Nightmare 10” drum brakes

[ShadeTreeMechanic]

The guy who got me my 9.5" SF 11" drum six-lug lives a bit south of Louisville, in Bardstown, KY and I believe he's got access to a couple of others if you want one.

He of course has access to 8.5" w/ 11" drums too, those are plentiful.

He's in his 60s and knows the GMT400s quite well.

He might assist with delivery. In my case, he met me in Indianapolis.

If you want his contact info, PM me.

Is my rear axle equipped from the factory with a 8.5"? I have a 97 K1500 SWB with the 5.7 with a 10 bolt, 6 lug, semi float, 10" drum brakes. My concern is not about getting a heavier duty rear axle. My only concern is getting rid of these junk 10" rear brakes. So far, Ive been searching for rear axles out of 2whl 2500's. What should I be searching for in order to find the 8.5" with 11? I would be willing to drive to Bardstown Ky, but want to exhaust all options here locally.

 

[1998_K1500_Sub]

Is my rear axle equipped from the factory with a 8.5"? I have a 97 K1500 SWB with the 5.7 with a 10 bolt, 6 lug, semi float, 10" drum brakes. My concern is not about getting a heavier duty rear axle. My only concern is getting rid of these junk 10" rear brakes. So far, Ive been searching for rear axles out of 2whl 2500's. What should I be searching for in order to find the 8.5" with 11? I would be willing to drive to Bardstown Ky, but want to exhaust all options here locally.

Your truck has an 8.5 inch rear.

If you want another 8.5 inch rear with 11 inch brakes, they’re fairly easy to come by.

You want one from a 4x4 (K1500) so that it’s got the proper width.

A truck with RPO JB6 will be equipped with the 11” drums.

The heavier duty (2500/3500) trucks came with 9.5” and 10.5” rear gears.

Check your rear end ratio, I’m guessing you have 3.73 but the RPO code in your glove box will tell the tale. 3.73 rear gears are fairly common in pickups, Suburbans and some others might have 3.42.

If you can’t find one locally, or you want someone who will work with you, the fellow in Kentucky is a nice guy to work with.

 

[ShadeTreeMechanic]

Well, I thought I would give an update since it's been a minute. I finally found me an axle in Louisville Kentucky. I went with the 8.5" with the 11" drums. I was going to put it in this weekend and discovered that the end of the pinion shaft had been cremated somehow (see attached picture). I noticed the pinion nut was missing but the washer was still there which seemed strange. Then I noticed the washer was still on there because the threaded portion of the pinion had been whooped so much that it had been mushroomed. The four ears on the flange also had signs of abuse which I worsened trying to get it off as it was stubborn. The only thing I can figure is someone needed the flange at the salvage yard and had such a hard time that they thought if they beat on the end of the pinion, it would cause the flange to come off. So, long story short, I ended up tearing the axle down to replace the pinion. It's in pieces in the garage and im waiting on parts. I understand the mechanics and principles of this process but am still reserved as I have never built an axle before and have no experience with setting backlash or preload. Anyway, I ordered two crush sleeves just in case! Stay tuned!

 

[Schurkey]

I ended up tearing the axle down to replace the pinion. It's in pieces in the garage and im waiting on parts. I understand the mechanics and principles of this process but am still reserved as I have never built an axle before and have no experience with setting backlash or preload. Anyway, I ordered two crush sleeves just in case! Stay tuned!

The worst part of ring-and-pinion work is getting the pinion depth correct. Be prepared for that. Youtube University, and the Genuine GM service manual are your friends.

Consider grinding the "mushroom" off of the existing pinion, and maybe rethreading the end by running a rethreading die over the existing threads. I can't tell if repairing the existing pinion is a viable process, but if you can, you can put the thing back together with the existing shims and not worry about pinion depth. If not, you're pretty-much starting from scratch ESPECIALLY if the new pinion isn't marked for + or - machining tolerance, which I'm told is now common.

Bearing preload on the pinion is not-so-bad, and bearing preload/backlash on the differential carrier is not-so-bad on the 8.5" axle, a piece-of-cake on a 10.5" axle, and somewhere in-between on the 9.5".

 

[ShadeTreeMechanic]

Update, I was able to grind the damaged mushroomed part of the threaded portion of the pinion shaft off and re-thread the pinion with a die and a little touching up with a thread file. Nice tip @Schurkey! Thanks.
I have the axle assembled and am trying to get the shoes and hardware on now. I have ran into a quagmire with the emergency brake cables however. I want to assemble the drums in the garage and have the cables off the truck. The factory D/S cable was compromised and requires replacement. This truck is a SWB single cab with 10" brakes. Do I need to order cables for 11" brakes now or stick with 10" cables? My existing RR cable for the 10" brakes is around 95" and the only RR cable I could find for 11" brakes was 103". Did they only offer 11" on extended cab trucks? If so, should I stick with 10" drum cables even though I now have 11" drums? The D/S 10" style cable is 85-86" and the 11" D/S cable is 83" which confuses me. I know that there is definitely a difference between the drum side of the cable when it comes to the 10" and 11" and im wondering if that is where the difference is. in other words, the only length difference I can see would be that the 11" shoes sit juuuuuuust a little further back on the backing plate then the the 10" shoes. By juuuuuust, I mean an inch or two I would think.

If I confused you, then welcome to the club!

 

[Supercharged111]

Parking brake cables are different for 10" drums and 11" drums. You need cables for your cab/bed configuration as well as the 11" drums.

 

[scott2093]

Parking brake cables are different for 10" drums and 11" drums. You need cables for your cab/bed configuration as well as the 11" drums.

ahhh. I've always wondered why when my 93 rear end was swapped (unknown truck) and it came with 11" brakes, why the parking brake wasn't put back..like the original was too short or something...
Any chance to clarify what the difference is?

 

[Supercharged111]

ahhh. I've always wondered why when my 93 rear end was swapped (unknown truck) and it came with 11" brakes, why the parking brake wasn't put back..like the original was too short or something...
Any chance to clarify what the difference is?

Just the way it hooks up. I believe it was a different length after it's snapped into the backing plate.

 

[Schurkey]

Parking brake cables are different for 10" drums and 11" drums. You need cables for your cab/bed configuration as well as the 11" drums.

I re-used the cables from my 254mm leading/trailing shoe drums when I installed the K2500 9.5" axle with 11.x Duo-Servo brakes. When the cables were replaced due to seizing, I merely ordered whatever cables would come on a regular-cab, long-bed K1500. When the cables were replaced the second time, again due to seizing, I did the same thing but from O'Reillys instead of NAPA.

Far as I know, the cables are selected based on the vehicle, not based on the brakes installed.

But I've been wrong before.

 

[ShadeTreeMechanic]

ahhh. I've always wondered why when my 93 rear end was swapped (unknown truck) and it came with 11" brakes, why the parking brake wasn't put back..like the original was too short or something...
Any chance to clarify what the difference is?

The only obvious difference I can tell BESIDES obvious length differences between wheelbases is where the cable fastens into the backing plate. There is not much difference in length if any BUT the spring that causes the release of the cable is longer for the 11" brakes as opposed to the 10" brakes as shown in the attached image.