Front Front shackles 1959

[dennislbrooks]

It seems to me that the last year of the front front shackles was 1959. Then after, anything with front leaf springs had the shackles on the Front rear - 4wds like my 67.

I fought a darting problem on my conversion 1959 GMC Fleet 4wd - 85 running gears. My 1959 front leaf springs have all new bushings and pins front and rear. Also a new steering box, new ball joints, all new joints in steering. It has had the toe set to zero.

The only thing I had left was front front shackles unlike my 67 with front rear shackles.

Changing my 59 to be like the 67 is very involved but I have improved the steering with a 3/4 ton 4wd sway bar.

I wonder how the pre 1960 Napcos drove with the front front shackles.

[leegreen]

is this picture at ride height?



That drag link angle looks like it would make it turn left on bumps, it needs to be closer to level. Can you get a pitman arm with less drop or steering arms for the knuckles that sit lower?
Or raise the steering box.
Or convert to cross steer.

[dennislbrooks]

My bad, that pic above is with a 2" rise steering arm. I have since put the stock one back on and the steering link below is near level like my 67.

[leegreen]

Not sure I have anything valuable to add.
in both pictures the front ball joint on drag link looks like it is twisted, an issue with that?


The original TF steering box location behind the axle also had a pretty short drag link, putting the drag link pivot in front of the rear spring pivot. As the spring flattens the axle will move away from the fixed shackle and the drag link will force in a bit of right steer. Same things happens with your setup. Based on looking at some pictures the factory built in some downwards angle to the drag link so that as the axled moved up in it's travel the drag link arc of travel would add some left steer to counteract. With the box in front you'd need to angle the draglink up like in the first photo.

so IF you get darting to the right on braking try going back to the steering arm in first picture and see if it reduces the right dart or changes it to left dart.

If it darts either way randomly or following road camber, check alignment, maybe add some caster with a shim. You have power steering now so can deal with more caster.

[dennislbrooks]

Leegreen, thanks for the input. It was not so much on braking as a very slight turn left or right. It seemed to dart so that it needed corrected the other direction. Again, the sway bar has stopped pretty much all movement left and right on the front shackles which makes me think it is the front shackles giving to a point. One carriage bolt holds them together. As you said, steering box in front may have contributed to the problem with front shackles.

It is very drivable but this winter I may switch the rear and front mounts - about 8 rivets each side. I checked and the leaf center bolt is in the middle of the eyes so I will be able to turn them around.

I think I can straighten the front ball joint on the drag link for now. I have already added some caster.

[leegreen]

"very slight turn left or right. It seemed to dart so that it needed corrected the other direction"

Maybe a bit more toe or play with front tire pressures a bit?


I'm assuming everything is nice and tight. including rear shackles

[dennislbrooks]

Front and rear all new bushings and pins. All seems tight but I will recheck including u bolts. I thot a hair more toe in also.

[leegreen]

don't discount the impact 5-10 PSI tire pressure change can have on highway handling, I have had a couple 4x4s that were much happier at 30-32 PSI than 36-38 PSI. And others where it did not seem to impact driving at all. Maybe tire dependent, but it is on my list of things to play with when something is not driving well for no more obvious reason

[dennislbrooks]

Ok, I straightened up the front ball joint on the draglink. I run 215/85x16 tires and reduced them all 5 lbs to 34 - also to soften the ride.

I gave the collar 3/4 turn -in- on the center link from the alignment shops zero.
I do not know what this equates to in inches.

Drives much better. Almost as good as my 67 -it has 265/70x17 tires on it.

[leegreen]

that's great! and no need to reverse your shackles.

[dennislbrooks]

Looks like no changing the shackles. I will turn the collar 3/4 more toe in just to see and will report back. Will still be less than 1/4 inch. The 59 has an 85 K10 front axle and the 67 has the same axle but from an 88 K5.


Total 1.5 turns more toe and the former addition of the sway bar gave me favorable results.
I am satisfied and thanks for the help leegreen.

[dennislbrooks]

Changed wheels and tires.

[leegreen]

looks good. any difference in drivability between the old and new tires?

[dennislbrooks]

Yea, but the 265x70R17s were almost as ok. But I want my tires inside the fenders. Also I wanted full right turn (front are spaced out 2 inches to clear pitman arm/draglink joint). Rear is spaced accordingly. I run 265x70R17s on my 67 with no issues.

Since this is my thread I can take where I want. I like the stock 59 hubcaps which the 58-59 GMCs are a little scarce (55-57 GMCs are a little hard to find also). And I wanted them on the 88-98 rally wheels. I finally conquered this. I do run 59 GMC caps on back and spare but have a 55-57 chevy with center removed on the left front. The cap was bent severely at the emblem so I did not mind cutting it. My other caps are too good to cut and I refrain also from cutting any GMC cap. I will find a suitable cap for cutting sometime.

It is a real GMC Fleet but not a real NAPCO just a 4wd.