Although this was mostly a running, driving vehicle, it had a lot of issues when we brought it home. The front passenger side brake was completely non-functional, making the pedal soft, stopping distance variable, and the ride hairy. The steering had a slight wobble under certain conditions. There is a lot of rust on the body which needs repair.
Some of the gages work, some don't. The factory clock is functional but the volt gage and oil pressure gage do not work. It has the usual interior cracking and upholstry damage, the cloth part of the headliner is missing, etc. The tailgate and rear glass are non-functional. The third-row seat is missing. The factory radio is present, but not installed.
This is a standard 2wd model, but it does have a G80 locking rear differential. The main thing it has going for it is the originality. We prefer these survivor-type vehicles.
Check out those rare factory full-cover hubcaps!
The front end is in nice shape with what appears to be the original grille and headlight assembly, etc. The hood ornament is intact and all factory trim and ornamentation is present.
The first order of business was to decipher just how original our Suburban was. We found the original RPO (Regular Production Option) sheet on the glove compartment door, so this made it simple. We copied the sheet, and cross-referenced the codes, then checked the vehicle to verify the equipment and specifications.
Digging through the glovebox also revealed automtive archeological gold: original paperwork, and fantastic condition manuals for 1986 and 1987!
We also noticed this truck still has the original dealer advertising on the tailgate:
We decoded this label using this reference for 1988 GM RPO codes. Here is the decoded factory options list:
AS3: SEAT, RR, SUBURBAN
AT5: SEAT, RR, CTR, FLDG
AU3: LOCK CONTROL, SIDE DR, ELEC
A33: WINDOW, POWER OPERATED, T/GATE OR BACK DR
A52: SEAT, FRT BENCH
BB5: ORNAMENTATION, INTR, HEADLINER
BC3: ORNAMENTATION, INTR, I/P, DELUXE
BY1: ORNAMENTATION, EXTR EMBLEM, BODY, VAR 3
B30: COVERING, FLOOR CARPET
B85: ORNAMENTATION, EXTR MLDG BELT REVEAL
B93: ORNAMENTATION, EXTR MLDG, DR EDGE GUARD (chrome door edge protection strips)
B96: MOLDING WHL OPENING
CD4: WINDSHIELD WIPER SYSTEM, PULSE
CMD: PLANT CODE, FLINT MI
C49: DEFOGGER, RR WINDOW, ELECTRIC
C5U: GVW RATING, 6800 LBS
C60: HVAC SYSTEM, AIR CONDITIONER FRT MAN CONTROLS
C91: LAMP, INTR, ROOF, COURTESY
D1E: GEAR, SPEEDO DRIVEN
D34: MIRROR, VISOR VANITY
D45: MIRROR O/S, SST
E2E: ???????????Bumper, FRT 5 MPH, RR 2.5 MPH ????????????????
E55: BODY EQUIPMENT, END GATE (code that specifies gate instead of doors for rear body work)
E7B: BODY WIDTH, INCR INTR TO 86.4 INCH
E8A: COVER, RR COMPT TONNEAU, RR COMPT - DELETE
F51: SHOCK ABSORBERS, FRT & RR, HD
F59: STABILIZER SHAFT, FR
GQ1: AXLE, STD RATIO
GU4: AXLE REAR, 3.08 RATIO
G80: AXLE POSITRACTION, LIMITED SLIP
JB5: BRAKE, POWER, DISC/DRUM, 6400 LBS
K19: REACTOR SYSTEM, AIR INJECTION
: K22: GENERATOR, 94 AMP
K34: CRUISE CONTROL, AUTOMATIC, ELECTRONIC
L05: ENGINE, GAS, 8 CYL, 5.7L, 1 TBI
: MD8: TRANSMISSION, AUTO 4 SPD, THM 700 R4
MX0: MERCHANDISED, TRANS, AUTO PROVISIONS, O/D
NA1: EMISSION SYSTEM, GVW, LESS THAN 8500 LB.
NA5: EMISSION SYSTEM, FEDERAL, TIER 0
NK7: FUEL TANK, 117L, 31 GAL
N31: STEERING WHEEL, CUSTOM
N33: STEERING COLUMN, TILT TYPE
N41: STEERING, POWER, VARIABLE RATIO
P01: TRIM DISCS, WHEEL, VAR 1 (hubcaps)
SLL: SALES PROCESSING, SOLD ORDERS
UN3: RADIO, AM/FM STEREO, CASS, MTR
UN9: RADIO, SUPRESSION EQUIPMENT
UP8: STEREO RADIO INSTALLATION PROVISIONS
UY7: WIRING HARNESS, TRUCK TRAILER HD
U35: CLOCK, ELECTRIC
U37: LIGHTER, CIGARETTE
U76: ANTENNA, WINDSHIELD, RADIO
VR4: TRAILER HITCH, WEIGHT DISTRIBUTING PLATFORM
V22: GRILL RADIATOR, CHROME
V73: VEHICLE STATEMENT, USA/CANADA
XHB: TIRE FRONT P235/75R15/X WS2 R/PE ST TL ALS
YD3: FRONT AXLE, BASE EQUIPMENT FOR SCHEDULING, GVW PLATE
YD6: REAR SPRING, BASE EQUIPMENT
YE9: CONVENIENCE PACKAGE, COMFORT AND DECOR LEVEL #3
YG3: ORNAMENTATION EXTR, HEAD & TAIL LAMPS, CHROME BEZEL
YHB: TIRE REAR P235/75R15/X WS2 R/PE ST TL ALS
ZHB: TIRE SPARE P235/75R15/X WS2 R/PE ST TL ALS
ZN3: SPRING FRONT FOR SCHEDULING GVW PLATE
ZY5: COLOR COMBINATION, EXTERIOR DECOR
Z53: CLUSTER, INST, OIL, COOL, TEMP, VOLTS
23D: ?????(probably the blue interior specification, carpet and upholstery)???????
