14 bolt conversion to disc questions/options

[kipps]

Also, if you're thinking of pulling an axle at a junkyard, the trickiest part is lifting the back of the truck enough to remove the axle without dropping the truck on yourself. On one axle I pulled, the truck was sitting on the side of a hill(reality in Virginia salvage yards!). I was lifting the truck with a handyman jack under the rear bumper. The whole truck kept scooching sideways, and threatening to pin me under it.

The disconnect procedure is simple enough. On mine, the u-bolt nuts came right off with a large breaker bar. The driveshaft unbolts easily, and the shocks come loose easily as well. The brake lines and parking brake cables need a good sharp bolt cutters. A cable cutter would be better, but I didn't have one. Once everything is disconnected, then lift the truck, and roll the axle out from under it.

Take the driveshaft and the spring u-bolts along with the axle. They can all be reused to one degree or another.

Remove the spring perches and shock mounts, and clean up the axle tube. Purchase new perches and mounts from OffRoadDesign. Loosely assemble the perches on the axle, and bolt them to the leaf springs. Don't weld anything yet. Adjust the pinion angle until it's correct, then tack weld it in place. Get the new driveshaft shortened to fit(the driveshaft shop can tell you how to take the measurements), and install that.

Drive the truck gently up to speed to check for driveline vibration, and if all is correct, have a skilled welder lock the perches to the axle. There is some risk of warping the axle tubes when welding on the spring perches, so make sure the welder takes proper precautions.

[hatzie]

Originally Posted by kipps

Also, if you're thinking of pulling an axle at a junkyard, the trickiest part is lifting the back of the truck enough to remove the axle without dropping the truck on yourself. On one axle I pulled, the truck was sitting on the side of a hill(reality in Virginia salvage yards!). I was lifting the truck with a handyman jack under the rear bumper. The whole truck kept scooching sideways, and threatening to pin me under it.

Find some tires on steel wheels to use as cribbing under the frame or bring some actual 2' timbers to use as temporary cribbing. Timbers will be an operation to get to and under the vehicle.
I make sure it's supported underneath with some kind of cribbing so you can disconnect the propshaft and parking brake cables.

At least one of the yards I frequent has a double A Frame on wheels with an I beam between the A frames and a chain fall hoist. It's for lifting engines and transmissions out of a rig and into a cart. You can attach it to the frame with your own chains or straps and lift the whole shebang after you have the axle is free of the springs, propshaft, cables, and brake line. Then you pull it out using chains or straps without getting underneath.

Originally Posted by kipps

The disconnect procedure is simple enough. On mine, the u-bolt nuts came right off with a large breaker bar. The driveshaft unbolts easily, and the shocks come loose easily as well. The brake lines and parking brake cables need a good sharp bolt cutters. A cable cutter would be better, but I didn't have one. Once everything is disconnected, then lift the truck, and roll the axle out from under it.

If the parking brake cables are in serviceable shape I'd keep em. SoCal is unlikely to have the rust we have in the Northeast. If you're in the rust belt they're unlikely to be in good shape. If they are... Chah ching...
You can keep the T800 parking brake cables in one piece by disconnecting from the frame and the pedal cable. I usually nip the sheet metal disconnect cage in two and then pull the rear cables out of the brackets and wire tie them onto the axle tubes. You can usually slide a box-end wrench over the cable and turn slightly to fold in the ears to get the cables out of the holes in the brackets/frame.
It's more work but those cables aren't cheap.

Originally Posted by kipps

Take the driveshaft and the spring u-bolts along with the axle. They can all be reused to one degree or another.

I usually go to a heavy truck spring and axle joint to get new spring pak U-bolts. Not worth re-using them unless they're perfect.
They'll ding you at the counter for the propshaft but it's probably worth getting as long as they didn't bend it with the forks on the loader.
Bring some tape to wrap around the Universal joint caps to hold them on assuming it's serviceable.
Assuming the U-joint yoke straps or U-bolts are in good shape, put em back in the yoke on your axle.

Originally Posted by kipps

Remove the spring perches and shock mounts, and clean up the axle tube. Purchase new perches and mounts from OffRoadDesign. Loosely assemble the perches on the axle, and bolt them to the leaf springs. Don't weld anything yet. Adjust the pinion angle until it's correct, then tack weld it in place. Get the new driveshaft shortened to fit(the driveshaft shop can tell you how to take the measurements), and install that.

Drive the truck gently up to speed to check for driveline vibration, and if all is correct, have a skilled welder lock the perches to the axle. There is some risk of warping the axle tubes when welding on the spring perches, so make sure the welder takes proper precautions.

