Been searching all morning and haven't seemed to find all the information I'm looking for. I have a 2000 Silverado 2500 with the 6.0 4L80 drivetrain and I'm still running stock suspension and tire size. This truck is used almost exclusively for towing my 10k trailer. It gets the job done but it could be better....so here I am....trying to fix something that isn't broken.

Quick caveat... I'm very familiar with most axles and I've even done several gear changes but I'll admit that I had to do some digging to figure out what this GM 9.5 rear axle was. Anyway, I was planning on pricing out the difference between a gear change and just a junkyard rear axle with the gear ratio I want but have hit too many unknowns. I think ideally, the Corporate 14 bolt axle would be a considerable improvement over the GM 9.5 but I don't know how necessary it is for just towing on the street. Looks like I could pick up a 14 bolt for around $350-$500 with the 4.10 gears and the GM 9.5 would be similarly priced. I think re-gearing would also be fairly similarly priced to buy new gears, bearings, etc and do the work myself BUT... I have to do the work which is no small task and I'll have to drive the truck around for a while to break in the new gears before towing with them which is more costly than driving around my normal car which gets double the mpg.

Here are my thoughts/questions on the axle swap:
Did all the GM 9.5's come with disc brakes or do I need to worry about getting one with drums?
Is it worth getting another GM 9.5 or should I just go straight to the Corporate 14 bolt with prices being so similar?
If I do go Corporate 14 bolt, what all needs to be replaced in order to make it work? Bigger u-bolts or cradles? Different driveshaft? Different brake lines? Different wheel bolt pattern?
Did the Corporate 14 bolt come with drums in the Silverado's?

Here are my thoughts/questions on the gear swap:
Similar cost to axle swap with gears and master rebuild kit but more work and more time/money to break in the gears.
Could go to 4.56 gear for the same price but I feel like that's overkill since I'd be running around 2900 rpm's at 75mph. Maybe it'd be better since I'd need less throttle but I feel like this is splitting hairs and fuel economy will be much worse.
All the brakes, axle bearings, and u-bolts will be untouched.

 

I guess everything from Silverado's 99+ was considered a 14 bolt which appears to include a 9.5", 10.5", and 11.5" ring gears. From the looks of it, the 9.5" was the only semi-float axle and the 10.5 and 11.5 were both full float.

 

How far is the towing when you do it and if is just street towing and local, you have all you need. What are you tow rates for your rig and what is all the trailer weight amounts? Are you exceeding rates? I could look it all up but it is your rig, so you look it up.

Spring perches may have to be moved. If use a 14 bolt you have to see what brake differences you have as far as master cylinder and calipers/pads. Hell, it is all doable. I had a 1973 Blazer that I set up for severe four wheeling and I had a 14 bolt under it and a Dana 60 at the front and I had to experiment with master cylinders to find the sweet spot. I am assuming you have hydro boost as well. Again, I did not look.

 

Shortest trip is about 75 minutes away and mostly highway while the longest is around 6-7 hours on the interstate. Average trip is 3-4 hours on the interstate with maybe 10-20% on 45-65mph back roads.

I'm well within my tow limits and the trailer averages around 8000 lbs. Yes I have hydroboost.

I'm very familiar with swapping axles and matching brake setups as I tow a custom offroad rig but that seems silly for a road vehicle.

I was really hoping to find more definitive answers but multiple forums and facebook groups have led me to believe that either no one knows or GM had a bunch of different versions where RPO codes can match but the axles won't. Some people swear they are direct swaps, some people swear the spring perches are different widths, and others claim the driveshaft u-joints are different. Maybe these people suck at picking axles or they have junkyards who suck and pulling the right parts. I don't really know but there's way too much conflicting information so if I swap gears I'll either do the gear swap myself or just buy the same GM 9.5 axle with different gears.

 

I don't see why this is so hard, any 14 bolt should fit fine, the spring perches are the same on all of them. If the u joint is different it isn't a big deal to get a conversion joint that will get the job done. I would look for one with 10K GVW brakes and 4.10 gears, I have that setup on my suburban and love it when towing, the braking is awesome.

 

It sounds like you're not sure of the ratio, I just replaced a a rear diff in my 02 Duramax 2500HD diesel, I found the code for the diff on a sticker on the bottom of the glove compartment, all the codes for everything on the truck are there.but they al have 2 letters at the start of the code so you need to know which letters to look for, it should start with a G or GU...