Vintage Air Gen V (5) or replace existing compressor, etc., for 1987 R20 Suburban?

YakkoWarner · Sep 13, 2024

beady said:
My 454 truck has the same fan. It runs all the time as soon as the key is turned to ON. From this thread I’m guessing something isn’t right with that?

The thermal switch is on the passenger side of the engine (single wire) - if the wire came off and is touching metal somewhere, it will trigger the fan to come on. If the wire isn't just hanging loose, try unplugging it from the switch and turn the key on; if the fan stopped than there is a good change your thermal switch is shorted and needs renewal. If the fan still runs, check its relay over on the driver side inner fender area. That could be stuck closed as well.

Normal operation is independant of the A/C - mine comes on anytime I'm in traffic - seems like the threshold is around 160-170 degrees and it will click on.

Snoots · Sep 13, 2024

beady said:
I already replaced it, those were pics when I took the one that was in there out.

I’ll look into the alcohol for flushing, thanks.

Flush it out WITHOUT the Orfice Tube.

Craig 85 · Sep 13, 2024

AuroraGirl said:
The heat bleed is still happening, albeit if you have the heater door blend door (fun fact, i think they sell them new still apparently they fall apart?) because there is still air leakage and the thing is radiating heat inside the box(better in a square than it would be in, say, a gmt800 or gmt400 which are going to be more in the cabin and a more insulated cabin at that)

The heater core , if you bypass the hoses with a valve thats hooked up, will not radiate the temp at all, and the temps are known to drop 15 degrees in the most extreme ones, expect less than 10 if your door is where it needs to be

You could modify your wiring to add another grounding event for the relay, i would, since low speed and idle that engine is at the disadvantage of the big block making heat already, and the AC will benefit the most simply because its got the air flow over the condensor. Unless youre using severe duty type clutch for the clutch fan (Icant tell if you have one or not)

I lived in Nor Cal for a couple years after I installed the A/C (95* occasionally) and now in Mid TN with heat and humidity. A/C temps were in the 40s. I only have Boom Mat in the cab right now, still need to add jute and carpet.

I only drive my truck 500-1000 miles a year and where I drive it now traffic usually isn’t an issue. I have a 195* thermostat, so it doesn’t take long for the fan to kick on. I have a factory 4 row radiator, so temps don’t creep too much.

Craig 85 · Sep 13, 2024

@beady when I added my fan I found out the ‘85 OEM style sensor was discontinued. I used one for a GMT -400. Look around page 13-15 of my build. I listed all the parts and numbers there.

AuroraGirl · Sep 14, 2024

Craig 85 said:
@beady when I added my fan I found out the ‘85 OEM style sensor was discontinued. I used one for a GMT -400. Look around page 13-15 of my build. I listed all the parts and numbers there.

i believe thats the GM tsb solution for it

beady · Sep 14, 2024

Craig 85 said:
@beady when I added my fan I found out the ‘85 OEM style sensor was discontinued. I used one for a GMT -400. Look around page 13-15 of my build. I listed all the parts and numbers there.

Are there other things I can use from a gmt400? I have my 1993 K2500 350 tbi/4L80E that was totaled, but the drivetrain and interior are in great shape.

Also, I can’t find your build thread for some reason.

AuroraGirl · Sep 14, 2024

beady said:
Are there other things I can use from a gmt400? I have my 1993 K2500 350 tbi/4L80E that was totaled, but the drivetrain and interior are in great shape.

Also, I can’t find your build thread for some reason.

Serpentine drive if you have a sbc in your square. but you have a 454. The TBI unit is too small to use the TBI, im not sure what it takes to get a tbi unit to transfer, or if you need the (larger capacity? another injector? Something. @bucket @Vbb199 )

That alternator if it works is a good upgrade but keep your OEM one in your truck somewhere, the one in the 1993 engine is more likely to die instant death and they run hot.

Is your 454 have a TH400?
If so, you can swap your 4l80e but youre gonna need to do some work because I believe shaft length, cooling capacity, youll need aftermarket controller.. youll need to change the column shift gate changed and the indicator changed if its a th400. BUT , I think a 93 non-airbag column could just be swapped if you didnt want to mess with the shift gate stuff. Fancy steering wheel.

The late th400 dipstick and the early 4l80e dipstick may be interchangeable, but i would only do that if you could remove both and then verify they would end up the same distance in the trans. The o ring seal and the red handle are the only advantages of that inherently.

bucket · Sep 15, 2024

AuroraGirl said:
Serpentine drive if you have a sbc in your square. but you have a 454. The TBI unit is too small to use the TBI, im not sure what it takes to get a tbi unit to transfer, or if you need the (larger capacity? another injector? Something. @bucket @Vbb199 )

That alternator if it works is a good upgrade but keep your OEM one in your truck somewhere, the one in the 1993 engine is more likely to die instant death and they run hot.

