Has anyone tried installing an GMT800 brake master cylinder on their GMT400?
Just been reading about people making this swap and how it apparently makes a huge difference to pedal feel.
Curious....

I was going to try this swap in the near future. Do you know of any specific applications that had drum brake rear and hydroboost on the GMT800. I think a lot of the heavy-duty gmt800s had rear discs?

Haven't heard of this, but I'm all ears now...

I've never heard of this, I wonder if they have a larger cylinder or something?

http://www.fullsizechevy.com/forum/general-discussion/technical-maintenance/418811-answer-squishy-GMT400-brakes-perhaps.html

Explains it all!
Sounds worth a try to me.

We are not alone....

http://www.fullsizechevy.com/forum/general-discussion/technical-maintenance/446339-hydroboost-gmt800-.html

http://www.classicperform.com/TechBook/BrakeTroubleshoot.htm



Last edited by CrazyHoe on Wed Aug 03, 2011 5:48 am; edited 1 time in total

Combine the Master cylinder upgrade with this kit:

Front brake conversion kit (knuckles) for 1988 through 2000 K2500 HD 8 Lug 4WD Suburban/Pickup. 40% increase in braking effectiveness with upgrade to later model 2-piston brakes.

http://performanceoilstore.com/products.asp?cat=60

And to this, you can add bigger rotors 14" and a relocation bracket to increase the braking power even further!!!


http://www.summitracing.com/parts/SSB-A126-47/


Wonder if they make this one for 8 bolts?
http://www.jegs.com/i/Stainless-Steel-Brakes/884/A126-42/10002/-1

http://www.catalograck.com/ImgVD/SSB/A126-42-42A.pdf

99bluetahoe wrote:

I was going to try this swap in the near future. Do you know of any specific applications that had drum brake rear and hydroboost on the GMT800. I think a lot of the heavy-duty gmt800s had rear discs?

hydroboost rear disc brakes

acdelco 1780683

CHEVROLET AVALANCHE 2500 (2003 - 2004)
CHEVROLET AVALANCHE 2500 LS (2005 - 2006)
CHEVROLET AVALANCHE 2500 LT (2005 - 2006)
CHEVROLET SILVERADO 1500 (2003 - 2006)
CHEVROLET SILVERADO 1500 CLASSIC LS 2007
CHEVROLET SILVERADO 1500 CLASSIC LT 2007
CHEVROLET SILVERADO 1500 CLASSIC WT 2007
CHEVROLET SILVERADO 1500 HD (2003 - 2005)
CHEVROLET SILVERADO 1500 HD CLASSIC LT 2007
CHEVROLET SILVERADO 1500 HD LT 2006
CHEVROLET SILVERADO 1500 LT 2005
CHEVROLET SILVERADO 2500 (2003 - 2006)
CHEVROLET SILVERADO 2500 HD (2003 - 2005)
CHEVROLET SILVERADO 2500 HD CLASSIC LS 2007
CHEVROLET SILVERADO 2500 HD CLASSIC LT 2007
CHEVROLET SILVERADO 2500 HD CLASSIC WT 2007
CHEVROLET SILVERADO 2500 HD LS 2006
CHEVROLET SILVERADO 2500 HD LT 2006
CHEVROLET SILVERADO 2500 HD WT 2006
CHEVROLET SILVERADO 3500 (2003 - 2006)
CHEVROLET SILVERADO 3500 CLASSIC LS 2007
CHEVROLET SILVERADO 3500 CLASSIC LT 2007
CHEVROLET SILVERADO 3500 CLASSIC WT 2007
CHEVROLET SILVERADO 3500 LS 2006
CHEVROLET SILVERADO 3500 LT 2006
CHEVROLET SILVERADO 3500 WT 2006
CHEVROLET SUBURBAN 2500 (2003 - 2004)
CHEVROLET SUBURBAN 2500 LS (2005 - 2006)
CHEVROLET SUBURBAN 2500 LT (2005 - 2006)
GMC SIERRA 1500 (2003 - 2005)
GMC SIERRA 1500 CLASSIC SL 2007
GMC SIERRA 1500 CLASSIC SLE 2007
GMC SIERRA 1500 CLASSIC SLT 2007
GMC SIERRA 1500 CLASSIC WT 2007
GMC SIERRA 1500 HD 2003
GMC SIERRA 1500 HD CLASSIC SLE 2007
GMC SIERRA 1500 HD CLASSIC SLT 2007
GMC SIERRA 1500 HD SLE (2005 - 2006)
GMC SIERRA 1500 HD SLT (2005 - 2006)
GMC SIERRA 2500 (2003 - 2004)
GMC SIERRA 2500 HD (2003 - 2005)
GMC SIERRA 2500 HD CLASSIC SL 2007
GMC SIERRA 2500 HD CLASSIC SLE 2007
GMC SIERRA 2500 HD CLASSIC SLT 2007
GMC SIERRA 2500 HD CLASSIC WT 2007
GMC SIERRA 2500 HD SL 2006
GMC SIERRA 2500 HD SLE 2006
GMC SIERRA 2500 HD SLT 2006
GMC SIERRA 2500 HD WT 2006
GMC SIERRA 3500 (2003 - 2005)
GMC SIERRA 3500 CLASSIC SL 2007
GMC SIERRA 3500 CLASSIC SLE 2007
GMC SIERRA 3500 CLASSIC SLT 2007
GMC SIERRA 3500 CLASSIC WT 2007
GMC SIERRA 3500 SL 2006
GMC SIERRA 3500 SLE 2006
GMC SIERRA 3500 SLT 2006
GMC SIERRA 3500 WT 2006
GMC YUKON DENALI XL (2003 - 2004)
GMC YUKON XL 2500 (2003 - 2004)
GMC YUKON XL 2500 SLE (2005 - 2006)
GMC YUKON XL 2500 SLT (2005 - 2006)



