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1990 Burb. 4L80/np241?

dyeager535 said:
Really need to dig into what PCM's were offered up to 1995.

I find it hard to believe that it's really that complex to retrofit a TBI/4L80E PCM into a pre-4L80E rig. AFAIK essentially all the TBI stuff was the same until 1995 (I think there was some injector oddity, and big block vs small block) but I would imagine at this stage, that has all been worked out.

Yes, probably takes some modifying of the PCM programming to work, maybe repinning some terminals, but those being newer units, may have a bit more support than the older ones.

I could be completely wrong, and it's far harder than I think. But given the 4L80E was used with TBI, and TBI had minimal changes from 1987-1995 on trucks, mixing the two just doesn't seem like it would be that hard.

Going forward with a computer controlled transmission, and going backwards from injection seems counterproductive.
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When you're having problems with the injection and no one to really diagnose it correctly was frustrating. Even with the snap on computer changing the parts it said were wrong my truck would backfire. I had the tbi setup from the orginal 350 on the 454. It ran good for a while then then it would start backfiring and blowing my header on the passenger side. Maybe I'll just put the 6.0 in there and go that route
 
Sliccricc310 said:
When you're having problems with the injection and no one to really diagnose it correctly was frustrating. Even with the snap on computer changing the parts it said were wrong my truck would backfire. I had the tbi setup from the orginal 350 on the 454. It ran good for a while then then it would start backfiring and blowing my header on the passenger side. Maybe I'll just put the 6.0 in there and go that route
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Did you change the injector setup as a unit (as in the larger throttle body and proper injectors for the b
454), along with knock sensor and PROM? Any one of those not changed would undoubtedly cause problems.

Those are different between 454 and 350. At least some of the early TBI 454's didn't even use a 454.

To be frank, if you can't make TBI run in an original TBI truck without throwing in the towel not sure how an LS swap is the easy route.
 
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Keitha said:
I don't think it would be that hard IF you have an OEM harness, just got to figure out which inputs from the TBI side of the equation are used for the transmission. The hard part is that I think the GM PCM uses the sensors that I mentioned above that drive the TBI to also control the Trans.
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What I was envisioning is a complete TBI/700R4 setup, which the 700 is pulled and a 4L80E is swapped in.

As you said, the PCM needs the inputs to control the trans, but as long as you don't hack it up and throw a carb on, from what I've seen, PCM to ECM or even ECM to ECM, GM simply moved inputs like TPS (made up example here) from pin A1 on the ECM for a TBI/700 truck, to pin B9 on a PCM for the same year truck but 454/4L80E. The wiring diagrams would spell out what had to be moved. A little brainwork to ensure things like VSS input is the right one, but that's about it I can think of.

I'm not aware of any functionally different sensors. TPS is TPS with the same voltage range, the injectors use the same wiring, VSS is VSS, Etc.

Same inputs required/available, just going to a different terminal on the ECM/PCM connector.

We are probably on the same sheet here, I just don't see the need or reason for a carb in this situation. Especially now given the understanding of why a carb is even a consideration.
 
dyeager535 said:
Did you change the injector setup as a unit (as in the larger throttle body and proper injectors for the b
454), along with knock sensor and PROM? Any one of those not changed would undoubtedly cause problems.

Those are different between 454 and 350. At least some of the early TBI 454's didn't even use a 454.

To be frank, if you can't make TBI run in an original TBI truck without throwing in the towel not sure how an LS swap is the easy route.
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My truck runs fine with the carb on it now. I just need a beefier transmission. The 6.0/4l80 swap is something I have already but didn't put it in because the 454 works fine. So i planned on using it until it gave out. Harness, computer, vats delete and crossmember customized, ls swap plates. I already have the correct fuel tank for the swap. I have everything for the swap except a few fittings. I would've just loved the 4l80 behind it the 454. I originally got the 454 from a 95 suburban with a 4l80 4x4. I just didn't know about the 700r not holding up to it well. Lesson learned for sure. Thanks for the information.
 
Oh my mistake, I missed that it was already carbed. In that case yeah, too late if the TBI stuff was cut out.

Can the LS PCM run a 4L80E? Some variant of the LS series in trucks had to have gotten a 4L80E, no? The LS series swap information/components are so common now I would expect it to be super easy. (?)
 
If you do the 6.0 I am interested in the 454. If it goes up for sale.
i see you are in LA how do you get by the emissions testing?
 
dyeager535 said:
Oh my mistake, I missed that it was already carbed. In that case yeah, too late if the TBI stuff was cut out.

Can the LS PCM run a 4L80E? Some variant of the LS series in trucks had to have gotten a 4L80E, no? The LS series swap information/components are so common now I would expect it to be super easy. (?)
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You and I are on the same page. IF he had the TBI system intact, it would be a far simpler path to using the PCM to control the trans. Because he went with a Carb, this won't be so simple. He would have to somehow add all the sensors of the TBI system, just not use the TBI itself. At that point, you might as well just convert to TBI.

There is a reason they didn't put the 700r behind may big blocks...
 
I just posted a 32 input with planetary for sale if you are still looking.
 
Keitha said:
You and I are on the same page. IF he had the TBI system intact, it would be a far simpler path to using the PCM to control the trans. Because he went with a Carb, this won't be so simple. He would have to somehow add all the sensors of the TBI system, just not use the TBI itself. At that point, you might as well just convert to TBI.

There is a reason they didn't put the 700r behind may big blocks...
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“There is a reason they didn't put the 700r behind may big blocks...”

Absolutely!
 
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