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Brake upgrades using factory parts for GMT-400(88-00 OBS), and 94-99 DODGE 2500/3500

The piston will travel back in the bore only as far as the oring will let it travel. Once the piston is pushed out and the oring is settled to tjat position, when the pedal is apllied and the piston pushes outwards, the oring will sort of roll in the groove and against the bore, when the pedal is released, the piston will return only as far as the oring had rolled.
There is no springs or mechanisms that will retract the piston in tje bore, only that springy action of the oring.
I hope that makes sense.
If the piston pushed out too far because of the thinner rotor, and, if the oring would be exposed, brake fluid is going to come dumping out.
 
MrMarty51 said:
The piston will travel back in the bore only as far as the oring will let it travel. Once the piston is pushed out and the oring is settled to tjat position, when the pedal is apllied and the piston pushes outwards, the oring will sort of roll in the groove and against the bore, when the pedal is released, the piston will return only as far as the oring had rolled.
There is no springs or mechanisms that will retract the piston in tje bore, only that springy action of the oring.
I hope that makes sense.
If the piston pushed out too far because of the thinner rotor, and, if the oring would be exposed, brake fluid is going to come dumping out.
Click to expand...


Thank You. I get all that, or at least I understand what you are trying to say.
According to the OP, and my own confirmation comparing parts at the part store, there are a few facts. The DRW pads are thicker, and have slightly more surface area than the SRW pads. The DRW rotor is 1/4" thicker than the SRW rotor. The mouth of the DRW caliper is wider to accomodate the thicker pads and the thicker rotor.

The piston is also larger on the DRW caliper than the piston on the SRW caliper.

So it looks like the DRW caliper and pads could be installed on a SRW truck. But the rotors for a 2WD DRW truck have the large offset rim mounting surface which makes installing them on a 2wd SRW truck impracticle compared to just swapping the hat style rotors on a K truck.

So you end up with rotors that are essentially 1/4" narrower than the DRW caliper is designed for when used with the 2WD SRW rotors.

Now, the caliper does not know that the rotor is thinner, and doesn't care at least initially. But it is likely that the pads would need to be changed before they are worn out so that the piston doesn't get too far out of the hole. This would be a fair trade for increased stopping power.

So that leaves the issue of the larger piston of the DRW caliper requiring more fluid for distance of travel, potentially resulting in increased pedal travel. How much? I don't know.

The DRW and SRW call for the same master cylinder as a replacement part so maybe it would be negligible.

I recently replaced the original 290,000 mile rear shoes, and installed the larger DRW rear wheel cylinders.

Pedal travel seemed to increase slightly. But that could be just due to the new shoes not yet matched to the radius arc of the drum, and possibly the old shoes being harder from age and glazing, rather than the extra displacement required for the slightly larger wheel cylinders. And that pedal travel "may" have reduced slightly as the new shoes have worn in this week. Or, I am just adjusting to it.

But I don't want to compound the pedal travel problem with larger displacement calipers as well. This JB8, (or is it JD8?) system has always had a nice high pedal, unlike some of the other trucks with different systems. But despite that it still could have better stopping power.

The larger DRW wheel cylinders definitely help increase rear braking that I can feel.

The fronts are due for a refresh, and I'd like to upgrade them similarly. I "think" I can put the DRW calipers and pads on and get a slightly larger pad surface area as well as the larger piston caliper. The only issue I see is that the pads will need replacing before they're fully worn out to prevent over extension of the caliper piston. And the possibility of increased pedal travel for the larger pistons.





Tom
 
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THEFERMANATOR said:
The DRW calipers on SRW rotors would eventually allow the caliper piston to come out of the caliper body once the pads got worn down most of the way. I've heard of somebody doing it, but I personally wouldn't do it.
Click to expand...
Yup! And the first time he spaces off checking pad thickness and pops a piston out, dumps his brake fluid, and has (hopefully) only his rear drums to stop on may very well be his last time, too!☠
 
THEFERMANATOR said:
The DRW calipers on SRW rotors would eventually allow the caliper piston to come out of the caliper body once the pads got worn down most of the way. I've heard of somebody doing it, but I personally wouldn't do it.
Click to expand...

I get that. I've been a professional auto tech for almost 40 years, and Master ASE for 35. My truck has been meticulously maintained and serviced since I brought it brand new, and I plan to drive it for the rest of my life. As long as the pads were replaced before the pads were worn beyond halfway, there wouldn't be an issue of the piston coming out of the bore. I am relatively easy on my brakes and get several years out of a set of pads.

I am trying to improve the front braking a little to match the improvement I got from the rears when I installed the larger diameter DRW wheel cylinders.
The slightly larger front pad surface area and the larger caliper pistons from the DRW system might do the trick, but I worry if I might have increased pedal travel operating the larger pistons. Since they list the same master cylinder for the SRW and DRW systems, I am guessing it would be minor.

