LSx Lessons Learned.
 

I thought I would write this so others that are performing an LSx swap will have some important info that will help them on their conversion. These are my observations and may not be true of every swap out there. Please feel free to add any info that you find valuable from your own personal swap adventure.

MODS: If you want you can make this a sticky that others can add to if you feel it will be a valuable addition to the board.



Some of this applies to everything, but some is engine/trans specific.

For ease of installation get the engine,trans,ECM,and pedal out of the at the very least the same year vehicles. The same vehicle is best.

6.2/6l80e
Somewhere in 2010 the e38 ECM operating system changed (OS). Make sure your ECM matches the trans computer (TCM) year for sure or the two will not communicate correctly.

The TCM can be exchanged between trans, but the valve body operations changed between years so they will have to be switched also. Much easier to just change ECM to match TCM.

Trying to overwrite a different OS onto a different year ECM will result in failures. Sometimes instant, sometimes glitches that cannot be resolved. Do Not do this! Just get the right year ECM.

The 6l80e needs the TCC wire GROUND when brake pedal not depressed, 12 volts when brake pressed. You can tap into the brake wire on the brake switch to accomplish this easily if you have regular brake light bulbs. If you are using LEDs then you need to set up a relay and use a 1k ohm 1/2 watt resistor to pull down when pedal not depressed. As I have learned, YOU MUST HAVE A GROUND WHEN PEDAL NOT DEPRESSED. An open circuit will not engage the TCC.

Early 6l80e trans received the TCC signal directly from the brake switch and from the ECM over the CANBUS system. Later 6l80e trans receive the TCC signal by ECM via CANBUS only.

Verify the function of the Body Control Module (BCM) in your donor vehicle. You may or may not need this depending on what functions you want to retain.

There is some debate about this, but there may need to be a 120 ohm terminating resistor put after the trans, and before the Data Link Connector (DLC). The CANBUS system needs to see this so there won't be any communication errors. The BCM from your donor vehicle usually has this in line between the trans and DLC. If you measure the voltage on either the high or low wire and it is 5 volts then you need the resistor. The voltage should be about 2.5 volts. Just put a resistor between the high and low wires.

After market harness are great, but not necessary. Modifying the stock harness is very doable and not that difficult. If you want the ECM mounted somewhere special then you may want an after market harness.

LS3 and L92 engines are not quite the same. The engine harness and sensors are not identical. Make sure you have the correct harness for your ENGINE.

A subscription to ALLDATADIY is a must! Spend the couple of bucks, it will help you find any issues you may encounter.

Buy a decent scantool to help you diagnose problems.

As a member found out, tuning with open headers will give you many errors and have you chasing ghosts. Get the exhaust done before fully tuning.

Hire a reputable/reliable tuner. Nothing beats a dyno tune. Mail order tunes are great for startup. If you have the time to learn it buy HP Tuners and tune/ learn yourself. Be wary of Craigslist tuners. Most of them bought HP Tuners and know a just enough to be dangerous. Or can only tune stock vehicles. Any kind of conversion/hybrid will baffle them. They are trying to recoup their cost and learn on your vehicle. Decide if your ok with that.

VATS MUST BE TURNED OFF TO START THE ENGINE! If you have double checked everything and it all checks out, have your tuner verify they removed VATS. not that he remembers disabling it, but have him verify. VATS can be disabled, but if the tuner doesn't REWRITE ALL then it may not take. You will chase ghosts forever and never get the engine to fire. The engine may start up and run for a few seconds, or it may not start up at all.

Custom fuel tanks are very nice and convenient, but not the only option for fuel tanks. In tank fuel pumps are best. There are many options.

At this time there are no DLC splitters that will let you hook up multiple scantools/gauges. One will overrule the other so you will only have one tool work at a time.

CANBUS gauges are great and convenient. However the verdict is still out as to whether or not they effect the ECM. They are not supposed to, but there are GM Technical Service Bulletins (TSBs) that claim add on devices are causing issues (scantools, insurance devices to monitor driving, etc).

