D44 TTB 8 lug with a rear D60 and large disc brake conversions

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Almost there on the rear axle. Remaining to be finished: T&B zip tying the bundle of tubes, hoses and electrical connecting the rear axle to the chassis (& trimming the zip-ties); lower shock mounts (waiting on the Fox RR's due in end of the week); routing and fastening down the p-brake cables (waiting on the shocks); Bleeding the rear brakes. I do still need to figure out where I'm going to put the pneumatic toggle switch for the OX locker, and route the tubing there.

 

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Can see in this pic why the wheels have to change:

I now have all 5 of the AR "Baja's" and will hopefully be getting them down to the tire guy next week.

Old beams are out.

PO said "it's got some sort of posi up front" When I got the assembly out from under the truck the diff case has "913A592" laser etched on it. That number takes me to this page: https://www.eaton.com/us/en-us/skuPage.913A592.specifications.html A TrueTrac, that's going to make deciding to go ARB up front a lot more difficult.

New DS beam is in, need some Right Stuff and some long shouldered bolts to guide the diff into place. Hope to make that happen this coming week.

I had bought the Autofab pitman arm thinking that it could use less bump-steer than it has. With both beams out that seemed like a good time to make the swap. Found that I didn't have the right size socket for the pitman arm nut. Figured that I had this 15" adjustable right there, that I'd give it a try. Took less than 20 lbs force to loosen that nut. Then I discovered that The arms are the same. wah! So I tightened it back up. Tight this time. I'll put the Autofab arm up FS along with the beams and the '96 4WABS Knuckle Assemblies when I get some pics of them.

The list is still long, but it is slowly getting shorter!

 

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Major milestone reached last night, the front brakes are assembled and complete. I just need to modify the radius arms for the side mounting trailing damper lower mounts, fab the reservoir mounts, and I'll be ready to bleed the brakes and go for a test drive. One thing that I noticed yesterday evening is that the steering stops of these 6 hole TTB knuckles do not match up well with the beams. I expect that I will need to grind on the front side cast stops to get back the turning radius that I had previously. The adjustable stops come nowhere close to making contact with the beams. Rotor looks like that because they're brand new and at least 5 years old. They came to me rusty so I blasted and then 80 grit long-boarded them. I don't expect that they'll look like that for very long.

A recap in case my meanderings have lost them: To put 12.5" rotor 3/4t 8 lug front brakes on a D44 TTB you need:
6 hole TTB knuckles (most are 5 hole).
GM 3/4t Outer axles, spindles, wheel hubs, rotors, and caliper brackets from just about any K20 donor that you can find. These will require at least a 16" wheel. The lug studs will be 9/16" I have seen one reference to there being a 1/2 stud that will fit these front rotor/hub assemblies, but I have not looked into them at all. I used a 1979 K20 Suburban (400ci) as my "Application" when ordering parts. Some of you OG may remember the Sub that I used to tow the dune buggy to BBBB I (Dusty likely has a pic somewhere of it parked in the driveway of that rental). It was a K20 Sub and it started my familiarity with these parts.

 

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Well, the floor jack bled down while I was at work allowing the DS beam to go to full droop, and in the process it leaked about a quart of diff juice onto the concrete. So now at least that whole side has to come back apart and possibly the PS as well.
dang! but I'm glad to know now that there's some sort of problem with the seal.

 

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On the last go-round I didn't take any pics of the GM 8 lug parts being assembled to the 6 hole TTB knuckles. So this time I did.

The modified 6 hole knuckle, caliper brackets removed and ground smooth:

The crucial second set of holes drilled in the caliper bracket that clocks the caliper body so that it clears the knuckle:

One side assembled:

 

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It's almost all back together. Waiting on a replacement reservoir mount. The shocks each came with one and they were carefully removed from the boxes and stashed in the same place, but one is AWOL and that is stopping me from finishing things up and trying to drive it with the vacuum booster. I have one inbound, but it isn't expected until this coming Sunday. The H-B conversion kit is due in the middle of this month, but I wanted to try driving it earlier than that so that I could get some initial impressions.

I moved to a same year application F-350 m/c and gutted it's P-Valve/RPV assembly and added a wilwood adjustable during the re-plumbing required by deleting the ABS pump/valve assembly. I was going to try just an LBS in the rear brake line, but I needed the distribution function that the wilwood p-valve offers so I took the easy way out.

 

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IT moved!

Under it's own power even. Just not in time to make it to BBBB. Unfortunately. Still badly needs an alignment before its safe to drive very far.

 

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With the pending H-B conversion I ordered the Saginaw PS pump be rebuilt with a remote reservoir body on it. I plan to return the box and the H-B to the remote res individually. I've long thought that such a reservoir would benefit from having the usual de-aeration methods used in dry sump oil tanks and have sort of been looking for an excuse to try this out. When in college I made some metal spinning forms for a Tooling Class that created the top and bottom of such a reservoir and used Ag sprinkler pipe (tube actually) for the body. I couldn't find them or the piece of the Ag tube that I had so fall back to some alternate plan.
I was never a great aluminum welder, but before my eyesight started to go I could do better than this. Oh well, beats the alternative to aging.....

MISF used one of these to make a coolant recovery tank ($20 on amazon) and it occurred to me that it was just about the perfect size for a PS reservoir:

I carefully cut it at a scientifically arrived at WAG and welded the -10AN bung to the bottom of it.

I wanted the top to have a mild conic shape and I needed the mid-disc to be that way. Ordered some Shore 90A 1/2" thick rubber from McMaster and made a press-forming tool from a rem:

Mid-disc:

I used the same bung and cap that MISF used for his recovery tank. Welded some -6AN bungs to short pieces of tubing and then welded those into tangentially milled cuts in the upper part of the paint cup. The 'candy cane' is a piece of 1/4" aluminum tubing that will become the reservoir's vent:

Shot of the mid-disc and the vent tube - it goes all of the way thru the bottom of the paint cup:

Top section welded together:

Welded assembly:

 

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Closer....

 

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Lots has happened since the last update. That PS reservoir is really cool, and doesn't work. Cavitates the pump. Replaced it with a Lee PS reservoir. HAd a heavy equipment type spin-on fluid filter in the box's return line. It too cavitated the fluid and made the pump make noise. Removed it. I've 'fixed' the high pressure PSF leak at the hydro-Booster 3 times. It needs a different adapter fitting.
And this happened 3 miles into the first test drive:

We know what the cause is, but I checked just for that and could not feel it happening. For reference, that is a ~Ø1.55" OD shaft and it gave no notice. Didn't even make any noise. Should have replacement shafts here on Thursday. Ouch!

In those three miles I did use the brakes a little bit and they appear to work better than I had hoped.

 

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Wheeee! Does this truck stop!!! 40 to 0 feels like about 2.5 to 3 truck lengths. 50 to 0 isn't noticeably further. I ended up dialing the p-valve down to it's bare minimum and might just be able to run w/o it at all. Simulated panic stop slid all of the tools sitting in the pass Mastercraft seat up, out, and onto the floor. Best part is that while not even slightly touchy the pedal effort is very low.

 

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After months of use as a DD I I'm calling this project a success. Pretty amazing to drive a Full Size on 35's that stops like a sports car. It has unintentionally lured more than one appliance driver into thinking that they can tail-gate me since 'they obviously can stop better than that old POS' only to find out suddenly that they can't.