1959 GMC Bus - 4x4 Build | OVERLAND BOUND COMMUNITY

1959 GMC Bus - 4x4 Build

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Baipin

Rank IV

Enthusiast III

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

Rank I

Enthusiast I

193
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

Rank IV

Enthusiast III

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:

Instagram Video
 

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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