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
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