JB5 Rear to JB6 Drums 6 Lug - Help with Models to pick

[someotherguy]

According the the charts I'm finding, 4.56 gears are probably best for this setup. Are they common in the 9.5" 14 bolt or should I prepare to re-gear one?

You won't find 4.56 in any of the 9.5" 14 bolts, factory original, anyway. 3.73 is common, 4.10 less common, as is 3.42. Look into what it costs to regear both your differentials before choosing is the best advice I can offer there. It's pricey.

RPO GU6 is 3.42, GT4 is 3.73, GT5 is 4.10. G80 is the locker option, Eaton Gov-Loc, which is notoriously weak in the 10 bolt variety, but reputed to be reasonably strong in the heavier 9.5" 14 bolt differential.

For proper width of axle you want a rear end from another 4WD. A RWD model will be too narrow. You can look at K1500 models if they have the RPO F44 which is the HD suspension; this includes the 9.5" 14 bolt; otherwise you're looking at "6 lug 2500's" also known as "light duty 2500" again only the 4WD models as the RWD axle is too narrow.

I saw someone else ask was there ever a 2500 Tahoe - nope. Don't think any ever came with F44 either. All of 'em 10 bolt 8.5" diff. There were diesel 1500 pickups which maybe? had the 9.5" and probably diesel 1500 Suburbans but finding one of those just sitting around is unlikely as they are very uncommon.

Richard

 

[Bearclaw]

You won't find 4.56 in any of the 9.5" 14 bolts, factory original, anyway. 3.73 is common, 4.10 less common, as is 3.42. Look into what it costs to regear both your differentials before choosing is the best advice I can offer there. It's pricey.

RPO GU6 is 3.42, GT4 is 3.73, GT5 is 4.10. G80 is the locker option, Eaton Gov-Loc, which is notoriously weak in the 10 bolt variety, but reputed to be reasonably strong in the heavier 9.5" 14 bolt differential.

For proper width of axle you want a rear end from another 4WD. A RWD model will be too narrow. You can look at K1500 models if they have the RPO F44 which is the HD suspension; this includes the 9.5" 14 bolt; otherwise you're looking at "6 lug 2500's" also known as "light duty 2500" again only the 4WD models as the RWD axle is too narrow.

I saw someone else ask was there ever a 2500 Tahoe - nope. Don't think any ever came with F44 either. All of 'em 10 bolt 8.5" diff. There were diesel 1500 pickups which maybe? had the 9.5" and probably diesel 1500 Suburbans but finding one of those just sitting around is unlikely as they are very uncommon.

Richard

Great info Richard. That is very helpful. Sounds like the best path forward is to find 3.73's in the 9.5" then re-gear if/when they go bad.

 

[HotWheelsBurban]

The 11” drums and 8.5” rear seem to be common on the 5.7L 1500 Suburban.

The 5.7L 1500 Tahoes that I’ve seen in the yards (was there ever a 2500 Tahoe?) were given the 10” drums and 8.5” rear.

I’m not sure about the diesels or the 2500 versions.

There are both 5-bolt and 6-bolt 11” drums on the GMT400s.

The 8.5” ain’t the best as has been mentioned. I rarely trailer anything heavy, yet I’ve spun the carrier in the bearings once already.

I would like a 9.5” someday.

I’ve 3.73 gears on 275/65-18 (IIRC) tires.

I might guess one would want 4.10 or 4.56 gears when using a tall tire.

Most of the Tahoe's I've seen in the yards have the 10" brakes. Some 4x4 ones seem to have the 11", but it's not common. Burbs have the 11" but as mentioned, you'll need a 4x4 donor for the axle to be proper width.

 

[L31MaxExpress]

Most of the Tahoe's I've seen in the yards have the 10" brakes. Some 4x4 ones seem to have the 11", but it's not common. Burbs have the 11" but as mentioned, you'll need a 4x4 donor for the axle to be proper width.

My 99 came with the factory 11s. Same drum that was on my Van.

 

[HotWheelsBurban]

My 99 came with the factory 11s. Same drum that was on my Van.

Probably the later ones had the 11s, trying to use up the old generation parts. Same reason most of these are heavily optioned....

 

[L31MaxExpress]

Probably the later ones had the 11s, trying to use up the old generation parts. Same reason most of these are heavily optioned....

Agreed, might also be something to do with the massive factory Class 4 Hitch. It had the factory trans cooler, factory 34x19 dual core radiator, factory oil cooler, factory 140a alternator, and factory pusher fan. I went to put the bigger police calipers up front and it already had them. I had previously gotten the wrong master cylinder. When I went to change it out, I assumed it had the 1.25" bore. Well I was wrong it had the 1.34" bore on the thing. Should have read the brake codes. Mine had the cop brakes and cop cooling upgrades but the standard suspension. No Bilsteins, rear sway bar or oversize front sway bar. I did however score the sway bars and 120 mph cluster from a very heavily picked Limited I found in the wrecking yard. I put KYB Monomax shocks on it. I already had the KYBs on the van and LOVE them.

 

[Caman96]

It seems the 9.5’s were much more common for Canadian market. My (former)98 Sierra 1500 came with a 9.5. Wish I still had it!

 

[HotWheelsBurban]

Here's a few pics of a 1500 Burb in the local yard, also most Burbs have the rear sway bar so you can do two upgrades for the price of one!

It seems the 9.5’s were much more common for Canadian market. My (former)98 Sierra 1500 came with a 9.5. Wish I still had it!

 

[Redsled]

Going down this path myself. I have been researching options for a while. I have a 91 K1500 with the crappy JB3 brakes. I have already upgraded the MC.

For the front, l plan to keep it simple and swap over the hub/rotor/calipers to a JB5.

For the rear, I don't want to do an axle swap. My truck is just a DD that will never tow or be driven “hard”, so I am leaning towards just swapping to the better 11” drums. My question is - did the trucks that came with 11” drums use the same size brake lines?

 

[JOHNGAAA1]

You will need to regear. 1996-1998 gmc sierra z71 or 1996-1998 silverado z71 g80 rear. It's a 14 bolt rear, with 6 lug axles, 11" drums. Sound like this is what you are looking for.