1959 GMC Bus - 4x4 Build

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Baipin

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Thanks for the tips guys. Much appreciated. I've also considered a Rockwell, or Detroit rear end from another school bus; have seen a good number already in 4.56 (what the D60 front is). Obviously I'd be adapting from 8x6.5 to a 10 bolt "big truck" pattern to match the rear, if I go with such a large axle. I've been mulling over the D80 vs D70 vs 14-bolt as well, and will probably end up with the latter if I don't go big truck stuff, if only because the D70 and D80 are a lot more difficult to find around here.

Dana 60s don't have crush sleeves. They use shims to set pinion depth and bearing preload. Have you tried looking for a Dana 70 dually rearend from a Chevy dually? That's what would have been the rearend most likely that came behind your front axle your using. Be aware they came in different widths depending on if it's a cab and chassis or pickup bed.

Cool build, looking forward to it.
Thank you - it's a fun build for sure! So with the D60, since it doesn't have a crush sleeve, can I simply re-torque the pinion nut, confirm the gears mesh properly with marking compound, and it should be fine? The last owner put a new yoke on it but never torqued it down properly - no issue with "reusing" the old shims like there would be with "reusing" a crush washer, correct?

If anyone has a steering arm for a Dana 60, I'd be interested in taking it off your hands, by the way. At some point in this axle's life, someone welded the nuts and studs together, and to the steering arm. I don't know what they were thinking, but it was hot enough to gouge halfway through the studs. The steering arm was even tacked to the knuckle and it was a pain in the ass to remove. Needless to say, I need a new one...

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In some better news, I managed to score a Sweet Mfg. hydro assist servo which mounts along the steering column. I will be keeping the nice, big, stock steering box, and adding an assist cylinder between the pumpkin and the tierod. My thinking is this should decrease force on the pitman arm, steering arm, and draglink, since hydraulic power is applied there rather than at the steering box itself.
 
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shortbus4x4

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Yes on the pinion nut. Though I would clean nut and pinion well with brake clean, blow dry and put some red locktite on it and then torque it down.

I think a 14 bolt would work ok for you and be relatively cheap. When you start getting into the 10 lug stuff it can get expensive quick converting it down to 8 lug. Figure out what width you need for your rearend and go shopping at your junkyard. I have a dually rearend under a 1989 Ford E350 Uhaul box truck you can have if you ever make it over to N ID.

That steering arm modification looks downright scary.
 
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Baipin

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Yes on the pinion nut. Though I would clean nut and pinion well with brake clean, blow dry and put some red locktite on it and then torque it down.

I think a 14 bolt would work ok for you and be relatively cheap. When you start getting into the 10 lug stuff it can get expensive quick converting it down to 8 lug. Figure out what width you need for your rearend and go shopping at your junkyard. I have a dually rearend under a 1989 Ford E350 Uhaul box truck you can have if you ever make it over to N ID.

That steering arm modification looks downright scary.
Hah, yup! I have no idea how someone would think welding high tensile studs (and melting halfway through the nuts) to a cast part, would go well... jeeze. I've since been able to find a new one, and that should be here within a week or so.

I think you and the others are right on the 14 bolt. Was looking at both the 10.5 and 11.5 AAM's - the 11.5 DRW Dodges (and GM's?) seem to have a 4.00" tube dia. with 0.559" wall thickness. The current axle under the bus is 4.5" tube dia., 0.437" wall thickness, from doing some rough tube strength calcs, the difference in strength is trivial.

I welded up some new hangers from 3/8" cold rolled. I may add a plate on the bottom to box in the hanger, to provide extra rigidity against transverse, side-to-side movement... we'll see. The original hangers were 1/2" thick, but smaller. I'm expecting these to be plenty strong:

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I did a FEA analysis on the frame section (simscale.com; free and very handy, if you're into that sort of thing) and found that reversing the shackles and therefore moving the hanger to the front of the frame where I was intending, led to an awful stress riser in the downward neck of the frame. The front hanger also ties in a very large crossmember. With the amoutn of fabwork involved, as well as the questionable amount of non-rusted C frame to work with up front for that purpose... I left the shackles in the front and just went with slightly longer springs. They'll sit like this:

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I have a buddy in the States with a front shackle bus. He added air helpers to the front and found that improved ride quality, so I'll likely do the same.

My DIY shackles are resting at the same angle +-5 deg. as the bus' original ones. I've heard mixed things on proper shackle angle for front shackle front springs. If you guys think it'd benefit from being closer to vertical, I can do that and add a zero rate spring to move the axle back to where it should be.
 
