GMT 800 front brake upgrade to GMT400 8 lug

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stutaeng

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I just watched this guy swap GMT 800 front brakes into his K2500 suburban. I honestly didn't realize it was that difficult....

Towards the end he mentions a hydroboost master cylinder upgrade from the big, heavy 10 lug 3500HD GVWR 15,000 trucks.

I may decide to do this to my K3500 beater, LOL.

Enjoy!

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454cid

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I dont think the hydroboost system from the hd is much different from the 8-lug.

I'll have to watch this later.
 

sweetk30

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Master cylinder yes maybe . But hydro boost unit dont think so .

He is a TV show guy so i take his stuff with a bit of my own thinking and not 100% truth.
 

454cid

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Watching now.... this is a known swap, but not super common. They're 800 brakes, not 900. The first guy I ever saw do it was on FSC, about 10+ years ago, but I can't find the thread. I actually had spindles at one time, wanting to do this. I sold them a few years ago, Though. This guy (and I've watched a few of his videos before) did things a bit different, Though.

It sounded like he was just interested in the 3500HD master cyclinder since it was a four wheel disc unit, to me, not the HD hydrobooster.

Other than the better working brakes, the other HUGE benefit is slide on rotors!
 

WV_Dave

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He's talking about the master cylinder just so it's matched up properly to the types of brakes he has now.

I'm pretty sure pressure is still regulated at the proportioning valve after the master cylinder though. That would be the part, I'd think, you'd want to match up to your system (4 wheel disc) or just use an adjustable one.
 

stutaeng

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Watching now.... this is a known swap, but not super common. They're 800 brakes, not 900. The first guy I ever saw do it was on FSC, about 10+ years ago, but I can't find the thread. I actually had spindles at one time, wanting to do this. I sold them a few years ago, Though. This guy (and I've watched a few of his videos before) did things a bit different, Though.

It sounded like he was just interested in the 3500HD master cyclinder since it was a four wheel disc unit, to me, not the HD hydrobooster.

Other than the better working brakes, the other HUGE benefit is slide on rotors!
Yes, corrected the title about the GMT800 and master cylinder comment.

That's what I was thinking about the slide-on rotors!

I guess another benefit would be you can also use the GMT800 LD/HD lower control arms? Like in case someone couldn't find GMT400 lower control arms at the junkyard?
 

454cid

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I guess another benefit would be you can also use the GMT800 LD/HD lower control arms? Like in case someone couldn't find GMT400 lower control arms at the junkyard?

I'm not worried about that and I live in MI. Replacing whole control arms instead of the ball joints is a newer idea. I'd rather have OEM control arms than new Made in China parts.

I tried looking for the thread on FSC last night, and I couldn't find it. I can't remember the guys username either.
 

BNielsen

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I'm not worried about that and I live in MI. Replacing whole control arms instead of the ball joints is a newer idea. I'd rather have OEM control arms than new Made in China parts.

I tried looking for the thread on FSC last night, and I couldn't find it. I can't remember the guys username either.

I had that thread bookmarked along with the 454 thread; it's all gone now. It was a twotone ECSB that was red up top and tan on the rockers, he did the swap and had everything documented.
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I'm for one pretty intrigued in the whole swap; from the Dana Super 70 rear and the knuckle swap up front. I'm happy to have confirmation on what works and what's needed for the most part.
 

454cid

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I had that thread bookmarked along with the 454 thread; it's all gone now. It was a twotone ECSB that was red up top and tan on the rockers, he did the swap and had everything documented.
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I'm for one pretty intrigued in the whole swap; from the Dana Super 70 rear and the knuckle swap up front. I'm happy to have confirmation on what works and what's needed for the most part.

The 454 thread is still there. I was looking at it last night.

Yeah, I thought that Dana swap was interesting... I did not look for anymore details on it, Though. I would think he had to move spring/shock mounts, just like for the GMT-800 10.5"FF. Maybe it was a case of availability? My uncles van has that axle. I should look for his video on it.
 

Schurkey

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How far apart are the ball joints spaced on the new-style steering knuckle vs. the original? That would affect front roll center and other steering angles.

Where is the tie rod arm on the new steering knuckle positioned compared to the original knuckle? That could affect bump steer and turning radius.

Why does it take 26 minutes of yap, yap, yap on the video? Do Youtube video posters get paid by the minute?

Given recent events--I just pulled the LF hub and rotor out of the steering knuckle--after yanking the steering knuckle off the ball joints--on my '97 K2500 8-lug, slide-on 8-lug rotors look pretty good to me. But by the time I figure out where to get the updated parts, I'm gonna have mine put back together; and it's not likely to wear out again for years and years. (And I've already been through the front calipers and pads.)
 
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