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1991 GMC Sub, Name TBD [Deleted]

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Fastereddie said:
Isn’t the tcm internal on the 6l80? The big pink wire that went to the stock hei distributor is hot in run and crank.
Click to expand...

Yes the 6l80 TCM is internal. Just heard back from the dyno guys and I called Howell EFI (made my harness) as well as the Chevy Dealer. I think my only option now is to buy a gen 5 TCM and plug it in.

My Chevy dealer has 2 in stock so I'm gunna pull my valvebody and bring it with me to make sure itll physically go into my 6l80. In theory they should be able to communicate!

And that pink wire is what I will tap into for hot crank/run. Thanks for that tip!

I'll keep yall posted today!
 
Just a few minutes searching the service manual online at work while I eat lunch.
Looks like the tcm inputs by individual pin seem to be the same, 13 to 14. So I don't think it's a compatibility issue there. I did just do a quick Google search on the L83 swap. Lots of hits. YouTube videos, forum posts, the normal stuff. Good info.

I did run into one link for Speartech. They build thier own harnesses specific to the type of swap. $1250 for a L83/6L80-90 trans. It sounds expensive now, but by the time you get all these goofy things ironed out you'll have that in time/money. It's worth it when they've figured out the issues.
 
Please note, I've not used Speartech so I can't vouch for what they do. Just an example off what's out there. There are probably a dozen more doing the same thing. Research whoever you intend to use.
 
ZooMad75 said:
Just a few minutes searching the service manual online at work while I eat lunch.
Looks like the tcm inputs by individual pin seem to be the same, 13 to 14. So I don't think it's a compatibility issue there. I did just do a quick Google search on the L83 swap. Lots of hits. YouTube videos, forum posts, the normal stuff. Good info.

I did run into one link for Speartech. They build thier own harnesses specific to the type of swap. $1250 for a L83/6L80-90 trans. It sounds expensive now, but by the time you get all these goofy things ironed out you'll have that in time/money. It's worth it when they've figured out the issues.
Click to expand...

Thanks for the info! I've already sourced my $1000 harness through Howell EFI, and I'm very happy with it. It was my own blunder not researching the 13-14 TCM issue, but alas...

...an update as promised! Today, after contacting everyone I could about it (harness builders, tuners, dealerships, etc) I've learned that in no way could the gen4 TCM be used with the gen5 motor, tuned or not!

So, I went to the dealer with the motor's VIN and got a matching generation TCM, and installed in in my 6l80. They advised that they need to program it to match my ECM, before using it (doing so would fry the TCM). Once it was in decent enough shape, I had the burb towed to their service department. They should get to it tomorrow (Friday), and I left them a laundry list of stuff they need to know about my swap.

ALL of my fingers are crossed that after they correctly program the computer(s), the motor fires. Find out, in tomorrow's episode!!
 
So the dealership was nice enough to tell me that they couldn't do my programming today... so they'll get to it Monday (Maybe Tuesday...). Like what??

So to toss in a filler episode, I'll post my most recent pics of the swap!

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Where is the intake and MAF?
Also, I think the upper hose is backwards.
I think...

lol

looks sweet in there
 
K85 Octane said:
Where is the intake and MAF?
Also, I think the upper hose is backwards.
I think...

lol

looks sweet in there
Click to expand...

You're right, I have the intake off right now waiting for a cold air to come in the mail this weekend. You're also right about the hose being backwards, that the only way it would fit without cutting lol. And actually I like it that way because it rests out of the way and doesn't hang.

I'm crossing my fingers this all goes well. If it does then I'll be able to take this thing out to CO early August! Every year I drive out there to visit my brothers, they're in Boulder.

Help cross some fingers y'all!!
 
SO LISTEN TO THIS.

I ended up having to leave my truck at the dealer last weekend like I mentioned. I got tired of not hearing from them so I called in on Tuesday, only to be ignored.
WEDNESDAY morning, I ROLL UP dressed nicely for the kill and eagerly awaited to speak my mind to the manager on duty. After (strongly) conversing with the manager and the tech in charge of my truck we determined that the tech started to poke at it on Friday, but was getting confused from my note (saying this is a custom swap if you have questions, ask me). He CLEARLY didn't ask me and let the truck sit there for nothing.

He then began the actual work when I explained to him that the tech who sold me the TCM said it had to be "turned on". An hour later the manager comes up to me with his tail between his legs and goes..."Sir, we got some bad news. We can't program it..."


WHAT

Rest of the story short I tow my truck the hell out of there to the Dyno (after speaking with them) in hopes they can get the TCM and ECM to talk. I'll hear from them Monday. So a week went by (where I could have done a ton of other work) as my burb sat on the dealers lot for no gosh darn reason!!