One more piece of shopping advice. Look on the Service Parts ID tag in the glovebox.

• A 2500 with an LQ4 engine will have the 10.5" 14bolt. The LB7, LLY, & LBZ will have the 11.5" 14bolt axle. You don't want the 11.5" AAM axle.
• G80 is limited slip on the T800 trucks. Useful information to have later on.

The other G code will be the axle ratio.

• GT4 : AXLE REAR, 3.73 RATIO
• GT5 : AXLE REAR, 4.10 RATIO

The other RPO code you'll be interested in is the Brake code. If you find a JBx or JDx it's a Disc/Drum truck. Not worth looking any further.

• JH5 : BRAKE, HYD POWER, 4-WHEEL DISC, 7200 LBS
• JH6 : BRAKE, HYD POWER, 4-WHEEL DISC, 9900 LBS

[kipps]

One other thing that I wanted on a gmt800 10.5 14bff axle is the infamous 'gov-lock' differential. These are usually considered a detriment, but most folks who hate on them are doing stupid stuff that the truck wasn't designed for. Burnouts and severe offroading aren't very kind to the gov-lock design.

I'm building a daily driver truck, and not something that I'll be beating on. Because of this, the gov-lock should last a long time for me, and actually be quite useful in low-speed slippery conditions. This gov-lock comes with a "G80" code on the glovebox sticker.

[hatzie]

I'm not sure the T800 G80 code diff is an Eaton Gov Loc.
It may be an actual limited slip diff.

[SunSoaked]

Originally Posted by Asshat

Not sure if this is the best place, but I am looking for info on disc brake conversion on a GM 14 bolt, 8 lug, semi float rear end. I just can’t seem to get the drum brakes right, so I’m thinking of a conversion.

Can I buy just the bracket for the calipers and rotor, or do I need to buy a kit?

Are there any other options for a parking brake? All the kits want to add $200 for the parking brake calipers. Are there parking brake calipers from other cars that would work?

When’d did the rear ends (3/4 ton) start getting disc brakes? 1999?

Any help would be greatly appreciated. I’m sure there must be somebody out there that has done this.

Just fix whatever issue you've created with the original brakes. They have worked just fine for GM for decades.

[Asshat]

Originally Posted by SunSoaked

Just fix whatever issue you've created with the original brakes. They have worked just fine for GM for decades.

I thought about that too. My biggest problem is trying to figure out what parts are correct. Not sure what year the one I have is.

[hatzie]

Originally Posted by Asshat

I thought about that too. My biggest problem is trying to figure out what parts are correct. Not sure what year the one I have is.

Download the parts and illustration books and take a look at the blowups.

The Axle Quick Req I scanned is useful as well. It shows where to find the axle Ident numbers on the corporate 14 bolt axles. Look in the manuals thread.

[Asshat]

Help!
The rotors I purchased won’t fit over the axle. Does anyone know the part number of the correct rotor for converting this 14 bolt?

Do I need to pull the axles and mount the rotors on the inside??

That means, every time I need to change rotors, I gotta pull the axles?

[hatzie]

Supposedly the Dana 44 8lug front rotors will work but i haven't tried it.

[Asshat]

So, my issue seems to be wheel studs now.
The axle flange has holes for .61 knurl studs, the rotors have holes for .65 knurl studs. So, I need to find a stud with a .65 knurl, but a short shoulder (1/2" or less).
This is due to the fact that the rotor will sit behind the axle flange.
I guess there was no other way to do this... to have the caliper fit behind the wheel without hitting the inside of the rim. I did not realize this.

I guess no one here has ever used a semi float 8-lug axle before. Hoping I can be the first to be successful. I sent an email to the guy at TuffStuff, hopefully he will have some answers for me. Thought I would save some money by buying the parts myself - not always that easy.

I already have the parking brake calipers (76 Eldorado) and rotors and brake hoses; hoping I don't have to try and return this stuff or sell it on eBay. Such a major pain to replace the whole axle, especially now that I don't have a truck to get one with.

Anyone have a good source for wheel studs?

[BASE]

lugnut4x4.com might be a resource. I think he sells kits for the semi-float axles. I've purchased parts for my full float conversion from him and he seems to be a pretty good guy (I think he'd sell you just the parts you need vs an up-sell).

[Asshat]

I think I have a few things figured out.

Got the correct wheel studs and the brake calipers have arrived.

Just got to find the time to get things assembled.

[Asshat]

Has anyone replaced the bearings in a semi float rear axle?

Special tools required?

