Differential Strength - opinions wanted

I'm planning on doing a straight front axle conversion on my 96 Yukon - kinda fed up with the IFS stuff. Not only are the spring rates too soft with the stock torsion bars, but the lack of available locking
differentials is also a problem. It rides like a car, but I want more traction and durability out of my truck.
It's currently lifted 6" and has 35" tires. This truck isn't my daily driver (though I do drive it quite often), I use it for trail driving around Colorado and Utah, over lots of rocks/ledges/etc, and I want some serious reliability. I'm OK with going a little overboard here - I'd rather get there and back, than have to walk out or get a ride because something broke.
I've read that for the front, a Dana 44 or Dana 60 out of an older Ford is the way to go, and a Dana 44 that is beefed up with aftermarket parts is about as strong as a Dana 60 is stock. For the front, I'm going to try to find a high pinion Dana 60, so his brings me to an 8 bolt front end, which should be pretty robust.
What should I do about the rear? I have the stock 10 bolt in there now, with 6 bolt axles. Since I'll be swapping this out to get 8 bolt wheel pattern in the back, I'm looking for advice on what diff I should consider for the back end. Should I look for a Dana 60 that is roughly the same width and alter the spring perches? I'd imagine that a 14 bolt out of another GM truck would be the right width and might bolt right in, but not knowing anything about those rear ends, what should I look for? Are some years stronger/weaker than others for the 14 bolt diffs? Does the 14 bolt have the same wheel bolt pattern as the Ford Dana 60 I'm going to put up front? From what I've found on the net, some of the 14 bolt rear ends are pretty strong, but I haven't found many details regarding what trucks/years the good ones came in.
I know that many of you have done rear end swaps before, and I welcome your comments and opinions on this.
SuperDave
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I've been doing a lot of studying and asking questions about this stuff... I'm no expert, but I'll give it a shot.
First off, as far as your rear axle goes, I'd go with the 14-bolt. They are strong, plentiful and cheap. There's a guy that rebuilds them up north (from me anyway, I'm in Atlanta) and he sells a rebuilt 14-bolt minus the brake parts for $385. He sells them on eBay although I have his number if you'd like. He's set up to ship with truck lines and quoted me a price of around $115 to ship it to Atlanta. $500 for a rebuilt and very strong axle isn't bad at all. In short, a Dana 60 won't have the strength, will be harder to find, and will cost quite a bit more.
For years the only locker most used in 14 bolts (about the only good one available) was the Detroit Locker--an auto-locker. ARB now makes a selectable air locker for the 14-bolt.
In reference to your question about which years the "good ones" came in, I'd say there's not a whole lot of difference. The biggest difference will be in which type of vehicle they came out of. For instance, an axle from a pickup or Blazer is going to be more narrow than one that came from a Van. But a Van's axle isn't as wide as one that came from a dually. The distance between the spring perches may vary slightly, but given all the work you're considering having done, relocating them should be a minor inconvenience. Just find one that's been professionally rebuilt, or at the very least inspected by someone who knows what to look for.
Do be aware that there are 2 completely different axles that use a 14-bolt cover. The semi-floating, and the full-floating. You can pretty much assume one is talking about the stronger full-floating design unless they specify otherwise.

