56 gmc napco

[ironhill]

I just picked up a 56 GMC NAPCO and was wondering if anybody has put power steering on one of these and how about they went doing it. Also does anyone have any parts for these NAPCO's

[Coronas56]

Nice Find!

[ironhill]

Thanks it was a great find. I am very honored to own one of these.

[OrrieG]

http://napco4x4.org/

http://67-72chevytrucks.com/vboard/s...d.php?t=320260



Lots of info. GMC to boot. Is it original? Usually they have a Napco trim on the front fender and operation decals in the glove box or on the dash.
Easy to move from truck to truck so it may have started life somewhere else. Should have Napco cast into the front axle tube. Adding power steering shouldn't be any different than 2wd. You can use a 70's box and make an adaptor plate for outside of the frame but it limits the right hand turning radius. Or you can use a 70's jeep box that mounts on inside of the frame in front of the crossmember. Another option is to use a 90's box that mounts in the same location as the stock one. You will need to figure out the ps pump mounting and steering wheel. With the wheel you can upgrade to later model, after market, or get a bearing adaptor to use the stock one. All of these have been discussed her before in other threads. My thread shows the first option, which I did in the 80's. I also have photos of the Jeep application.

[ironhill]

Thanks for the info. It is all original except back in the late 80's the owner pulled the long stepside box and put a short box so he had room to run the stacks between the cab and the box and had it repainted. Guess that was a neat thing to do back then. I do have a long step box to make it back original. Thanks again for the help.

[ironhill]

Hey Orrie, I have all my parts gathered up to do a setup kind of like yours. On your power steering gear bracket I see you have it spaced out off the gear itself was that for clearance for the bolts that you used to bolt it to the frame?

[OrrieG]

That was for clearance for the steering case. On the mid 70 frames there is a recess for the bump to set in so the mounting flanges set flush. I was not ambitious enough to cut out the center of the plate to move it close to the frame. Also I ran the bolt all the way thru and nuted them in place., I found two of the threads were already striped in my box and the other two did not feel like they would take a whole lot of torque.

[ironhill]

Ok that definately makes sense, thanks for the pic. Your truck looks great by the way!

[bajabob]

Iron
That thing is sweet.... What direction are you going with her ?? Cool thing is there are not many around that were not completely tore up. I have some extra chevy truck parts but nothing NAPCO (maybe some worn out leaf spring bolts ??) Napa still carries parts and I just found this place tonight http://www.rareparts.com... check them out

[ironhill]

Bajabob - I think i'm going to probably leave it mostly the way it is. The previous owner was in the middle of converting it over to power steering so I'm going to continue on where he left off there, put some nice ralley wheels on it and get rid of those smoke stacks . Thanks for the help. It is amazing how much old parts the parts stores carry. My dad and just finished his 56 Bel Air and O'Riellys had pretty much everything in stock from suspension parts to brake parts.

[bajabob]

Iron
Keep us posted on the progress (with photos), lots of cool cats floatin around here to help... Worked on the hinges tonight and ordered some new hinge pins... might be able to paint them up this weekend.

[OYMC]

HOLD THE PHONE!

I have a 55' GMC 2wd that I have been building into a 4x4...

For my application I bought a 1968 Impala Saginaw steering box (Rebuilt from Napa). Now this steering box has a full set of splines around the pitman arm mounting shaft that allows you to mount the pitman arm 90 degrees from the typical 4x4 Saginaw steering box mount for a cross over steering conversion. This steering box is also setup to mount on the inside of the frame rail as apposed to the 4X4 box pictured by "OrrieG's" post above that mounts to the outside of the frame...

The problem with mounting the steering box to the outside frame rail, is that your turning radius is greatly reduced when making right hand turns (Steering box to tire clearance).

I have set my steering up just like a FJ40 land cruiser: Steering box mounted to inside of frame rail (Plenty of clearance for right hand turns), and have converted to a cross over steering setup (Greater handling geometry)...

The photos below shows a BJ40 (Factory Diesel Version of an FJ40) that I converted

The last photo shows the only photo I have of the inside frame rail of my 55' GMC... You will want to box the inside of your frame rail and weld in sleeves for the mounting bolts....I'll take photos of my setup soon and post pics...

Best of Luck!

[bajabob]

that is one serious spring mount, rip that thing out and you got big problems....

[NORMSCOLORADO]

awesome truck.... i knwo where there is a 59 chevy napco.... cant get the fella to part with it.....

[OrrieG]

Originally Posted by OYMC

HOLD THE PHONE!

I have a 55' GMC 2wd that I have been building into a 4x4...

For my application I bought a 1968 Impala Saginaw steering box (Rebuilt from Napa). Now this steering box has a full set of splines around the pitman arm mounting shaft that allows you to mount the pitman arm 90 degrees from the typical 4x4 Saginaw steering box mount for a cross over steering conversion. This steering box is also setup to mount on the inside of the frame rail as apposed to the 4X4 box pictured by "OrrieG's" post above that mounts to the outside of the frame...

The problem with mounting the steering box to the outside frame rail, is that your turning radius is greatly reduced when making right hand turns (Steering box to tire clearance).

I have set my steering up just like a FJ40 land cruiser: Steering box mounted to inside of frame rail (Plenty of clearance for right hand turns), and have converted to a cross over steering setup (Greater handling geometry)...

The photos below shows a BJ40 (Factory Diesel Version of an FJ40) that I converted

The last photo shows the only photo I have of the inside frame rail of my 55' GMC... You will want to box the inside of your frame rail and weld in sleeves for the mounting bolts....I'll take photos of my setup soon and post pics...

Best of Luck!

That is like the Jeep set-up I mentioned. I am curious how big of a pain the reduced turning radius will be. If its too much than I'll change it.

[ironhill]

That looks like a great idea. Thanks for the help

[OYMC]

Part of the reason your steering is effected so much by just the steering box is because of the frame rail width on a stock 55-59 Chevy Pickup... The later model trucks have narrower frame rail widths, which is one incentive to frame swaps on these trucks.

Another advantage to a frame swap is the elimination of the front shackle mounted leaf spring on the front axle. As suspension travels on a front shackle mounted leaf spring the Caster angle moves from proper alignment (Slightly Positive) to a more negative alignment as the spring rebounds pulling the shackle back towards the vehicle which then drops the front spring mount in proportion to the frame. All this movement alters the spindle angle (Caster)...

Is this a major issue? No...

If you spend the time to do a Shackle reversal (Moving the Shackle from the front of the leaf spring to the back) you will achieve a slightly better handling result. As the suspension rebounds on this type of system, the Caster angle becomes more positive rather than negative.

Just so we all know what the caster angle effects: A positive caster angle will aid in keeping the front wheels pointing forward while driving, while a negative Caster angle will cause the front wheels to wonder (While under an emergency braking condition the vehicle will pull hard one way or another, or in a turning situation the vehicle keeps trying to turn rather than return to it's original straight position.

A negative Toe angle can also cause similar issues, but if aligned properly, and you experience these types of conditions, you might look into alternative means...

[OYMC]

Just found this photo on the board: