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

[ntsqd]

I'm in the middle of one. Some of the things that I've learned:

With a LOT of fabrication work it is possible to include the '96s ABS sensor up front, but after several nearly bad experiences off pavement I'm ditching the whole system. This is too bad because I think it is a good system to have on pavement. Can think of it as a smart proportioning valve that is able to automagically compensate for different loadings. However, it is not smart enough to handle dirt use very well. I tracked down a Stewart Components LBS to use if it proves necessary.

Looks like you can transplant the GM 3/4t D44/10 bolt front 8 lug outer assemblies to a TTB with 6 bolt knuckles. Early and late (4WABS) TTB's have 5 bolt knuckles and these won't work. I have not investigated what it would take to make them work. You will need at least 16" wheels to clear these rotors, 15's will NOT work*. For the GM 8 lug stuff to fit you need from the donor:
Caliper brackets
Stub Spindles
Wheel hubs
Rotors
Outer axle shafts
To clear the caliper & GM bracket the knuckle needs to have the cast-on caliper bracket completely removed.
The GM caliper bracket needs a slightly different clocking than where the OEM holes place it. A second set of holes between each of the existing are required.

I will update this thread as I learn more.

*Do not talk about grinding on the calipers to make them work. Anyone who does that is a fawking idiot!

 

[Dusty]

Nice! Our first actual TECH post I have nothing of value to add but thanks for lending your expertise to the group Thom

 

[ntsqd]

You're welcome!

At the rear I opted to go with a D60 as I wanted to keep the unsprung mass low. All of my research showed that once you ditch the big drum brakes that a D60 isn't all the much heavier than a 9", but a 9" housing with floater spindles gets spendy real fast and if you don't spend a bunch on such a housing they bend or break fairly easily in off-road use. I got to stand by the side of the road when a Speedway Engineering FF 9" housing cracked under an FSB while BCG 7 glued it back together with a battery powered Mobi-Arc spool gun. This happened on the road between Insurgentes and San Juanico, Baja. No real desire to go there again.....

Replacing the drums will be an muchly modified Exploder RDB kit. Diff will be an OX of the integral air operated variety. Converting it to cable shifted only requires the purchase of the shifter and the cable. Drive axles are 4130 alloy from Dutchman. Jesse at High Angle makes a D60 pinion flange compatible with the stock drive-shaft. From my years with Toyotas I find that I much prefer companion flanges to U-J yokes.

Stock D60's have axle splines punier than a 31 spline 9" so that wouldn't work. The common upgrade is Ø1.50" 35 spline drive axles, however those don't fit thru the unmodified stub spindles. You can rent the special tool to bore out the spindles from Yukon for a very large chunk of money, or you can risk it and yourself with nested hole saws. OR you can build your own special tool. Those who know me know what I did. Any project worth doing requires fabricating at least one special tool.

Uses a Hougen annular cutter to bore the ID of the spindle to 1.56" Total cost was less than the Yukon rental by about $30. These cutters ideally want to run at about 100 RPM, which is a bit slow for most 1/2" drill motors. Shown is the 3 amp Craftsman that I inherited from grand-dad. I could load it up enough to slow it down form it's advertised no-load speed of 425 rpm, but that made it over-heat. So not wanting to kill a perfectly good drill motor bore a little, let it cool for a while. Bore a little, let it cool. Took me about 2 hours actual work time spread over a couple of days to bore both spindles. I have the tool now, can be used to bore other spindles. FWIW 14bff's use the same spindle nut thread size as the D60ff's, so this tool could be used on one of those as well. Not sure why you'd need to do so, but it could.

A not very good measurement says that the pinion angle on the D60 housing is 2.5° lower than the current 8.8's. Trying to decide how I want to deal with that. Cut off the existing perches and weld on new ones, or angle mill the already angle milled OEM spacer blocks that corrected the bad pinion angle of the Deaver Q80 springs.

Next big project is to make the pieces that bolt the Exploder RDB's into place. That is not looking easy. Spinning parts come really close to stationary parts, with not a lot of room to create any additional clearance.

 

[ntsqd]

The Exploder RDB project suffered a set-back in that the subscription use of SolidWorks that I had expired and was replaced with a sub-par piece of something generously called 'software.' I *think* that I've mostly solved the problem, but the models were all made in SW2020 and what I now have is SW2017. Just need to do some file conversions with a SW2020 license and then I can open my old work in SW2017. SW is notorious for not being backwards compatible.

In other news, it appears that the inner stub axle and slip-yoke are not made by anyone aftermarket, and there doesn't appear to be much in the way of service parts made either. Leaving luck at the junk-yard the only option for a more or less stock axles set-up.
Unless you step up to RCV. I was put off by their rather short service interval for the center CVJ (3500 miles then removal to grease it), but I'm being told by a reputable company that in less strenuous use that the service interval is far greater. It IS the $2200 dollar option that I'm not sure that I need.

