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

Messages
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Location
Fort Washington PA
#21
Ok Great,

So if i replace my front calipers with the 3500 version will they just bolt right on to my spindles without any modifications to the mounting? As well, will I need to use the 3500 brake lines (which need replacing anyway). I am figuring that while I am at it....replace the calipers, front brake lines, rotors and pads to the 3500 parts and upgrade the performance. Seems simple. Can i use my original proportioning valve or doe that need replacing as well.
 

THEFERMANATOR

FRANKENBURBAN
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ZEPHYRHILLS FL
Thread starter Staff #22
Swap to the 3500 dual rear wheel calipers, pads, and rotors, that's it. It all bolts right on, and gives a nice bump in front braking. It is nothing like doing the gmt-800 conversion, but it does help. I reused my russel braided brake lines on mine, so I assume the rubber lines would work as well. Just make sure you buy the dually stuff as GM also made the 3500 in a single rear wheel truck, and it used the same brakes as the 2500 with 8 lugs and a 10.5" rear axle. There is only 2 different spindles for these trucks, 6 lug or 8 lug, so theres no concern there. All 8 lug 4X4 trucks use the same hubs, so you're good there as well(dually trucks had a 3.5" spacer that bolted on to make them a dually).
 

staatsof

New Member
Messages
21
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12
Location
N. NJ United States
#25
I've been through this thread a half dozen times and I still can't figure out if or what I might be able to try for a 99 K2500 Chevy Suburban which has a g80 14 bolt 10.5" diff with I beleive full floating slide on drums in the rear. So I'm thinking of just sticking with the drum brakes. I'm not thrilled with this but ... the after market conversion kits com up short for me for usage as winter vehicle in salt & snow country.

I can't tell this vehicle ever got it's proportioning valve upgraded or if it came with the upgraded one. The GM dealer can't find anything either. Looking at the part for identification is hard to do with it in place.
 

THEFERMANATOR

FRANKENBURBAN
Staff member
Lead Moderator
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Location
ZEPHYRHILLS FL
Thread starter Staff #27
I've been through this thread a half dozen times and I still can't figure out if or what I might be able to try for a 99 K2500 Chevy Suburban which has a g80 14 bolt 10.5" diff with I beleive full floating slide on drums in the rear. So I'm thinking of just sticking with the drum brakes. I'm not thrilled with this but ... the after market conversion kits com up short for me for usage as winter vehicle in salt & snow country.

I can't tell this vehicle ever got it's proportioning valve upgraded or if it came with the upgraded one. The GM dealer can't find anything either. Looking at the part for identification is hard to do with it in place.
No stock production vehicles got the valve to my knowledge, so if GM doesn't have a service record for it, then it most likely wasn't done. As far as brake upgrades, you can use the drw 1 3/16" wheel cylinders in the rear along with the acdelco rear brake shoes. Up front you can swap calipers, rotors, and pads to those off of a drw truck and get some more braking there. There is also a bigger master cylinder and stronger booster you can swap in, but I don't reccomend it for any of the stock single piston caliper setups.
 

Tusabes

New Member
Messages
1
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1
Location
California
#28
Hi there , I just picked up a 1993 k1500 blazer 4x4 with 6 lug wheels and want to upgrade the front brakes as my wheels are 22 inches and stopping power needs improvement .

I see from the first post I can upgrade to k2500 suburban calipers and pads , and it also says a gmt800 upgrade is possible. Reading through the gmt800 thread I see you need to change spindles and tie rods etc if you want to go with gmt800 parts .

My question is that I found another thread stating the larger gmt900 rotors are a direct swap into gmt 800 Trucks...

http://z71tahoe-suburban.com/iboard/index.php?showtopic=28846

So since it’s possible to upgrade the gmt400 to gmt800 - is it also possible to just use the gmt800 spindles and tie rods with gmt900 13 inch rotors and calipers (instead of the smaller gmt800 parts) since the gmt800/900 is a bolt on swap for the gmt800 trucks ? Why not just go for the biggest and best and go 13 inch with gmt900 parts ?

Im likely just to go with the simple upgrade so need to pull the trigger soon on buying parts . the first post says just buy the k2500 srw 8 lug calipers and pads ,but why not go with the larger piston drw calipers and pads? Is there a reason to use the srw parts instead of the drw parts ?
Thanks in advance !
 
Last edited:

Big T

Well-Known Member
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Location
Fullerton, CA
#29
Hi there , I just picked up a 1993 k1500 blazer 4x4 with 6 lug wheels and want to upgrade the front brakes as my wheels are 22 inches and stopping power needs improvement .

