K2500 Suburban Rear Axle Replacement

[1ton-o-fun]

My '93 C3500 is rated at 9000 gvwr and JB8 brakes. Going to find out this weekend if I have the slide on drums or not. (Hope so)

 

[454cid]

I was under the impression that the JD7's had the drums on the back of the hubs. It seems when I've been in discussions with people before on the topic of where the drums are mounted, it's been the 3/4 trucks or Suburbans that had the drums on the back of the hubs. Almost without fail people think I have a 9.5" semi-floating axle as soon as I mention the drums sliding off. It usually ends up that my truck being a 3500 is the differance..... I have the SRW JB8 brakes. I mention SRW, because instead of using another RPO, GM also used JB8 for DRW brakes, with the obvious and not as obvious differances.

OP how are you telling the yards what you're looking for? Do they use your VIN? If they're saying Suburban axle or SRW 3500, that doesn't make much sense to me.... although, I don't think you've mentioned a year for your Suburban, which maybe makes a differance. Is there a chance you have one of the ex-GOVT. Suburbans that was more like a 1-ton? I've recently read that the govt. had ordered Suburbans that were more like 3500s, although I'm not really sure of the timeframe.

I would assume that the whole axle with the JB8 brakes would swap right in, giving you the bigger brakes, but I'm not sure if the driveshaft would change at all.....u-joint? Also the truck wouln't have provisions for an anti-roll bar, if you have one.

 

[stutaeng]

Yea, I was also hinting at just swapping the entire axle to get the larger (or better?) brakes. The driveshaft would not be an issue because they are both 14 bolts. But that's still a lot of work. Replacing an axle shaft on a full floater is way easier.

Look at these part on RockAuto. I compared a K2500 truck to a K3500 SRW truck to a C2500 Suburban (not sure why the 10.5" was not showing on the K2500 Suburban?), and there does seem to be a bit difference in part number, so now I'm going to say OP should just pull his existing axle shaft and needs to just compare and match:

https://www.rockauto.com/en/catalog...n,7.4l+v8,1303467,drivetrain,axle+shaft,10439
https://www.rockauto.com/en/catalog...p,7.4l+v8,1358704,drivetrain,axle+shaft,10439
https://www.rockauto.com/en/catalog...p,5.7l+v8,1358715,drivetrain,axle+shaft,10439

Oddly, the same USA21601 part number is listed for the 2500 Suburban and the 3500 SRW truck...But when you click on the USA21601, hyperlink, it's basically all the 2500 and 3500 models:

You must be registered for see images attach

Am I looking at that correctly? Maybe I'm comparing a left to a right side? I believe the Left and Right are different lengths.

I was at junkyard a few weeks ago looking and I saw a guy pulling a part from the hood one of these GMT400 trucks. I quickly glanced at the door stickers and it said 1500, so I was going to pass, then I spotted an 8 lug SF rear axle! I asked the guy if this was a 1/2 ton or 3/4 ton and he responded with 1/2 ton. Then I pointed out the 8 lug and he and I were like, "WTH?!" Door paint color looked original to the truck also. LOL.

 

[Steve Addy]

I believe JD7 is the hydroboost 13 x 2.5 shoes. @Pinger has a 99 C2500 Burb that he's done a lot of rear brake work on, that is that brake code. But I don't remember if his Burb has a full floater rear axle or not. My only 2500 Burb had a semi floating axle, but it did have the big ass brakes. He's in Scotland, so he may be on the forum now....

I guess I didn't clarify which was which on the Jx7 series brakes, but the point was that regardless of the axle type (SF / FF) you could option to have the bigger brakes (or not) and it wouldn't matter to the axle assembly you have. IOW you can option up the brakes without having to also buy the FF axle on certain vehicles.

On 3500 trucks I think you always got the JB8 hydro boost brakes as a matter of standard equipment, you also got the FF as standard equipment I think, at least back in the early 90's.

Steve

 

[Steve Addy]

My '93 C3500 is rated at 9000 gvwr and JB8 brakes. Going to find out this weekend if I have the slide on drums or not. (Hope so)

I think you'll find you have the slide on drums like I do, the backside mounted drums are earlier although I don't know for certain how much earlier but if I had to guess I'd say square body or very very early GMT400. I haven't seen enough examples to be able to say for certainty on this, but if my C3500 has slide ons I believe you will.

I was under the impression that the JD7's had the drums on the back of the hubs. It seems when I've been in discussions with people before on the topic of where the drums are mounted, it's been the 3/4 trucks or Suburbans that had the drums on the back of the hubs. Almost without fail people think I have a 9.5" semi-floating axle as soon as I mention the drums sliding off. It usually ends up that my truck being a 3500 is the differance..... I have the SRW JB8 brakes. I mention SRW, because instead of using another RPO, GM also used JB8 for DRW brakes, with the obvious and not as obvious differances.

