I have been digging into the pile of parts I have been collecting for my 1976 D100 for the last 11 years and I have discovered that I ordered a set of the Moog "problem solver" upper control arm bushings with the offset bushing. This places the sleeve for the UCA bolt almost touching the edge of the bushing shell.

Obviously the offset means that there is now an optimal orientation at which to install the bushing to obtain the greatest benefit from the offset bushings.

My admittedly tenuous grasp of caster, camber, and toe and how those adjustments affect handling leads me to the following conclusions:

(1) the best "handling" or steering stability (tendency of steering tires to self-return to center and for the vehicle to track in a straight line) is achieved with POSITIVE CASTER (the upper ball joint is farther to the rear of the vehicle than the lower ball joint)

(2) to achieve the maximum increase in POSITIVE CASTER, the forward offset bushing should be installed in the UCA with the sleeve for the retaining bolt as far OUTBOARD as possible and the rear bushing should be installed in the UCA with the offset sleeve as far INBOARD as possible.

Are my conclusions correct? Is there a better way to install these offset UCA bushings? Any insights are appreciated.

Yes, more positive caster will be more stable and usually better with modern radial tires. However, do not go crazy. Maybe add 2-3 deg positive beyond the stock number.

You want the upper control arm to be pushed backward at the upper balljoint, so installing the bushings to bring the rear of the UCA inboard and front of the UCA outboard is right. The way you have written it is ambiguous or maybe looks backwards regarding where the bolt goes through the bushing and the UCA.

Lou

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Home of Slant6-powered fun machines since 1988

Right, we're saying the same thing, I am just not saying it well. Putting the forward UCA attaching bolt outboard and the rearward UCA attating bolt inboard would have the effect of pushing the upper ball joint toward the rear of the truck. I will keep your 2-3 degree number in mind when I go in for the alignment. Thanks!

Yes. Lou's instructions are correct and may differ from what it says in the package instructions.

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http://www.youtube.com/hyperpack

Thanks! I didn't know they came with instructions. I will check the boxes again.

As Greg said, the instructions are usually NOT what you want to do as they say to install it with both bushings in the same orientation.

Lou

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Home of Slant6-powered fun machines since 1988

Right. I figured there wouldn't be instructions since if you know enough about suspensions to buy these bushings, you probably know how the installation orientation affects the suspension. So, fore OUT, aft IN.

If you have problems finding a shop that knows how to align your truck take it to a toyota dealer. As stupid as it sounds they will likely have a tech that is familiar with adjusting camber,caster,toe with eccentric bolts. Those adjustments have been standard on 4wd toyota trucks/full frame suvs for years. I was at a toyota dealer doing truck frame replacements about 15 years ago and had to do many alignments from a clean slate on fresh frames.

Tell the tech to ignore the printed specs for the vehicle in regards to camber and caster. The numbers they should shoot for is the maximum positive caster that can be achieved on both sides. So if they can get 2.1 max caster on the drivers side then 2.1 would be the target for the passenger side. If +2.1 can't be achieved on the passenger side they would have to go back and match the drivers to the new lower number from the passenger side. To throw a nice added curveball in the camber is adjusted while adjusting caster. A good target for camber would be -.5 degrees per front wheel.

So the TLDR version is to run as much caster as you can get with -.5 camber.

A good tech will know how to edit/adjust the specs on the alignment program to reach the desired goal. And make sure to get a printout of all 4 wheels. The rear end is not adjustable BUT if you have a wonky total toe number (bent housing) or a high steer ahead number (housing not straight in frame) the printout can tell you much.

Thanks, McNoople! This is good info. I will try and find a shop that will align to MY specs and knows how to work on older technology.

OK- please check my math.

Stock alignment specs for my 76 D100 are:

Toe-in: 1/16-1/8
Camber: 1/2 degree
Caster (no load): OTO + 1/2 degree

First, what is "OTO"? "On the Order of"?

Second, the FSM also states that caster is preferably checked with the vehicle loaded, but if the vehicle cannot be checked loaded the no-load caster is 5 to 6 degrees for power steering.

I do have power steering, so my calculations for recommended caster and camber with the Moog offset bushings are:

CAMBER: -0.5 degrees
CASTER: +7 to 9 degrees
TOE IN: 1/16-1/8 (measured at leading edge of tires at the height of the center of the hub)

Sound reasonable?

BUT beware
You don't necessarily want "the most caster you can get"
If you have manual steering especially. Unless you really like "Armstrong steering". Specs on most manual steering vehicle were negative caster
And you want around 1/2 degree less on the left than the right for road crown. Definitely not much more than that for most vehicles. The difference between left and right in camber and/or caster is where "pulls" come from
A vehicle will pull to the side with more camber or less caster.
You want "some" "cross caster" and/or "cross camber to compensate for road crown which varies in different places.
You may have to experiment a little.
Back before machines like the hunter ones that store the specs and on which you punch in what you're working on we used to set all rwd vehicles pretty much to the same set of specs and they drove straight and didn't wear the tires. This being back in the late 80s.
We used +1/4 to +1/2* camber on the driver side. +1/4 to -1/4* camber on the right. We would set caster wherever it fell but mostly looked at the difference between sides, watching more that we had 1/4 to 1/2* more caster on the right side than the left, than the actual numbers. And about 1/16 to 3/32 toe in. If the tie rods were in front of the control arms but the same amount of toe out instead of the tie rods connected to the spindles behind the control arms.
On everything that came onto the alignment rack. I might be slightly off on the exact numbers as that was 40 years ago when I first started doing alignment work. Bit the idea of what we set positive and what we set negative is what I remember even if I'm slightly off on actual numbers. I definitely remember though that there were a lot of fractions involved.

"0TO" means 0 degrees to 1/2 degree.
I wouldn't go more than about 2-1/2* positive caster on that truck. 3 at most.
And that's the "high" side. I'd set the driver side about 3/8 to 1/2* less.
Remember a lot of people telling you 6 to 7 degrees run their cars different than how most people use a pickup. You're not gonna be doing roundy round or running something like pikes peak are you?
I remember the 70s monte carlos and similar bodied GM cars spec'd more caster than most any other cars on the road at the time

Things like dump trucks tow trucks etc that were loaded heavy we had to set much lower if empty.
I forgot but there was a number for how much droop in the frame in the back end from the load equaled 1* more positive caster while loaded. A regular pickup we usually didn't have to worry about it.

The 1976 factory service manual says the no-load caster for a D100 with power steering (and stock suspension) is 5-6 degrees, which can be increased if the vehicle wanders. Manual steering truck had 1-2 degrees recommended from the factory. Using that as my base setting, if the Moog offset UCA bushings allow 2-3 additional caster, then my caster setting should be +8-9 degrees.


I've got the tools, so i will try maybe 7.5-8 caster to start.

I don't ever remember any of those trucks being 5-6* caster

This is what the factory service manual says and the specifications I am going by:
I am reading the reference denoted by the asterix to say that the no-load caster is 1-2 degrees for manual steering truckks and 5 -6 degrees for power steering trucks. Assuming "OTO" means "zero degrees."

Unless "OTO" is a reference to the manual/power steering numbers given in the asterixed footnote. If that is the case, then for an unloaded manual steering truck, "OTO + 1/2" would be "(1-2 degrees) + 1/2", or an acceptable caster range of 1.5-2.5 degrees. Power steering would be 5.5-6.5 degrees.

THis is all moot because I think I installed the offset bushings incorectly on the driver's side. I am struggling to get even 4 degrees positive caster on the driver's side, but the passenger side has almost seven with more room to adjust. I really hope I don't have to take this all apart again.