Difference b/t GM and Rockwell 2.5 ton axles?? - Pirate4x4.Com : 4x4 and Off-Road Forum
 
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Old 03-23-2002, 10:24 PM   #1 (permalink)
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Question Difference b/t GM and Rockwell 2.5 ton axles??

Went and picked up a np435/205 today and the guy had a set of GM 2.5 ton axles sitting back in a field with some dry-rotted military tires on them. Said I could have them for $200. It was 1 front, 1 rear, and another rear with the hubs missing.

What's their worth compared to the rockwells?? What gears do they likely have?? Can you get rid of the drum brakes on the front?? I wouldn't use them right away, but I'd like to pick them up and hold on to them if that's a awesome deal.
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Old 03-24-2002, 01:25 AM   #2 (permalink)
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I can't tell you a monetary worth of GM 2.5tons, but i can tell you not to buy them if you are going to wheel. They are 3rd member style, not top-loaders, and so the ground clearance sucks monkey turds. Dunno much about the gear ratio either, sorry.
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Old 03-24-2002, 01:49 AM   #3 (permalink)
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dont those thing have like 20" ring gears?
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Old 03-24-2002, 02:58 AM   #4 (permalink)
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GM 2.5 ton have bigger axleshaft diameter( = 1.75" )than the Rockwells (= 1.62). BUT they are not top loaders, and this is actually almost the only reason why you would want such heavy monsters in the first place.
so, if you do'nt get an upper pinion entry to help with all that lift and tose nasty driveshaft angles, why would you want 650 lb of an axle to deal with?
oh, i forgot that with such an axle which has lousy ground clearance you can't have anything less than 44" which is another 220lb(a pair) per axle!!
coclusion = if you're not in for a huge monster, and if you can't live with the fact that you'll have at least 6000lb of a beasty weight(with the big block to go with it), just leave'm to rott there for another 20 years...
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Old 03-24-2002, 12:06 PM   #5 (permalink)
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GM 2.5 tons

The gear ratio is 6.17. NoSpin (Detroit Locker) is available. A guy with a built F250 named "Swamp Donkey" has them on his rig. He has a Powerstroke, ZF 5spd/Spicer 3053A 5spd/NP205, the GM axles and 11.00-20s
I think they are a bit lighter than Rockwells.
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Old 03-24-2002, 08:53 PM   #6 (permalink)
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I think that shafts are kinda weak for the size, too. A kid I know has a M211 (the truck they come outa) and it had 1 broke rear shaft and 1 broke stub shaft. The rear sheared off at the splines and the stub shatterd. I am not sure how hard it was beat on to brake em, but the way they broke,it seemed like the metal was weak.
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Old 03-25-2002, 09:55 PM   #7 (permalink)
 
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Also the GMC axles WILL NOT work with any of the transfer cases you might want to run, the front axle spins contrairy to most all other axles (front axle will go forward, rear will go in reverse and vise versa). These axles are virtualy usless without the GMC transfer case.

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Old 03-25-2002, 10:06 PM   #8 (permalink)
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That is one heavy transfer too!!, the thing looks like it weighs 1000 lbs, prob not that much, but still, it is only a single speed case too... (the low on those beasts is through the range box on the hydromatic 303) It still would make an intersting swap though. While there is a thread on old military axles, i have a few Q's, I can get a 40's or 30's IH 6x6, looks to be 2.5 ton, wonder if those axles are any better?? also, there is a old militray dodge dually in a local yard, looks 1.5 ton but I could be wrong, are those axles as tough as they look??
thanks
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Old 04-03-2002, 05:16 AM   #9 (permalink)
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Unhappy hmmm

Quote:
Originally posted by Junkyard Slug
Also the GMC axles WILL NOT work with any of the transfer cases you might want to run, the front axle spins contrairy to most all other axles (front axle will go forward, rear will go in reverse and vise versa). These axles are virtualy usless without the GMC transfer case.

JYS
so how is the guy with the above mentioned "swamp donkey" runnin em in his f250 with a 205?

not bein a smart ass,just wonderin how he made it work...
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Old 07-04-2005, 02:36 PM   #10 (permalink)
 
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2.5 ton gmc

as far as the rotation on the diffs. i am currently in the process of swapping in a set of 2.5 ton gmc axles. if you rotate the housing and flip the pinion over to where it is a high pinion it will spin the right direction. i am using a second t-case to get better driveshaft angles. all is going well so far.
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Old 07-04-2005, 07:36 PM   #11 (permalink)
 
