Having alignment issues (caster)

[Tahiti or Truck]

I have a 66 C20. While at the junkyard gathering stuff to convert it to power steering I stumbled across a 1976-77 ish GMC Sierra grande with big 8 lug disc brakes. I went back the next weekend and pulled the spindles, rotors, tie rods ( and sway bar). I read that I had to replace the ball joints to that year which I did.

It all installed ok and I took it to the alignment shop and they told me I needed one degree offset upper control arm shafts. Stating that there is no adjustment left because of the spindles not have caster built into them. So 544 dollars later I get the truck back and notice a bad over steer that progressively gets worse the faster you go....as in kind of dangerous I called them and they said that it's probably my steering box and that I would probably have to pay them to replace that too. .bull ****! Anyways. I am pretty confident that it is a lack of caster causing the problem. There is one shim in the rear control arm of the drivers side and no shims at all on the passenger side.

Like I said, scary oversteer...that you have to counter steer and the wheels do not come back towards center if you let go of the steering wheel after a turn.

My long story short.... Do the upper control arms off of a 1977 C20 have caster built into them? More so than the stock 66. I ordered a long acre bubble alignment gauge so I ll know in a couple days what my angles are.

[chevyrestoguy]

Driving a vehicle with virtually no caster is freaky, to say the least. From what you're describing, it sounds like caster is your primary issue. Many of the alignment techs today do not fully understand suspension theory, and what the effects that each of their adjustments do to the driving experience. When you give them an older vehicle to align, which takes a very different approach to adjust correctly, they're really lost. Today's alignment machines are very sophisticated, and when used properly, work very well. Too many techs are just looking for green lights on their monitor, which means that the parameter is within spec.

The trick is to find a shop that understands older vehicles and has a tech that understands suspension theory. There is a sequence of events that a tech must follow to get the best alignment. If they get out of sequence, then you'll see stuff like too many (or too few) shims on the upper control arms, excessive toe-in/out, camber mismatch, etc.

This is a wild speculation, but maybe the mechanic got the offset shafts installed backwards?

With an older vehicle, make sure you tell the tech to try and get the maximum caster that he can and not go by what the book says. Remember, our trucks were designed with manual steering, oil filled shocks, and tall, bias ply tires. That takes a different alignment compared to today's radial tire, gas shock, and rack and pinion cars.

About your question on whether the '77 control arms have more caster, I'm not really sure about that. Hopefully, one of the suspension experts can chime in and answer that for you.

If you have the time, can you post up the numbers from your latest alignment sheet? They should have given you one at the alignment shop. I'm interested in what your caster, camber, and toe measurements are.

[ERASER5]

If the spindles had no caster, how did the original truck steer? Maybe it is a C20 thing, but I've never heard complaints before. Things that could have gone wrong are left/right UCA swap. You can/could redrill the divots on the LCA to move the arm forward 1/2/". Some say 3/4", but for the years your arms came from, there will be clearance issues.

BMWDOC (?) has a good write up on caster problems and adjustments.

[cg285]

of course it is impossible to diagnose with only the information given but the description sounds like a gear box that someone screwed with the sector adjustment and it's too tight. that makes it drive scary and the wheel doesn't return to center on it's own.

[Tahiti or Truck]

Thanks for the responses.

Chevyrestoguy...it is an old school alignment shop specializing in older cars and hot rods. I have used them several times before but the last two times I haven't been happy with. They do have a new tech there, maybe he is trained in the newer ways I don't know. They didn't give me my new alignment specs. I'm not sure if they ever have. I did order a gauge from long acre so once I get that I will post them

ERASER5. I ll be tearing into it this weekend. I did do a couple things at once with it. I added the discs and spindles and I converted it to power steering. It did steer ok with the manual especially considering the four inches of slop I had in the wheel. Maybe the power steering but my gut is telling me it isn't.

[69chevytrucker]

jack the front off the ground fire it up and have someone turn the wheel back and fourth see if the power steering is doing something funky that way you will know if it is power steering related then take the power steering belt off and take it for a drive see how it works manually that should eliminate steering prob then take it back to the shop and tell them to fix it right like the others said alot of these monkeys only know how to look at a screen that tells them what to do sometimes you need to reboot them lol

[69chevytrucker]

not saying you would do it but when i swapped my front end i first put the a arms on backasswards and that would really mess up caster just a thought i noticed mine before i got it together so i dont know if it would bolt all the way up but i know the left will go on the right

[Tahiti or Truck]

Originally Posted by 69chevytrucker

not saying you would do it but when i swapped my front end i first put the a arms on backasswards and that would really mess up caster just a thought i noticed mine before i got it together so i dont know if it would bolt all the way up but i know the left will go on the right

I never removed the control arms when I did the front end work. I did take pictures pictures during the conversion so when I tear into it this weekend I ll use them as a reference to make sure that the alignment shop didn't make that mistake. As for the power steering they did have me do a quick test. They told me to drive the truck and bring it to a stop with the wheels straight and not touching the steering wheel. Once stopped he said to turn the truck off then start it and see if the steering wheel twitches or moves when it fires up...which it didn't.