Current status: Waiting on the 4" modified beams from Solo. GM backing plates have a new set of mounting holes centered between the original holes as this clocks the caliper and locates it in the OEM clearance on the knuckle. Spindles are thoroughly cleaned and have glyptal sealed bores with new spindle bearings installed. Knuckles have had the OE caliper mounts removed and ground smooth, been painted, and will get new TTX ball-joints in the next couple of days.
Rear axle is ready for the diff assembly. I've made my R&P set-up guy a set of set-up bearings for the D60 as he hasn't had any until now. I need to install the new wheel hub bearings and get the design of the RDB adapters finished and made before sending the housing out for the diff assembly.

 

[ntsqd]

22/04/29 UPDATE:

Exploder RDB's are a no-go. They parking brake drum diameter is too small for the some of the internal parts to clear the wheel hubs. Hoping this weekend to get out to the yonke to look at Expedition RDB's and see how adaptable they might be.

Since we like pitchures, the Solo Motorsport beams are here and they are pure welding pron. Am thinking that they're going to get a coating of Steel-it Black.

I was also able to score a "bolt-in" type diff assembly. This means that a front ARB is possible, probable and very likely!

A set of TTX ball-joints are here, need to press them in. Then the knuckles can go on the beams. Need to get the 3 U-Joints so that I can rebuild the axle shafts when they come out.

 

[ntsqd]

EDIT: Made the pics display rather than links.

On the rear disc brake conversion:

Expe RDB's looking like they'll work

They register and bolt on! Bloody amazing that 2000 vintage SUV brakes exactly fit a ~1976 work truck housing!

Needs a little detailing of the housing flange to bolt-on correctly, but that's easily done.

Thinking to reverse them; Expi LH become Blanc-Oh RH to make the p-brake cables work well. Need to look at the OEM p-brake cables to see what those look like.

Clears all of the whirrly bits:

Even more amazing, now that I know to look for a 2000 Expedition on Rock Auto I'm finding that I can buy it all new. Including the caliper brackets! The lone part that I've not found available on RA are the rear caliper hose banjo bolts. An odd thing to not have. They have those for the front, but not for the rear. All-in, I think that you can "kit" this RDB conversion from Rock Auto for under $500. My'96 8.8 has what looks like the 'Torino' housing flange bolt pattern, but my donor Expi had a 8.8 not a 9.25 I'm thinking that if a later F-150 8.8" housing or a 9.25" housing were used that these brakes would possibly bolt on.

 

[ntsqd]

Got the rotor spacers made except for the final reaming to size of the stud holes. Waiting on a 9/16" R8 collet. Normally I'd put the collet closer in the lathe and turn the shank down, in this case to .500. Two problems, the reamer's size etching is right where I'd be reducing the shank's OD and I don't have a 9/16" 5C collet either.

Am using Dorman 610-189 wheel studs. They will press thru the spacer and into the wheel hub with their splines engaging both the spacer and the flange. These are a 9/16UNF thread to match the front GM wheel stud's threads. Need to ream both the spacers and the wheel hub flanges. The flanges are close already, I'm mostly reaming them for GP. There is no way that this truck needs eight 9/16 wheel studs per wheel, but that is the path of least resistance.

The wheel hubs have a 5.000" pilot step on the rear of them for the original drum. The spacers index on those, and then have a 5.000" pilot step on them for the rotor. This diameter interrupts the OE wheel stud holes in the rotor. Placing the rotor's mounting holes on the same 6.5" bolt circle in between each wheel stud made making them easy. I turned the spacers to their profile on the lathe and then placed them on a wheel hub and using a reducing bushing transfer punched one hole location to the spacer. Drilled and tapped that M8x1.25 Then I turned a locating bushing that piloted in a wheel stud hole in the wheel hub and bolted the spacer to the wheel hub before transferring the other 7 holes to the spacer. I drilled those with a Ø3/16" 135° split-point and then marked 1/2 way between two adjacent holes. Then those holes all got drilled and tapped M8x1.25. Aligning my 1/2 way mark in one of the flange holes I repeated the process of transferring one, drilling and tapping, then transferring all of the rest of the holes. These holes were thru-drilled Ø39/64's and had a [EDIT] Ø1-3/16" X .75 [WAS: Ø1-3/16" X .50] deep counter-bore machined centered on them. The head on the wheel studs is roughly Ø1.10" so the C-bore has a little clearance around their OD's.

With the mock-up rotor, a new pair are in the mail:

Can see how ineffective the "Black Beauty" blasting media was on whatever that orange paint is. Currently thinking that I'll just apply Steel-It black over it and call that good enough.

 

[RichardS]

CRAP, you should have asked if anyone has that tool at i bought one years ago when i put my 60 in.

 

[ntsqd]

What tool is that?

Second pass thru the blaster removed a bunch more of the orange (I H8 orange!) and they got coated with Steel-It Black last night. Tonight the Ø9/16" R8 collet should show up. Then I can ream the 32 stud holes and do the final assembly of the spacers, studs, and wheel hubs. Once to that point I can make an appointment Vta 4x4 to get the OX and gears set-up and move onto assembling the front beams. One 760 UJ showed up with one damaged grease seal on the cup. Thinking that I should exchange it.

