Tech: 88-89 GMT400 Quad Sealed Beam upgrades (Bosch T84 E-code headlights)

[88gmctruck]

Making a harness would be more difficult without knowing where to get the stuff. You can get H4 pigtails easily but a male 9005 and 9006 base not so much.

 

[kojo]

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.

Actually that is parking lamp, amber parking lights are illegal here in europe so that is easiest way to make bright park light..

 

[88gmctruck]

Interesting. Good to know.

 

[88gmctruck]

Just an update for anyone interested. The LMC conversion headlight housings are actually a very viable option. A friend of mine bought an 89 blazer with a set of the lowbeams LMC lights. I can actually say I'm impressed with them. They use 9006 bulbs, are of quality construction and actually have a very proper light output. I would highly recommend them if you cannot find the Bosch lights.

 

[sledtrash]

Just letting you all know, I have a contact that has a large supply of the the High Beam H4 bosch lights. They include the OSRAM H4 bulb in them. You can use them for both low and high beams, however they wont' have as good of a pattern as the lowbeams would so you can point them farther down.

Asking $100 for highbeams, let me know if anyone is interested.

You still have access to some of these?

 

[MrMarty51]

Several years ago I had pulled this system from a truck that was in the junk yard. I had it installed on My 93 K1500, before selling the K1500 I changed it back and installed this onto the K3500. I set it up with a relay so that when the brights are on, the dims also stay on.
It has just the basic over the counter bulbs installed, but, it sure beats the original equipment lighting.

 

[GM Guy]

So do you guys feel that even in stock form these are an upgrade over OEM 90+? Is there much change in the 90-93 and the 94+ lenses?

I dont recall much of a change between the 93 and my 95, but there was close to a year gap from when the 93 died and the 95 was purchased, in the gap there was just the big single sealed beam equipped rigs.

Also, if a guy wants to just swap harnesses to try it out, does the harness terminate at the firewall, or does it go into the cab?

 

[MrMarty51]

So do you guys feel that even in stock form these are an upgrade over OEM 90+? Is there much change in the 90-93 and the 94+ lenses?

I dont recall much of a change between the 93 and my 95, but there was close to a year gap from when the 93 died and the 95 was purchased, in the gap there was just the big single sealed beam equipped rigs.

Also, if a guy wants to just swap harnesses to try it out, does the harness terminate at the firewall, or does it go into the cab?

On Mine, I clipped the terminal blocks behind the lamps and soldered in the ones needed to make the lights functional.

 

[deejaaa]

On Mine, I clipped the terminal blocks behind the lamps and soldered in the ones needed to make the lights functional.

did the same.

 

[1994ch]

Also, if a guy wants to just swap harnesses to try it out, does the harness terminate at the firewall, or does it go into the cab?

I believe (from my experience swapping harnesses for my tahoe project) that the harness could be unplugged. I was not really paying much attention to which wires went to the headlights, but I unplugged the entire dash and engine harness so I obviously unplugged it somewhere. (this was on a 96)

 

[Twisted Steel Performance]

So if I read this correctly to change from composite to quad about all that's needed is a light bucket kit from LMC and swap out the bulb connections ???

 

[MrMarty51]

So if I read this correctly to change from composite to quad about all that's needed is a light bucket kit from LMC and swap out the bulb connections ???

That will do it.

 

[Twisted Steel Performance]

Thanks, searching ebay for adapters and I will need to figure out what I need to go from the plug on the composite's to the other type, I'm sure they make them I just don't know what to look for yet...

 

[MrMarty51]

Thanks, searching ebay for adapters and I will need to figure out what I need to go from the plug on the composite's to the other type, I'm sure they make them I just don't know what to look for yet...

Most automotive parts houses have the plugs d pig tails for the older sealed beam headlamps.

 

[88gmctruck]

You still have access to some of these?

I do not. That was some time ago.

So do you guys feel that even in stock form these are an upgrade over OEM 90+? Is there much change in the 90-93 and the 94+ lenses?

I dont recall much of a change between the 93 and my 95, but there was close to a year gap from when the 93 died and the 95 was purchased, in the gap there was just the big single sealed beam equipped rigs.

88-89 sealed beams, IMO, perform equal to or better than OEM composite lights. And with the LMC housings (or if you can find any bosch housings) they are ever better.

90+ composite headlights never changed design.

Also, if a guy wants to just swap harnesses to try it out, does the harness terminate at the firewall, or does it go into the cab?

I believe (from my experience swapping harnesses for my tahoe project) that the harness could be unplugged. I was not really paying much attention to which wires went to the headlights, but I unplugged the entire dash and engine harness so I obviously unplugged it somewhere. (this was on a 96)

The forward lighting harness has a plug just past the firewall bulkhead on the engine bay side. There are two variants of round early and later rectangular plugs, with a split somewhere in the 96/97 range.

So if I read this correctly to change from composite to quad about all that's needed is a light bucket kit from LMC and swap out the bulb connections ???

Best bet is to get a set of buckets and adjusters off ebay or the junkyard, will be MUCH cheaper than LMC for those parts. You can splice the proper pigtail or swap entire harnesses.

Thanks, searching ebay for adapters and I will need to figure out what I need to go from the plug on the composite's to the other type, I'm sure they make them I just don't know what to look for yet...

Most automotive parts houses have the plugs d pig tails for the older sealed beam headlamps.

The H4701/H4703 lights use a unique plug that isn't commonly available, although I'm sure parts places can order as they were use in a few vehicles. The easiest solution would be to use the LMC conversion lights for the 88-89 headlights, as they use 9005/9006 bulbs just like the composites and require no wiring modifications to use them.

 

[1994ch]

The forward lighting harness has a plug just past the firewall bulkhead on the engine bay side. There are two variants of round early and later rectangular plugs, with a split somewhere in the 96/97 range.

Both my 96 tahoe and 96 truck had the round plug......

 

[Twisted Steel Performance]

Thank you for the info, I did get a complete set for 50$ yesterday off ebay, I just installed a new harness and the info on the lmc lights was just what I needed to know about the plug, will have a set of the conversion lights headed this way also...

Again thank you for the good info...

 

[Leo Gustafsson]

I wish I'd leanred of this conversion before I got a set of Glass Lensed composites,

while they're plenty bright with the LED bulbs, I found a fantastic resource for long lasting high wattage H4 bulbs Flösser GmbH & Co.KG when I ran Hella Vision + H4 housings on my van.

http://flosser.com/index.php?id=99&L=1&tx_mmproductlist_categories[loadCategory]=10510

 

[snarl95]

You can't get those headlights anymore. But LMC truck has a version of them
http://www.lmctruck.com/icatalog/cd/full.aspx?Page=65

 

[Bodi069]

I live in Switzerland and would send the beams to you.