[hatzie]

Axle bearings, carrier bearings, or pinion bearings?

[Asshat]

Originally Posted by hatzie

Axle bearings, carrier bearings, or pinion bearings?

Axle bearings.

[kipps]

If it were me, I wouldn't bother trying to pull those bearings, but would cut them out instead. A die grinder would take a while, but would be reasonably controlled, and likely less frustrating than trying to pull them.

Slice the cage with the die grinder, and remove the rollers. Cut through the outer race, trying to minimize contact with the axle housing. Once you've cut the outer race completely through, it should practically fall out.

But I've never done this on that particular axle. I only speak from experience with other bearings that need to be extracted from blind holes.

[Asshat]

Originally Posted by kipps

If it were me, I wouldn't bother trying to pull those bearings, but would cut them out instead. A die grinder would take a while, but would be reasonably controlled, and likely less frustrating than trying to pull them.

Slice the cage with the die grinder, and remove the rollers. Cut through the outer race, trying to minimize contact with the axle housing. Once you've cut the outer race completely through, it should practically fall out.

But I've never done this on that particular axle. I only speak from experience with other bearings that need to be extracted from blind holes.

That may be an option, however, it seems a little more radical.

I'm on the fence about replacing the bearings, I just thought that since I was this deep in, I should maybe change them out.

That puller set from Harbor Freight still requires a slide hammer, so I still have to get one of those.
Geez - nothing is ever easy.

[kipps]

Originally Posted by Asshat

That may be an option, however, it seems a little more radical.

I'm on the fence about replacing the bearings, I just thought that since I was this deep in, I should maybe change them out.

That puller set from Harbor Freight still requires a slide hammer, so I still have to get one of those.
Geez - nothing is ever easy.

It is radical, but it works. I've never had any luck with a slide hammer.

If you're pulling the pumpkin anyway, it opens up another option. With the pumpkin out of the way, you could square the end of a piece of 1/2" rebar, and drive each bearing out from the opposite end of the axle.

I doubt it's possible to do this with the pumpkin in place, but it might be. This diagram shows one possible method using rebar. You'll need a second person to hold the rebar in place against the bearing with a large screwdriver.

[cadillac_al]

So those Cadillac calipers are supposed to stop a 3/4 ton? Oh my. The internet is flooded with threads about those Cadillac calipers. I hate them on my Caddys and wish I had drum brakes. I would always buy a kit from a reputable company before trying to make those Cadillac calipers work. I'm not seeing a happy ending here. I'll wish you better luck than other people have had.

[hatzie]

There are tools similar to toggle bolts to remove axle bearings when you aren't pulling the diff out of the pumpkin.
You can rent a slide hammer for $0 plus a deposit from The Borg (O'Riley AutoZone etc)

Originally Posted by cadillac_al

So those Cadillac calipers are supposed to stop a 3/4 ton? Oh my. The internet is flooded with threads about those Cadillac calipers. I hate them on my Caddys and wish I had drum brakes. I would always buy a kit from a reputable company before trying to make those Cadillac calipers work. I'm not seeing a happy ending here. I'll wish you better luck than other people have had.

Dual piston calipers are one of many reasons to use the 10.5" AAM out of a T800.

[Asshat]

Anyone have a part number for a proportioning valve?

[kipps]

Originally Posted by Asshat

Anyone have a part number for a proportioning valve?

I purchased a complete line kit from inline tube before deciding to go with disk brakes. Because I already had lines, I wanted a proportioning valve that would fit in the stock location. I purchased this one, but haven't installed it yet. It's a factory-correct unit for the 1970's Corvettes with four-wheel disk brakes.

https://www.inlinetube.com/products/pr101

If I were starting from scratch with my brake system, I'd either mount that proportioning valve up beside the master cylinder like the gmt400 trucks did, or better yet, I'd install an adjustable proportioning valve up there.

[Asshat]

Originally Posted by kipps

I purchased a complete line kit from inline tube before deciding to go with disk brakes. Because I already had lines, I wanted a proportioning valve that would fit in the stock location. I purchased this one, but haven't installed it yet. It's a factory-correct unit for the 1970's Corvettes with four-wheel disk brakes.

https://www.inlinetube.com/products/pr101

If I were starting from scratch with my brake system, I'd either mount that proportioning valve up beside the master cylinder like the gmt400 trucks did, or better yet, I'd install an adjustable proportioning valve up there.

I picked up this valve, but just want to confirm…

On most master cylinders, the front brake port is on the rear of master cylinder, correct?

[Asshat]

Calipers are mounted.