I initially pulled parts from a 2500 Suburban before realizing that I hadn't checked the rpo to verify JB8. It was a 99 Sub and it had hydro 13x2.5 in back and the drums were slide on. Now that is a late production Sub but I kinda think the backside mounted drum is a much older thing, from the square body series.

OP how are you telling the yards what you're looking for? Do they use your VIN? If they're saying Suburban axle or SRW 3500, that doesn't make much sense to me.... although, I don't think you've mentioned a year for your Suburban, which maybe makes a differance. Is there a chance you have one of the ex-GOVT. Suburbans that was more like a 1-ton? I've recently read that the govt. had ordered Suburbans that were more like 3500s, although I'm not really sure of the timeframe.

I would assume that the whole axle with the JB8 brakes would swap right in, giving you the bigger brakes, but I'm not sure if the driveshaft would change at all.....u-joint? Also the truck wouln't have provisions for an anti-roll bar, if you have one.

That's something I considered too, we really don't know what year he's talking about. I checked for 95 and RA didn't list the 10.5" as being an option, then again I can point at a mountain of errors for interchange info for RA too...

Yea, I was also hinting at just swapping the entire axle to get the larger (or better?) brakes. The driveshaft would not be an issue because they are both 14 bolts. But that's still a lot of work. Replacing an axle shaft on a full floater is way easier.

That is a mountain of work, not something I would like to do personally unless it was completely warranted. I think unless you have a bent axle housing you're better off keeping the one you have, especially if it's been well maintained and is lower in miles.

There's a risk with JY parts that you're getting something that had poorer maintenance than you personally do, and you won't know that until it's installed and you head out for a test drive and the rear end whines like a banshee. I would want to see sample of diff fluid from the donor and especially inside the pumpkin before accepting it.

Look at these part on RockAuto. I compared a K2500 truck to a K3500 SRW truck to a C2500 Suburban (not sure why the 10.5" was not showing on the K2500 Suburban?), and there does seem to be a bit difference in part number, so now I'm going to say OP should just pull his existing axle shaft and needs to just compare and match:

https://www.rockauto.com/en/catalog...n,7.4l+v8,1303467,drivetrain,axle+shaft,10439
https://www.rockauto.com/en/catalog...p,7.4l+v8,1358704,drivetrain,axle+shaft,10439
https://www.rockauto.com/en/catalog...p,5.7l+v8,1358715,drivetrain,axle+shaft,10439

Oddly, the same USA21601 part number is listed for the 2500 Suburban and the 3500 SRW truck...But when you click on the USA21601, hyperlink, it's basically all the 2500 and 3500 models:

You must be registered for see images attach

Am I looking at that correctly? Maybe I'm comparing a left to a right side? I believe the Left and Right are different lengths.

Yes, for some reason RA doesn't list the 10.5" rear end for 2500 Suburban for a few years in the mid-90's, not sure why that is, I don't think that's actually true. If I can find part numbers from GM for it I'll know for sure, and IIRC not long ago there was a 2500 Suburban in the JY with FF rear end and the JB8 brakes, I noticed it because it was bagged in the rear and setup for HD towing. I'm almost sure that was 93 or 94 but since it's gone I can't say for certainty, but I do know it was before 95 update.

As I mentioned above I don't necessarily trust the interchange integrity of RA. There's a lot of bad information in there and RA isn't interested in correcting any of it. I've brought it up before but they just say that's what their vendors tell them. I just let it go now and find all the stuff I need on my own, typically with OEM part numbers, that way it's exactly what I need and if there's an error I take RA to task over it.

Do not take RA to be gospel. I use it as a guide but I also am skeptical of the information. Case in point, look at 93 C3500 SRW leaf spring u-bolts. The ones that apply aren't even listed by RA, you have to go to 2500 truck and look there to find the correct bolts for C3500 SRW to find the correct ones for 8 bolt axles.

Part of it is the confusion over 3500HD trucks that most parts vendors don't know that much about and don't work to know that much about, so knowing more about what you have then the vendors is pretty much the status quo.

I was at junkyard a few weeks ago looking and I saw a guy pulling a part from the hood one of these GMT400 trucks. I quickly glanced at the door stickers and it said 1500, so I was going to pass, then I spotted an 8 lug SF rear axle! I asked the guy if this was a 1/2 ton or 3/4 ton and he responded with 1/2 ton. Then I pointed out the 8 lug and he and I were like, "WTH?!" Door paint color looked original to the truck also. LOL.

I do see that a lot too, but more frequently on square body trucks. But it's not unheard of and there's the weirdness of the heavy half ton or the light 3/4 ton truck too...what does that actually mean for equipment? I try and not get caught up in the weirdness of all these slight modifications.

