2.5 Rockwells is anybody running these

Overland Suburban

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I've taken a big turn in my build and have decided to make a snow wheeler out of my 89 suburban! My plan is 2.5 rockwells with Detroit lockers on 54 mickey Thompson's. There are a few things I would like to get some advice on and that is what to run for transfercases as I want to have as low of a low, low, first gear as possible. The other advice I'm looking for is what springs to run that will work with the torque 54" tires will produce and I will also need a lot of flex. Thanks for any ideas or advice
 

Vbb199

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Best bet on a transfer case will be a drop transfer case, like from SCS, profab, chain reaction or whoever you choose. I still have my old 18" drop case from my 5 ton k5 project. 1.55:1 with a 4:1 change-out

Using even a divorced np205 is out of the question at that much height.

Unless you run twin 205's with a bunch of fabbed up hangers.
You must be registered for see images attach

Take note, straight thru cases will be divorced unless you buy from SCS who sells adapters to marry them to a transmission.

Chain reaction, profab, etc are all divorced, meaning you'll need to run a jackshaft after the trans to drive it.

Meaning, you'll need a 2wd trans if you run divorced.

If you have any knowledge with automatics, that's easy enough to do, simply change output shafts and put a 2wd tailhousing on.
Would no advise running a 700r4 with 54" tires and 2.5 tons. It's gonna hate life in real short order unless you run like, 2 external coolers with electric fans on them

Since gas mileage has now exited the chat, you'd be better off with a stout 2wd th400, deep pan, and cooler. HD sprauges, etc.


2., any and every spring you run will have deflection at that height.
If you're wanting to run leaf springs, Trac bars are you friend. I can also send pics of what I was doing to give you ideas.

Suburban and k5 frames get weak in the middle under big tire, big axle stress, and Crack and break.

You'll need to weld up a sub frame for
A. Cradling the transfer case
B. Adding strength to your frame
C. Having something for the Trac bars to run off of.
D. Optionally, a step to climb up in it.

I welded up a subframe out of 2.5"x.250 square tube.


3. I figure this is my time to make a sales pitch.
I have some 24" lift springs. They're what's setting the k5 above 53's. Carrier LTD springs. Thats real deal sheit. Google those and you'll find their purchase price is around 3500.

I never actually got to use them, as I never finished the k5. I took it all apart and sold it. So...... if you are looking for a cheaper option on lift, 2500 bucks takes all 4 of them. That's mega cheap for that much lift.
I can send all the pics you want, video chat with you, whatever you need and palletize and ship them to you via whatever carrier you like.

Something to think on :)

They do actually have a little give in them. Believe it or not.


I have a contact for military surplus if there is no yards near you.

He sells his stuff cheaper than any other person I've met.

He's got a yard out in California.
But home base is in Florida.

He delivers, if you pay for drive time.
He sells detroits if you are wanting them.

If you're new to this mega truck stuff, I can recommend multiple names and contacts for parts and such, cheaper than the average red barn customs ripoff.


They're too proud of a bunch of heavy ass **** hardly nobody messes with.

The aforementioned contact in florida will sell all sorts of axles. Whatever you like.
Meritor, axletech 5k, Rockwell 2.5 ton, Rockwell 5 ton, Rockwell 7 ton with airlockers.
Clark 20 tons, Pettibone. Whatever you need !

I also have information stashed back on how to 4 wheel disc brake swap your 2.5 tons with part numbers and info.


Also, do yourself a favor and get 1 inch drive stuff.
I did.

I have sockets that go up to 4" in inch drive stuff. Just for the said heavy axles


Steering is another.
You'll need to plan for you're gonna do it.
I can guide you in the direction of DIY hydraulic assist or, just get the money for real deal full hydraulic steer from PSC.

Stock steering gear with no hydraulic assist won't cut it. It will L I T E R A L L Y rip the steering box off your frame.
I've seen it already.


Powerplants.

Unless we're returning back to 1965 where we used millions of gear reduction boxes and cases and 10 speed transmissions with a motor that made a whopping 180hp, you'll want a good healthy motor to lug all that.

