1957 Chevy 4x4 NAPCO conversion...

[the1ted]

First off, a HUGE thanks to OrrieG for recognizing the bottom plates and helping me get GM (left in photo) parts for the rear 3/4 ton axle. I believe he has it correct that the one on the right is likely a NAPCO casting, one off of the original GM. They are identical except the GM is much better material as evidenced by the washer indents on the NAPCO casting that has an all around rougher material look and finish. They also bear different part numbers.
I have posted a second photo of the Warn lockouts that came with the 3/4 ton axles after polishing. WOW!

[buggy5872]

I did not realize there were different castings for the NAPCO bottom plates. I'll have o look at mine and see what ones I used. If I recall correctly. I had a bunch of them and picked the best looking ones to use. I do not throw stuff like that out so I will most likely have the NAPCO ones if I did not use them on the truck. There is so much good info on this site.

[the1ted]

If you look at my other rebuild I have 1/2 ton 1966 GMC cast bottom plates on the rear that have been machined to fit the 1-ton rear housing. I have always believed the U-bolts down configuration is the best. http://67-72chevytrucks.com/vboard/s....php?p=5463595

[the1ted]

Pictured here are the 2 bottom plates for a 3/4 ton axle I got from OrrieG (thanks again!). On the left one I show where ground down the casting gate remnant you can see on the right. I think it is a much cleaner look. The plates have a front and back, and I am assuming this because the 1/2 ton cast bottom plates (pictured) actually have 'REAR' cast into them on the heavier end (where the grinding was done on the 3/4 ton set). This must be to allow for the axle twist on the rear U-bolts.
Now they are off to the sandblast and paint!

[gearhead72]

Looking good Ted. I need to come out one of these night to see what ya got goin on. I know I still need to prime the oil pump on the 57's motor. Just call me some time with a list il help any way I can. By the way I started driving the ol 72 GMC today. Don't know how long that's gonna last with gas on the rise again

[the1ted]

Here is the finished GM 3/4 ton bottom plate next to the NAPCO knock-off casting. I showed the NAPCO casting to a foundry owner/operator and he called it a 'junk' casting. No metallurgy involved in the alloy. If it is NAPCO it is frightening to think the same science was used on their front axle housings (also pictured)!?!

[Dieselwrencher]

Great build, and great info! I love seeing these trucks. You sure don't see them around very often either!

[the1ted]

Here is a link to Wikipedia on Metallurgy:

http://en.wikipedia.org/wiki/Metallurgy

Good info on materials used in casting and all treatments to metal including
plating.

[meter swinger]

Subscribed. Very interesting build.

[the1ted]

Here are a couple of views of the front axle and frame during tear down. The first shows a view looking down at the axle. Good fortune was that this truck was a factory V8, so the front motor mounts are riveted to the frame. This truck took a hit in the front at some point. It had a bent passenger side frame horn, a broken shock mount, and a repaired tie rod. In the second photo you can see the gussets welded into the tie rod bends for strength. My guess is that the entire tie rod was homemade after the accident as it was so distorted.

[the1ted]

Footnote:Another problem pictured in the latest photos is broken leaf spring clips. They are visible on the driver's side in the first image and passenger side in the second.

[wayne4252004]

I have the same problem on my rear leaf springs. Does it matter where these are installed?

[the1ted]

Originally Posted by wayne4252004

I have the same problem on my rear leaf springs. Does it matter where these are installed?

Wayne,
I spoke to the guy who builds my springs. He said the major cause is rust between the spring leaves-this starts them working against the bracket and bolt, ultimately snapping it. Shocks also play some part in the flex and return of the spring. I have always put the clip towards the rear. Hope this helps.

[the1ted]

Here are some comments by a friend who works as an engineer in suspension manufacturing:


The spring clip is only there to keep the spring leaves lined up. Multi-leaf springs tend to “splay” or “fan” apart during use because of a little movement in the clamp area. Some springs use one clip, and some will have two. If the clip broke from the leaves fanning out then that would suggest that the center clamp could be tighter. If the clip broke from the leaves trying to separate that would indicate high brake or torque loads that were trying to pull the leaves away from each other. The clips can be crimped from one piece with a plastic or rubber liner, or they can be “U” shaped with a bolt like yours. They can also occasionally cause a spring leaf to break because they are usually riveted to the end of the shortest leaf in the stack.

