malibudave

Before I found the 6 lug axles in the junkyard and I didn’t think that I could find axles for less than $200, I priced out what it would cost to get the 8 lug axles plugged and re-drilled for 6 lugs. The prices I were quoted were from Moser (I couldn’t find anyone local in Houston to do this). The plug and the re-drill would have been $80, the flange would need to be machined down ($25), machine the hub from 4 1/2" to 3” ($25), machine the back side of the flange flat ($25). The total cost would have been $155 without shipping to and from Moser. With shipping, the price would have been what you could get from Summit Racing for the 33 1/8” axles, summit part number ALY-17106. These are $82.95 each or $165.90 for 2. At check out, you can use the discount code, 2RETYV (good until August, 25, 2010), for a 10% discount. Total with shipping to Houston would be $161.25 as of October 25, 2009. As of this date, they are on back order. Or you can choose the Superior Axle brand for $99.95 each, Summit part number SAG-PA5565. With shipping to Houston and the discount the total would be $191.85 as of October 25, 2009.

Dave

malibudave

Because the axle housing flange on the 2001 1500HD Silverado 9.5” 14 bolt is further inboard than the 2005 1500 crew cab 8.5” 10 bolt, there will have to be a spacer between the axle housing flange and the backing plate fabricated. From the axle dimensions listed above in post #5, I “mathematically deduced” the measurement for the spacer.

The distance between the axle shaft flange and the axle housing flange of the 8.5” 10 bolt:

(68.000” – 62.500”) / 2 = 2.750 inches per side

The distance between the axle shaft flange and the axle housing flange of the 9.5” 14 bolt:

(67.625” – 60.125”) / 2 = 3.750 inches per side

Subtracting 3.75” from 2.75” tells me that I will need a 1 inch spacer between the axle housing flange and the backing plate to mount my stock drum brakes off of the 8.5” 10 bolt to the 9.5” 14 bolt. These are preliminary measurements and I will have to wait until I mock everything up on the 9.5” 14 bolt to be sure.

Dave

1FastBrick

iTrader: (17)

Dave, did you ever finish this swap??? Did you have to make spacers to get the correct brake offset???

Some one asked me about doing a similar swap but retaining the factory 2500 rear calipers. I was thinking it might be possible to do using the rotors from a 1500 SUV and getting new 6 lug axles.

Atomic

iTrader: (42)

When did the 2500s come with rear disc?

xXxSilveradoxXx

iTrader: (5)

I believe it was when the NBS came out until 2002.

I'm doing this same swap into my 2002 Silverado. I've got a 14-Bolt SF out of a 2001 2500. I'm currently looking for axle shafts.

1FastBrick

iTrader: (17)

Starting in 99 with the new body style. But the brake flange were the caliper bracket is different. See the housing I built for EvilGMC. I cut them off and made the new ones for the 1500 series brakes.

malibudave

Not done.

I had a 3/8" thick steel plate made with both the nbs half ton rear disc flange arrangement and the nbs half ton drum brake flange arrangement. Think of a 8 pointed symmetrical star.

I did this so I could bolt either brake system to the nbs semi float 9.5" rear using 5/8" thick 1/2" size nuts. This gives the equivalent one inch spacer needed to move either the disc or drum brake assembly out to the stock mounting location to use with the stock 9.5" replacement axles.

It also allows extra mounting flanges to bolt the adapter plate to the irregular shaped flange of the nbs 9.5" semi float differential.

I started drilling 1/2" holes in the "bench" mounted (floor) nbs 9.5" semi float to mount the flange adapter and that is as far as I got.

The nbs 9.5" flange will need to be clearanced at little because some of the flange adapter plate bolt holes line up with the edge of the nbs 9.5" flange. Even though its incomplete, it looks as if either of the stock brake systems will bolt on (I have an extra stock drum brake and stock disc brake setup).

1FastBrick

iTrader: (17)

I have got to see this. So you made a custom flange and then use a 1 inch spacer to move the backing plate away from the custom flange???

Interesting thought I am in for the results.

malibudave

The 9.5" flange stays on the housing. The 8 point flange will bolt to the 9.5" flange. The 8 point flange has the same outside bolt patterns of both the disc and drum brake configuration and has a hole in the middle to slide over the axle tubes and line up on the lip that holds the backing plates centered on the 9.5" housing. Here is a rundown of how it should bolt together.

-Take the 8 point flange and slide it over the axle tube.
-Line the 8 point flange so 4 of the 8 bolt holes matches the stock 8.5" bolt pattern on your year truck. 99 to 04 uses disc brakes. One set of the 4 holes should point top to bottom and front to back. 05 to 07 classic has drum brakes and should have 4 of the 8 holes parallel to the ground.
-c clamp the 8 point flange to the 9.5" flange that is still on the housing.
-using a drill, drill out the 4 holes that will match your rear brake setup. More than likely 1 out of the 4 cannot be drilled out, because there is not sufficient 9.5" flange material, and you need to drill out 1 of the other 4 bolt holes so the flange can be bolted down in four locations.
-For the 1 bolt hole that was not drilled out, clearance the flange so a bolt can be slid through the backside of both 9.5" flange and a 5/8" thick, 1/2" nut can be used on a 1/2" bolt to mount the 8 point adapter flange to the 9.5" flange. The 1/2" bolts should slide through the back of the 9.5" flange through 3 of the bolt holes you drillled that match your stock brake configuration. I am estimating the 3 bolts should be 2 inches long (thickness of the 9.5' flange plus the thickness of the 8 point flange plus the thickness of a 1/2" bolt will equal 1.5 inches plus a 1/2" left over to bolt the brake assembly on the axle. For the offset mounting hole, the bolt should be 1.5 inches long and slide through the front of the 8 point flange and the bolt tightened down from the back of the 9.5" flange. The clearanced part of the 9.5" flange should be either be clearanced a little for the bolt head to lay flat against the 9.5" flange or clearanced a little more for the bolt to mount against the 8 point flange.
-From this point you should be able to bolt your stock braking system on your truck. Since the disc brake assembly is a thicker than a drum brake backing plate, your bolts may need to be a 1/2 inch longer.

Short version:
-Line up 8 point flange to 9.5" flange on truck to match your brake configuration
-c clamp 8 point flange to 9.5" flange
-drill 4 holes in the 9.5" flange that match your brake bolt pattern configuration, clearance one of the holes if needed
-drill 1 hole next to the hole you may have clearance to have four mounting points on the 9.5" flange
-bolt the 8 point flange to the 9.5" housing using the 5/8"" thick 1/2" size bolts
-bolt your braking system on to the 1/2" size bolts.
-replumb your brakes lines.

I have not finished putting this together, but from my measurements and eyeballing, it should work with out welding or major fabrication. I don't know when I will have this done because this project has went down on my priority list.

Doing it this way you can use your stock disc/disc, stock disc/drum set up, or convert your disc/drum to stock disc/disc from earlier model trucks. You won't have to worry about redrilling rotors. The disc set up on the semi float has cast iron calipers (not aluminum) and is pretty heavy also. You should be able to use these adapters on OBS 9.5" housings that have the same width and convert them from its drum setup to your nbs disc/disc setup or your nbs disc/drum setup.

I hope this makes sense. Please let me know if there is something confusing about the write up.

Atomic

iTrader: (42)

Why try to make an adapter that will fit both drum and disc when you are only going to use one or the other? If you dont want to weld, you can just use a spacer with longer bolts. To simplify the process you can make two different spacers; one for disc and one for drum, and just use whichever one you need.