The Dark Side of Wil

My dad has a '90 Suburban with 500 cid Cadillac, customized HEI distributor running LT1 OBDI PCM (using LT1 Edit and TunerCat) with 4L80E and 3.23 14 bolt full floating rear. It turns ~2250 at 80 MPH and has plenty of torque to tow in 4th gear lockup.

I'm thinking of building a 540 Caddy for him, but I'd like to run it on LS controls. I was thinking that I could mount a 24x or 58x wheel from www.eficonnection.com inside the front cover and use the now unused mechanical fuel pump port for the crank position sensor.

I'd also like to be able to, at a later date, swap out the 4L80E for a 6L90E. The 40 extra cubes, a bit of extra compression and roller cam should give it enough grunt to pull 6th gear lockup, even with the 3.23 rear... RPM should be about 1900 at 80 mph.

Since this is a towing and road trip truck, cruise control is essential.

I understand that the 6 speed auto had its own separate control module, which was fed operating parameters via CANbus. Was the 6 speed ever used with a 24x ECM, or was the six speed used only with 58x engines?

I also understand that in the 58x vehicles, the BCM is wired to the cruise control switches, and passes the cruise operating parameters to the ECM over the CANbus. That means that cruise control isn't available for 58x ECM's without the BCM.

So... 24x or 58x?

Which one do I need to make this system work to my needs?

Thanks!

vannatta20

iTrader: (4)

Just get a rostra cruise control unit.Its the easiest way to do this

MontecarloDrag

iTrader: (3)

The 6L90E uses a T43 TCM installed inside it. I haven't seen any aftermarket controller capable of running a 6 speed transmission.
So I think you need to use a Gen4 ECM to be able to control the TCM inside the 6 speed trans. The problem is going to be the year of the transmission, you need a ECM of the same year with a compatible OS so they can talk to each other.

If you install a 58X system to the engine then you can use a E38 or E67 ECM from the same year of the 6L90E you purchase. You also need to convert to DBW since all ECMs capable of talking to a T43 are DBW only.
After that you need to add everything for cruise control.
You may also want to swap a 2008-2012 truck steering column and BCM, it will be easy to set it up since all controls and wiring for cruise are built-in.

The Dark Side of Wil

What's necessary for a BCM install? I @$$ume it needs key input among other things, hence your mention of the steering column as well.

Does the BCM also need vehicle speed? Does it get that from the ABS when in the original body?

MontecarloDrag

iTrader: (3)

The BCM uses a lot of inputs and controls many things, but you can wire only what you need.
Basic things are battery, ignition, grounds and CAN network.
Then wire the things you want to use. I have installed a few of them and they are nice because you can control lights, locks and everything.
The speed signal goes from the Vss in the transmission to the TCM directly. No need for ABS module.

The Dark Side of Wil

And then the TCM passes the speed data over the CAN, I guess.

Interesting. I'll have to take a look at how much of the column is actually necessary.
I agree BCM's can be handy, but I'm not really expecting to rewire the truck.

MontecarloDrag

iTrader: (3)

Yes, the ECM is the master module for the whole CAN network then modules talk to each other.
Critical signals are transmitted over the high speed bus between modules, that's how ECM and TCM share information like speed, torque, rpm etc.

The Dark Side of Wil

I get how CAN works... but the specifics like the TCM knowing speed, the BCM having the cruise input switches, etc. are different from MFG to MFG.
BMW's always had their VSS in the diff, which mean it ends up as BCM data.

MontecarloDrag

iTrader: (3)

You'd need to check wiring diagrams for the donor vehicle.

The Dark Side of Wil

I will. I just didn't know which basic building blocks I'd have to put together.

If I break the build into stages and do the engine first, is there a way to control the 4L80E alongside an E38/E67?

For '06, the Corvette had the 58x trigger and the 6L80E, but all the 4L80E applications still used the 24x AFAIK.

For '07, GM Powertrain's product information archive says that the van and some full size trucks still had the 4L80E, but also received electronic throttle... I @$$ume that means they had 58x ECM's, but had a CAN TCM controlling the 4L80E.

Thanks for your info!

Info per:
https://archives.media.gm.com/us/gm/...pig_index.html

Also found a few other threads on different parts combos:
https://ls1tech.com/forums/conversio...38-t42-os.html

https://ls1tech.com/forums/pcm-diagn...ns-detent.html

https://ls1tech.com/forums/generatio...-reluctor.html

Edit: Does anyone tune BCM's to eliminate VATS or anti-theft key fob provisions?

Edit2: How does the "OK to start" signal from the BCM to the ECM work? If I keep the "dumb" cranking system, can I make the BCM work just by running a sense wire from the crank circuit to the BCM so it knows when the key is turned?

MontecarloDrag

iTrader: (3)

Yes you can use the 4L80E with a 58X engine and controller. You need to find a T42 TCM of the same year as the E38, flashed with a 4L80E OS. Then the ECM shall also be flashed with an automatic OS
Such combination exists in trucks so it's not hard to do.

You don't need anything related to key/ignition switch in the BCM, just disable VATS in the tune and the engine will start and run good

The Dark Side of Wil

Per http://www.antivenomefi.com/ an '09 Trailblazer OS has the cruise direct-wired to the ECM, eliminating the need for a BCM.

I *think* that application had a 4L60E or 4L70E... I'm not sure what OS massaging would be required to get it to work with a 4L80E T42 controller... or a T43 6L90E controller for that matter.