good.
You can also go for an alignment and see what they say needs to be replaced and then fix it yourself.

 

with the engine off, window rolled down, hood open, take two finger to gently move the steering wheel left to right while watching the steering shaft where it goes into the box, if you see movement without the pitman arm moving you can adjust the box with the screw on the cover. Loosen the lock nut and gently turn the screw clockwise an 1/8 of a turn until you notice you no longer have play in the wheel, do not over tighten it. When satisfied with the adjustment re-tighten the lock nut.

 

If your tie rod ends are tight, your pitman arm isn't shifting in the bottom of the box, then you can adjust the box.

Have someone swing the steering wheel left and right bumping from resistance to resistance. if you have a good few inches of swing and the pitman arm isnt moving with the rotation of the wheel you can tighten up the internal gears by screwing the adjusting rod into the box.

Loosen the lock nut,
Screw the adjuster into the box while someone wiggles the wheel
When you get the slop adjusted out, tighten the lock nut.
My 68 had a tiny amount of slop and I adjusted out easily.

Heres some pics of the guys so you have an idea




All the internal parts




This is how the shafts sit internally



You can see the gears are wedge shaped and the slop can be adjusted out.
Dont go to far in as you can cause binding and bushing wear

 

This is correct. The incorrect way posted here for years is to tighten the lash screw then back it out 1/4 turn. You have to be sure you are on center since the center tooth is machined larger then the off center teeth. Adjusting the lash off center will put too much load on the center tooth. Yes it will feel great but it will not lash as long. Most of steering box play is in the gears and loose end bearings, stock type bushings also allow side movement, incorrect lash screw shimming results in vertical play as well. If you see there are no threads above the cover jam nut on the lash screw, your gears are most likely shot.

 

Piling on a little here, I have this issue - zero threads and my internals are shot, as I have 2-3" of play - I completely rebuilt the steering but should have done the steering box at the same time .
'70 big block with Power brakes, power steering. What's the best way to get the box out to R&R? Unbolt the master cylinder, bend out the way and extract from the top? Thanks for any advice.

 

I pulled mine out the bottom but I have a small block and I had the rest of the steering already out

 

Bumping this one, I am about to attempt it again (arrival of a small baby boy 2 days after post stopped all work on the 'vette). Anybody have this situation and can advise on the best way to remove? It's so tight with the 454 and power brakes. I'm tempted to remove the valve cover and give it a go, but any pointers from BB owners would be helpful, thanks.

 

Bumping this one, I am about to attempt it again (arrival of a small baby boy 2 days after post stopped all work on the 'vette). Anybody have this situation and can advise on the best way to remove? It's so tight with the 454 and power brakes. I'm tempted to remove the valve cover and give it a go, but any pointers from BB owners would be helpful, thanks.

 

Try this in the car box adjustment first. You should be able to tell/feel if there is slop between the rag-joint and the pitman arm. There are two adjustments on the box, not one as commonly mentioned, and both are required to eliminate all slop in the box. Box adjustment procedure document attached.

This is the common adjustment screw that pokes out the top of the box.

This is the main bearing/wormshaft adjuster that the input shaft goes thru. Just as important as the other. I dropped 4 inches of slop on one car tightening this one.

 

All great suggestions, especially from Gary Ramadei, GTR1999 and the only expert here on the forum who custom blueprints/rebuilds the C3 recirculating ball steering boxes routinely for others for years now...Gary custom rebuilt and blueprinted my C3 78 OEM box back about 10 years now at his shop in New Haven CT (I brought my steering box to him personally and picked it up about 1 week later since I am within his driving distance). A couple of comments and thoughts after his service on my OEM 65,000 original steering box after 10 years being on the car:

• My suspension and steering on my 78 was new OEM or upgraded before the box was custom rebuild. An OEM box that is within OEM specs will always have some play due to the recirculating ball steering design..no getting around this fact and don't delude yourself that the factory box will be as good as new cars today..it will not.
• GTR1999 custom blueprinted and rebuilt the OEM box which completely eliminated all factory play in the box which I could not achieve with a 100% up to date steering and suspension on my 78. Even with all new suspension components before Gary's work, a properly adjusted factory 65,000 mile OEM steering box, properly adjusted control valve, new GM factory rag joint etc....you will still have play.
• Gary adds custom parts to his rebuilds which eliminates recirculating ball steering play which is inherent to the box design.
• Even if everything is perfect in the steering and suspension, if you are using a factory new or rebuilt OEM steering, the car will still have some play..only a custom rebuild, borgeson, or R&P will eliminate the play in these cars.

Most factory steering and suspension C3's will requires constant steering correction going down the road. I can literally drive with relaxed comfort my 78 going down the road and the car tracks perfectly straight, with no steering corrections, and with one hand if necessary to grap something on the passenger seat....(my suspension is factory, upgraded factory, with some aftermarket upgrades, though). Karol on this forum with his 115,000 mile factory L82 4 speed base suspension car has to saw at the wheel going down the road, constantly steering correcting, versus my car which steers almost like a modern car. and goes where you wanted to with no steering correction...almost. My car TODAY is infinitely better steering C3 than when it was factory brand new..no question.

 

The power steering control box has play in it with the engine running.

Can this play be adjusted out?

I would normally order a repair kit, but al the vendors seem to be out of them.

 

Thanks for the suggestions. I have already looked at both adjustments, and am pulling the box to send to Gary for a rebuild. Still looking for the best way to get it out, but I think from the top it will be, unbolting the MC from the brake booster and removing the valve cover for a little extra wiggle room. A big block with power brakes and steering leaves little room to work.

 

I am not aware of any adjustment on the control valve. I think it just wears and many hard parts need to be replaced, not just seals.There is an adjusting nut but it is used for centering the system. Here's a pic that shows the cups and the spring that should keep it all snug.

Here's a link or two to show how to rebuild it:
https://www.corvetteforum.com/forums...d-rebuild.html

 

The part that looks like it make take the play out would be the Ball Stud Adjuster Nut.

Does that work on a used / worn one, or is it just for setting up a new one?