Welcome to our page regarding refurbishing our 1988 Chevrolet Suburban and getting it roadworthy once more.

We include this page as an interesting reference of our own experiences, in hopes that it might be useful to others in some manner.
 1988 Suburban Arrival condition
 1988 Suburban Information
 1988 Suburban Repairs
 1988 Suburban Final
 1988 Suburban Resources



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Arrival condition


We purchased this Suburban with the intent of getting it back on the road and into the hands of someone who could appreciate it. It appeared to have good potential and was in fairly original, unmolested condition.

The issues we intended to deal with were a fairly long list. It had some standard square body rust for the era that would have to be cut out and new panels welded in, a cracked rear door window, some bad door seals, some broken and missing exterior cosmetic parts, the headlights had some issues, there were some interior cosmetic issues and missing parts, and many other little things and needed fixed or adjusted like the hood that would not open correctly.

A good bit of it is just turning wrenches and finding parts, but the major stuff is the rust. We knew about this of course when we bought it, and made sure the rocker panels were mostly ok. The rust is mainly confined to more easily manageable areas in the rear quarter panels.

Another major issue was the peeling clearcoat over much of the body. It isn't readily evident in the photos, but it was very bad, and unfortunately typical of this era with a lot of sun exposure. This is an easy repair from materials standpoint, but requires hours and hours of elbow grease to repair. Our goal was to keep it as original as possible, so a repaint wasn't planned. We prefer the original paint-scheme, look, and feel. In the photo below a good example of the clear coat peeling can be seen below the window in the rear barn door.

1988 Chevrolet Suburban

As can be seen from the inital photos, the vehicle looks pretty decent. But there were a lot of cosmetic issues and things not readily visible that we knew about, having done a detailed inspection prior to purchase. Here are some close-up shots of the rust issues.

1988 Chevrolet Suburban

In this shot the peeling clearcoat is slightly visible on the hood, upper fenders, and above the front door. The roof is almost entirely peeled from sun exposure. The dashboard pad can be seen to be cracked and damaged also.

1988 Chevrolet Suburban

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Information


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.

1988 Suburban RPO codes

We decoded this label using this reference for 1988 GM RPO codes. The 'WA-' codes at the bottom are the body and interior paint codes (which are also repeated in the RPO codes). Here is the decoded factory options list:

AJ1: WINDOW TINTED, DEEP, ALL EXCEPT W/S AND DRS
AK9: RESTRAINT SYSTEM, RR SEAT, SHLDR, RETR, 3 POINT
AT5: SEAT, RR, CTR, FLDG
AU3: LOCK CONTROL, SIDE DR, ELEC
A52: SEAT, FRT BENCH
BC3: ORNAMENTATION, INTR, I/P, DELUXE
BY1: ORNAMENTATION, EXTR EMBLEM, BODY, VAR 3
B30: COVERING, FLOOR CARPET
B32: COVERING, FRT FLOOR MATS AUX
B85: ORNAMENTATION, EXTR MLDG BELT REVEAL
B96: MOLDING WHL OPENING
CMD: PLANT CODE, FLINT MI
C5U: GVW RATING, 6800 LBS
C60: HVAC SYSTEM, AIR CONDITIONER FRT MAN CONTROLS
D1V: GEAR, SPEEDO DRIVEN
D34: MIRROR, VISOR VANITY
D45: MIRROR O/S, SST
E4I: ADAPTER, SPEEDO (E4I)
E7B: BODY WIDTH, INCR INTR TO 86.4 INCH
E8A: COVER, RR COMPT TONNEAU, RR COMPT - DELETE
F51: SHOCK ABSORBERS, FRT & RR, HD
GU6: AXLE REAR, 3.42 RATIO
G80: AXLE POSITRACTION, LIMITED SLIP
JB5: BRAKE, POWER, DISC/DRUM, 6400 LBS
KC4: COOLING SYSTEM, HEAVY DUTY ENGINE OIL
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
NA5: EMISSIONS SYSTEM, FEDERAL, TIER 0
NE2: FUEL TANK, 151L, 40 GAL
N31: STEERING WHEEL, CUSTOM
N67: WHEEL, RALLY TYPE, VAR 2
SLL: SALES PROCESSING, SOLD ORDERS
TT4: HEADLAMPS, HALOGEN, 4
T63: ALARM, HEADLAMPS ON WARNING SYSTEM
UA1: BATTERY, HEAVY DUTY
UM6: RADIO, AM/FM STEREO SEEK/SCAN, AUTO REV MUSIC
UN9: RADIO, SUPRESSION EQUIPMENT
UP8: STEREO RADIO INSTALLATION PROVISIONS
UY7: WIRING HARNESS, TRUCK TRAILER HD
U73: ANTENNA, FIXED, RADIO
VR4: TRAILER HITCH, WEIGHT DISTRIBUTING PLATFORM
V02: RADIATOR, HEAVY DUTY, WITH TRANS COOLER
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
ZW9: BASE BODY AND CHASSIS
ZY5: COLOR COMBINATION, EXTERIOR DECOR
Z82: TRAILER PROVISIONS, SPECIAL EQUIPMENT, H.O.
39U: PRIMARY COLOR, EXTERIOR, DK ADRIATIC BLUE MET (94) [incorrect-should be DK MESA BROWN]
56A: STRIPE COLOR, ACCENT, TWO TONE, DK BROWN/ALMOND
60D: TRIM COMBINATION, CLOTH, LT DRIFTWOOD (D)
60I: INTERIOR TRIM, MED COGNAC (91)
61L: SECONDARY COLOR, EXTERIOR, TAN (91)

