LS engine swap info

[ls1nova71]

Originally Posted by 69BUCKET

Reliable place to send ECM to verify proper things deleted/bypassed?

If you're just looking for a standard mail order tune with nothing fancy but will get you up and running, lt1swap.com is hard to beat. Cheap and reliable.

[69BUCKET]

Thanks Nova...

Hopefully he'll be able to tell me what ECM is looking for for VSS senor? Dakota Digital said that was crucial before ordering the VSS sensor from them.

[Willie Makeit]

Originally Posted by 69BUCKET

Thanks Nova...

Hopefully he'll be able to tell me what ECM is looking for for VSS senor? Dakota Digital said that was crucial before ordering the VSS sensor from them.

you've already been told WHAT to order

[69BUCKET]

Dakota digital asked me what the ecm pulse reading is i think...128 or something different. I am not sure and ecm doesn't have any labeling on it. I sent lt1swap an email to ask about bad sensor reading from ecm.

[Wildkarde]

The ECM is looking for 40 pulses per driveshaft revolution(this is tens of thousands of pulses per mile), but it uses some math to determine how many pulses per mile that is since it changes with gear ratio/tire size. This is adjustable in tuning software.

The ECM can output a vehicle speed signal on one of two wires, one sends 4000 pulses per mile, usually used for speedometers/cruise, the otther 128k pulses per mile, used for ABS and traction control.

You need to know your rear end gearing and tire size to make the calculations you need. Is your current speedo gear in the trans giving you a correct speed reading on the speedo?

[69BUCKET]

I am running a TH350 behind the 5.3...no ABS, traction, or cruise. No modifications to engine, just stock DBC set up.

I will look at rear end for code to see what I have. Truck has never been running while in my possesion, so no idea if current Speedo gear in trans. is being translated into correct speed. It is a fresh rebuild.

I decided to run a VSS sensor instead of hoping I had no issues w/o it. I am sending ECM to lt1swap to be sure it is done properly. On his site he mentions tire size and gear ratio doesn't matter if I'm running a TH350. As stated before, Dakota Digital asked me what signal was from ECM...128K or something else. I told him I have no idea and didn't say how I can find out. So I am hoping lt1swap can tell me when he gets ECM so I can order correct sensor. Or can anyone reassure me of what part will work with flashed ECM from lt1swap?

[davepl]

Just kind of wandered into this 275 post thread so forgive me if I don't have all the context, but from what I've gathered:

You have an ECM that needs a speed signal sensor. You have a TH350 trans that does not provide a digital speed signal.

So you're adding a VSS sensor that will provide the ECM with a pulsed signal. The ECM and the sender need to agree on how many pulses per revolution. Normally for a GM auto transmission it is 40 pulses per rev.

If, for whatever reason, the speed sensor you wind up using is a different number of pulses per revolution, you can change it in the LS3 computer if you have HPTuners or similar. Odds are you're going to have to edit it to change tire size and gear ratio anyway.

For example I bought the "automatic" LS3 that comes set up for 40 pulses per rev but then put it in front of a TKO-600 trans that is (I think) 17 pulses per mile so changed it in the ECM before I ever installed it.

[Wildkarde]

The pulse generator from your other thread should be able to be made work, just need to get a vague idea of pulses per rev and pulses per mile. Don't need to be accurate just someplace sane, the things the engine relys on vehicle speed for dont need very high accuracy. It may even be able to work without it completely, out of all the swaps I've done harnesses for no one has ever wanted to stick with the old 3 speed, they wanted the new transmission almost as much as the ls.

The guys at lt1swap should know for sure, and be able to help you get it set up which ever way you need.

[69BUCKET]

He emailed me back yesterday...i think i got it sorted out. Hopefully just a week away from first ride to alignment and muffler shop!

[Thealien]

Just reviving my old thread. I may be getting back into a Blazer and looking at all my options!

[Chvy2NV]

thealien, THANK YOU and the others that have contributed to this thread, tons of great info here..