88gmctruck
02GMCtruck
I’ll start this thread off by simply stating that the output of the 88-89 sealed beam headlights are a joke. This thread will outline the OEM lighting in the quad headlight trucks, and available upgrade options. Many people simply say switch to composite headlights; while this is a valid option, I personally have an attachment with the quad headlights as they are the original style of the GMT400 truck and were only used for 2 years. They are much less common and have a more distinct look, IMO. If someone was to want to "upgrade" to quad headlights, swapping a newer truck (90-98) to the quad headlights is simple. All you need are the light adjusters and the proper electrical plugs. All the grille shells setup for composite headlights have the appropriate step in them for the quad headlights, and they mount in the exact same location on the core support.
Stock Sealed Beam H4703/H4701
The H4703 lowbeam and H4701 highbeam are DOT approved sealed beams that GM used in 88-89 trucks, 90-91 blazers and suburbans, 98-03 firebirds, and a few other, less popular car applications. The lights are a 55w lowbeam and 65w highbeam. Up until a few years ago the aftermarket for them was marginal and a few people were modifying the Sylvania brand replacement units (as they had a bulb that was easily removed) by gluing their own bulb in place of them. This still did not overcome the shortfalls in the light itself. The small size (92mmx150mm) and marginal optics of the DOT spec are what makes these lights very poor. I originally overcame the marginal output by adding factory fog lights to my truck. Also, another great upgrade is to run larger gauge wire and relays for the headlights. The factory wiring is ran through the headlight switch and column dimmer, and smaller 16ga wire. My first lighting upgrade was to power the lights with relays and 10ga wire. This increased the output of the stock lights greatly, and is a must if you upgrade to any of the following lights as the higher wattage will run too great of resistance.
Stock H4703 lowbeams (the blue is paint on the non-reflective portion to add a different look)
Eurolight conversions
About 6 years ago, a company called Eurolights came out with a non-sealed beam version of the headlights, which utilized a replaceable H7 bulb. I quickly picked up a set of these. While they suffer from a very similar (although not DOT approved) cut lenses as the sealed counterparts, they are an ok upgrade from stock. They allow you to use a higher wattage bulb, which overcomes the cruddy optical quality. The glass lenses on them are considerably thinner than the stock sealed beams, and within a year or so both been broken due to rocks. I eventually replaced the lenses with those from a set of sealed beams, keeping the h7 bucket and brighter bulbs.
Eurolight H7 conversions compared to stock h4703 sealed lowbeam
LMC “euro” conversions
About two years ago, LMC truck also came out with a replaceable “euro” style clear lense/diamond reflector style light. They are DOT approved however I have never used them, as they do not fit the style of my truck. I’m assuming them to be a decent upgrade over stock, probably similar to the eurolight conversions.
LMC conversion lights
Bosch H4 headlights
And finally, the ultimate upgrade to quad headlights; Bosch H4 E-code headlights for GM export option T84.
I first learned of the Bosch E-code version of the headlights from another forum member, DaBurb. He has an Australian spec Holden Suburban. They came with quad headlights as well, but used a bosch capsule and H4 light. He's actually replaced them with the clear lensed conversions available from LMC. I've done a literal ton of research after these lights, but alas, for years I could only find the RPO T85 (Export-Left Rule of Road) via the Holden Suburbans. Howard gave me the part numbers off them and they are still in the GM parts system. They are, however, designed for the incorrect side of the road over here.
Eventually (about 4 months ago) I found that Bosch also made these in right hand rule of the road (GM RPO T84). They were used in German export Firebirds (of all things, they use the same headlights as 88-89 trucks here in the states). I found GM and Bosch part numbers. The GM part number no longer works, nor are there any in the system. I contacted Bosch and the lights have been discontinued for over 8 years now, and they also don't have any. Turns out there is a little place in PA called Susquehanna MotorSports that bought about 200 of them that were in a GM warehouse in Ontario. They have about 32 left, and apparently when they are gone, they are gone.
Part numbers:
Lowbeams:
T84 lowbeam (RHD) – 16506324
T85 lowbeam (LHD) – 16507483
Highbeams (T84 or T85, it has no rule of road cut since it's a highbeam.)