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Quote:
Originally Posted by greengumbytruck
as far as the rotation on the diffs. i am currently in the process of swapping in a set of 2.5 ton gmc axles. if you rotate the housing and flip the pinion over to where it is a high pinion it will spin the right direction. i am using a second t-case to get better driveshaft angles. all is going well so far.
when you flip the diff the axles are the wrong length
one is to short and one is to long
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Old 07-04-2005, 11:11 PM   #12 (permalink)
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A guy on the M715 Zone has a set of M211 axles under his M715. He did the flip of the 3rd member. It takes a bit of grinding to get it to work, and one axle has to be cut and the other doesn't engage fully, if I remember correctly. It will work, but it is no where near the same as the more "modern" Rockwells. With all that in mind, unless the axles are free and you only plan to build a pavement cruiser, leave the axles alone. Also, nothing compares to the 2.5 ton Rockwells in the older trucks. Anything pre-'50s is going to be inferior as far as design, and metallurgy.
The only thing that might be better than 2.5 ton Rockwells is a set of 5 ton axles, and they are way too big, heavy, and just plain overkill in a rock crawler. Besides, where do you think you are going to find parts for a 60 year old axle? True, there are still a lot of them around, but it's not worth the effort when the aftermarket is supporting the 2.5 ton Rockwells and it's less work to put those in. Just my .02
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Old 07-05-2005, 12:01 AM   #13 (permalink)
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El, that guy is I think getting a set of Rockwells... a certain someone in PA has a set earmarked for a guy w/GMC axles in his truck currently.
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Old 07-05-2005, 12:12 AM   #14 (permalink)
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Quote:
Originally Posted by saprobe
so how is the guy with the above mentioned "swamp donkey" runnin em in his f250 with a 205?

not bein a smart ass,just wonderin how he made it work...
See for yourself, he has an extensive website, here:

http://hometown.aol.com/jzettel73/Swamp_Donkey.html
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Old 07-05-2005, 08:33 AM   #15 (permalink)
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Quote:
Originally Posted by tacoma73
El, that guy is I think getting a set of Rockwells... a certain someone in PA has a set earmarked for a guy w/GMC axles in his truck currently.
Ahh, cool. I was trying to convince my cousin to buy those for our next project, but he's not finished with his YJ yet, so he doesn't want to spend the cash. Oh well, there are lots more of them out there, but that wasn't a bad price though.
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Old 07-07-2005, 10:21 AM   #16 (permalink)
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Quote:
Originally Posted by convertiyota
Can you get rid of the drum brakes on the front??
Dunno if anybody else has found this, but I found that a 1994 Ford B700 bus rotor has the same Bolt pattern and seemingly everything required to fit onto a rockwell hub:

Outer Diameter: 15.38 in.
Height: 6.02 in.
Hub Register: 6.44 in. (Reo's are like 6.40'sh right?)
Bolt Size: .844 in.
Bolt Circle: 6x8.75

You'd have to run the hubs flipped out, unless I find the same rotor that doesnt have the u-shaped hat. Not to mention you would also need a fair sized rim unless by chance (due to backspacing) the rim would not interfere. Anyone else looked into this at all?

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Old 07-07-2005, 10:51 AM   #17 (permalink)
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If what you say is true, the rockwell overpriced disc brake business might be over!!
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Old 07-07-2005, 11:10 AM   #18 (permalink)
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Quote:
Originally Posted by Tim84K10
If what you say is true, the rockwell overpriced disc brake business might be over!!
Ya I was destined to find a rotor (took a while but I think I found it) I do have a full dimensioned pic of the rotor I'll scan and put up later, there seemingly 130 bucks a piece at napa part number: 86839 (I'm going to look today to be sure), havent gotten a caliper quote yet though (these jokers are 1.50" thick).

Scratch that napa had it wrong, cheapest I've found so far was on brakewarehouse.com part number AR-8971 for 180 a piece.
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Old 07-07-2005, 11:37 AM   #19 (permalink)
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Chevy D60 rotors are 1.5" thick too. Modding the brackets would likely bet the hard part. I don't have any experience with rockwells at all but I'm sure it can be done.

If so, I might have to get me a set of rockwells for a buggy in the future.
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Old 07-07-2005, 11:40 AM   #20 (permalink)
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Quote:
Originally Posted by Tim84K10
Chevy D60 rotors are 1.5" thick too. Modding the brackets would likely bet the hard part. I don't have any experience with rockwells at all but I'm sure it can be done.

If so, I might have to get me a set of rockwells for a buggy in the future.
You have an exact year and model with the 1.50" thick? It would help because the cheapest loaded caliper I'm finding so far is 163.99 (core added). Would help to take a simple trip to the local auto parts store.

Oh and the way it seems fabbing a mount off the Spindle bolts would be easy but I have to take a closer look
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Old 07-07-2005, 12:08 PM   #21 (permalink)
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I see what your talking about now, I'm so used to looking at C20 calipers (self supported bolt on), I figured C30's would be the same. I guess finding a bolt on caliper that accepts a 1.50" thick rotor.
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Old 07-07-2005, 12:22 PM   #22 (permalink)
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There will likely be no "bolt on".... the trick is to find a caliper that's going to easily mount to a flat plate that engages, on the other side, the 1/4" bolts that hold the spindle on.

Thanks for the tech on the disks up front. I found a very easy way to mount up 2wd F250 disks and calipers to a rear rockwell...

http://www.planetbantz.com/imghost/b...wellhubs_2.jpg
http://www.planetbantz.com/imghost/b...wellhubs_3.jpg
http://www.planetbantz.com/imghost/b...wellhubs_4.jpg
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Old 07-07-2005, 12:37 PM   #23 (permalink)
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i think the school bus to which you are reffering uses a rockwell axle.
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Old 07-07-2005, 01:03 PM   #24 (permalink)
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I as well came up with a way to mount a vaned rotor onto the rockwell hub. This process could also be applied to front flipped in hubs, but it would require a 15" vaned rotor (225 a piece).




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Old 07-07-2005, 01:04 PM   #25 (permalink)
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Oh and I think a 2000 Chevy C3500 is self supported bolt on, just want to look further into the piston size and rotor thickness.
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