Sometime on or before 2015 GM stopped putting FF axles on the 3500. My 3500 has a 9.5" 14-bolt SF which surprised me to. Best I can tell with RPO codes it came from the factory like that. I'd rather have the FF but not bad enough to swap one in.

Edit: This is what a 9.5" 14-bolt semi-floating axle looks like.

 

even if you size the axle shaft diameter large enough?

 

learn something new every day.

is the cargo capacity the same? they must have done something for the axle to support 1ton.

 

GVWR 9600 lb
GAWR Frt 4300 lb
GAWR RR 6084 lb is what my sticker says.
2015, 3500, 6.0l, short wheelbase

 

I had a 95 1-ton G30 and it had the semi-floater. Like a 3.23 ratio in it too. Nothing new under the sun.

 

Just got a replacement rear axle. It came from a 2013 with only 51k on it. It was a church van, didn't get beaten. I'd normally do the replacement myself but my current place doesn't have a suitable driveway. I could probably improvise and get it done, but I'm worried about the weight of the axle. Last one I did was a ford crown vic and that was a much smaller, lighter axle. I'm wondering if this one will be too hard to manage with only a floor jack (or 2 floor jacks). Also a bit different with the leaf springs - would I remove the leaf springs from the hangers or remove the axle where it bolts onto the leaf springs?

 

I've done it a few times before on various vehicles. Get some tall sturdy jack stands and new u-bolts/nuts. It isn't that bad but you do need it to be high enough. Unbolt the axle from the springs. Toss the old u-bolts. Re-torque them after driving a bit. The axle is heavy but wheeling it underneath on a floor jack is easy. It's getting it on the floor jack that is the hard part.

 

Very belated (my apologies!) update from 2023:

Just realized I had forgotten to update this thread for anyone who may be experiencing similar issues. I have a good local mechanic with a full shop. I cleaned up the donor axle and took it to him. I had him replace the outer axle seals and pinion seal for good measure since it has 51k on it and this will be the easiest time to do it. He did the swap and replaced the fluid, cover gasket, and u-bolts. Got the van back and it feels totally different, so the old axle was definitely not right, as we suspected. The oscillating vibration is completely gone and the entire driveline feels more "precise". Not sure what had been done to the old axle in the past but this is a huge improvement.