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Baipin

Rank IV

Enthusiast III

Springs are up, more or less! I haven't drilled the actual bolt holes yet, but this is about where they'll sit. This is with both springs compressed, as if the bus were sitting normally. I tried it out with a single spring (full weight of the bus on both rear springs and one front spring, shackle angles still looked very good. I'd like to move the axle forward 1" - there is more than enough room on the axle's perches and on the ubolt plates to do that safely. I could also fab a zero-rate spring, but I figure that's more parts that's just another failure point to add in.

I might add a leaf to the current pack - the springs have about 400lbs higher capacity than the originals.

My main problem right now is figuring out the draglink and steering system, overall. I had intended to keep the push/pull with the stock steering box, however with the position of the axle,m the knuckle, and the position of the Dana 60 steering arm on the knuckle, relative to the location on the original axle, my drag link would be 10" (red) instead of 14.5" of the original. I'm assuming this is too short and will cause bump steer issues? Or, am I misunderstanding this?




My other option would be to put a steering box at the front; one of the "International/Freightliner/step van" style ones (yellow draglink). See pic below, too.

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The issue with this, is that the steering box is on the side of the shackle, which I'm told is not ideal, though I can't help but see that the steering arm on the axle will move the relative same distance towards/away from the steering box, regardless of which side its on. If the steering box is on the front, the axle moving up will bump steer to the right, if it's where it is now, it'd bump steer to the left, correct? Regardless, is it worth having the longer drag link? I had considered crossover, but have heard bad things about road manners compared to push/pull, and would have some clearance issues with the front-mounted shocks and a crossmember.


EDIT: I played around with the above design in CAD and it'd lead to some pretty horrible bump steer, so that's out. I could do crossover as a Y-link setup; I would have room to place a steering box near the current one; inside the frame rail and about 8" to 12" forward of it. The pitman arm would come down before the low-slung crossmember you can see at the front of the frame. Seems like it'd work well.

That said, I'm thinking the short, 10" drag link to the current steering box might be alright after all? Below is a bit of an exaggeration; more flex than springs even have. It shows the 47" springs with a stock steering arm atop a 3" block GTiven a static pitman arm, the axle-end of the draglink stays the same distance from the axle's steering arm, throughout the axle's entire spring travel, +-0.35". I think that's pretty good? Turning the steering arm on the axle 0.35" hardly turns the wheels and seems pretty manageable as far as bump steer goes. Can anyone see issues with this?

 

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Baipin

Rank IV

Enthusiast III

WOW! I like how much thought is going into this project.
Thank you! I have a habit of overthinking/overengineering things, but... if you're gonna' do it, do it right, eh?

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I decided to drill new holes to locate the springs, instead of making a zero rate. I figure that's one less point of failure and one less part to fab. Standing on the drill press worked surprisingly well...!

I've been looking at wheels and tires for this thing in the meantime. Was planning on going with XZLs, but they're expensive and new ones are impossible to find; the best I can find up here has nearly 10 year old date codes... I'd also consider humvee wheels and running super singles rather than duallies as those are much easier to find, but I don't like that there are so few 16.5" tire options. I'm aiming for a 37" tire, but can fit anything up to 42". I don't want the knobbiest, most aggressive AT/MT/traction tires I can find... something that's decent on road and off.

Also, here she is running:

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Baipin

Rank IV

Enthusiast III

I like it very much, go on, will try to follow this.
Thank you Robert. :)

For anyone curious, you can follow the progress of the build here: Login • Instagram I generally loathe social media, but Instagram seems to be a quick, simple way to record my progress.

Recent updates include a new tierod and draglink for the D60...
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As you can see, I'm using the stock steering box. I mulled this over a bunch but decided to stick with it. I inspected the inside and it's in fabulous condition. It's also quite a bit larger than other Saginaw manual boxes I've come across, let alone through-frame ones. The only other options to add power steering: 1; a front-mounted box with a push/pull draglink going the opposite direction of the original (so, the modern-day setup in all MD and HD trucks). That necessitates moving the shackles to the rear, something I was not inclined to do for a variety of reasons as mentioned a few posts back. 2; the other option would be Y-link/crossover steering. This would work fine, but would of necessitated and outside-of-frame P30 stepvan box which I had trouble finding for a decent price. With front-mounted shackles and therefore shocks in front of the axle, there would of been some interference with the draglink.

The option I chose, which keeps the original steering box, lets me add in a Sweet Mfg. servo inline with the steering column. I can power a hydraulic cylinder on the axle, which I think will give superior power steering and dampening versus just a PS box. It's also the simplest setup, and the one which I am certain offers good geometry. Anyways, it's pretty cool that a 62 year old Pitman arm will accept modern Chevy TRE's (not DRE's, surprisingly). Love it when things fit together like that.

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The axle has also been painted, just waiting on a few more seals before I put it all back together...

