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Discussion Starter #1
I'm trying to figure out why this truck is a handful to keep on the road...I'm at my wits end right now. This thing will chase any imperfection in the road surface, I know it is a 30 year old truck, but I've never had one this bad...

Here is what I have:

1990 W250 D61/D71 combination with a 727. I've checked the king pins, the tierod ends, the drag link...I have a barely perceptible wiggle in the driver's tierod and the on end of the drag link. I adjusted the steering gear box. I added a dual steering stabilizer, this was the one biggest improvement I had. It has a Borgsen shaft, and I know the steering column bushing has play. The frame at the steering box is NOT cracked.

The front springs are weak, it has a slight negative arch. It had tapered lift blocks, I pulled them for zero-rate springs.

It has new 315x75r16 AT in Load Range E, these were the tamest AT I could buy. It had worn MTs on it...the ATs helped only a slight bit. The MTs were worn on the inside, which may have been a result of the tapered blocks under the front springs...

Since this trip, I replaced the steering gearbox and drag link and I checked the toe-in (I have 1/4"-3/8" toe-in over a 24" span which should be good). I made a jig that bolted to the hub faces, so I know it's accurate.

I'm at a loss, nothing jumps out as a culprit for this much wandering...today I was pulling on the jigs to see if anything jumped out, and everything moves together, there isn't anything that shows slop or play...

Short of throwing parts at it, I'm at a loss...

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Not certain about the older trucks, but... I know caster plays a big role in drivability in the second gens. I went through my 02 for months chasing parts and it turned out to be a caster issue. Hopefully someone with some real knowledge will pipe up.


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Are your wheel bearings tight? Your front end is out of alignment. Fix that. You may find an alignment fixes your wandering and increases tire life. If it can not be aligned put it back to stock so it can be aligned. Remove your steering column bushing play with the proper repair.

I once had a car that wandered. The whole problem was the front end bushings. The hole was worn into an oval. Once replaced the issue went away. Prior to that braking would cause the car to change direction. A sudden turn to the left, right, or even going back straight was possible with any brake pedal push.

An automotive teacher at the local voc. ed. ruled out the front end bushings as the problem. After thinking about what could be wrong knowing I had no rust issues making the entire front end unstable, and having tight front end parts that would not cause wandering, and the steering box being tight the bushings were the only thing left. It took me a day to replace them. By thinking and ignoring some advice I fixed my problem. I simply removed whatever was possible then determined that whatever remained however improbable must be the problem (and it was).
 
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Discussion Starter #4
Are your wheel bearings tight? Your front end is out of alignment. Fix that. You may find an alignment fixes your wandering and increases tire life. If it can not be aligned put it back to stock so it can be aligned.

I once had a car that wandered. The whole problem was the front end bushings. The hole was worn into an oval. Once replaced the issue went away. Prior to that braking would cause the car to change direction. A sudden turn to the left, right, or even going back straight was possible with any brake pedal push.
How do you know it's out of alignment?

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usually putting new bushings and springs in your kingpins is a good start. if you have any kind of play in a tie rod end, id replace them all.
cant tell from your photo if you have a lift. but with the 727 or the getrag things get a little sketchy with the way they clock the front axle to make the driveline work with that short of distance to the 205 (especially on the 4-6" lifts). any minor issues become amplified with all that caster.
 

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I too would recommend all new hardware in your king pins, including new lower bearings etc.....sounds like all the rest is good and that is the last thing left that could be causing your problems.
 

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Discussion Starter #7
It's probably around 1-inch between the zero-rates and the sagging springs...I'm looking at a 2.5 skyjacker lift with rear springs and shocks, but it would be next spring before I get around to that...

From the FSM, I think I read that the toe-in is adjustable (easy enough), camber is set and non-adjustable, and caster is set by rotating the axle? So removing the tapered block would have taken that back to more an OE range?

As far as I can tell, there is no play in the king pins, no play in the bearings, the axle u-bolts are tight...

It just feels very disconnected from the road...and once it takes off, getting it back under control is daunting.

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As far as I can tell, there is no play in the king pins, no play in the bearings, the axle u-bolts are tight...
I would also say that your king pins are the problem. I wonder if you are using a bar to check them.
 

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The cones, bushing and spring are not going to be able to be "felt" going bad....if they were your spring has probably broken.
 

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Discussion Starter #10
Well, I'm taking it for inspection and will have them look at the kingpins since it seems I don't know how to diagnose them.

If a joint is tight, then it is tight...can see how that would be hard to diagnose.

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Discussion Starter #11
Passed inspection...told him to scrutinize the king pins. He told me they put a bar to them and they are "tight"...

In a factory setup, is there a shim under the leaf spring?

Should I pull the cap off the king pin to see what the plastic looks like?

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Have you added any caster yet?

There is so very little caster on these trucks stock, that a little spring sag and some minor kingpin wear is all it takes to make it disappear. If your truck has rake (high in the rear) you have less caster too. I believe Dodge spec is only 1-3 degrees, whereas GM (same Dana 60 outers) is 4-7 degrees depending where you read.

Longer shackles, or shimming the pinion down, are likely your easiest options.
 

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Discussion Starter #13
I'm going to drive it a few days...it's feeling better the more I drive it, still not good; but I can anticipate it better. On a straight even road, it tracks straight as an arrow.

Keep in mind, I pulled tapered cast iron blocks out of the front axle that pushed the pinion down...it was worse before I pulled them for no taper.

New deal I noticed tonight...when turning the steering wheel, it almost "snaps" at times. It sounds like it is coming from under the truck...so Kingpins binding? I also noticed it doesn't return to center like it should, which is a caster deal if I remember my reading correctly?

I'm going to pull the kingpin caps this weekend and see what that looks like.

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Discussion Starter #14
Oh, and this thing is almost level, maybe a 1/2" of rake front to rear...

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The block/spacer could still be causing tracking issues with the extra leverage. The main leaf (which locates the axle laterally) on your stock springs is less that 5/16" thick.


Caster is angle applied to the steering axis so that gravity (the vehicle's weight) assists the steering in settling at its lowest point (i.e. when the tires point directly ahead; center).

The steering not being smooth can be a multitude of reasons. I don't tear into kingpins on suspicion. They can't be checked using a bar unless there is some weight on the axle, because the kingpin springs take up slack.
 

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Discussion Starter #16
I've basically eliminated every steering component short the kingpins...that's why I'm still leaning towards that, to at least eliminate them.

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Discussion Starter #17
I guess another reason I am now suspecting the kingpins is that everything was kinda dry on this rig. My good truck oozes grease from every fitting, this w250 looked like it never got hit with a grease gun. The kingpins did expel clean grease though...

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Discussion Starter #18
I guess my point is, I can check the kingpins in the driveway. I need to have a garage check the alignment...I better know the kingpins are good before I go down that road.

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How do you know it's out of alignment?
You told me that previously.
The MTs were worn on the inside, which may have been a result of the tapered blocks under the front springs...
Tires do not wear on the inside when a front end is properly aligned. What causes a misalignment can take some troubleshooting.
 

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If you are hearing a "snap" when turning the wheel from time to time you probably have either a cracked frame near the steering box, or the frame to steering box adapter is coming loose or is cracked as well.
 
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