The bigger reason I don't think it's the box is because let's say your are on a long slow right hander getting onto the freeway (interstate for everyone east of California lol ). The steering wheel starts pulling harder and harder to make a sharper turn. I have to make numerous steering adjustments to the left to counter act the wheels pulling harder and harder to the right. Seems like once I made the first left correction then it wouldn't want to pull back to the right. If the caster/ camber angles check out then I will explore the PS

And the Delivery guy just dropped off my new Longacre caster/camber gauge. Maybe I ll start tinkering on it tomorrow if I get off work early.

Thanks again for the responses.

[69chevytrucker]

that sounds like toe in

[69chevytrucker]

the a needs to slope toward the front of the truck /- if you get what i mean

[Tahiti or Truck]

So I got the truck leveled out on all fours and put my new Longacre caster camber gauge on. This is what I came up with.

Drivers side -.15 ish camber
+1.2 caster

Pass side. 0 deg camber
+ 1.1 deg caster

I haven't checked toe in. But I do know that I want/need a bit of toe in

I would like more caster and was planning on doing the lower control arm re drill mod but it looks like I have the older style lowers so now I'm not sure what to do.

[robnolimit]

Just a bit of info for you. The design of a spindle has a lot of geometry in it, pin inclination, pin height, set back, ball joint spacing, steering arm location (X, Y, Z axis) - which also has an effect on acreman. But, there is no way to put 'caster' into a spindle. Caster is only determined by the position of the ball joints for/aft. A suspension design can have "caster gain" as the suspension travels upwards - also can be part of the anti-dive. So, be wary of the alignment tech who tells you that the spindles don't have any caster built in. None do.
It's not too hard to get these front ends to have 4 to 5 deg of caster, and they really like it. camber should be close to -.5* for a streeter. I like to toe them out, 1/8" or so. - but only if you can get the caster in range. - check out BeamerDoc's thread on alignments

[cg285]

u toe out on a frt whl drive. not rr whl. ur caster is fine also if u are not on turn tables ur readings are approximate u r over thinking. good luck.

[69chevytrucker]

if you want more caster raise your rear end will make more caster

[Tahiti or Truck]

Originally Posted by 69chevytrucker

if you want more caster raise your rear end will make more caster

Wouldn't that do the opposite? Seems like if you lowered the rear it would increase caster.

While looking at the upper control arm shafts. I was thinking that there is an extra amount of metal on both sides of the shafts where it bolts to the frame. I would say an 1/8th wider on both sides compared to the rest of the shaft. I was going to pull the uppers and grind them down to just larger then the shaft. That would give me an extra 1/4 inch or so of adjustment.

Thoughts???

PS it is a gently driven 3/4 ton.

[robnolimit]

Originally Posted by Tahiti or Truck

Wouldn't that do the opposite? Seems like if you lowered the rear it would increase caster.

While looking at the upper control arm shafts. I was thinking that there is an extra amount of metal on both sides of the shafts where it bolts to the frame. I would say an 1/8th wider on both sides compared to the rest of the shaft. I was going to pull the uppers and grind them down to just larger then the shaft. That would give me an extra 1/4 inch or so of adjustment.

Thoughts???

PS it is a gently driven 3/4 ton.

yes, this is backwards. Positive caster occurs when the upper ball joint is 'behind' (side view) the lower ball joint. Caster is like the rake in the neck of a bicycle, it's what helps the bike want to go straight, and lean into the corner. A bike with '0' rake would suck.
How about some picts of these parts.

[Tahiti or Truck]

Originally Posted by robnolimit

yes, this is backwards. Positive caster occurs when the upper ball joint is 'behind' (side view) the lower ball joint. Caster is like the rake in the neck of a bicycle, it's what helps the bike want to go straight, and lean into the corner. A bike with '0' rake would suck.
How about some picts of these parts.

Here are some pics of the passenger side. Would it be worth the trouble to remove some of the meat so I can get more caster out of these uppers?

[Tahiti or Truck]

Proposed idea. Grind these areas back.

[Acorn]

It looks like your a arm shaft is facing the wrong way. The concave part of the shaft and the spacers are supposed to face towards the frame. The shims go between the spacer and frame mount. Look at a service manual ( or a LMC catalog) Can't really tell from the photo but do you also have spacers between the shaft and frame?

[Tahiti or Truck]

That's interesting. Pay 544 bucks and they can't even put them on correctly. The more I found out the madder I get. I wonder if they put them in backwards to get the camber in spec. Seems like if they installed it correctly there might be too much positive camber with concave spacer. It's dark now. I ll take a closer tomorrow to see if there are round spacers

Thanks for the replies

[69chevytrucker]

here is mine you can see yours is backasswards

[69chevytrucker]

that is why you get the wheel stuck in a turn your binding on the top a arm in a turn

[Tahiti or Truck]

Yep. I just did a little research and was coming to post my findings. That's unbelievable. Anyhow. Yours looks great! So I will be pulling them off this weekend. Is there a reason that they go that way? If I can't get the specs right would it hurt to leave it like that?

[69chevytrucker]

yes it would hurt if you look at mine you can see about 4 shims that is for setting camber which if not right will screw the rest you need to take it apart and start over pull the top a arm and put the shims on first then slide the a arm on tighten put coil back in and re connect bottom ball joint if out of wack you add or subtract shims but y

[69chevytrucker]

you dont have to take apart to add more shims after you get it put together right you just loosen the top bolts on the shaft and tap in a shim or 2