Steve

 

[LikeABoat]

I was under the impression that the JD7's had the drums on the back of the hubs. It seems when I've been in discussions with people before on the topic of where the drums are mounted, it's been the 3/4 trucks or Suburbans that had the drums on the back of the hubs. Almost without fail people think I have a 9.5" semi-floating axle as soon as I mention the drums sliding off. It usually ends up that my truck being a 3500 is the differance..... I have the SRW JB8 brakes. I mention SRW, because instead of using another RPO, GM also used JB8 for DRW brakes, with the obvious and not as obvious differances.

OP how are you telling the yards what you're looking for? Do they use your VIN? If they're saying Suburban axle or SRW 3500, that doesn't make much sense to me.... although, I don't think you've mentioned a year for your Suburban, which maybe makes a differance. Is there a chance you have one of the ex-GOVT. Suburbans that was more like a 1-ton? I've recently read that the govt. had ordered Suburbans that were more like 3500s, although I'm not really sure of the timeframe.

I would assume that the whole axle with the JB8 brakes would swap right in, giving you the bigger brakes, but I'm not sure if the driveshaft would change at all.....u-joint? Also the truck wouln't have provisions for an anti-roll bar, if you have one.

1999, I haven’t been giving them my VIn

 

[LikeABoat]

I measured everything on my rear ended and went back to the salvage yard this afternoon. There was 3 3500 trucks with FF 14 bolt, all missing glove box, so no rpo codes. I measured them all ans they fall seemed the same as the same as my axle. 2 were 2wd and 1 was 4wd. I was able to Jack two up and spin the wheel to check the ratio, they were both 4.10. I need to 4.73 ( or just the hub ans axle shaft) . I told them to pull the one I could t check the ratio ( since the other 2 were the wrong ratio. ), 1998 2wd 3500 srw for me. It was the cleanest, hopefully lowest miles, maybe the right ratio,... I get it tomorrow, hopefully just swap the hub and axle shaft and get my burb back on the highway. I’ll post an update. Thanks for all the information and experience.

 

[stutaeng]

I measured everything on my rear ended and went back to the salvage yard this afternoon. There was 3 3500 trucks with FF 14 bolt, all missing glove box, so no rpo codes. I measured them all ans they fall seemed the same as the same as my axle. 2 were 2wd and 1 was 4wd. I was able to Jack two up and spin the wheel to check the ratio, they were both 4.10. I need to 4.73 ( or just the hub ans axle shaft) . I told them to pull the one I could t check the ratio ( since the other 2 were the wrong ratio. ), 1998 2wd 3500 srw for me. It was the cleanest, hopefully lowest miles, maybe the right ratio,... I get it tomorrow, hopefully just swap the hub and axle shaft and get my burb back on the highway. I’ll post an update. Thanks for all the information and experience.

The 3500 from 96-00 were all 4.10s from the factory. It did not matter if 2wd or 4x4. 4.56s were available as an option. Same applied to the DRW.

I understood yours were 4.73? I think after 4.56 the gears available aftermarket were 4.88 and then 5.13, but these were not factory options.

I don't think the axles depends on ratio through. I thought the axle shafts were like 32 spline or something like that? Maybe 30?

Last time I was trying to confirm my ratio by spinning the driveshaft, I had to try a few times. I think the G80 kinda messed things up. Seems like the first try I got 2.5 ratio, LOL. I think I had to lock one of the rear wheels from spinning if I recall and I got the 4.10 ratio correct. Don't really know how those G80 work, honestly.

 

[LikeABoat]

I measured everything on my rear ended and went back to the salvage yard this afternoon. There was 3 3500 trucks with FF 14 bolt, all missing glove box, so no rpo codes. I measured them all ans they fall seemed the same as the same as my axle. 2 were 2wd and 1 was 4wd. I was able to Jack two up and spin the wheel to check the ratio, they were both 4.10. I need to 4.73 ( or just the hub ans axle shaft) . I told them to pull the one I could t check the ratio ( since the other 2 were the wrong ratio. ), 1998 2wd 3500 srw for me. It was the cleanest, hopefully lowest miles, maybe the right ratio,... I get it tomorrow, hopefully just swap the hub and axle shaft and get my burb back on the highway. I’ll post an update. Thanks for all the information and experience.

Fat fingered my ratio, mine is 3.73. Sorry for confusion

 

[stutaeng]

Gotcha. So yeah, better stick with axle shaft only.

As the entire axle swap would get you a 4.10 from the said 3500. Speedo would require calibration, in addition to other things pointed out...

Seems like you figured it out. Let us know how everything shakes out.

BTW, what junkyard did you go to? I'm always looking for parts for my 3500. It's in rough shape, if you know what I mean...