[the1ted]

I am looking for 4 16.5 x 9.75 8-hole slotted mags if anyone has a suggestion.

[the1ted]

"TAH-DAH"...found a matched set at AKH wheels (Ellensburg WA). Backspacing was identical to my 6-lug slotted mags. I will report more when I recieve them.

[the1ted]

HUGE disappointment, the wheels offered turned out to be a different width than specified. I don't believe I would do business again with AKH Wheels...

[mud.man.rj]

Sooo what was the difference on the wheels that matter.

[the1ted]

The wheels offered on the website for AKH were matched Rockwell 9.75 wide and they were ready to ship after I sent payment and discovered they were 8.25 in width. I was trying to keep the original look of the 6-hole slotted mags/B.F. Goodrich 33 x 10.50 x 16.5 Mud Terrains I took off for this rebuild. I really looked hard for these. They did offer to try and put a set together from other wheels they had and another source, but I decided to just wait. I really want the classic look.

[mud.man.rj]

Ya that sucks on the wrong rim width, had a 4x4 company try that with my 12" MT classics, I had to have 12" due to the tires being 14.50 width but no they tried and tried to sell me 10" which they actually ordered in for me, waited 3 months and finally just had the tires shipped and bought the 12" rims from another place that got them for me in 1 day only, head scratcher, but really glad I waited cause they rock now on the truck, one of the main things that make the truck especially being satin black.

[the1ted]

Now I know what they refer to as 'writer's block'. I simply haven't done any work on the truck all summer, it seems. A few things I did accomplish were finding slotted mags for the truck. Actually ended up with 2 sets and by the time I got them polished I was $100 over what I was going to spend on the first set I found, but later discovered they weren't the right width. So I guess it worked out better!
A few things I learned along the way: My tire dealer won't mount any tire over 6 years old?!? Said it is regulations on his industry. He showed me how to read the date molded into every tire-so hope that helps someone. As the wheels go, one is a name brand and the other is a 'no-name'. Nearly identical except the back of the brand name wheel has an extra rib cast into the spoke (pic). I think this is called 'webbing' in cast metals and provides strength-so likely I will use the name brand (Shelby). I pictured both styles side by side polished, and they look identical.
One more photo is of the rear differential housing I am using. I took it for sandblast and learned that if you leave the oil sludge in the housing it will adhere to the sand during the 400 degree bake for powder coating. I took it to a truck service place in town and had it steam cleaned to remove all of the surface crud that remained. You can see in the photo that some oil bled out of the casting when it did get baked. Also see the excellent job the sandblaster did in masking areas you don't want painted. Now that Fall has fell I hope to get back to the project.

[the1ted]

Hey, almost fergot that I got the front fenders, hood and fender wells back. So a little more progress!

[dug224]

the1ted: Glad to see a little progress. Between a near miss hurricane, my real job and some family issues and family fun, mine has come to a stand still as well. Looking forward to a restart soon myself. Panels look great. dug

[OrrieG]

There are no Federal Laws governing tire life. Manufacturers limit their warranties to a maximum of 6 years and recommend replacing tires after 10 years. The media has jumped on the 6 year band wagon with tales of doom and gloom, Ralph Naderism at its best. The dealers lawyers have probably told them that 6 years is the defacto standard and they are in a defensible position if they stay within that. More tires are sold and everyone wins except the consumer.

[wayne4252004]

Originally Posted by the1ted

Wayne,
I spoke to the guy who builds my springs. He said the major cause is rust between the spring leaves-this starts them working against the bracket and bolt, ultimately snapping it. Shocks also play some part in the flex and return of the spring. I have always put the clip towards the rear. Hope this helps.

Thanks for your help.