While dumpster diving the local pull-n-pay for a CTM I saw an '03 with a disk brake rear axle. Even assuming it is the right ratio (which I doubt, I'm at 3.92), would you bother swapping out your present perfectly good axle to get disks?

 

Depends how much your drums irritate you. My drums never want to stay adjusted. If it were me I'd definitely buy it if it was there (and the correct ratio). At that point it would probably sit around for a long time until I got around to installing it.

 

I swapped my 98 to an 03 rear. I had to replace it though. My limited slip 3.92 was beyond gone. I couldn't just swapping a new rear end in without at least going for the disc brakes. I had the same trouble. They would NEVER hold adjustment. They would also lock up when it rained The first time I hit the pedal after it sat. They were also full of gear oil from my axle bearings and seals going bad so instead of going back to drum and dealing with replacing all the internals of the drums I decided I would not buy without getting discs. I had to have it immediately and I checked multiple yards. No 3.92 03's because they were all 4.7's. Didn't find a single 3.92 rear end. So I got a 3.55 rear end. Here's the thing, I currently can't use 4WD because my transfer case chain needs replaced so I pulled the front drive shaft to keep it from spinning that chain full time. so I'm not hurting anything by running 3.55 except making the truck work harder at high speeds or with a trailer. Still glad I did it though. Can't stand drums. Will eventually have 3.92 in the rear some day. And maybe even some 4.10 or 4.56 at some point but that's a lot more money than I'm willing to shell out right now. So If you find a 3.92 03 axle or better yet 3.92 LSD 03 axle I would get it because I think they're pretty hard to come by. Will save you from having to swap gears like I'll have to.

 

the 4.7 did have an option for 3.92 gears IIRC, but it was not a common option so not being able to find one is not surprising.

as far as swapping the axle just for the brakes, i probably wouldnt, there is quite a bit of stuff that has to come along with the swap IIRC, i put together a spreadsheet of the requirements for that and the larger front brake swap. if it were me id wait till i needed to replace the rear end and then go for it

 

I didn't know if any 4.7's ever came with 3.92. But I do know I've never seen one so yeah definitely rare. As far as the swap is concerned, all you have to change is the yoke and you use the 03 parking brake mechanism with the original cable but you do have to cut the original cable end to like 1/2 inch to match the cable on the 03. Some people replace the proportioning valve. I haven't. If I do I'll probably get an adjustable one.

 

Thanks for the continued replies on this. I think I've decided to not bother. I have zero issues with the drum system, is working fine. If the replies here were all "Hell yes! Amazing braking upgrade!", I would look into it.
Thanks...

 

Well it was an amazing upgrade for me but my situation is not the same. I have 261,000 miles. And my rear brakes were worthless due to all the 90 weight in the drums. But in your case the drums are fine. And it takes a lot of effort to do such a simple task of swapping a rear axle. I thought it would be easier than it was. So if I were in your position, I would do as you're saying and leave it be since the drums still work great

 

my dad had a loaner from the dealer with the 3.92s in it so i know they exist, but most dealers werent ordering them that way around here, they were mostly sold as kid haulers to soccer moms who didnt want a minivan (unfortunately) sooo efficiency was king, no need for acceleration or towing in that case so everyone got 3.55s. (not sure if your area is the same, but my guess is it was similar)

 

Makes sense. Besides, If people had towing in mind, most would get the 5.9 anyway. Hence the reason there's almost no 3.92 in 4.7 trucks which is understandable. I can't wait to have mine back. Or just go all out and change both front and rear to 4.10 or 4.56 to make up for my tire size.

 

the swap isnt worth it imo.
drum brakes have longer service life, require less maintenance and unless your towing heavy, disc aren't needed. If you live in a rust belt, you do not want rear disc brakes.