Interesting to note is the primary paint code is incorrect in the RPO list. It is possible it was changed somewhere after production order and was never changed in the RPO printout that made it to the truck. Everything matched this list except that the radio was missing. We even verified the limited slip rear differential when we changed the fluid. This truck has a factory installed towing package, which is a nice feature. 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. It has a 50 gallon fuel tank, which is nice (we later calculated the fuel mileage at 18.8 MPG on a 900 mile trip). It also has the higher option GVWR. This truck is rated to tow 6000 lbs, which by today's standards isn't high for a half-ton truck. The rear 3.42:1 axle ratio is a nice mid-range ratio to give a nice mix of acceleration and highway mileage. The engine is equipped with a heavy-duty oil cooler independant of the radiator, which is also rare in this era for half-ton trucks. A later owner also added an independant transmission fluid cooler. It is interesting to note that a later owner also installed a keyless entry system for the factory electric locks, which includes a remote start feature.

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.

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Repairs


Most of the repairs were cosmetic in nature, as this was a running, driving vehicle (albeit with some trepidation). Obviously driving a vehicle any distance which has been sitting for a while requires some form or either stupidity or bravery. While having a perfectly functining tow dolly and truck, we opted for luck and drove it twenty miles home.

Primary to our concern, the oil pressure gauge was not functioning. However this did not seem to matter to the previous owner as he claimed to have driven it that way for a while in the past. Seeing as how the engine ran nicely with no seemingly destructive internal issues, we opted to assume it was just a bad pressure sender. Surprisingly, the truck drove nicely and did not explode or burst into flames on our trip home.

Speed: normal, fuel: normal, temperature: normal, battery: normal, oil pressure: none!

1988 Suburban no oil pressure

The suspension felt in good shape, there were no evident fluid leaks, and the vehicle looked like a previous owner had regularly maintained it. There were new exhaust parts, including the manifolds. The air conditioning, although not working, showed evidence of having been converted from R12 refridgerant to R134-A. So someone had cared enough to maintain even the more expensive and non-critical items. It is worthy to note that this is often a good indicator of a well cared-for vehicle; if non-critical items have been maintained or updated.

One of the first items of business was dealing with the hood. When released, the hood would not spring up an inch to access the catch release as it normally should, and had to be pounded to jog the catch before it would spring up. This is a fairly normal problem in older vehicles, or those that have been sitting a while. The catch release or spring can get corroded. This proved to be the case, and some grease and working the latch resolved this issue. If the hood catch will not release, the latch is not accessible from below. It can be released with a bend wire coathanger as pictured below, if there is enough room between hood and radiator support to snake it in the gap.