And no, that wasn't an insult, lol I just mean there's two ways to move that rig.

Raw torque and gear reduction, or LOTS and LOTS of gear reduction.
 
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Vbb199

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More information for you,
A Rockwell 2.5 ton with be a 6.72 gear ratio.

I don't think there's any variations of that. That's what you get unless you got a fat wallet to pay Overson engineering for custom 2.5 ton 3rd members that are setup with other gear ratios.
They'll cut whatever gear set you want, but their hustle is, you have to buy their fancy aluminum or iron 3rd members to house the gears. Probably bs, but I don't know.


5 tons however are 6.44, but also came in 10.24 (missle carrier trucks), and there's some civilian trucks that had more friendly gears like 3.73, 5.xx etc.

The cool 7 ton ones I mentioned have airlockers as standard equipment, they're yellow. Sometimes red.

That's a little more info for you.

2.5 ton stuff has SOOOOOO MUCHHHH aftermarket support with ARB air lockers, detroits, aftermarket axle shafts, planetary conversions, bull gear saddles, pinion brakes, and what have you. But it's expensive, because they're the more popular axle.

There's ball and claw, rhezzpa joint, and sometimes, u joint axles.

The u joint is the most desired. Rhezzpa joint (think early CV) is the next favorable one.

Ball and claw is the most common, they're not necessarily crap, but it's STRONGLY advised when you get your pair of axles to cut the weld on the steering stops , and unscrew them some more.

The big breaker of ball and claw axles is oversteering, or sharp turns, which binds them, ESPECIALLY with a detroit.



I dunno what's what in 2.5 ton trucks, but you'll also probably want to get a hydraulic drum brake Rockwell.
The airbrake type aren't as easy to really run, and I believe they don't allow for you to flip the hubs inside out to run a wider track width. At least thats how it works with 5 ton. I think also in 2.5 ton.

I know the 900 series 5 tons are non reversible hubs (air brake)
And the 800 series 5 tons are reversible hubs. (Hydrualic brake)

Maybe with a little digging on the web you can find out which series duece and half trucks had hydraulic brakes.


the hydraulic drum brake type will be able to be flipped out on the hubs. Meaning you can literally take the hubs off, and put them on backwards

Speaking of, if this rig will never see the road again and 4 wheel disc isn't your thing, I can recommend a cheap source for pinion brakes for the 2.5 tons, or 5 tons. All you need is chevrolet 3/4 ton front calipers.

Just please do not run it on the road with pinion brakes.

The shaft spins 6.72x faster than the axle, and when trying to stop a load that's say, 10,000 pounds, at 3500 rpms, that means that cheesy ass brake is stopping a rotor spinning 23,000 rpms.
It'll fade, glaze, and in some cases, explode from overheating.

It's no joke. In most states, the patrol man would immediately flag that **** anyways. Trust me.

Not to mention, if you can successfully stop a 23,000 rpm brake rotor, it'll send you thru the windshield because that's stopping driveline. Not tires.

Also trust me on that. You'll want a proportioning valve to turn the brake pressure back on pinion brakes so you don't fly out your seat.


I'll keep posting and adding stuff as I think on it.
I've already edited the last post 6 times now.
 
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SquareRoot

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More information for you,
A Rockwell 2.5 ton with be a 6.72 gear ratio.

I don't think there's any variations of that. That's what you get unless you got a fat wallet to pay Overson engineering for custom 2.5 ton 3rd members that are setup with other gear ratios.
They'll cut whatever gear set you want, but their hustle is, you have to buy their fancy aluminum or iron 3rd members to house the gears. Probably bs, but I don't know.


5 tons however are 6.44, but also came in 10.24 (missle carrier trucks), and there's some civilian trucks that had more friendly gears like 3.73, 5.xx etc.

The cool 7 ton ones I mentioned have airlockers as standard equipment, they're yellow. Sometimes red.

That's a little more info for you.

2.5 ton stuff has SOOOOOO MUCHHHH aftermarket support with ARB air lockers, detroits, aftermarket axle shafts, planetary conversions, bull gear saddles, pinion brakes, and what have you. But it's expensive, because they're the more popular axle.