I was trying to get feedback as to how much improvement that swap might offer, or if there was another solution for the 2WD SRW truck. If it is a noticeable improvement, it would be worth it to have to change the pads a little earlier. As long as the pads were changed by the time they were down to 1/8th", there should be no danger of the piston coming out.

Certainly if I was to sell the truck (which I won't), it would be prudent to put the correct calipers back on so someone didn't find out the hard way.





Tom
 
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Husker6.5 said:
@C30454 , just bite the bullet and do the GMT-800 conversion on the fronts and enjoy larger diameter rotors and dual piston calipers for some serious whoa power.
Click to expand...


I would have to research that some more. I would be concerned about altering critical steering and suspension angles, and I wouldn't even consider such a modification if that would be the case. IMO "MOST" modifications I see people do often sacrifice function for appearance, or all around function for a small narrow gain. This truck is a pristine driver still 22 years out, mostly because it has been maintained, not abused, and not dicked up. I will work it when neccesary. Everything is bone stock except for Kodiak door handles on all 4 doors, and towing mirrors. And now the rear wheel cylinders. I am very careful about choosing to modify, that's why it is still mostly stock.

I am not against modifying per se. I have a '64 442 that has a 9" with a spool, a TH400 and a .700 lift solid roller cam in a 496 Olds engine. That's my vehicle to do stupid stuff to and go out and stand on the gas.

My truck however, I want completely reliable and dependable, and ready to drive cross country if I need it to.

I treat a "toy" and a daily driver very differently. This truck is my daily driver.


Tom
 
C30454 said:
I would have to research that some more. I would be concerned about altering critical steering and suspension angles, and I wouldn't even consider such a modification if that would be the case. IMO "MOST" modifications I see people do often sacrifice function for appearance, or all around function for a small narrow gain. This truck is a pristine driver still 22 years out, mostly because it has been maintained, not abused, and not dicked up. I will work it when neccesary. Everything is bone stock except for Kodiak door handles on all 4 doors, and towing mirrors. And now the rear wheel cylinders. I am very careful about choosing to modify, that's why it is still mostly stock.

I am not against modifying per se. I have a '64 442 that has a 9" with a spool, a TH400 and a .700 lift solid roller cam in a 496 Olds engine. That's my vehicle to do stupid stuff to and go out and stand on the gas.

My truck however, I want completely reliable and dependable, and ready to drive cross country if I need it to.

I treat a "toy" and a daily driver very differently. This truck is my daily driver.


Tom
Click to expand...
Several people on here have done it, it's all pretty much bolt-on with the exception of re-reaming the taper in the knuckles for the outer tie rod ends. Several people have done it on here on their DD's with excellent results on the steering, and especially the braking, end of things. If a banker like @Big T can successfully do the conversion on his Burb and then make multiple trips back and forth between Montana and Cali, as well as tow his boat and make multiple trips into the mountains with steep grades with no problems . . .

Besides, this conversion has been done multiple times, with step-by-step threads on here, because members wanted more, safer, whoa power towing or in normal driving than the weak, stock, GMT-400 front brakes.

Doing the GMT-800 conversion is no different than putting a Mustang front end under your '32 T-bucket roadster. Tried and true. VERY surprised you haven't done any of the longevity/performance mods to your 6.5 like remote mounting the PMD on an external cooler or upgrading the exhaust system to a 3" down with 4" back or upgrading to a balanced flow 2000+ m.y. water pump with a spin-on clutch and Duramax fan to improve overall cooling and help prevent overheating of the rear passenger head and cracking the head. I'm really surprised, as a professional mechanic, that you aren't familiar with the weaknesses of the GMT-400/6.6TD platform and the tried and true fixes to address those issues.
 
Husker6.5 said:
Several people on here have done it, it's all pretty much bolt-on with the exception of re-reaming the taper in the knuckles for the outer tie rod ends. Several people have done it on here on their DD's with excellent results on the steering, and especially the braking, end of things. If a banker like @Big T can successfully do the conversion on his Burb and then make multiple trips back and forth between Montana and Cali, as well as tow his boat and make multiple trips into the mountains with steep grades with no problems . . .

Besides, this conversion has been done multiple times, with step-by-step threads on here, because members wanted more, safer, whoa power towing or in normal driving than the weak, stock, GMT-400 front brakes.

Doing the GMT-800 conversion is no different than putting a Mustang front end under your '32 T-bucket roadster. Tried and true. VERY surprised you haven't done any of the longevity/performance mods to your 6.5 like remote mounting the PMD on an external cooler or upgrading the exhaust system to a 3" down with 4" back or upgrading to a balanced flow 2000+ m.y. water pump with a spin-on clutch and Duramax fan to improve overall cooling and help prevent overheating of the rear passenger head and cracking the head. I'm really surprised, as a professional mechanic, that you aren't familiar with the weaknesses of the GMT-400/6.6TD platform and the tried and true fixes to address those issues.
Click to expand...