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...and I got some new seats! These are from a van, but will mount on an air suspension base from an International, Freightliner, etc. with a bit of work. It's been damn near impossible to find integrated belt seats around here. Very glad I got these, and a thank you to VanGuard in Toronto for the excellent service and price.

The current hurdle now is figuring out what tires go on this. That also may determine which rear end I use. Almost certain I'll go with a 14 bolt, but if I go with 11R22.5 wheels, that may change things. This is the bus on 37" Humvee super singles... I've mocked up the images so the tires are exactly to scale.

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I think these tires look good. Maybe a bit on the small side, but no real complaints. I'm mostly worried with how these tires would behave on-road versus, say, a 11R22.5 mixed-use commercial tires. I imagine I'd get a lot more life out of the commercial tires than humvee ones? Bottom line, I want 37" tires at minimum. Ideally 40" or so. Something good for a lot of paved roads, plenty of gravel roads or offroad, few highway miles, not planning on taking this past 100km/h...

The current options are:
1. Humvee tires, super singles, no adapters required, 14 bolt rear. Seems great, but, tread life?
2. 22.5 10-lug big truck, dually, adapters needed on front + rear if 14 bolt. No adapter on rear if larger Rockwell (e.g. RS152).
3. Some sort of 22.5" or 20" steelies with an 8x6.5 pattern. Could be dually or singles. I assume this would need to be custom made? Not aware of anyone like Stazworks here in Canada. There seem to be plenty of aluminum rims in that size, but I don't want to look like a massive mall crawler.
4. 40" Toyo M/T's. Tread life? Mileage on such an aggressive pattern?
5. Something else that I'm missing? Ideas???
 
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Baipin

Rank IV

Enthusiast III

Fabbed up (half of) this tube clamp/bracket and steering column today; the Sweet Mfg. orbital valve sits in the center, and controls a hydraulic cylinder on the axle to provide power steering. After the steering box gets reinstalled, I'll finish the clamp with an upper bracket to center the orbital valve about the steering column, add rigidity, and support the whole assembly on the original column mounts in the cab.

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I also welded on some rings around the grease nipples for the lower kingpins. Worth the few minutes of work to stop them from getting sheared off any rocks the axle may bump into... ;-) Saw this done on some tractor axles, and figured it'd be a good idea to try here!

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I've also settled the tire decision; humvee tires it will be. The newer BFG Military Baja T/A's seem to do everything I want; good offroad but not overly aggressive, beadlock, split, good on road, and in snow. I found a Chevy Viking chassis identical to mine with the older bias-ply humvee tires, and Photoshopped them to scale, onto my bus. I think tires any bigger than these would look a tad absurd...

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Baipin

Rank IV

Enthusiast III

Not much new stuff that's worth photographing. Front axle is about ready to go under the bus - just waiting on a couple of seals to wrap that up. Current focus is finalizing tire options. BFG Baja Humvees still seem to be the best option as far as tire age, condition, right mix on of and offroad manners, and cost, goes... I'll size 'em up in person on the bus this Friday.

In the meantime, here's what the completed power steering valve/column setup looks like:

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Old pic, but this demonstrates how it mounts. Hydraulic lines will be properly sheathed and shielded from the driver.

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Before I finalize tire options, I still have one other option: The 43" 11R20 Michelin XL's I'd consider putting on them would bring the weight per wheel/tire assembly to 190lbs with Hutchinson MRAPs. Think that's manageable for a Dana 60 front axle 4.56, drivehsaft with 1410's, NP205 32 spline front output, SM465, 283SBC? This would cost only slightly more than the Humvee tire option, adapter price notwithstanding (best I've seen is $190/ea from Western Canadian Rockwell).

My biggest concern is having the power to turn such large wheels - yes I will be swapping to a 6BT in the future, and have designed provisions for that into the build, but I'd like to drive this thing around with the SBC beforehand until I get the funds to do the swap right. Of course, these tires would be run as singles. I'm assuming that the weight of 2 military wheels + tires at 190lbs/ea. equals the weight of 4 of the original wheels + tires in DRW setup. They're 10" larger than existing and oddly small tires though... (33" rear 36" front)! In any case, my concern here is mostly with if the Dana 60 can handle it. I'm also not sure if such big tires are all that necessary when 37" humvees seem to do everything I want, aside from being a little small.

Thoughts?

For fun, here's a bus the same size as mine - but on a Dodge chassis - running the 37" Humvee singles:

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Baipin

Rank IV

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Humvee tires it is... with half an inch of diameter to spare on the rear lol!

The bus is sitting very low on wooden cribbing right now. When all is said and done the front will be about 6" higher up front and the rear will be 8" from where it's currently resting. They will be run as singles and the rear tire will be inside the wheel well. I was freezing my butt off and didn't want to bother moving cribbing around just to push the tire in a little more. :grin:

I have a Dana 80 (11,000lb GAWR) and a 11.5 AAM (9,750lb GAWR) lined up. Of those two, which would you go with and why? I'll be running some sort Detroit or selectable locker. The 10.5 AAM at 8,600lb would be too light for my needs.
 

