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! This truck also still has the original factory GM keys also.
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
The paint codes translate to Dark Blue WA7349/29/B8139 and Gray Metallic WA8798/90/B8629
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. 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.
Update: a month after this the window motor started to refuse to operated after sitting for a while, even after multiple disassemblies and inspections. The motor appeared fully okay internally, but something is weakened that doesn't seem to be repairable. We opted to replace the motor with a new unit.
Unfortunately these motors are slightly different than the ones used in the regular doors, and after efforts to track down an affordable exact replacement we opted to modify a window motor to work using this procedure.
The dashboards in these vehicles are known to eventually crack over time. Replacements can be purchased, or just the covers, or some companies offer carpet-style dash covers. These options are either expensive or do not lool great. And even the expensive reproduction dash units never fit exactly as well as the original.
There are several internet threads about possible repair procedures, but none of them really present a factory look. Several involve filling the cracks and using a texture sort of spray, like bedliner, to try to give it an even look.
None of the existing methods result in a long-lasting, good looking repair. We opted to use our own procedure detailed below.
These dashboards are constructed with a metal core, covered with an approximately 1/4" foam and then a vinyl outer covering. This gives it a solid core with a flexible and durable outer layer. In order to reproduce this either the entire outer layer must be replaced or the filling must be done with an equally durable and flexible material.
Our method is to cut back the cracked areas to remove all curled edges, down into the foam layer. This will give a deeper anchor for our filler. We then fill the void with expanding foam insulation and allow it to set. This yeilds a firm yet slightly flexible base for our repair.
The foam is then trimmed down. This will reveal the slightly porous nature of the foam, but this is acceptable in this lower layer. The top surface is then smoothed and filled with weatherstrip adhesive. Weatherstrip adhesive is both durable, flexible, and made to resist torturous strain. It can be lightly sanded and smoothed with high grit sandpaper after drying and results in a flexible surface not unlike vinyl when complete.
After the surface is completely smooth we add layers of paint, sanding in between layers to build up a thicker overall coat. Then the paint is blended into the exising dash coating.
We find that although the final surface will not have the same factory texture, smooth spots are acceptable in this sort of repair and mostly unnoticable to the untrained eye because in aged vehicles worn-smooth vinyl in some areas is normal. For a full frame-off restoration with many thousands of dollars and hours, a full replacement would be normal but for standard refurbishing this repair is a wonderfully cheap and acceptable, lasting option. It also preserves the original factory parts which is a bonus in any vehicle.
For the body work the goal was not for a factory-perfect body but rather an aged patina look with the major issues fixed. In this case there were the usual large rust issues in the rear wheel areas and some in the rocker panels.
We cut out the rust-through areas and welded in new sheet metal, and sanded and touched up any deteriorated spots. This truck body should be good for more long years of use for someone as a useful driver vehicle, while still looking good.
There were several spots that required cutting, welding, grinding and then final smoothing before a repaint. Here is the process for the passenger side rear panel:
We went over the vehicle body, sanding and fixing any particularly worrisome surface rust spots that might cause issues down the road, while trying to preserve the nicely weathered patina.
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. While we had the cluster out we cleaned everything and checked all the lightbulbs.
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, and replaced all the window seals, as well as greasing all internal mechanical assemblies.
The front passenger door had a deformation at the mirror, appearing as if someone had yanked hard outwardly on the mirror. With this door completely disassembled, we pulled the metal back into shape.
This truck came from the factory with delay/low/high wipers, an upgrade option over the standard low/high functionality. The delay function no longer works. After testing the switch and determining the resistance provided by the delay potentiometer was incorrect (only showing zero or infinite), we replaced the entire switch assembly.
On the drive home we observed the cruise control was non-functional. Starting our troubleshooting at the control stalk revealed two wires broken from their solder joints, as well as a broken wire where the bundle passes into the stalk. We pulled out and repaired these connections.
These early GM cruise control switches come with a baked-in defect that was corrected in later units. The wires pass from the steering column into the tube of the stalk, and out the end to the switch. The edges of the metal tube eventually wear through the wire casing, or break the wires on the sharp edge. Later designs changed the 'spray' assembly to a larger plastic piece to allow the wires to pass alongside the metal tube rather than through it.