sound like you do a lot of real serious off road driving (rock crawling and mud racing). 35" tires aren't huge, but not particularly small either. Yes, with stronger axle shafts and upgraded u-joints a Dana 44 can be upgraded to be nearly as strong as a stock Dana 60. It seems the article I read involved swapping the knuckles out with aftermarket units to accomodate the bigger u-joints. But keep in mind that those parts are intended for perfomance, and with that performance comes a premium price. That route seems best for those who already have a Dana 44 and want the added strength, but don't want to sacrifice its ground clearance and lower weight. All I'm saying is, a stock Dana 60 may cost the same and require less work than buying a 44 and totally reworking it. As for the difficulty of installation, if you're setting the front end up to accept a solid axle, then either should bolt right in provided you stick with GM spring spacing and use a GM-spec'd axle.
I'm not 100% certain, but I'm pretty sure the the front output shaft on the transfer case is on the driver's side on newer model GM trucks. I don't know if that applies to your truck or not. The Ford axles you're speaking of are indeed a high-pinion design, which adds strength (because of the way the gears are cut) and improves the angle of the driveshaft, leading to less vibration (and hence less worn parts). However, if your front axle connects to the transfer case on the passenger side, you'll either have to stick with a GM axle or swap the transfer case with a Ford-style case with a driver's side output shaft.
One axle I'm not too familiar with is the GM 12-bolt. It's beefier than a 10-bolt, fairly cheap, and has a bigger ring gear than a Dana 44. I cannot speak for its strength vs. a Dana 44 or 60, but I'd imagine it's worth investigating. In fact, mentioning this kinda has me wondering. I'm going to look into that option and I'd advise you to do the same.
Personally, I'd vote to go with a Dana 60 front and GM 14-bolt (full floating) rear. It's a well proven combination of parts, and there's plenty of aftermarket support for these axles.
Good luck in your search, and let us know what you decide and how it turns out.
~jp / '86 K5 Blazer
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My truck has the drivers side transfer case output - so a front Dana 60 (or Dana 44) from a 77 to 79 Ford pickup will fit perfectly - even the spring perch width is almost ideal.
I don't do any racing, or serious mud with this truck, but I have done lots of rock crawling with it - with this height and because it's a 2 door Yukon, it has pretty good approach/departure angles for a bigger truck. I don't plan on going much higher with it, maybe another inch or two, and probably 36" tires when these ones wear out.
Thanks for the details JP. I'm going to look around locally to see what kind of $$ a 14 bolt rear end goes for. If all goes well, maybe I can get one with the right spring perch spacing for a reasonable price. Depending on what I find out, I might ask you for details on that diff rebuilder in your area.
What are the newer GM trucks coming with for rear diff's now? They have disk brakes on them and might be a good swap as well...
SuperDave
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Where are you located Dave? After reading my own post I see that I wasn't totally clear in my wording. The guy that sells the rebuilt axles is in Wisconsin.
Here's a link to a 14 bolt he has for sale right now. He has plenty of them. This one is only $285. http://cgi.ebay.com/ebaymotors/CHEVROLET-GMC-TRUCK-14-BOLT-ROCK-CRAWLER-3-73-REMAN_W0QQitemZ8021005995QQcategoryZ46104QQrdZ1QQcmdZViewItem
Again, the spring perch location may not be a big deal. I'm not sure what the differences are between Ford and GM spacing, but I'd stick with a GM spacing for compatibility's sake. Who knows, one day you may decide to sell the truck and may not want to get rid of your nice 1-ton axles! It would be easy to swap in a set of10-bolts (especially if you keep your existing rear).
Keep in mind that 15" wheels may not have enough clearance for the disc brakes on a Dana 60 front end. You may need to grind the calipers or get 16" wheels. Unless your new axles have a 6-lug pattern, you'll need new wheels anyway. I've never seen a full-floating 14-bolt with 6 lugs, although the weaker semi-floating axle was available in a 6-lug version. I suppose a custom job is possible, but it wouldn't be worth it to me. Just spring for some nice 8-lug 16" wheels. I'm eyeing the American Racing Mojaves. They're simple yet tough looking to me.
I like those 2 door Yukons...sorta like the younger brother to the K5 :-)
~jp
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Also, you might find this info useful:
http://www.coloradok5.com/axleguide.shtml
~jp
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SuperDave wrote:

    If you want to spend the money on a good axle, go with a Dyna-Trac 60. They will build to specs. You can get high pionion. I would use a 60 Rear or a 70 Rear from them with Disks.
    Either a E-Locker or a Air Locker up front, and a full time Detriot Locker in the rear.
    Little Remembered fact about 88 UP C/K Trucks. The 1992 UP till 2000 3500HD trucks came with a solid front axle and leaf springs. Even 2WD trucks, 2WD's even use a steering stabilizer. They did make 4WD 3500HD's with Rockwell axles from the factory. The Differance between a 3500HD and a regular pick up frame is thickness, and rail height.
    What you can start with is 3500HD Steering Gear, leaf springs, shakles, and spring hangers/frame perches. Best bet is to get a frame cut from a salvage yard. From what I recall the 2WD and 4WD HD's used the same srpings, frame mounts, ect. I beleave they use the same steering gear as well.
Charles Yes I miss my old 93 3500HD 2WD with a 6.5TD and a NV Low+3+OD. Poor old truck still lives, over 600,000 miles. Rode so hard the frame snapped on the drivers side. Yet some inbreads patched her up and still use & abuse her.
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I'd love to go with Dynatrac, but they want $3k for a Dana 60 rear, with drum brakes and no locker. By the time I get a locker in there, disks, and have it shipped, it's probably around $4500 for the rear end alone. I WISH I had $10k to spend on a set of axles...
I also don't have the garage space and the tools to fabricate what I'd need to build the brackets needed to get the 3500 running gear in place. I get pretty jealous when I watch Stacey build all those toys on the show Trucks. I was planning to get some front end brackets from Off Road Unlimited. The brackets are pretty pricey, but I'd probably end up spending that much trying to engineer them myself.
SuperDave
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SuperDave wrote:

    Other then a 10 inch frame vs a 8 inch frame, all the 3500HD (big differance in 91 to 99 HDs vs regular 3500's) is bolt in stuff. You might have to add a mounting plate here or there, but that's about it. Charles
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Actually, I've already got a set of the 16" American Racing 6 bolt rims with the black beadlocks. I really like the look, so I'll probably spring for a set of them with an 8 bolt pattern. I'll dig up a pic and post it somewhere one of these days.
Charles, are you talking about the front or the rear end? I haven't looked at any newer GM 1 ton 4x4's. Is the pumpkin on the passenger or drivers side of the diff on the front of those trucks?
I've been asking around, and I've found a couple of corp. 14 bolt rear ends, and the spring perches aren't the right distance apart. The ones I've found are 40.5 and 42.5 inches apart, and the 10 bolt in my truck now has them spaced at 44.25 inches apart.
I would think that a 14 bolt out of a newer Suburban should be a bolt in, it would make sense to me that GM would use the same size part, same sized frame, etc... especially since the body style is nearly identicle.
I haven't even started looking at the entire width of the assembly yet. I'm hoping that the width differences between the different trucks is minimal.
SuperDave
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SuperDave wrote:

    You have a Yukon which means it's a 1994/1995 and up truck. Which is the same body type as the truck I was talking about. Im not sure what side the Front rockwell axles gear set is on. You could just use the suspension and any Front GM or Dana axle that has the gear set where you need it.
    Any 88 to 98 10.5 inch 14 bolt rear end should bolt in as long as it's not a dual rear tire rear end. Charles
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Charles Bendig wrote:

No need to go to the 10.5, you can used the much overlooked 9.5 inch 14 bolt semi floater. They can be found with 6 lugs and are about the equal of a D60 in strength and far stronger than a stock 10 bolt. Actaully in my opinion, GM should srape the 10 bolt is full sized 4x4 because it is the smallest rear axle used in any such truck from detriot and really too light for a 3ton truck with 31 inch tires.
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TheSnoMan wrote:

    My 91 C-2500 (7200GRVW) has the 9.5 14bolt 6 lug. I have seen them under 1/2 ton 88 and up trucks where someone has replaced a 10 bolt. Both in 2WD & 4WD trucks. Charles
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Since I'm going to an 8 bolt pattern in the front, I'll want an 8 bolt pattern for the rear as well.
What would be the advantage of the 9.5" units? Are they any cheaper than a full floating 10.5" unit? I have found a few locker options (Detriot and the ARB) for the 10.5" units. Are these also available for the 9.5" units?
I'm going to call a few wrecking yards today to see what's available.
SuperDave
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SuperDave wrote:

There are a lot more locker options for the 9.5, a weigh about 75 pounds less and it has more clearance too. It is solid up to 38's or so even with a locker. It is about a even match with a D60 in strength. Not to say a 10.5 is a bad axle, it is just over kill most of the time. (they have had ARB's for 9.5 for over 2 years too)
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