23I: INTERIOR TRIM, LIGHT BLUE
29U: PRIMARY COLOR, EXTERIOR, DK BLUE
75A: STRIPE COLOR ACCENT, RED
90L: SECONDARY COLOR, EXTERIOR GRAY MET
This is a very original truck. Everything matched this list down to even the hubcaps, except that the third row seat was missing. All of the engine compartment emissions equipment is still there and working, which is rare for a vehicle of this era. Someone along the years had repainted the original argent wheels to a black shade. The rear 3.08:1 axle ratio is a nice highway cruising range to give good highway fuel mileage.
In total, this is a nicely equipped, useful, and repairable half-ton suburban, and a great candidate for getting back on the road. While not particularly rare, it is still in original, drivable survivor condition and unrestored, which is getting harder to find in square-body suburbans.
The first order of business was to fix the braking issues. We attempted a quick fix in the parking lot before driving the three hours home, with no success as it turns out. The previous owner said the passenger front caliper needed bled, but the bleeder valve was snapped off and unable to be removed easily. We replaced the caliper on-site, but had no sucess bleeding the lines. We tested the other brakes and opted to drive home as it was, albeit with some clenching and stress in the drivers seat.
On disassembly, the front passenger brake hose proved to be a clogged mess. There was also a splice in the brake line done with compression fittings instead of the appropriate pressure-rated flare fittings. Once these issues were fixed, we proceeded to successfully bleed the passenger side and moved to the other wheels.
Bleeding the rear brakes proved difficult, and eventually we began to search for leaks in the line because somehow air seemed to keep intruding somehow. We found and fixed a leak in the line close to the patch of the front brake line. This seemed to help.
The drivers side front caliper also proved to be just as old and crusty, and that fitting proceeded to snap off also requiring caliper replacement. After bleeding, the brake pedal was still mushy and unresponsive, and generally awful. The truck had sat for so long we opted to just replace the brake booster and master cylinder instead of fussing with it anymore. After a final bleeding and check, the brakes functioned normally.
Brake systems that sit for long periods of time unused sometimes tend to deteriorate, as they did in this case. The vacuum booster relies on a rubber diaphragm, and the brake system has many other steel and rubber parts which can corrode or break down over time and weather exposure combined with time and disuse.
Next we needed to figure out how to get the tailgate open, hopefully without damaging anything. This truck has an electric rear window (currently not operating), and the window must be lowered to open the tailgate.
The tailgates in these trucks are widely disliked. This whole opening issue thing is part of the reason. If something fails in the window assembly, the tailgate cannot be opened at all, and must be disassembled from the inside. The preferred rear opening for these trucks is barn doors. In our opinion both have advantages. The tailgate has a rear defroster option and much, much better driving visibility, as well as easy grocery loading by just rolling down a window with the key instead of fighting a door open. The barn doors are more durable though, as the tailgate hinges tend to rust. The barn doors tend to have more sealing issues, as they have many more sealing surfaces.
In this case the tailgate was locked up as tight as a drum, and the window refused to operate electrically. We first took the dash switch out to make sure it had power, then proceeded to take the gate apart from the inside to diagnose it.
Initially, removing the window motor and connecting power did nothing. We cleaned the motor electrical plug contacts, tried to loosen it as much manually as possible, then tried again. It started turning slow at first and gradually gained speed. We reinstalled the motor and tested in place, and it grudgingly moved the glass down a little bit. Pulling the motor back out we greased the window assembly rollers, tracks, and gears, working the grease through the system by hand. Reinstalling the motor resulted in a smoothly operating rear window.
The tailgate itself was still stuck shut by time and dirt. Some muscle and carefully applied force opened it up, showing us that the hinges and straps were in working shape, but there were some rust holes in the lower inside corners. We might have to replace the sheet metal at some point but it works for now.
Up next was to diagnose and fix some guage cluster issues. The volt guage and oil pressure guage show, respectively, no reading and a pegged needle. We removed the cluster and the volt guage proved to be defective. We replaced the volt guage and the oil pressure sender, and all the guages worked perfectly once more.
The electric locks were next on our list. Neither of the front switches seemed to do anything. Pulling out the switches, we first checked for power, then checked the relay circuit operation by jumping connections. Power was present and the relay activated.
Suspecting that the door lock actuators and switches were victims of time and disuse, we further disassembled the doors and cleaned and checked each actuator and switch. The electrical contacts on both the switches and motors were badly corroded, but careful cleaning brought the entire system back into operation again.
While we had the doors apart to fix the electric locks, we popped the dent out of the drivers door.
The final completed project:
We found these resources valuable for our work:1988 GM light duty truck service manual