Highbeam (either) – 16506325
So after ordering the lowbeams from Susquehanna MotorSports, I decide it’s time to get a set of highbeams. The highbeam part number was still good in the GM system, so about a month ago I dug into my part numbers to order the highbeam light. Very funny phone conversation with my normal parts guy, List is $68/ea but he needs a vin for them and questions wtf they were off of. Anyway he tells me there are two left in the US, in a small dealership in Kansas. Called them and talked to their parts guy. He said they have obviously been there a LONG time, offers them to me for $51/ea just to get rid of them. So, I just may have bought the last set available. And I was worried about a rock hitting the lowbeams and breaking them, these ones are really going to make me sweat. So, the high-beams are no longer available from GM; I ordered the last 2 in the system.
First off, the glass lenses on the Bosch lights are thick, thicker feeling than the sealed beams and WAY thicker than the eurolight conversions. They include a very large rubber boot that cover the light and keeps moisture out. Under it is a very nice locking setup for the bulbs. The lowbeams also include a “citylight” which is a separate 194 blub that is effectively the European equivalent of a DRL. I choose not to wire this up in my truck as I hate DRLs.
Lowbeams (notice the Bosch and GM part number tags)
Lowbeam compared to Eurolight H7 light (with highbeam glass)
Highbeams
Highbeam compared to Sealed Highbeam H4701
Side by Side (lowbeam on left, highbeam on right)
Bulbs, boots and city-light
The lowbeam light output is simply amazing. Being they are E-code, they have a much cleaner and better focused light pattern that puts the light where you need it. They also have a very sharp (almost projector like) cutoff line. I have noticed much less eye fatigue on long drives or in inclement conditions. Now, being the lowbeams are H4 bulbs (dual filament) I wired them as a true low and high beam. So when they change between filaments the optics change, and illuminate farther up.
The highbeam lights are of course the same quality. They are a similar cut to the US highbeam; however the cuts are much more pronounced and create a much better light spread on the road. Combined with the high beam filament of the lowbeam (and my other lights) the output is nuts. It is also worth noting that the lowbeams light pattern and output is far better than any composite headlight I have seen, OEM or not, in a GMT400 truck.
So I have a full set of T84 lowbeams & highbeams in the truck now, and have a second set of lowbeams sitting in a box just in case something happens. I also covered my lights with a layer of 3M stoneshield just to help protect them. Nothing like losing $300 in headlights. I’ll try to get some pictures of them in the truck, as well as the lighting pattern.
Stock Sealed Beam H4703/H4701
The H4703 lowbeam and H4701 highbeam are DOT approved sealed beams that GM used in 88-89 trucks, 90-91 blazers and suburbans, 98-03 firebirds, and a few other, less popular car applications. The lights are a 55w lowbeam and 65w highbeam. Up until a few years ago the aftermarket for them was marginal and a few people were modifying the Sylvania brand replacement units (as they had a bulb that was easily removed) by gluing their own bulb in place of them. This still did not overcome the shortfalls in the light itself. The small size (92mmx150mm) and marginal optics of the DOT spec are what makes these lights very poor. I originally overcame the marginal output by adding factory fog lights to my truck. Also, another great upgrade is to run larger gauge wire and relays for the headlights. The factory wiring is ran through the headlight switch and column dimmer, and smaller 16ga wire. My first lighting upgrade was to power the lights with relays and 10ga wire. This increased the output of the stock lights greatly, and is a must if you upgrade to any of the following lights as the higher wattage will run too great of resistance.
Stock H4703 lowbeams (the blue is paint on the non-reflective portion to add a different look)
Eurolight conversions
About 6 years ago, a company called Eurolights came out with a non-sealed beam version of the headlights, which utilized a replaceable H7 bulb. I quickly picked up a set of these. While they suffer from a very similar (although not DOT approved) cut lenses as the sealed counterparts, they are an ok upgrade from stock. They allow you to use a higher wattage bulb, which overcomes the cruddy optical quality. The glass lenses on them are considerably thinner than the stock sealed beams, and within a year or so both been broken due to rocks. I eventually replaced the lenses with those from a set of sealed beams, keeping the h7 bucket and brighter bulbs.