1988 Suburban hood latch

For peace of mind, we chose to next resolve the oil pressure issue. This issue is almost always the sender, assuming that the engine still runs and does not make horrific noises. The gauge rarely fails, and the oil pump also rarely fails in these engines. So barring a wiring fault, we hoped it would be the sender. We checked the wiring for faults, and finding none decided to replace the sender. This proved to be the issue and the gauge then showed normal oil pressure.

1988 Suburban oil pressure sender

There are many reproduction, aftermarket, and original parts available for these vehicles. We opted to use as many original parts as possible; repairing what we could or finding replacements from other vehicles. We specifically needed a third row seat which was missing, a replacement driver's seat (it was very torn), a rear window glass, a headlight trim bucket/bezel, a radio, a dashboard pad, and some tiny odds and ends like hardware. A good source for high quality replacement parts is LMC Truck.

Tracking down parts: Our first search netted the seats we needed, as well as a complete set of middle doors with rusty panels to supply our window glass. The original glass was factory tinted, but all we could find were clear replacements, so we opted to replace all four middle door glass pieces (the small glass filler pieces were tinted as well). We also found an original brown dashpad in fantastic shape to replace our cracked one.

1988 Suburban replacement parts

Window glass: While we had the doors disassembled, we replaced rubber seals with new, and lubricated window slides and locks and internal moving parts, since most of the door must be taken apart to replace the glass. It is a fairly simple process; just disassemble and remove old parts, then replace. The replacement windows are from a crew cab, and untinted, but they are original factory parts in great shape, and they match. They can be tinted if another owner desires.

1988 Suburban rear doors refurbished

Replacing the door parts and installing the seats and dashboard pad was straightforward.

The new dashboard installed:

1988 Suburban dashboard

While we had the dashboard apart, we also took advantage of the opportunity to pull the gauge cluster and replace burned out bulbs, as well as dealing with our missing radio.

Radio: The radio was a more difficult proposition. A previous owner had cut the dash to install an aftermarket unit, so this had to be dealt with in some fashion at the same time we chose our stereo. Obviously a direct factory replacement would no longer work since the dash metal was cut, but fortunately options exist for this situation.

We wanted to keep a period-correct look for the vehicle, even if exact factory correct was not an option. In the 70's and 80's, Sears was one of several companies offering stereo upgrades for vehicles. We managed to find a brand new Sears Dashmate unit still in the original box that would fit and match the existing dashboard perfectly. It is an easy splice into the existing wiring harness, as long as someone before hasn't managed to totally mess up the wires (which is usually the case). The Dashmate radio has its own front cover plate, which is chrome on one side and black on the other. It was made to fit a variety of vehicles, and is a perfect period look for our suburban.

Below is an original advertisement for the Dashmate series, and some pictures of original units and packaging. Styles and options varied slightly over the years, but the basic design remained the same. Two stalks on the side and a center radio unit, with casette, 8-track, or just radio. All had an overlapping central cover plate for the front.

1988 Sears Dashmate stereo advertisement 1988 Sears Dashmate stereo

The headlights were causing issues, as they had a tendancy to start to flicker after a few minutes of operation. Low and high beams were both affected. We checked out the system and discovered several issues. A previous owner had spliced the wiring harness so that both low and high beams were always active, by itself not an issue. But the bulbs they chose were high amperage draw halogen style lamps. This put approximately a 150 amp load on the entire circuit, which runs directly through both light switches. This high amperage draw also quickly overheated the main switch internal circuit breaker, and it would activate, turning off the lights until the breaker cooled. This created our flickering scenario. We ended up replacing both light switches due to damage from the high current. A better description and detailed explanation is available here for those who are interested.