I see from the first post I can upgrade to k2500 suburban calipers and pads , and it also says a gmt800 upgrade is possible. Reading through the gmt800 thread I see you need to change spindles and tie rods etc if you want to go with gmt800 parts .

My question is that I found another thread stating the larger gmt900 rotors are a direct swap into gmt 800 Trucks...

http://z71tahoe-suburban.com/iboard/index.php?showtopic=28846

So since it’s possible to upgrade the gmt400 to gmt800 - is it also possible to just use the gmt800 spindles and tie rods with gmt900 13 inch rotors and calipers (instead of the smaller gmt800 parts) since the gmt800/900 is a bolt on swap for the gmt800 trucks ? Why not just go for the biggest and best and go 13 inch with gmt900 parts ?

Im likely just to go with the simple upgrade so need to pull the trigger soon on buying parts . the first post says just buy the k2500 srw 8 lug calipers and pads ,but why not go with the larger piston drw calipers and pads? Is there a reason to use the srw parts instead of the drw parts ?
Thanks in advance !
I did the GMT 800 conversion on two K2500s and they have more than enough stopping power. It's crazy good.
 

THEFERMANATOR

FRANKENBURBAN
Staff member
Lead Moderator
Messages
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Location
ZEPHYRHILLS FL
Thread starter Staff #30
Hi there , I just picked up a 1993 k1500 blazer 4x4 with 6 lug wheels and want to upgrade the front brakes as my wheels are 22 inches and stopping power needs improvement .

I see from the first post I can upgrade to k2500 suburban calipers and pads , and it also says a gmt800 upgrade is possible. Reading through the gmt800 thread I see you need to change spindles and tie rods etc if you want to go with gmt800 parts .

My question is that I found another thread stating the larger gmt900 rotors are a direct swap into gmt 800 Trucks...

http://z71tahoe-suburban.com/iboard/index.php?showtopic=28846

So since it’s possible to upgrade the gmt400 to gmt800 - is it also possible to just use the gmt800 spindles and tie rods with gmt900 13 inch rotors and calipers (instead of the smaller gmt800 parts) since the gmt800/900 is a bolt on swap for the gmt800 trucks ? Why not just go for the biggest and best and go 13 inch with gmt900 parts ?

Im likely just to go with the simple upgrade so need to pull the trigger soon on buying parts . the first post says just buy the k2500 srw 8 lug calipers and pads ,but why not go with the larger piston drw calipers and pads? Is there a reason to use the srw parts instead of the drw parts ?
Thanks in advance !
Most of the swaps people here do and post about is in regards to 8 lug trucks, 6 lugs are a slightly different animal. Your cheapest bolt on is to use k2500 burb calipers but use your stock pads. The k2500 pads work with 5 lug 2x4 trucks, but a member found out when he did it to his 4x4 6 lug, he had to grind the pads to clear the rotors. Otherwise you need to look into newer trucks, swapping spindles, and all that is entailed in this. For 6 lug trucks many do go with the much later model gmt-900 stuff as sometime around 12/13 GM went to the even larger rotors. You won't hear much about this swap here as 8 lugs are a different story,
 

spdgofast

Active Member
Messages
210
Likes
81
Location
Florida
#31
Hey guys, I've been searching for the thread that had the part number for the newer brake proportioning valve for the GMT 400 K2500 Suburbans. I think it increased the rear brake pressure to like 800 lbs I think. I thought I saved it but I can't find it, does anyone know where this was or know the part number?
 

spdgofast

Active Member
Messages
210
Likes
81
Location
Florida
#34
Here is where I got the part number I posted, I know the 92-94 Suburbans use a different ABS unit than the 95-99s. So that's probably one reason for the different part number don't you think?

I hope you don't mind I posted the TSB technical info here.

https://www.thetruckstop.us/forum/threads/project-rear-disc-brakes.45238/ post #57 and #58

Found the Suburban Brake TSB. Note the comments about having to file the steering knuckles to get proper caliper clearance. First I've heard of that. Sounds like a great overall engineering effort. Oh and I found this in a thread where the guy had wrecked his truck because of the crap brakes. Said he was only getting 8K to 10K miles out of the pads.