There's ball and claw, rhezzpa joint, and sometimes, u joint axles.

The u joint is the most desired. Rhezzpa joint (think early CV) is the next favorable one.

Ball and claw is the most common, they're not necessarily crap, but it's STRONGLY advised when you get your pair of axles to cut the weld on the steering stops , and unscrew them some more.

The big breaker of ball and claw axles is oversteering, or sharp turns, which binds them, ESPECIALLY with a detroit.



I dunno what's what in 2.5 ton trucks, but you'll also probably want to get a hydraulic drum brake Rockwell.
The airbrake type aren't as easy to really run, and I believe they don't allow for you to flip the hubs inside out to run a wider track width. At least thats how it works with 5 ton. I think also in 2.5 ton.

I know the 900 series 5 tons are non reversible hubs (air brake)
And the 800 series 5 tons are reversible hubs. (Hydrualic brake)

Maybe with a little digging on the web you can find out which series duece and half trucks had hydraulic brakes.


the hydraulic drum brake type will be able to be flipped out on the hubs. Meaning you can literally take the hubs off, and put them on backwards

Speaking of, if this rig will never see the road again and 4 wheel disc isn't your thing, I can recommend a cheap source for pinion brakes for the 2.5 tons, or 5 tons. All you need is chevrolet 3/4 ton front calipers.

Just please do not run it on the road with pinion brakes.

The shaft spins 6.72x faster than the axle, and when trying to stop a load that's say, 10,000 pounds, at 3500 rpms, that means that cheesy ass brake is stopping a rotor spinning 23,000 rpms.
It'll fade, glaze, and in some cases, explode from overheating.

It's no joke. In most states, the patrol man would immediately flag that **** anyways. Trust me.

Not to mention, if you can successfully stop a 23,000 rpm brake rotor, it'll send you thru the windshield because that's stopping driveline. Not tires.

Also trust me on that. You'll want a proportioning valve to turn the brake pressure back on pinion brakes so you don't fly out your seat.


I'll keep posting and adding stuff as I think on it.
I've already edited the last post 6 times now.
Vince, you ever consider switching to decaf? lol
 

Vbb199

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Vince, you ever consider switching to decaf? lol


lol right.

It's just this sort of information isn't readily available out there. You either gotta do it yourself, or spend weeks upon weeks falling asleep at the computer reading and learning about the do's and dont's

I figure if I give the man a good head start on information, he'll be better off than I was when I began. There's not a lot of forums/writeups out there about such big axles and the physics involved. Some people just bolt on a set of the axles with 12" tall lift blocks and tractor tires and then snap a frame in two sadly.
 

Overland Suburban

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Vbb199, thanks for all that info it will most certainly come in very useful! I do fully understand the torque that 54" tires with that type of running gear will generate. I'm planning DIY hydro assist steering so will probably send you a PM when I'm getting started. My plan is mostly rounding up parts all year and building next October when work gets slow. Thinking I may do a DIY 4 link with the front axle so I can get some flex which is important for the type of snow wheeling we do. Power isn't a big part of equation with wheeling in 15ft of snow. It's slow and low,low gearing. The sluggish 350 tbi will actually be perfect for what we do. You gave me a ton of info I can use so thank you so much it is very appreciated! I have a lot more thoughts but no time to post everything right now but wanted to chime in to say thanks
 

Overland Suburban

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Also forgot to add that I won't be even close to as tall as your project. My fenderwells will be cut bigly and I will only lift as little as is needed to fit things underneath. I'm planning to set up suspension mostly for downtravel
 

Dooley

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Plenty of time spent with Rockwells, just not under civilian vehicles.
I can tell you that my 4x4 gps' out at 74 mph with 47" Goodyears on paved road.
I have room for 1600's which are 53 inch but, it kills the power on grades while holds speed good with the smaller tires.
For serious off roading definitely need lockers in rear and front if you also install lockout hubs for 2 wheeling down the road.
AFTERALL, HOW HIGH DO YOU NEED TO GO, EH!
 

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ballencd

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What about putting your Suburban body on a M35 frame? That would be the easiest thing to do and probably cheapest too...?
 

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