1991 v3500. Correct way to pull 4l80e and tbi.

[obijuank5]

I sold my 350 out of the crew cab so now I've got to pull it. I would like to also separate the tbi by itself and then the 4l80 system by itself as well to sell.
What is the correct way to remove these systems without forgetting anything for someone else to swap it in to a non equipped truck?

The tbi my thinking is it's all coming out of the right side grommet of the firewall. Unplug every connector from the motor within that harness and pull the bulkhead connector through the firewall from cab to engine bay.


The 4l80e I am completely dense on. I honestly have no idea where anything is on this one.
I do know I'll need the column shift rod.

Thanks for the help!

 

[sweetk30]

no clean way to keep gas engine tbi and 4l80-e separate in junk pull .

its one side or the other . 1 gets the part only and no wiring or computer .

if it was a 6.2 and 4l80-e then thats a different story .

and the tbi wires can be a bit funky to the novices in a pull out job to make swap / standalone later a easy install job .

tbi at firewall goes over to dash also after computer feeds . you got lights / obd1 plug under dash / you as 89-91 got DRAC under radio for speedo function / its not a super clean unplug job .

 

[obijuank5]

Cool. I have no issue sacrificing the tbi.

 

[Bent77]

Tbi harnesses are easier to find

 

[sweetk30]

i do recall talking with howell efi the later 4l80-e stuff chips and computer are worth more . just the E-prom is worth money on them if its the right one .

 

[dyeager535]

There would be no point trying to separate the wiring between TBI and 4L80E correct? Since the PCM is completely different from an ECM or TCM, isn't the wiring itself worthless unless being used for another tbi/4L80E app?

 

[obijuank5]

Whether its worthless or not, I'd like to have it to include with this trans when its sold. My intent is to sell it as a squarebody swap kit to put a 4l80 205 in.

 

[USSkoval]

Personally, I'd include the complete TBI harness and ECM with the trans. These days, I'd say there's far more value in a complete 4L80e swap than a TBI swap.

 

[nvrenuf]

I agree with @USSkoval , since the 4l80e swap is the holy grail of parts keep all of that together. A harness for a TBI motor is a dime a dozen.

 

[Tnsejed]

Include the complete harness and PCM. The 4l80e section goes straight to the PCM and is integrated into the TBI harness IIR. The wiring is useless if attempting to use the transmission as standalone from a TBI motor, and the same ECM numbered TBI motor.

There were a few of those depending on the year and they are different pinouts. That's one of the things I had to do with my truck and swap.

 

[sweetk30]

howell efi can or back in the day if i recall modify a tbi/4l80 computer for stand alone trans only .

it only uses the tps signal and tach and brake switch if i recall .

 

[1-ton]

There really is no separating a 1991 TBI wire harness from the 1991 4L80E wire harness because they function as one unit. The only way for a TBI engine and 4L80E transmission to function separately is if they have stand-alone ECM's to control them, and that is an expensive proposition. The 1991 TBI/4L80E wire harness is a one-off aberration that never existed in any other GM square body truck, but the 1991 V/R series 1-ton. Because of this there is no aftermarket wire harness for one of these. I know because I own one.

My 1991 V3500 Silverado Crew Cab

 

[obijuank5]

Well here I am. Trans is pulled and whole bulkhead harness is on the ground. I forgot my 91 factory service manual at home like a dumdum.

I have separated the the starter wires. Coolant temp. Alternator. I dont know where oil pressure for the gauge comes from.
And lastly, what do I do with all these that go in to the bulkhead connector?

 

[obijuank5]

And what is this to? Lol

 

[sweetk30]

did you have a oil sender on driver side above the oil filter with a single brown wire if i recall ? if so then this is the gauge sender .

 

[dyeager535]

1991 should use a three wire oil pressure sender/switch, tied into the fuel pump circuit.

 

[obijuank5]

So yall got me wondering. I dont have the single brown wire. According to the manual that's accurate for 6.2l 91s.
I do have the three wire one behind the distributor. Now I've got to figure out which one in my harness will send it back to the gauge.
I'll probably get back at it this week while I got some coverage watching the kids.

Thanks for the guidance guys!

 

[dyeager535]

It's 31(.5? can't quite make out what is after the period) on the connector in that image. Follow that wire and you'll see it go to the IP connector.