Lowly banker eh? Officially I am now a banking regulator with the Federal Reserve.

Conversion works great. It does not impact alignment angles, but do get an alignment done after the conversion.

I just hope my truck lasts long enough to fully enjoy the conversion. I think I have 30K miles on the conversion. Another 70K and I will feel satisfied.
 
Besides, the GMT-800 platform is essentially a beefier version of the GMT-400 designed to handle the weight/size of the D-Max/Allison powertrain.

With the GMT-800 front knuckle/brakes conversion, it's pretty much no different than a 68-72 GM A-Body conversion from front drum to front power disc brakes - knuckle swap, disc hardware of calipers, hoses - but WITHOUT having to swap out proportioning valve, master cylinder and adding the vacuum booster. All factory steering geometry is maintained, and as with all front end work you put it on an alignment rack and set the toe-in, caster and camber just as you would with a GMT-400 front end if you'd just done the upper and lower ball joints. In fact, there are direct parts interchange between the two different front ends such as the ball joints. If you want really improved front braking, just bite the bullet and do the GMT-800 conversion and quit piddling around with a potentially fatal, dangerous mish-mash of SRW/DRW calipers, rotors and pads that are not meant to work together to gain only minimal improvements in stopping power.
 
Big T said:
Lowly banker eh? Officially I am now a banking regulator with the Federal Reserve.

Conversion works great. It does not impact alignment angles, but do get an alignment done after the conversion.

I just hope my truck lasts long enough to fully enjoy the conversion. I think I have 30K miles on the conversion. Another 70K and I will feel satisfied.
Click to expand...
I never said you were a 'lowly banker'. Was just pointing out that you weren't a professional wrench, but had the ability to D.I.Y. the GMT-800 conversion without any major issues.
 
ak diesel driver said:
I believe his is a gasser
Click to expand...
Yeah, I guess I should have picked up on that from his user name. It would help if @C30454 would fill out his signature so we'd know what he's driving. Yeah, with that 7.4L in it, there isn't much he can do to improve power, performance or longevity without dumping some serious bucks into it with little gain. Not like gaining 100 hp and 200 lb/ft with a 6.5 and getting a more reliable motor in the process.
 
Husker6.5 said:
Besides, the GMT-800 platform is essentially a beefier version of the GMT-400 designed to handle the weight/size of the D-Max/Allison powertrain.

With the GMT-800 front knuckle/brakes conversion, it's pretty much no different than a 68-72 GM A-Body conversion from front drum to front power disc brakes - knuckle swap, disc hardware of calipers, hoses - but WITHOUT having to swap out proportioning valve, master cylinder and adding the vacuum booster. All factory steering geometry is maintained, and as with all front end work you put it on an alignment rack and set the toe-in, caster and camber just as you would with a GMT-400 front end if you'd just done the upper and lower ball joints. In fact, there are direct parts interchange between the two different front ends such as the ball joints. If you want really improved front braking, just bite the bullet and do the GMT-800 conversion and quit piddling around with a potentially fatal, dangerous mish-mash of SRW/DRW calipers, rotors and pads that are not meant to work together to gain only minimal improvements in stopping power.
Click to expand...

I really want a clean GMT 800 Suburban 2500 4wd model years 2001 to 2005 with the metal bumpers to do a Duramax conversion.
 
Big T said:
I really want a clean GMT 800 Suburban 2500 4wd model years 2001 to 2005 with the metal bumpers to do a Duramax conversion.
Click to expand...
Used to see quite a few of those, professionally done out of SoCal and Aurora, CO, on eBay up until a few years ago. Don't know if those upfitters are still in business, or if such a conversion is strictly a D.I.Y. deal now of finding the parts/harnesses/computer and making it all function.
 
Big T said:
Did not realize the GMT 800 had a problematic dual tank set-up. Just like the look, interior and obviously the braking set-up of the GMT-800 in the years noted.
Click to expand...
Yeah, to get the spare out of the rear cargo area, it was mounted underneath in the rear like the pickups. To maintain fuel capacity like the old Burbs, twin tanks. There's a couple of threads on here dealing with in-op fuel transfer and gauge issues between tanks.

Now, I'd like to go to a dual tank setup on my 98 K2500 Burb, by installing the big pickup tank in the side position, and using a 'Y' filler tube to fill both tanks from the same place, use the factory sender unit in the side tank, and an aftermarket switch and valve assembly to change between tanks/level senders. Retain the stock lift pump. Would also love to do like the member on here (can't remember who, help?) who built runningboard side saddle tanks for his C/C dually that added about 20 gal/side. I would LOVE to get about 100+ gallon fuel capacity and then be able to drive to either coast non-stop on one fueling! And do it running homemade B-100!
 
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