Squarebody Differentials.

[Buicknut]

To the best of my knowledge, just stronger carriers like Detroit Locker or ARB, and chromolly axle shafts is about all I'm aware of. The later 10 bolts, I think 89 up, not positive on that so check to be sure, but they have 30 splines instead of 28 for what it's worth. You can go with the 30 spline axles in the earlier axles too but have to use the 30 spline spiders to match. However, the axles are the same thickness so they snap just like a 28 spline would, so unless you're having a problem shearing splines off, the 28 spline is just as strong/weak.

The good news is, many people look at a 10 bolt as a POS and as plentiful as they are, you can usually pick up a spare 10 bolt for next to nothing. I've seen them from haul it off for me, to $25, $50 and $100. Not bad to scoop one up if it's cheap and throw it behind the shed for a spare set of axles, stub shafts, carrier, hubs, knuckles or whatever, and the gear ratio doesn't matter if the purpose is just spare parts. I'll be keeping this 3.08 open front 10 bolt that's coming out of my K10 just for spare parts after I swap in the 10 bolt set up with 4.10's and ARB Air Locker.

So, is it true that the 89 up K5s have 30 spline axles? And if so is there a way to tell this from the outside as to whats inside?

 

[Radiohead]

Sure enough. Go ahead. Just do it. Try to break it. It'll hold up just fine. Provided it's in good shape, and most are up to about 500,000 miles or more if kept full of good oil, you'll break a transmission or transfer case before you break the rear end in a 14b Full Floater. Yes, the Full Float is stronger. About equal to a Dana 70.

Burnouts. Lots of burnouts. I see lots of burnouts in my future after reading this thread.

 

[HotRodPC]

So, is it true that the 89 up K5s have 30 spline axles? And if so is there a way to tell this from the outside as to whats inside?

Sorry noone answered this way back then. But yes, I do believe it was 89 when the 10 bolts went from 27 spline to 30 spline axles, but to the best of my knowledge, there is no way to tell from the outside. If you can decode the axle and find that's it's an 89-91, it may be safe to assume it's a 30 spline since I don't see anyone taking the time to downgrade it to a 27 spline. Also, I do think the axles are backwards compatible also. So you could put 30 spline axles in your older 10 bolt, but you'd also have to use 30 spline outer spider gears and being usually a matched set, you'd have to buy a complete 30 spline set of spiders or 30 spline Limited slip carrier or Locker. However, I don't really see the point, since MOST times the axle break, it's not at the splines so the 27 spline is probably just the same. It's not like the 30 spline is thicker axles. Just a bit finer splines is all.

 

[voodooskin]

Hopefully this works I don't post a lot.

My 1985 GMC K2500 has the below. My counting skills allow me to guess this is a 14-bolt. The pumpkin, she's a'leakin just a bit, for how long no idea. Purchased from my boss 2y ago. Guessing just the seal but to be honest I've never worked on a diff. (Broken plenty of other stuff on mechanical things though doing routine maintenance ). Where's the fun if you learn from your mistakes?

If this was a real easy "drain the oil, unbolt the bolts, buy a gasket off rockauto, reassemble, fill with gear oil" I'd probably try to do it myself. But if this is a "Well, you might have a dana model foo or you might have a corporate model bar there count the gears do the math see if the cover is rounded or less rounded" its going to a mechanic.

I do have a shudder while driving so something between engine and wheels is not happy. Open to your thoughts.

My concern with a professional shop is who the hell knows anymore how to work on the legacy stuff, they might just quote me an entire new rear end from GM at 4K rather than figure out the issue and charge me for a relatively minor service.

Thanks all!

 

[HotRodPC]

Hopefully this works I don't post a lot.

My 1985 GMC K2500 has the below. My counting skills allow me to guess this is a 14-bolt. The pumpkin, she's a'leakin just a bit, for how long no idea. Purchased from my boss 2y ago. Guessing just the seal but to be honest I've never worked on a diff. (Broken plenty of other stuff on mechanical things though doing routine maintenance ). Where's the fun if you learn from your mistakes?

If this was a real easy "drain the oil, unbolt the bolts, buy a gasket off rockauto, reassemble, fill with gear oil" I'd probably try to do it myself. But if this is a "Well, you might have a dana model foo or you might have a corporate model bar there count the gears do the math see if the cover is rounded or less rounded" its going to a mechanic.

I do have a shudder while driving so something between engine and wheels is not happy. Open to your thoughts.

My concern with a professional shop is who the hell knows anymore how to work on the legacy stuff, they might just quote me an entire new rear end from GM at 4K rather than figure out the issue and charge me for a relatively minor service.

Thanks all!

So it's likely a 14B Semi Float rear axle unless it's a Big Block truck then it got the 14B Full Float. As far as your shudder, the rear axle is the last thing I'd consdier. If the rear axle was having issues it's more than likley going to be a howling issue at about 40mph and faster. In your case, I know some 3/4 tons did get a 700r4 transmission. Torque Converter Lock up converter clutch is more common for a shuddering type issue. Next, I'd consider checking your engine, Tcase and transmission mounts. You don't have a carrier bearing since it's a K2500 Fo Buh Fo right? If you do, I'd be checking the carrier bearing also, but that's going to be if it's a Tuba Fo Drive as in 2x4 2 wheel drive. Keep us updated, what you find out.

EDIT: I didn't realize you're a newb guy. Welcome Aboard. Or I probably wouldn't have used the slang for 4x4 and 2x4. Hopefully you get it. Sometimes, we're not always upright around here.

 

[voodooskin]

Thanks for the info! My GMC is a 2WD with a 5.7L (350) brand new(ish) factory crate motor*, everything else in the truck has been around a while. TH400 trans IIRC.

Yes, new here and glad to find the forum. I'll post up when I know more whats going on.


* the PO's kids drove it but never checked the oil with results you might guess, he put in a factory crate then sold it to me