Tow/Haul mode, LMM Swap in an 84 C30

[THEFERMANATOR]

Good thing too, it only takes about 30 seconds to flash the TCM, so it wouldn't be too much of a headcahe to switch back and forth until you get the T/H figured out.

Fwiw duratothemax or Ben Tyler of BT Diesel Works could probably tell you all you need to know. He has some sweet BCM tuning out that can give you a few neat upgrades like manual high idle.

I sent him from facebook to try and get Ben, kidturbo, or Russ to see if they could help him out. I'm just not versed on how the GMT-900 handles BCM power on requests and such. As to copying the tow/haul tables into the regular tables, this is no guarantee he will get lockup in 2nd as there IS a lockup inhibit table for normal shift mode. I chased it for years before chavez helped me out and sent me a .cax to unlock it so I could get lockup below 50 mph.

 

[THEFERMANATOR]

I've got a stock fresh Lmm tcm file I can send to who ever for you. You can just have your tuner flash the tcm. Or have someone bench flash you one and exchange you

Theres SEVERAL different LMM OS's, theres even 2 different style TCM's for an LMM. You have to know what he has now to find a base tune for it. And even if you get the right base tune for his TCM, the OS MUST match or else he will have to full flash it, and depending on which TCM he has, that could be VERY difficult since EFILIVE doesn't typically do full reads on A40/A50 TCM's.

 

[c20elephant]

Like the others have said nice build, if someone did not know any better you would swear that LBZ CAI was original to the truck like the engine.

I had a 1982 C20 and their a slew of GM brackets/panels that secure the radiator to the core support and that one fits like the CAI one would never know it did not belong...:thumb:
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[Harbin_22]

If you copy all the TH shift speeds and converter speeds into the normal tables, regular driving will lock the converter just like tow/haul will. At WOT, it's a crap shot if it will lock or not even in tow haul mode. EFI did introduce some slip inhibit tables, but they aren't 100% reliable

 

[Ls1nova]

I sent him from facebook to try and get Ben, kidturbo, or Russ to see if they could help him out. I'm just not versed on how the GMT-900 handles BCM power on requests and such. As to copying the tow/haul tables into the regular tables, this is no guarantee he will get lockup in 2nd as there IS a lockup inhibit table for normal shift mode. I chased it for years before chavez helped me out and sent me a .cax to unlock it so I could get lockup below 50 mph.

Thank you for asking about that for me! Greatly appreciated man!

If you copy all the TH shift speeds and converter speeds into the normal tables, regular driving will lock the converter just like tow/haul will. At WOT, it's a crap shot if it will lock or not even in tow haul mode. EFI did introduce some slip inhibit tables, but they aren't 100% reliable

Thank you man. I think at this point I'm going to concentrate on trying to get the BCM to work. There has to be some kind of power, gnd or ign input that I missed. Sucks working without a schematic of this thing.

 

[clrussell]

Wish I was at work I'd get ya a diagram

 

[WVRigrat05]

That is very clean. I'm no help on wiring but I'm in for updates.

 

[THEFERMANATOR]

If you copy all the TH shift speeds and converter speeds into the normal tables, regular driving will lock the converter just like tow/haul will. At WOT, it's a crap shot if it will lock or not even in tow haul mode. EFI did introduce some slip inhibit tables, but they aren't 100% reliable

Have you tried it and verified it will stay locked at zero throttle? I was told the same thing with my 5 speed, and quickly found out they were wrong. Even after I proved them wrong, they still posted up it would work, and that I had messed up copying the tables because there was no inhibit table visible in efilive. Then chavez found the other table, and I can now get lockup whenever I want. But I've never had a reason to try it with a 6 speed, so I haven't tried it on one yet.

 

[Harbin_22]

I have done it on an 08 and 09 with no problems

 

[THEFERMANATOR]

Did it stay locked down into 2nd when you let off the throttle? I know the 5 speeds will not stay locked below a certain speed at 0 throttle. If you hold the throttle just a tiny bit it will stay locked up, but as soon as you completely let off, it would unlock. For a stock lb7 it was around 46 mph, and I believe lly was around 42 mph. Didn't matter where you set the tables, it would unlock when you let completely off the throttle.

 

[Ls1nova]

Like the others have said nice build, if someone did not know any better you would swear that LBZ CAI was original to the truck like the engine.

I had a 1982 C20 and their a slew of GM brackets/panels that secure the radiator to the core support and that one fits like the CAI one would never know it did not belong...:thumb:
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Thanks man! That was the goal with this project. I want to have a factory reliable tow rig that is a good mix of old school cool and modern technology.

 

[kidturbo]

My ears were burning, then tap talk flagged this thread.. Sounds like ya need a BCM wired into the network so ya can manually control the trans.

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[rodder55]

Any incite on how this is done same idea as stand alone engine power grounds ignition and should work or any kinda thing it needs . I'm putting an 09 lmm into 95 h1. Wanna keep cruise tap shift and tow haul if you have info I could compensate you for knowledge as stand alone bcm is new to me. Thanks

 

[kidturbo]

Get the BCM and plugs from under dash, plus shift lever from same truck if ya can. There are two sets of high speed CANbus wires on the BCM, one set goes out to the glow plug harness, then onto ECM & TCM. That's set ya need to connect up.

Then power the BCM same as truck would be. The tap shift / tow haul switch wires run directly to the BCM. When you push a button for M mode, the BCM sends a CANbus data command to the TCM to change shift tables.

The BCM is no more than a solid state relay bank and analog to digital converter. When you flip a switch or button, it tells a relay to turn on, or send that signal to another module. In your case the TCM. So just need to plug it all back into the system and it works.. But everything needs to match models and VIN's.

Ya still disable VATS in the ECM unless your pulling the keys and security module from same truck to match. But lets say you swapped the whole steering column, then you could really update things with volume control buttons and such. The BCM is the main brain for controlling everything non-powertrain in the vehicle.

I have all the pintout and harness diagrams from GM. Shoot me a PM if ya need them.

 

[rodder55]

I got all the diagrams at my disposal. Bonus to have a good buddy work at Gm. I'll give it a shot. U might have a im in the future if I get hung up think I got a good idea just never actually executed a project of this type . Have a complete donor truck do getting all matching modules Ect isn't a problem. Can I ignore the low speed data connections to the bcm since the h1 will use the hvac windows radio. And other creature comforts that came with it thanks for your help

 

[kidturbo]

Sounds like ya have it. Only other thing that might need the low speed Lan is keyless entry if you wanted that added feature.

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