We chose next to move to the rear of the vehicle. There were a few usual issues like the license plate bulb burnt out. The housing was too rusty and destroyed, so we opted for a one-piece LED replacement unit. The rear barn door seals were long shot, and someone had tried to fix this with caulk and weatherstripping. We obviously opted to replace the seals. Of note is the fact that rear-most door seals are extremely difficult. Cheap seals are a bad idea, but even the most expensive ones require a great deal of wearing in before the doors will seat properly. We have found the best method is to adjust the door hinges only if absolutely necessary, as tempting as this option will be outright. After installation, the doors may not close properly because the seals have not shrunk or adusted to fit their new home yet. Only when properly heat-cycled will they adjust. This can be done with a heat gun or just lots of time in the heat with the doors shut tightly. The latter option tends to take much longer. Do not get discouraged if the doors still fail to shut properly, but continue to heat-cycle the seals. Sometimes it is extremely difficult and only time will do the job, especially with the cheaper seals.

Another issue with the rear doors was the inability to lock them with the key. In this case the previous owner was fortunate in that the electric lock option provided a secondary option. There is not a lock pop-up button on the rear doors, so without electric locks only the keyed lock will work. After disassembling the door to check out the situation, we discovered the pawl and retaining clip missing from the inside of the lock, allowing the rod to slip free and disabling the keyed lock. Some seaching fortunately discovered the pawl lying in the bottom of the door panel, and we reinstalled it with a replacement clip. Of note here is the fact that the rear lock pawl is different from the front two, being more of a long extension of the cylinder. The mechanism is different, so only the lock cylinder and cylinder retaining clip is interchangable.

We next chose to tackle the body work. While not easy, with hard work the end result can be extremely satisfying. We ordered replacement sheet metal, and cut the sections we needed from these pre-formed parts. While not an exact mould, these reproduction sheet-metal parts are close enough to hammer-and-dolly into factory specification to match existing metal.

The first step was to mark off our cut areas, then remove the old metal sections with an angle grinder. Then we cut the new sections to match, and spot welded them in. Then we went back and carefully made our final bead welds, making sure not to overheat and warp any sections. After grinding the welds smooth, we applied body filler to get a completely smooth seam and sanded, primered, and applied paint. Below are a few quick pictures of the procedure from cutting to primer. The welding and patching of the interior sections of panel are not shown since they don't have to look particularly nice. Care should be used not to leave bare metal inside the panel; weld-through primer should be used where possible.

1988 Suburban body repair 1988 Suburban body repair

As can be seen in the original photos, the lower body moulding trim is missing large sections. Fortunately, this is easily obtainable in reproduction form. Our last portion of bodywork was to get a roll of trim and cut new sections. We opted to replace all the sections so that none would look out of place. Pre-cut sections can be ordered, but if you have the time and skill one large roll is cheaper. It takes some time and care to do properly, as a ragged cut will be visible forever. Clean cuts and smooth ends are a must. The pieces come with backing adhesive to hold them in place.

A very in-depth mechanical inspection revealed several issues that were dealt with, including a bad wheel bearing, sticking rear brake shoe from sitting, and a bad center driveshaft carrier bearing. The bad rear bearing had eaten into the axle shaft, so we also replaced that and checked out the differential at the same time. A final change of fluids all around and our suburban had a clean mechanical bill of health.

The air conditioning system being difficult in its own right, we saved that for last as it was one of the less critical items on our list. After a careful preliminary inspection, the system seemed complete, intact, and capable of functioning. The compressor would build pressure under a test charge, but the system would quickly leak down. We disassembled the entire system and replaced all seals and o-rings and the dryer, checked the orfice tube screen, and reassembled. After re-pressurizing the system it held a charge and cooled properly with no leaks. This is normal of well-maintained systems, but if the system was abused or not given the proper oil mix along with refridgerant it may be necessary to replace the compressor. Usually the evaporator and condenser only require replacement if they develop a leak, and of course the same for the lines and hoses themselves.

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Final


The final completed project:

1988 Suburban 1988 Suburban 1988 Suburban 1988 Suburban 1988 Suburban 1988 Suburban

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Resources


We found these resources valuable for our work:

     1988 GM light duty truck service manual
     1988 GM light duty truck wiring manual
     Reference for 1988 GM RPO codes

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