Caliper TSB

Tech - Brake Lead/Pull and Frt Brake Wear (Repl. Frt
Brake Pads, Rr Brake Shoes) #99-05-24-001A
Brake Lead/Pull and Front Brake Wear (Replace Front Brake Pads And/Or Rear
Brake Shoes)
1992-1999 Chevrolet and GMC C/K Cab Chassis, Crew Cab, and Pickup Models
with Power Brakes (RPO JB8)
1992-99 Chevrolet and GMC C/K Suburban Models with 8600# GVW (RPO C6P)
1996-2000 Chevrolet and GMC G Vans with Power Brakes (RPO JD7 & JB8) and
GVW's of 7,700# up to 9,500# (RPO's
C3F, C6P, & E23)
This bulletin is being revised to update information in the Models Section
and Correction Information. Please discard Corporate
Bulletin Number 99-05-24-001 (Section 5 -- Brakes).
Condition
Some owners may comment about the vehicle leading or pulling to either side
while applying the brakes, and premature front
brake wear, especially vehicles that have been used to tow a heavy load.
Cause
The condition may be caused by wearing of the front brake material.
Improvements to the above conditions can be gained
through brake material modifications. On the Suburban models, the best
performance from this new brake material can be
achieved with replacing the brake combination valve.
Correction
Replace the rear brake shoes with P/N 18029651. THIS FIX DOES NOT APPLY TO
THE 13 x 2 1/2 BRAKE,
DURASTOPT P/N 18029650, OR ANY OTHER SIZE. On Suburban models, a brake
combination valve must be
replaced. ALL OTHER MODELS (C/K, G Van), NO BRAKE COMBINATION VALVE CHANGE
IS REQUIRED.
Refer to the Drum Brakes or Hydraulic Brakes subsection of the appropriate
Service Manual. For G2/G3 Series Vans only
(with GVW's of 7,700# up to 9,500# -- RPOs C3F, C6P, E23) also replace the
front brakes pads with P/N 12471685.
Refer to the Disc Brake subsection of the appropriate Service Manual.
Important
The new front brake pad material has been selected for improved wear
characteristics. Some customers may experience
increased brake noise from this brake pad and should be advised that some
squeal is a characteristic of this particular material.
Important
If you encounter disc brakes that are extremely worn on the inboard side,
with very little wear to the outboard side, verify the
clearance between the caliper and the steering knuckle bracket stops.
MEASURE THE CLEARANCES INDIVIDUALLY AND ADD THE CLEARANCES TOGETHER FOR
TOTAL
CLEARANCE BEFORE REMOVING THE CALIPER. If the caliper (total clearance) to
the steering knuckle stops is under
0.26 mm (0.010 in), correct this by filing metal off at the steering knuckle
stops in order to obtain a total clearance of
0.26 to 0.60 mm (0.010 to 0.024 in). DO NOT FILE METAL OFF OF THE CALIPER.

Refer to the Disc Brake subsection
of the appropriate Service Manual for additional information on this
procedure.
Parts Information
Part Number
Description
Qty
18029651 (17452R Canada)
Shoe Kit, RR Drum Brk (13 x 3.5 in.)
1
12471685
Pad Kit, Frt Disc Brk
1
15650150 (92-94 Suburbans)
Valve Asm., Brake Comb.
1
12548265 (95 and Newer Suburbans)
Valve Kit, Brake Comb.
1

Parts are currently available from GMSPO.
Warranty Information
For vehicles repaired under warranty, use:
Labor Operation
Description
Labor Time
H0257
Shoes and Linings, Drum Brake - R&R or Replace (Rear)
Use published labor operation time
H0042
Pads, Disc Brake - R&R or Replace (Front)
1.0 hr*
H0780
Valve, Brake Combination - Replace
Use published labor operation time
*This time is updated from the current Labor Time Guide. The next issue will
contain this change .