Eurolight H7 conversions compared to stock h4703 sealed lowbeam
LMC “euro” conversions
About two years ago, LMC truck also came out with a replaceable “euro” style clear lense/diamond reflector style light. They are DOT approved however I have never used them, as they do not fit the style of my truck. I’m assuming them to be a decent upgrade over stock, probably similar to the eurolight conversions.
LMC conversion lights
Bosch H4 headlights
And finally, the ultimate upgrade to quad headlights; Bosch H4 E-code headlights for GM export option T84.
I first learned of the Bosch E-code version of the headlights from another forum member, DaBurb. He has an Australian spec Holden Suburban. They came with quad headlights as well, but used a bosch capsule and H4 light. He's actually replaced them with the clear lensed conversions available from LMC. I've done a literal ton of research after these lights, but alas, for years I could only find the RPO T85 (Export-Left Rule of Road) via the Holden Suburbans. Howard gave me the part numbers off them and they are still in the GM parts system. They are, however, designed for the incorrect side of the road over here.
Eventually (about 4 months ago) I found that Bosch also made these in right hand rule of the road (GM RPO T84). They were used in German export Firebirds (of all things, they use the same headlights as 88-89 trucks here in the states). I found GM and Bosch part numbers. The GM part number no longer works, nor are there any in the system. I contacted Bosch and the lights have been discontinued for over 8 years now, and they also don't have any. Turns out there is a little place in PA called Susquehanna MotorSports that bought about 200 of them that were in a GM warehouse in Ontario. They have about 32 left, and apparently when they are gone, they are gone.
Part numbers:
Lowbeams:
T84 lowbeam (RHD) – 16506324
T85 lowbeam (LHD) – 16507483
Highbeams (T84 or T85, it has no rule of road cut since it's a highbeam.)
Highbeam (either) – 16506325
So after ordering the lowbeams from Susquehanna MotorSports, I decide it’s time to get a set of highbeams. The highbeam part number was still good in the GM system, so about a month ago I dug into my part numbers to order the highbeam light. Very funny phone conversation with my normal parts guy, List is $68/ea but he needs a vin for them and questions wtf they were off of. Anyway he tells me there are two left in the US, in a small dealership in Kansas. Called them and talked to their parts guy. He said they have obviously been there a LONG time, offers them to me for $51/ea just to get rid of them. So, I just may have bought the last set available. And I was worried about a rock hitting the lowbeams and breaking them, these ones are really going to make me sweat. So, the high-beams are no longer available from GM; I ordered the last 2 in the system.
First off, the glass lenses on the Bosch lights are thick, thicker feeling than the sealed beams and WAY thicker than the eurolight conversions. They include a very large rubber boot that cover the light and keeps moisture out. Under it is a very nice locking setup for the bulbs. The lowbeams also include a “citylight” which is a separate 194 blub that is effectively the European equivalent of a DRL. I choose not to wire this up in my truck as I hate DRLs.
Lowbeams (notice the Bosch and GM part number tags)
Lowbeam compared to Eurolight H7 light (with highbeam glass)
Highbeams
Highbeam compared to Sealed Highbeam H4701
Side by Side (lowbeam on left, highbeam on right)
Bulbs, boots and city-light
The lowbeam light output is simply amazing. Being they are E-code, they have a much cleaner and better focused light pattern that puts the light where you need it. They also have a very sharp (almost projector like) cutoff line. I have noticed much less eye fatigue on long drives or in inclement conditions. Now, being the lowbeams are H4 bulbs (dual filament) I wired them as a true low and high beam. So when they change between filaments the optics change, and illuminate farther up.
The highbeam lights are of course the same quality. They are a similar cut to the US highbeam; however the cuts are much more pronounced and create a much better light spread on the road. Combined with the high beam filament of the lowbeam (and my other lights) the output is nuts. It is also worth noting that the lowbeams light pattern and output is far better than any composite headlight I have seen, OEM or not, in a GMT400 truck.
So I have a full set of T84 lowbeams & highbeams in the truck now, and have a second set of lowbeams sitting in a box just in case something happens. I also covered my lights with a layer of 3M stoneshield just to help protect them. Nothing like losing $300 in headlights. I’ll try to get some pictures of them in the truck, as well as the lighting pattern.
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