New Dorman and Cardone master cylinders

east302 said:

Have you done this?

Would it need to be with a master cylinder from a disc/drum setup? I know they had disc/disc for a while, but not sure when they went back to disc/drum on the 99-06 generation.


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I have not done this and don't honestly know if it's an actual upgrade, or if people are perceiving an advantage because they simply replaced a bad master cylinder with a good one.

If you want a for sure disc/drum application GMT800 master cylinder though, look up a 2006 or 2007 Silverado SS. Those are RWD, not the AWD of previous years (2005 had RWD as an option but AWD was still on many of them) - the RWD-only models for 2006-2007 were all drum rear because they got the hybrid 9.5" 14 bolt.

Richard

I bought the Dorman M630031 and it's been installed for about 18 months with no issues. It fixed the spongy brake pedal feel which my truck suffered from which is why I made the change.

Master cylinders are a total hit-or-miss. I rebuild my own single master cylinders for my mid 60s GM cars, I install ancient made in USA rubber seals that I stashed for 30 plus years. Never have a problem. But dual Master cylinders? I had trouble with those 35 years ago, failing after a week or two. And I put one in my K5 Blazer diesel plow truck a few years ago, and it lasted one plowing season, which is about a thousand miles. So I put another one in under lifetime warranty, that one's been okay for a couple of years. But it doesn't matter what you buy, it's just hit or miss. Whether it's a starter or shocks or bushings, you name it, you have no idea what you're getting in the colorful box. I just watched a video of South Main Auto ranting about Maiden Asia starters, I think it was a year old video. You just never know what's going to work, the quality control on made-in-canada starters was junk 35 years ago, and it obviously hasn't gotten any better. A friend of mine runs the largest starter-alternator caliper rebuilding shop in Eastern Canada, employees over a hundred workers, and I go there from time to time, and the last couple of years he's been buying Chinese starters alternators and calipers,. He takes them apart and puts in made in USA or Canada rubber seals, but that's his source of cores now, brand new Chinese caliper and starters and alternators. He buys them in huge quantities for less than you can buy junk cores, and you never know what you're getting with cores, and if you can even get them when you need them

The ACDelco professional series is manufactured using GM's specs for all parts, from the rubber components to bore smoothness. This is what is in the box at the dealership and engineering specs are for 5,000 hours of usage. This is the equivalent of 150,000 miles. The "Dura Stop" is a value line, usually made in south Vietnam, to compete on the global market. These are the same ones sold in parts stores in Turkey, Greece, India and the rest of Asia Minor. Remember, this is a global market and market share is key, but you always get what you pay for...not the box color. I always go with OEM as a design change occurs mid-run in just one part makes it a new part number due to a TSB perhaps. But the original, is copied, then reproduce. I have seen this in ABS sensors used in Buicks. Buy this part form elsewhere, you get first design.
The photo below is about 22 years old now, but the ignition module was cracked open at the GM training facility in Troy, MI. The one on the left was an ACDelco and the right was brand-X (We were told to use that term, but I don't care anymore) was delivered by a truck w/big fiberglass yellow cap on top. Box was marked Standard. The part was new for same GM application. "Question; "What's in your wallet...Wait, I mean What's in your distributor?"

Alternative to the GMT800 master is the master used for the somewhat rare 2000 GMT400 2WD Tahoe SS, also used on LEO Tahoes.

AC Delco part number 174-722
GM Part number 18029968

It will provide a firmer pedal by increasing pressure to the rear brakes. Bolts right up with no adapters, works with ABS etc. If your ABS is no longer working use the original master. This master will easily lock up the rear brakes on damp pavement.

FWIW... and mostly obvious but to get the firmest pedal on the GMT400, adjust the rear brake shoes and keep the aduster lubricated along with a thorough bleed, including the abs system. Don’t forget to bench bleed the master cylinder.

Tahoe SS? Did you mean to type Tahoe Limited ?

Richard

blackburb said:

Alternative to the GMT800 master is the master used for the somewhat rare 2000 GMT400 2WD Tahoe SS, also used on LEO Tahoes.

AC Delco part number 174-722
GM Part number 18029968

It will provide a firmer pedal by increasing pressure to the rear brakes. Bolts right up with no adapters, works with ABS etc. If your ABS is no longer working use the original master. This master will easily lock up the rear brakes on damp pavement.

FWIW... and mostly obvious but to get the firmest pedal on the GMT400, adjust the rear brake shoes and keep the aduster lubricated along with a thorough bleed, including the abs system. Don’t forget to bench bleed the master cylinder.

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NBS ACDelco master and the little line adapter is about $80. That special OBS master is $250. The work is all the same except for the extra 2 minutes it takes to add the adapter. No brainer. That's almost $200 to spend on other cool stuff!

I just bought the master without a reservoir on top and speed bleeders from AutoZone.
Master works fine and the speed bleeders made quick work of the swap.
I have a mightyvac and still prefer the speedbleeders.
Something like 8 years on one no issues and just put one in my wife’s 97 Burban no issues there after a few months

Bought the Raybestos. Like everything else its a made in China piece. Got it bolted up, now i am installing russell braded lines. Will report back once i get it all bled and drive it a bit.

Raybestos master installed RWAL removed, solid pedal. Stops nice. Honestly the problem was in the RWAL, since replacing the master cylinder didnt solve the issue, removing the ABS however did. The bonus was i bled about 2 quarts of brake fluid thru it at all 4 wheels thinking i had an air pocket caught somewhere.

What was the eye opener was that 4 pin module comparo pic that Ken K posted. A am using a Standard automotive 4 pin module on an adaptor bracket attached to a mid 70s mopar electronic distributor to convert it to HEI. Works good but had i known it was that much different than a factory GM 4 pin i woulda opted for the GM one. My 94 has a delphi module in it after the oem GM one popped at 148K. I hope that one doesnt look like a science project inside either.