Article on the Brake TSB

When faced with a RWD vehicle
experiencing a lead or pull and
premature pad wear on one side you would
want to focus your attention on the front
brakes, right? Not necessarily. While it is true
these symptoms usually relate to a brake
imbalance caused by such items as a
restricted brake hose or caliper problem
this is not always the case. I recently had an
opportunity to work on such a vehicle. The
vehicle in question was a 1994 ? ton Chevy
Suburban. The vehicle had been experiencing
a lead or pull and premature wear for
over a year. All traditional fixes had been
applied with some of them being done twice
but to no avail.
This vehicle and others like it demonstrate
some important aspects of performing brake
diagnostics. The key aspects demonstrated
by these vehicles are:
• You must diagnose brakes as a system,
• There are exceptions to every rule, and
• In today’s times you must have access to
TSB’s.
GM issued a TSB for the 1992 to 1999
Chevrolet & GMC C/K Cab Chassis, Crew
Cab, Pickup and Suburban as well as 1996
to 1999 G Series Vans (TSB 99-05-24-001,
June 1999) that involves customer complaints
of a lead or pull that may be accompanied
by premature pad wear. Sound familiar?
The fix listed for all but the Suburban
models is the installation of a new set of
rear brake shoes. Yes, you heard it right,
rear brake shoes. The installation of the
new brake shoes changes the front to rear
brake balance of the vehicle shifting more
work to the rear brakes. The overworking
of the front brakes makes them very sensitive
to slight side-to-side differences which
may cause the lead or pull and the heavy
front bias causes the premature pad wear.
On the Suburban models equipped with
13” by 3-1/2” brake shoes the fix involves
not only replacing the brake shoes but also
the combination valve. Both of these steps
are aimed at directing more braking to the
rear brakes. With access to this information
we ordered the necessary parts for our
Suburban. Before replacing anything we did
some pressure tests on both front wheels
and from front to back. Not surprisingly, the
front side to side pressures were near identical.
This gave the front hydraulic circuit a
clean bill of health. The front to rear pressure
demonstrated why the Suburban needed
a revised combination valve. The combination
valve on these vehicles houses a
metering valve, pressure differential switch
and proportioning valve. The proportioning
valve is designed to prevent the rear brakes
from locking up during a panic braking situation.
Apparently someone made a mistake
on the Suburban models
because the valve
on these vehicles is
cutting the rears off
way too soon causing
the front brakes to be
overworked and over
sensitive. Typically, a proportioning valve
will start to work at about 600psi. Front and
rear pressures will stay the same up to this
point and then start to differ with the fronts
continuing to climb and rears being limited
to somewhere
between
650 to
800psi. The
proportioning
valve on
the
Suburban
we were working on began limiting rear
pressure at about 400psi and stopped it at
around 600psi.
After getting the new parts we installed the
revised rear shoes and the new combination
valve. We left the pressure gauges
attached so we could take pressure readings
with the new valve installed. After finishing
installing the parts we pressure tested
the system. With the new valve installed,
the front and rear pressures stayed the
same to just over 600psi. The rear pressure
stopped climbing at about 800psi. Both the
starting point and ending point represented
a significant difference from the original
valve. This change, combined with the
revised rear brake shoes, had a dramatic
impact on the front to rear brake balance
of the vehicle and solved the pulling problem.
We must assume that the repair will
also improve the front pad wear.
Here is a case that all indicators point to a
problem with the front brakes. The demonstrates
there are exceptions to every rule and
why you have to look at the entire system
when performing brake diagnostics. Not having
access to the TSB leaves the shop to try
and come up with the solution on their own
which in this case would be near impossible.
Checking for TSB’s should be a routine part
of the brake diagnostic process. The earlier
this is done the better.
The part information for the vehicles
involved in this TSB is as follows:
Correction: Replace the rear brake shoes
with P/N 18029651. This fix does not apply
to 13 x 2.5” brake shoe, the Dura Stop P/N
18029650, or any other size brake. On
Suburban models, a proportioning valve
must be installed. All other models no proportioning
valve is required.
®
AUTO PARTS
BRAKE LEAD/PULL & PREMATURE
WEAR ON GM TRUCKS & VANS
by Bill Williams
for Mighty Auto Parts
© 2001 Mighty Distributing System of America • Norcross, GA 30092
FOR INFO ON MIGHTY PARTS: 1-800-829-3900
mightyautoparts.com
 

Joseph~

New Member
Messages
1
Likes
1
Location
USA
#35
THEFERMANATOR, Would you know or have the part numbers for the rotors, calipers, pads, etc for the 3500 ?

Is it correct , that the rotors, calipers, pads, etc for the 3500 are a direct bolt on swap to an 8 lug?

Thank you

Joseph
 

staatsof

New Member
Messages
21
Likes
12
Location
N. NJ United States
#38
No stock production vehicles got the valve to my knowledge, so if GM doesn't have a service record for it, then it most likely wasn't done. As far as brake upgrades, you can use the drw 1 3/16" wheel cylinders in the rear along with the acdelco rear brake shoes. Up front you can swap calipers, rotors, and pads to those off of a drw truck and get some more braking there. There is also a bigger master cylinder and stronger booster you can swap in, but I don't reccomend it for any of the stock single piston caliper setups.
I'm finally putting the parts list together for rebuild of the entire rear axle braking system. I am going to replace the prop valve.
I found the recommended uprated rear shoes from the tech bulletin. But the pads they suggest gm 12471685 don't confirm as fitting my 99 K2500 Suburban with 454. The alternate part number with those pads definitely says that it does not fit.