While we had this unit apart we modified the stalk to use the newer plastic 'spray' assembly to prevent this happening again.
On the drive home we had noted a momentary shimmy sometimes in the steering. During our examination, we discovered the front sway bar was disconnected on the drivers side because the bracket was deformed. It appears as if someone used the sway bar for towing purposes and pulled the bracket and bar forward, which also unseated the sway bar from the A-arm bushing and bracket.
We removed the sway bar brackets, reseated the bar into the A-arm bushing, and rebent the bracket into the correct shape by pulling backwards from underneath the vehicle with a winch and strap. We were fortunate that the pulling angles resulting from the strap route were perfect for what we required.
This truck came with an empty hole and half the wiring connectors for the factory radio. Although the factory radio was in the back of the truck, it was quickly determined to be not working after we spliced the correct connectors back into the wiring harness. Hoping for an easy fix we disassembled the unit and determined the problem was most likely with the audio integrated circuits. This being an expensive repair we opted to look into other options.
The original factory unit had a cassette tape deck, but we found a working replacement for a reasonable price with just the AM/FM functions. We opted to use this unit as it provided the closest to original functionality at the best price. Yes the old unit is probably rebuildable, but that is not in our price range. If this was a high dollar rebuild, or a valuable (rare) vehicle, we would definitely opt for the original unit, but in this case it doesn't matter to that degree.
Once operating, it was evident that only the front speakers were operating. Disassembling the rear speakers quickly showed rodent damage. Apparently rodents had opted to tunnel into the speakers from behind, steal all the internal fabric and wiring, and take them elsewhere for nesting. We purchased a set of used speakers and replaced the damaged units. Below, a mouse-chewed speaker:
The air conditioning system was the original R12 refridgerant with the original Harrison R4 compressor. Examination revealed a slight R12 pressurization remaining inside the system after all these years. We decided to try converting and pressurizing the system with R134, which revealed that everything worked but the system did bleed down over several days.
These R4 compressors are known to have weaknesses at the shaft seals and the case o-rings. Examination showed oil leakage at the front seal so we opted to re-seal the compressor and re-test. While the system was bled and disassembled, we replaced all the joint o-rings and dryer, as well as examining and cleaning the orfice tube screens.
Bringing an old vehicle back to life involves lots of little tedious details, as well as the big obvious things. In this case there was lots of cleaning, and chasing down little parts that had been taken off or broken over the years.
We chased down a replacement dashboard clock knob, cleaned and greased all the moving parts throughout the vehicle, and replaced lots of deteriorated rubber parts.
The blower motor had a squeak, which was fixed by pulling and disassembling the unit for cleaning and greasing.
The headliner was in need of some attention, as someone had stripped the factory fabric and painted some kind of blue textured paint on the backing board. We completely removed the headliner boards, stripped them down, and fixed some bows in the material caused by leaking water from the roof-rack fasteners (we patched those holes previously).
Then we laid out the backing board and applied new fabric with the proper adhesive, and waited 24 hours for it to set properly.
After that we trimmed around the edges and holes carefully, making sure to follow all contours for fasteners and dome lights.
We installed the completed headliners, reinstalling all trim and lights. The suburban headliners are two pieces, joined by a metal strip down the center of the vehicle side-to-side. The front should be installed first for easier access to the rear, and then trim pieces can be installed working front to back. The sun visors should be installed first as some of these screws are partially covered by plastic trim.
We polished and cleaned the hubcaps, touching up sections missing black paint and replacing the center stickers.
The only blue matching third row seat we could find was from a 1991 Suburban with third row shoulder belts. We did have to purchase a missing armrest ashtray. On these seats there are three seat belt sockets and one lap belt, rather than three belts and one socket. We opted to replace the sockets mounted to the vehicle floor with belts since an exact match for the belts could not be located. The less-matching belts will have less contrast being not mounted to the seat itself. After a good thorough cleaning the seat was ready for install.
Since this project is intended as a driver and not a complete factory restoration, we did not replace the front bench seat upholstry. We could not locate a better condition used seat, and replacement with new was just too expensive for the intent of this project. We will let the new owner either drive it as-is, opt for replacement, or just cover it with a seat cover as we would for a daily driver. It is quite workable in its present condition.
We found these resources valuable for our work:
1988 GM light duty truck service manual