Baipin

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Not much new to post at the moment... Been working over the winter, and I'm STILL waiting on brake rotors to finish putting the Dana 60 axle. Just impatiently waiting to bolt that thing up...

In any case, I've finished the twin sticked 205!

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Brushed the sticks by turning a sanding belt inside-out, chucking it in a belt sander, and keeping tension with the steel rods... It worked shockingly well lol.

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I used Princess Auto's miniature 3/8 NF rodends and some rod ends from a little tractor for the linkages. They work well!

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I also swapped out the slip yoke output for a much nicer, much stronger, 32-spline from RDP Xtreme/Precision Fabrication Plus. This will let me run a parking brake on the rear output. Any recommendations on calipers to use, would be appreciated. I'll probably end up fabbing my own bracket to bolt onto the bearing retainer.
 

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Baipin

Rank IV

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Would appreciate some input on this...

So, as those following this project may know, I have a SM465 and NP205. They have the 10-spline coupler in-between, as opposed to the 32 spline. I'm more seriously considering a diesel swap; I've made provisions for either a 4BD1T, 4BT, or 6BT. I'm really not looking for power here, mostly fuel efficiency, given that this is a bus and I will be living full-time in it. Highway cruising isn't important either, as I'd mostly be on country roads, dirt, or gravel (but I could get a brownie box overdrive if needed).

In any case, the SM465 is up to the task, especially if I swap to a 1.5" input from the current 1.125" one. (The bus originally came with a SM420). But, I'm worried about the 10-spline coupler between the T-case and transmission crapping itself. I've heard that the 10-spline adapter/shafts get worn down from a lead foot and sudden acceleration. I've also heard they don't like the torque from a 6BT (now, I'm not sure if they mean a stock or a tuned 6BT). On the other hand, I've heard of this combo living just fine behind 402 and 454 BBC's, towing well over my bus' weight of 14k or so, or turning 40"+ swampers in mud. I have no intentions of abusing this drivetrain like that. Can I expect to be fine? If not, what would the best alternative be? I've explored divorcing the 205, swapping to a 32 spline input. I've seen it done before successfully.
 

shortbus4x4

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I picked up a 78 GMC 3/4 ton years ago for cheap with a SM465 and NP205 combo, didn't move because that 10 spline coupler was no longer whole. I would probably go with a 6bt just because it's a bus and I think a 4bt or 4bd1t would be working pretty hard to move that load. If you're going to repower it down the road I would just run what your have for now, just keep a spare coupler on the bus.
 
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Baipin

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So I've decided on a 6BT. Reading some concerns on 4btswaps.com about the clutch size in the SM465 for a Cummins diesel, with a 14,000lb bus... I'm inclined to go with a 6BT + Eaton-Fuller trans and divorced transfer case. That means either divorcing the NP205 I currently have (anyone have a divorced input shaft to sell?) or selling the 205 and buying a Rockwell T136 (probably overkill with a Dana 60 front, Dana 80 rear, but I can certainly fit it).

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Testing out flex and looking for any steering linkage binding. So far so good. This is about 3/4 of the way flexed out. There's a lot more to go ;)

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Had this custom steering arm CNC'ed for me. Turned out fabulously!

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Also fabbed up my own springless kingpin cap for the opposite side. They work well! I've always heard that th Viking trucks had pretty good steering geometry, in spite of having such a short draglink compared to most trucks these days. There's surprisingly little bump steer throughout the entire flex of the suspenion, and I can turn full lock at minimum compression.
 
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shortbus4x4

Rank II

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Definitely go with the medium duty Eaton Fuller transmission and SAE bellhousing so you can run a big clutch. I would also go with the Rockwell transfercase if you have a line on one.
 
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Baipin

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Definitely go with the medium duty Eaton Fuller transmission and SAE bellhousing so you can run a big clutch. I would also go with the Rockwell transfercase if you have a line on one.
I can get a non-sprag Rockwell T136 for $650 shipped to my door, pulled out of a truck, or $1400 if it's rebuilt. I assume I can just do that rebuild myself, get serial numbers off of bearings and such as required. Know of any parts that may be hard to source for 'em? I'm yet to come across someone selling T-136-specific rebuild parts aside from the air shifter.

I don't feel too bad about running the 205 in spite of this being a 2 ton truck. I know of 3 Ford F600's with T223's swapped to 205's - one being an expedition truck - and 2 Isuzu NPR's with 205s. All as heavy or heavier than my build. Right now, it's the trans I'm keeping an eye out for, and I'm going to go divorced regardless.