For the rear shoes this is what's on there now and due to the system being constantly maladjusted as well as that prop value issue they still have lots of wear. But ... they've been on there forever and I'm going with all new parts in the rear.

https://www.porterfield-brakes.com/product_info.php?productID=4000

I've also used these on the front till last year when as an emergency my mechanic put "something on". Well "something" is now already shot.

https://www.porterfield-brakes.com/product_info.php?productID=2795
I had two sets of these pads on for a span of 80K miles and 11 years which isn't too bad.

What's not very clear about the GM/AC Delco recommended parts is whether they truly are higher performance or just longer lasting.
I'm after performance.

This why I went with the Porterfield in the first place: https://www.porterfield-brakes.com/images/portstrt2008_11_06_02_45_30.pdf

Even with these in place the braking has deteriorated terribly and so I'm just replacing everything in the rear and putting new pads on the front. It got new slotted rotors two years ago and new powder coated rebuilt OEM calipers up front with new stock hoses one year ago.

I'm going to try and replace all of the hoses with the SS braided ones but as noted already references for this vehicle are hard to fine. I see a Russel kit and one from Inline which fits the K1500 suburbans. When I called they said that it also fits the K2500? Hmmmm.
Presumably then so would the Russel kit.

https://www.inlinetube.com/products/CT1012

This kit from Goodridge 14116 Gstop does claim to fit. It doesn't have any abrasion cover though and braided SS can do a lot of damage.

https://www.ebay.com/itm/Goodridge-USA-14116-G-STOP-SS-Braided-Brake-Line-Kit/302887203325?fits=Year:1999|Model:K2500+Suburban|Submodel:LS|Engine+-+Liter_Display:7.4L|Make:Chevrolet&epid=1617867533&hash=item46857bf1fd:g:~oEAAOSwj8hboA0J:rk:6:pf:0

Your suggestion for a set of rear wheel cylinders @ 1 3/16" creates some issues. I can't confirm if it will mount and clear properly. But the inlet port is definitely different. Since I am going to be replacing the rear axle hard line with a preformed one from Inline it's going to have the oem size fitting on it.

https://www.ebay.com/itm/1995-99-Ch...h=item5d5e6bb426:g:slwAAOSwo6lWKqXp:rk:5:pf:0

What's the thinking on the larger diameter? While it should provide more leverage it's also going to require longer pedal travel.

I know the Porterfield pads will fit but which ones from GM that will amongst those so called upgraded ones isn't clear.

Thanks for any input other than suggesting discs on the rear.
 
Last edited:

THEFERMANATOR

FRANKENBURBAN
Staff member
Lead Moderator
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ZEPHYRHILLS FL
Thread starter Staff #39
The 1", 1 1/16", & 1 3/16" wheel cylinders all mount and connect the same. I've swapped them all and had zero problems hooking them up. I'm currently running 1 3/16" drw wheel cylinders in the back of my k2500 burb with the acdelco durastop rear shoes from the tsb with my 13 x 3.5" drum brakes. I put the proportioning valve in 9 years ago to correct my brake bias after the duramax swap. I've never heard of the porterfield brake parts. I normally use raybestos advanced(which is what I have on the front), but I switched to the durastops in the back as per the tsb and they're definately a much more aggressive material. They also wear a good bit faster than the oem did. Not rapidly, but they actually wear down whereas my stock shoes still had good meat left at 200k miles(almost new thickness still), the durastops showed noted wear after 50k miles.
 

staatsof

New Member
Messages
21
Likes
12
Location
N. NJ United States
#40
The 1", 1 1/16", & 1 3/16" wheel cylinders all mount and connect the same. I've swapped them all and had zero problems hooking them up. I'm currently running 1 3/16" drw wheel cylinders in the back of my k2500 burb with the acdelco durastop rear shoes from the tsb with my 13 x 3.5" drum brakes. I put the proportioning valve in 9 years ago to correct my brake bias after the duramax swap. I've never heard of the porterfield brake parts. I normally use raybestos advanced(which is what I have on the front), but I switched to the durastops in the back as per the tsb and they're definately a much more aggressive material. They also wear a good bit faster than the oem did. Not rapidly, but they actually wear down whereas my stock shoes still had good meat left at 200k miles(almost new thickness still), the durastops showed noted wear after 50k miles.
Thanks. The specifications show a differing inlet thread size on the stock wheel cylinder versus the 1 3/16" diameter one?
 
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