I've been working on a drawing of the spacers just in case anyone wants to do this rear disc conversion too. SolidWorks can output the drawing as a pdf and I *think* as a jpg as well. Looks readable to me.

 

[RichardS]

I have the tool that opens the rear end housing ends for 31 spline. I used this years ago then had a custom housing made instead. yup, wasted money spent!!

 

[ntsqd]

Oh, yeah I'm way past needing that tool! I actually built and used mine well before this forum went live, but I didn't think to ask the list about the tool. Oh well.......

I read a post on that rock crawler forum where a guy was wondering why anyone would put in a rear D60 when 14bff's are out there. For a crawler I think he's got the right idea. Just enough more strength in all of the right places over a D60 that for a serious crawler I'd completely agree with him. Not so much for other uses, particularly where unsprung weight is a concern.

 

[RichardS]

Yea, I'm not competing anywhere and 39 or 40 inch tires I should be fine with. Strange built my housing to my specs and even welded the ends on that i sent them. mine used the same brakes as the Front 60. same spindle and rotors and dual piston calipers so less parts to carry if i decide to. seems to stop good but i might try to get it to stop a little better with a different master. keep up the updates on the build. looks Great!!

 

[ntsqd]

It is weird to think of a D60 rear not being strong enough. That's a level that I don't want to play at. For me it will be more than strong enough. Overkill even.

Found that I could order an 8"x8"x 1/2" steel plate from amazon delivered for less than I can buy it locally. That's crazy! Anyway, it will become the jig for drilling the bolt holes in the (future) rotors to mount them to the rotor spacer. I need to make drawings for it and the mods to the rotors and post them too. The other rotor should get here today so by tonight I should have both ready to have the mounting bolts holes drilled in them and at that point they'll be ready to use.
Now I just need the guy that I have do R&P set-up's to be less buried. Once the gears & diff are set-up I can put it all together and plumb it.

The TTB is waiting on pivot bolts for the SRE's and camber/caster adjusters. then it is ready for the front to be torn down, the diff swapped over, and re-assembled with the new beams & 8 lug outers. I'm going to wait a bit on rebuilding the other diff with gears and an ARB. I've a trip planned for the middle of Sept that likely won't need a front locker and I've a lot of other things to get done before then.


Given what 2 gallons of Delo 400 just set me back I'm dreading ordering the diff oil. Haven't decided if Redline or Swepco yet, but those are the short list options. Break-in will happen with CarQuest house brand dino oil.

 

[ntsqd]

Suffered a set-back yesterday. The shop that is my go-to for diff gear set-ups can't look at it until the second week of July.

 

[ntsqd]

New rear rotors are modified and mounted. Ø0.041" safety wire sucks. I'm using it in a single string thru the rotor mount bolts ala old school, non-aero, non-astro safety wring practice. Bolts are torqued with 271 in the threads, so the wire is just the "belt" to the Lock-tite's "suspenders." Installed new Timken races too. I figure to leave all of the brake stuff off the housing until the gears are set-up. Both to reduce damage to them in handling and to make it lighter to move. Made what I think (hope?) is the last parts order yesterday. Was tempted to go with the Ø3-3/2" GM calipers, but went with the std & far more common Ø2-15/16" calipers. If/when I upgrade to hydro-Boost I'll likely need to substitute those the calipers then.

 

[ntsqd]

Parts dropped off, hoping for an assembled D60 diff by the end of the week.

 

[ntsqd]

I have the D60 back, but it's now too close to my annual NV trip to make the changes and have them fully sorted out in time. I've put this on hold until after I get back, which will be early October. It hurts though, having this done in time for this trip was the goal.

 

[ntsqd]

End of the Year update:

Looks like I might have the 8.8 sold, so things will need to move fast. er.

 

[ntsqd]

Got this far before the rain shut me down.

Part of the delay was that I had to build this first:

Not the most ideal location for that, but the hole in the 1/4 panel had me tightly constrained.

 

[ntsqd]

Getting closer to working on the front. Which was the original point of this thread!

Rotors came with painted wear surfaces, so I didn't bother to keep my paint off of them since I'll have to clean off all of the paint anyway. Technically the rear wheel bearing run in diff lube, but I've been cautioned that it sometimes can take too long for the lube to get there and the wheel bearings get wiped out before the happens. So I packed the wheel bearings per normal front wheel bearings, only with a more generic disc wheel bearing grease. The front bearings will be packed in Redline CV-2 synthetic CV joint grease. I've found this grease when used in wheel bearings to be nearly a lifetime greasing.

I skrewed up though, one of the Dutchman axle shafts is about 3/16" too long. They made them to my measurements, so it's on me. This is as far in as it will go. I'll get it trimmed down this week. The Dana axle flange bolts are also a wee bit too long to fit the threads in the hubs. I chased all of those threads with a bottoming tap, and took them to the bottom of the holes, so that is why there is an AN washer on each bolt.

I couldn't resist, I had to put one of the new wheels & tires on to see how it looked.