angular relationship of caster to pinion angle on Dana 60?

[knaffie]

I'm having a bit of trouble setting my caster up. I know how much I need, but not how to measure it. I realize its through the center of the kingpins, but how do I tell where that is without disassembling the axle? The pinion angle would be the easiest thing to measure. Surely somebody can tell me what the angular relationship between pinion angle and caster. 1978 Ford HP60. Thank you!

[72fj40]

There is really no relationship between the 2, other than if you need more positive castor your pinion angle will rotate towards the ground. You probably should take the knuckles off. You might get lucky and the proper
castor will not put the driveshaft in a bind. If it does screw the pinion angle,
then you will have some work ahead of you.

[knaffie]

Let me try to explain this again, this time with a picture.

Draw a line through the center of the kingpins. Now draw the pinion angle line. I'm looking for the angular difference between those lines. Its a fixed angle ("X" in my drawing).

So if I know that angle, I can set my pinion angle to a known degree and know that my caster is at another known degree without tearing my axle apart. Make more sense now?

http://pic5.picturetrail.com/VOL81/1991351/3851173/142311450.jpg

[72fj40]

I realize its through the center of the kingpins, but how do I tell where that is without disassembling the axle? The pinion angle would be the easiest thing to measure.

According to this statement you don't know what that angle is. According to your drawing you could do it that way, but you need to know what the current caster angle is when it is mounted in your truck w/the weight of your truck on the axle and springs w/the truck being level .

[knaffie]

You're still not understanding, or I am really mixed up.

If I draw a line perfectly horizontal and a line perfectly vertical, then are 90 degrees apart, regardless of how I rotate the two of them together. Same thing I am asking, except the pinion angle and the caster angle are probably not 90 apart. I want to know what that angle is. It doesn't matter what my caster is now or if there is weight on the vehicle. The axle could be upside down and backwards and the relationship between those two lines won't matter.

[72fj40]

I understand. Don't know. Good Luck on that 1. How much did you pay for the frt end anyways. Just wondering.

[HsOffRoad]

Ok bud, this should give you the info to get you set up properly.

From the factory, front axles on 4wd vehicles generally have between 4-8 degress of positive caster. That means that the upper balljoint/kingpin is behind the lower one, raked out like a chopper motorcycle. You need to retain at least 2 degrees of positive caster if the you want to be able to operate the vehicle at any speed, otherwise you'll just be constantly correcting to keep it straight and the wheels won't want to return to center after a turn.

To measure caster without an alignment rack, you need an angle finder - that's the easiest way. Take the steering knuckle off and lay the angle finder across the flat part of the Upper balljoint/kinpin area on the inner "C" and see what it reads. That reading is the ammount of caster in your front axle.

Now what you need to do is first set the pinion where you want it, and then measure the caster on the "C"s. If the caster falls in between 4 and 8 degrees positve, you are golden. If it's around 2 or 3 degrees you are in the danger zone handling wise. It's not really right but it should still work if you are careful. If it's below 2 degrees positive, or any ammount negative (meaning the upper balljoint/kingpin is in front of the lower) then you are SOL. At that point you either need to angle the pinion down to correct the caster, or cut & turn the inner C's to correct the caster for the new pinion position.

You follow?

Hans