Is your 454 have a TH400?
If so, you can swap your 4l80e but youre gonna need to do some work because I believe shaft length, cooling capacity, youll need aftermarket controller.. youll need to change the column shift gate changed and the indicator changed if its a th400. BUT , I think a 93 non-airbag column could just be swapped if you didnt want to mess with the shift gate stuff. Fancy steering wheel.

The late th400 dipstick and the early 4l80e dipstick may be interchangeable, but i would only do that if you could remove both and then verify they would end up the same distance in the trans. The o ring seal and the red handle are the only advantages of that inherently.

The 454 throttle body has larger throttle plates, higher #/hr injectors and also uses the other style of GM IAC valve. The one fastened with a couple machine screws, rather than the whole thing threading in.

AuroraGirl · Sep 15, 2024

bucket said:
The 454 throttle body has larger throttle plates, higher #/hr injectors and also uses the other style of GM IAC valve. The one fastened with a couple machine screws, rather than the whole thing threading in.

so basically his tbi setup is best destined to find its way in a square , but a different one! Lol

I also wonder if the 2500 (heavy) gmt400 tbi is any different than the ld 2500 or the 1500s?

because if it came with a 4l80e its probably out of a 8 lug 3/4 ton

Craig 85 · Sep 15, 2024

beady said:
Are there other things I can use from a gmt400? I have my 1993 K2500 350 tbi/4L80E that was totaled, but the drivetrain and interior are in great shape.

Also, I can’t find your build thread for some reason.

Here’s the page that lists my parts.
https://www.gmsquarebody.com/threads/1985-k30-resurrection.18494/page-13

I did use the fan temp sensor for a 350 as I couldn’t find a 454 version at the time. I haven’t had a GMT 400 in 20 years, so I can’t tell you what would interchange other than the sensor and fan ( the core support mount is different though).

beady · Sep 15, 2024

My squarebody is 1987 454/TH400 R20 3/4 ton 2wd 3:42 suburban.

My gmt400 is a 1993 350/4L80E k2500 3/4 ton 4wd 4:10’s suburban. Was a fire dept truck and base, base, base Cheyenne model. Tailgate with vinyl bench seats, rubber floor mat, manual windows and locks, w/t single headlights, no airbag, etc. Not even rear defroster or wiper. AC was its only option. I loved it. Engine and trans are in excellent condition.

I was going to swap steering wheels as I like the smaller, more modern one better. I thought about swapping the trans, but the TH400 in the ‘87 was rebuilt right before I bought it and it shifts great. Plus, I really want to do a manual swap, so no point in sinking time and money into the 4L80E swap only to replace it (hopefully in the next year).

On the 454 I just bought and replaced the fuel injectors with brand new ac Delco units snd rebuilt the top half of the tbi.

I’ll look into the alternator, thanks.

Was thinking I’d pull the drivetrain and interior (all in very nice shape) out of the gmt400 and keep it for another project in the future.

AuroraGirl · Sep 15, 2024

beady said:
My squarebody is 1987 454/TH400 R20 3/4 ton 2wd 3:42 suburban.

My gmt400 is a 1993 350/4L80E k2500 3/4 ton 4wd 4:10’s suburban. Was a fire dept truck and base, base, base Cheyenne model. Tailgate with vinyl bench seats, rubber floor mat, manual windows and locks, w/t single headlights, no airbag, etc. Not even rear defroster or wiper. AC was its only option. I loved it. Engine and trans are in excellent condition.

I was going to swap steering wheels as I like the smaller, more modern one better. I thought about swapping the trans, but the TH400 in the ‘87 was rebuilt right before I bought it and it shifts great. Plus, I really want to do a manual swap, so no point in sinking time and money into the 4L80E swap only to replace it (hopefully in the next year).

On the 454 I just bought and replaced the fuel injectors with brand new ac Delco units snd rebuilt the top half of the tbi.

I’ll look into the alternator, thanks.

Was thinking I’d pull the drivetrain and interior (all in very nice shape) out of the gmt400 and keep it for another project in the future.

if you want to column swap you can but youd need to make the gmt400 column a 3 speed shift gate lol and then find out which direction it shifts you toward, because one of the 4 spots wont be useable lol

bucket · Sep 15, 2024

AuroraGirl said:
so basically his tbi setup is best destined to find its way in a square , but a different one! Lol

I also wonder if the 2500 (heavy) gmt400 tbi is any different than the ld 2500 or the 1500s?

because if it came with a 4l80e its probably out of a 8 lug 3/4 ton

Light duty and heavy duty use the same throttle body. Iirc, the 4.3 TB is identical to the small block TB's too.

MikeB · Sep 16, 2024

If someone hasn't suggested it yet, check out Old Air. They have kits to replace OE compressors with a Sanden, but they also have rebuilt OE compressors as well as a new "Pro6Ten" compressor that looks like an OE compressor. https://www.oldairproducts.com/category/factory-replacement-parts

MikeB · Sep 16, 2024

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Vintage Air Gen V (5) or replace existing compressor, etc., for 1987 R20 Suburban?

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