That's the latest y'all. As of now my options are these two:

1. The dyno guy can get the TCM and ECM to talk and everything goes hunky dory, I'm done!

2. The dyno guy can't get them to talk.

If we reach option two then I'll ask the dyno to program my ECM to think it's running a manual trans, essentially stripping its need to communicate with the 6l80. Then I'll be getting a standalone 6l80 controller that operates like factory from a TPS feed and an RPM feed.

I'll keep you posted. One of these options will likely unfold come Monday. Cheers til then!!
 
I'm surprised the dealer ever took the truck in, I really am. There is no way any dealer would ever touch that around here.
 
K85 Octane said:
I'm surprised the dealer ever took the truck in, I really am. There is no way any dealer would ever touch that around here.
Click to expand...

Honestly, I don't think I would have taken it on at our shop. My guys are good, but between the mix of parts and GM's dazzling way of making the easy be very hard it would be a no win situation for the tech. Normally customer pay programming events run an hour of labor on regular stuff. We get cars in from independent garages that buy GM modules from us that require programming after installing all the time. But when the parts are mixed from different model years and modules typically compare vin numbers stored in memory for security reasons, this one was doomed for failure before they ever plugged into it. To take it on we'd have to go "straight time" meaning whatever time my tech has in it, you pay. Even if it don't work in this case. Again, because of GM's awesome service programming system that could have us banging our heads into the wall because the system won't connect due to wiring issues or other unforeseen issues means we would surpass the normally 1 hour programming time pretty quickly and not be further along.

Just an example of the state of lockdown GM has on things for us dealers when it comes to programming. I had a guy come in with a 2013 Silverado, came with the uplevel radio, but it didn't have the touchscreen nav system. He bought a used unit off of a buddy that upgraded to some high end aftermarket radio equipment. In this case the Radio does have the vin programmed in from the factory and dealers can't override it. Since the VIN in the radio gets compared to another module to show that it's not been stolen, attempting to install a unit from one truck to another as I advised the customer it may not work even if we could update the calibrations and it's still looking for a different vin. The customer insisted, even after me telling him he's going to pay my tech's time if it works or don't and I warned him it probably won't. He agreed and handed me a set of instructions from some web forum on how to "hack" the system into thinking it's something else like calling it a different year/model to allow us to overwrite the vin in the radio. Needless to say as I predicted it wasn't working. We spent a couple hours on something that should have taken 1/2 hour and the guy gets pissy with me over the bill. Moral of the story is, getting GM's own programming system to do something it wasn't designed to do will almost always end in failure.
 
Well at first I was hesitant (as we all would be) to bring them the truck because of how custom it was, but I decided what the hell let's tell them about it and hope. After I told them everything about it they said literally all that was needed was to plug into the 6l80 and that was it. No ECU programming. Nada. They said they could do it and that they had to do it to prevent the TCM from frying.

That's what was so confusing because nothing about the TCM had changed prior to that. It was literally a brand new gen5 TCM purchased from them!

But oh well! I'm at my current position now and Monday it shall be decided! Once it's done I feel like I need to meme the experience so I can be happy and laugh about it lol
 
UPDATE: The dyno tuner was able to get a full read on the ECM and TCM! It is now programmable!!!

I took the burb back home after the dyno was able to read the computers, simply to button some stuff up. At that point , whatI had left was: bolt on the headers, mount the gas pedal, change my spark wires to my nicer ones, install CAI, fill ATF, fill coolant. My list has dwindled to coolant and pedal now, almost done.

I'm currently visiting my girlfriend in NY so when I get back this week, I'll be finishing the last two items! Once those are done it's back to the dyno for some programming/mapping. At that point the suburban will be drivable on its own power and I'll drive it down the street to my custom exhaust shop (love those guys, if anyone is in my MD area, Tony's Custom Exhaust, great work there). Once my piping is complet then it's back up the road for the final dyno runs, and voila!!

I'll update you all on the dyno when I get there. My phone just broke so I'm on the new one and I lost all my photos. I'll get you updated pics soon, and if I can remember I'll video the start up! Updates soon!
 
GUYS! I'm hitting a tiny block...

I mounted my gas pedal (niiiiiightmare, trial error trial error trial error, lol). The only thing I have left before the dyno maps the computers is my cooling system. My friend gave me the radiator out of his 2003 Yukon that had the 6.0 in it. However, the drain plug isn't there.

IM STUMPED.

I went looking for the plugs and I've found two kinds, both of which are threaded plugs. One white and skinny and the other is black and a little thicker. None of them go in!!!

Is there a 3rd type of radiator drain plug that I've never seen before??

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