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Old 03-15-2017, 08:44 AM   #1
95 S_Trucker
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GMT800 Brake Upgrade

I did a brake upgrade on my truck, and there is some uncertainty about some of the parts needed.

This applies to all 8 lug 4wd trucks

First step is to get a set of steering knuckles for a 3/4 ton or 1 ton GMT800 Truck. It doesn't matter if its from a 2wd or 4wd, the knuckles are the same

*If you can find a 99-00 knuckle, it will save you some time and money*

I couldn't find any around here, so I got a set of 01-07 knuckles.

The tie rod taper is a different size between the 99-00 and 01-07. The 99-00 uses the same taper as the GMT400.

Next, youll have to enlarge the taper on the knuckle for the upper and lower ball joints. It sounds intimidating. Its not. I had some spare ball joints, and I reamed the knuckle until the ball joint can be installed and the castle nut can be threaded enough to fully insert the cotter pin.

I used this reamer:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

I installed new hub bearings in the knuckles. I also installed new backing plates. The used ones were damaged.

Next, I had to figure out the tie rod end. the 01-07 tie rod taper is larger than the GMT400. I had to figure out how to adapt a 01-07 outer tie rod to the GMT400 tie rod adjuster sleeve. I took a GMT400 tie rod to a local machinist. He cut the end off, and machined and threaded half of it to M14x1.5(same thread as 01-07 inner tie rod. That piece threads into the 01-07 outer tie rod and is held in place with a jam nut. The other end threads into the tie rod adjuster sleeve. Pics are easier to understand

Part machined from GMT400 tie rod:

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Part installed into 01-07 outer tie rod with jam nut:

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Tie rod installed into GMT400 adjuster sleeve

Name:  IMG_5083.jpg
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After that, its just bolting stuff together:

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And the before picture:

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Total parts list:

Steering knuckles
Hub bearing(2 needed)
Front backing plate(2 needed)
Brake rotors(2 needed)
Brake caliper(left and right)
Brake hose(1 for each side, I chose braded stainless)
Outer tie rod end(2 needed)
Tie rod adapter(custom made, 2 needed)
M14x1.5 nut(jam nut, 2 needed)
CV Axle(2 needed, GMT400 will interfere)

All parts interchange from01-07. I just ordered everything for an 06 2500HD.

Now, the reason for this swap. The previous owner had a rear disk brake kit installed with elderado calipers. The brakes didn't work well, and the parking brake didn't hold. I swapped to a piston with a larger caliper and the truck stopped great. But I really wanted a parking brake. So a couple years go by and I decide to put a GMT800 axle under the truck to get disc brakes and a parking brake. It was a relatively simple swap, weld on new perches nd shock mounts. Then I figured the front brakes should match the rear.
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Old 03-15-2017, 09:38 AM   #2
95 S_Trucker
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Re: GMT800 Brake Upgrade

If you do decide to use the GMT800 brake hoses, you will need to install a different flare nut on your steel brake line. The GMT400 nut has 3/8-24 flare nut. The GMT800 hose will require 7/16-24 flare nut. You'll have to cut the line, replace the nut, and put a new flare on the brake line.

AGS part number for 7/16-24 nut with 3/16 line is BLF-11



Obviously you'll need an alignment after a knuckle swap.
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Old 03-20-2017, 10:36 AM   #3
Chris95GT
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Re: GMT800 Brake Upgrade

Nice!

Do you know by chance if arms are the same on a 2wd truck and this could apply to them as well?
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Old 03-20-2017, 02:04 PM   #4
95 S_Trucker
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Re: GMT800 Brake Upgrade

The upper ball joints are the same between 2wd/4wd.

Let me look at a 2wd lower ball joint and compare it to a 4wd joint I have here.
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Old 03-20-2017, 03:39 PM   #5
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Re: GMT800 Brake Upgrade

The taper is the same between the 4wd lower ball joint and 2wd lower ball joint on the GMT400.

The GMT800 knuckle will still need reamed, but it will work
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Old 03-21-2017, 09:07 AM   #6
Chris95GT
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Re: GMT800 Brake Upgrade

Quote:
Originally Posted by 95 S_Trucker View Post
The taper is the same between the 4wd lower ball joint and 2wd lower ball joint on the GMT400.

The GMT800 knuckle will still need reamed, but it will work
Awesome. Thanks!
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