not the answer you're looking for but looks like the front where improved in 2005...

http://www.performancetrucks.net/forums/gm-drivetrain-suspension-22/year-gmt800-trucks-switch-bigger-brakes-front-452462/

Howard your not happy with the hydroboost as is? The main reason I swapped besides the vacuum booster started leaking is I hated the pedal travel feel and on that note those guys in that link on FSC are idiots every single 95-98 chev with vacuum brakes Iv ever drove feel the same way all the brake work in the world wont make them feel any better. I wonder if there is any truth to what they are saying about the pushrod being a 1/4 inch to short on them? Obviously they are talking about the one between the booster and master and not the booster to pedal on but some of those guys musta gotten confused.

Yeah...I like the HB brakes. MUCH better than the standard vac brakes.
I'm always looking for improvements though...and was just curious if anyone here had heard of or tried this.
I'll be interested to see what difference the enormous 14bolt SF drums and stainless braided lines makes.

The big drums help alot I sometimes had a hard time powerbraking and now with the hydro I cant hardly do it at all Still need the trutrack tho

Ok. So I want to to this to my suburban. So do I just go to the parts store and ask for a 2006 master cylinder? Get the fitting adapter and this will bolt up to my current vacuum booster?

My current booster is very rusted and I thought about getting a new one. Would a GMT800 vacuum booster work on my truck too or should I buy another GMT400 one?

Thanks for the help guys. This seams a lot easier than the hydroboost.



Ken

Well I spent ALL day today working on the burban. Put on new calipers, drums, shoes, wheel cylinder and spring kit. Replaced all 3 rubber lines feeding the calipers and rear drums. Twisted off my rear lines and had to go buy some new hard lines. Broke 2 double flare tools that made such horrible flares that I had to go back to the parts store and just buy pre-flared line sections and piece them all together.

So I had my 9 year old son help me bleed the brakes. I am pretty sure that I got most if not all of the air out. The brakes still feel soft though and pedal goes pretty far down.

Are you supposed to bleed the brakes with the vehicle running? If air is trapped in the ABS unit how do you get that out?

And Please someone answer my previous post. I would like to change the master cyl and brake booster but really don't know what parts to buy.


Thanks guys.

Ken

Can't help with the MC swap. You will need a Tech 2 to open the ABS valving for bleeding. If the lines were open long enough to let air into the ABS, it would be best to let a shop bleed them. I generally bleed brakes with the engine off. I have the helper pump about 6 times and hold, then let the pressure out while they are holding pressure on. You bleed them right rear, left rear, right front, left front.

The GMT800 Brake Fluid Cap would be worth it to me...........LOL

-Justin

Ben T's trick of engaging ABS on gravel road seems to work well.

I know the cap on my current mc sucks and the rubber part always separates from the lid.

Next time you have a brake line that wants to twist off like that take your torch (propane or butane works fine) and get that fitting glowing then take your wrench and work the fitting back and forth itll come out.

I mention this because not everyone knows it but... it's better to give hollow metal lines a good, hard, sharp twist than to try to loosen it slowly. You'll be tempted to go slow and easy with it, but this is the worst thing you can do. If the fitting is grabbed onto the line, the hollow line will hold for a bit, then will bend before the fitting breaks loose. A good, sharp twist will break the fitting loose before the line starts to bend. If it's rusted, a little emery cloth around the line and a bit of Break Free will help with the last bit.

When bleeding make sure you don't go too far down, put a 2x4 or your other foot under the pedal to prevent the pedal from going to the floor when the bleeder is opened.