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Steering geometry tech

Russell

Russell

3/4 ton status
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I need some help figuring out how to fix my steering woes... Vehicle in question is my 95 Tahoe, but you can pretend it is an 80s Chevy with a Dana 60.

Same goodies as you guys run -- Saginaw steering box with a pitman arm hooked up to crossover with hi-steer.

The distance from the center of my sector shaft to the center of the drag link is approx 7.25". From the center of the drag link to the center of the upper king pink is approx 6.5". My problem is that my steering from stop to stop on the diff is just under 2 turns. If I disconnect the drag link, my steering box has the normal 3.25 turns internal lock to internal lock.

I need to get the steering sorted out so I have the steering wheel centered and the same number of turns left to right so I don't have issues when I install my hydro assist ram.

Does anyone know of a calculator to determine just how long my pitman arm should be to make things work properly? I need to replace my existing arm with a 2 - 4" drop pitman arm due to clearance concerns with the oil pan regardless. If you can't get anything but that length of pitman arm, how would I go about calculating how far from the center of the kingpin I should drill a new set of arms? If it makes any difference, I am running solid axle industries outers and steering arms. I had them drilled and tapered to match the ORD arms I was running before...

Also, my steering ram is a 6" stroke due to the truck having hi-steer. How far from the center of the king pin should the tie rod be to ensure I actually have 6" of travel in the tie rod? Last thing I need is to only have 4" of throw because the tie rod is too close to the knuckles and start wrecking stuff when I hit my steering lock.

I should mention, my steering was pretty dang good before I switched my outers and put the new arms on.
 
Ideally your steering arm should be the same length as your pitman arm, but there's no reason you can't have everything centered anyway. With a shorter pitman you will get more leverage, with a longer pitman you will get faster steering. Just disconnect one of your drag link ends, set the passenger tire straight ahead (or whatever equals straight when you account for toe), center the steering box, and adjust the drag link ends in/out and reconnect.

Make sure you are measuring the "length" of the pitman arm by the horizontal distance between the sector shaft and the DLE, not necessarily along the length of the arm. The two lengths are only the same if the pitman arm is completely straight. If there is any bends (i.e. any drop), the length along the arm will be longer than the actual length of the lever. The same would go for the steering arm although most are flat anyway.

For the tie rod throw, you really need to know what your max steering angle is going to be at the knuckle to truly calculate it. If the stock tie rod hole on the GM knuckles is 8" of throw with 6.25" pitman/steering arms, then I'd say IF you had that same steering arm/pitman setup you would want to mount your tie rod about 75% of the distance from the kingpin that the tie rod normally is to have 6" of throw.
 
The drag link and the arms have to, according to Mr. James Watson, be the same size. Or you get what you are experiencing.

He knows a bit more about it then I, I just run his system :waytogo:
 
kgblazerfive said:
The drag link and the arms have to, according to Mr. James Watson, be the same size. Or you get what you are experiencing.

He knows a bit more about it then I, I just run his system :waytogo:
Click to expand...


So I found a thread on pirate that gives a formula for calculating the lenghts based on angles. I am assuming 40 degrees steering angle at the knuckles and 43 degrees rotation in the sector shaft. Tells me that with my arms drilled at 6.5", I need a 6" pitman arm.

Andrew tells me he has a 4" drop pitman arm from his ranger that should fit the bill... If I drop the pitman arm down a bunch, I should be able to swap to a straight drag link and be able to center my steering box properly too (angled was always a hair off)

That means I just need to make sure that the throw of the tie rod isn't too long for my ram. If it is shorter than I need, just a matter of putting stops on the ram to keep it from hurting anything. Easy enough
 
Russ
my steering arm is 6 7/8" center of kingpin to center of drag link.
drop pitman arm is 6 1/2" center to center and 3" drop (measured top to top, nut is 3/4" thick)
I've got the tie rod in the stock location with a 6" 8" travel ram and everything runs out of travel at the same time (within .25") and it turns pretty tight.
IMG_0054.jpg

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IMG_0052.jpg
 
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Interesting that you only have 6" of travel in the stock location? I thought D60s were normally 8"? My D60 has hi steer, which means that the tie rod is closer to the body of the axle. I am hoping I have slightly less than 6" of travel so I can put a spacer inside the ram to limit it to exactly what I need. I want the steering stops to hit the inner C at the same time that the ram runs out of throw, while the steering box still has a bit left to go. If the steering box is the stop, the ram can push the knuckle further and break the steering box internally. We did that on our KOH truck this year
 
I"ll go measure it again just to be sure.

EDIT: your right 8"......and my neighbors are loving me right now, my truck needs a little tuning, running rich, so I had to rev it for a few second to clear it out.
 
I was thinking (may be dangerous) if a ram mounted in the stock location is 8" travel, and if I measured correctly, the mounting location of the tierod is 8" from the king pin centerline. so if the ram is 6" travel, then shouldn't the tierod be mounted 6" from the centerline of the kingpin?

I realize that there is a little effective travel take out of the ram because it doesn't travel at the same arc as the tierod, but that should still get you pretty close.
 
ChrisPerry said:
I was thinking (may be dangerous) if a ram mounted in the stock location is 8" travel, and if I measured correctly, the mounting location of the tierod is 8" from the king pin centerline. so if the ram is 6" travel, then shouldn't the tierod be mounted 6" from the centerline of the kingpin?
Click to expand...
Yes that's about it (like Owenst7 stated earlier)

Regarding pitman arm to steering arm ratio, I think a factor of 1:1.1 is OK
(for eg. with a 6" pitman arm you can use a 6.6" steering arm)
That's because the maximum angle of the steering box is bigger than the spindles.
I did a lot of measuring and calculating when I made my steering arm.

Just make sure it's the ram that sets the limit and not the box or the spindles
And also consider that the ram will need to have a larger diameter the shorter the tie-rod arms are.
The cylinder area should be inversely proportional to the length of the tie-rod arms, to maintain the same force.
 
I finally got my axle shafts today and got to work putting my diff back together a bit better. Ran into a TON of clearance problems between my inner c and my inner axle shaft, as well as clearance issues with getting my outer stub shaft through the opening in the knuckle. I also have problems with the knuckle hitting the inner axle shaft when the steering is at full lock opposite the side with the stops.

After flipping my steering wheel 180 degrees, getting my pitman arm installed straight (was a tooth off) and centering my steering wheel as best I can with the bent drag link, I am now 1.25 turns to lock left and 1.5 turns to lock right. I am still hitting the stops on the inner c before the steering box runs out of play, but it is fairly close. Close enough that I think I am going to run with it. I measured the throw of my tie rod from lock to lock and found that it is exactly 4". I'll put a 2" stop in my steering ram and I think I should be good to go.

I also picked up a new toy today -- Miller 252 mig welder :D Worked very nicely for mounting my new shocks in phase.

Hopefully by the end of tomorrow I'll have my axle shafts fully clearanced not to hit anything from lock to lock, my wheel bearings and king pins all lubed up and installed, and the diff finished. Wednesday it goes in for exhaust, thursday it goes in to get the air intake fabricated. With some luck I can get my track bar in on Friday and still have time to load up and haul the truck out to the mountains for a day run to see how it performs with the new engine and transmission.

Once it gets home, I am parking it for a little while, I'm sick of working on it again, lol!
 
Hmmmmm well I was going to try to drop some knowledge but as usual Russel is too fast for me. :D:D

Sounds like you got it figured out Russ.
 
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