Be very careful with switching throttle bodies and intakes. Some throttle bodies have different values during acceleration and the ECM tables won't match. This will cause major issues. Also the intakes will also change airflow, so be warned.

Re: LSx Lessons Learned.
 

WELL SAID sir. sounds like you have some experience right there. when i sell a engine and trans out of a wrecked truck i sell my customers the engine,trans,ecm,engine harness and mass air flow sensor and electric gas pedel out of the same vehicle. every thing is matched that way. and it does help alot with the 6L80-6L90E transmissons.

Re: LSx Lessons Learned.
 

Ha! I have some experience with headaches and chasing my tail! That is for sure!

Re: LSx Lessons Learned.
 

My biggest lesson learned: Trying to move the mounts back to the six cylinder position on a '67-'72 truck to keep the stock truck A/C location is more trouble than it's worth. You run into all sorts of exhaust clearance issues.

Re: LSx Lessons Learned.
 

Sub'd so I can add a bit to this later

Re: LSx Lessons Learned.
 

Man...I don't even know where to begin on this one.....:lol:.

Re: LSx Lessons Learned.
 

me neither :lol:

Re: LSx Lessons Learned.
 

Lesson #6
Your are 90% drunker in the garage environment than a bar. 6 beers in a bar is a good buzz, and maybe some over-sharing....

6 beers in the garage, usually results in 2-3 extra hours of work the next day, fixing all those "good ideas" you had the night before.

Re: LSx Lessons Learned.
 

great info! gathering parts now for the swap. 6.2 from 2009 denali 6L90 from 2011 express van.

Re: LSx Lessons Learned.
 

I've seen the results of that statement. My buddy and his dad took the Skill saw and removed the roof of his Comet but left the posts intact.

Re: LSx Lessons Learned.
 

Really? I had really good luck going this route. I used 3" forward motor mount plates, and moved the v8 stands back to the 6 cyl. location (2.5"). Everything bolted up nice, then used shorty headers for 2nd gen F-body LS swap...and factory a/c compressor fits like a glove, even though I don't have a/c yet :lol:

Re: LSx Lessons Learned.
 

Interesting! I think the key here is what exhaust setup you used - seems you found one that works well with that combo. I didn't. The exhaust clearance was the only real issue.

The truck manifolds wouldn't fit at all, so I got a set of 5th generation Camaro manifolds. The problem wasn't quite as bad, but still a problem. So I ended up cutting several parts out of the engine stands, flipping them side to side and upside down, and welding them back together. If there's a set of cast manifolds that will clear this combo, I'm not aware of it. Interesting to hear that the F-body swap headers work well here.

Re: LSx Lessons Learned.
 

Replace the water pump while the engine is out! It isnt expensive and nothing sucks more than finishing the swap only to have to pull that right back off and drain all the new fluid...

Don't use the stock rad. Pro performance sells an aluminum one for around $200 that is MUCH better than the OE style.

Buy a 5.3 style CAI. Filter on maf on TB plays hell with the sensors.

AN fittings are expensive. Nothing you can do about it, just be prepared.

Get your swap trans checked out before you install and test. You don't want to fire it up and then not be able to drive it. And THEN have to drop the tranny that you just put in.

I have more to add later unfortunately haha

Re: LSx Lessons Learned.
 

FAQ woulda told ya that :lol:

Thats why we love the TBSS manifolds or DT swap headers.

Re: LSx Lessons Learned.
 

^ yup. DTs were $$$$ but definitely worth it IMO. No problem at all to drop in.

Re: LSx Lessons Learned.
 

Do you have the part #'s?

Re: LSx Lessons Learned.
 

Take my word on this, PLEASE Reconsider. Match the engine and tranny year. mismatching this will cause you massive headaches! your dealing with different operating systems on the ECM and TCM. you will have to manually enter info for the engine tables. TRUST ME!!!! Get the an '09 trans. YOU HAVE BEEN WARNED!!
(I know I'm being a little dramatic, but I feel very strongly about this. The swap is much easier and will work better with matching equipment. I'm still trying to sort my stuff out.)
Shawn

Re: LSx Lessons Learned.
 

From what I've seen, the TBSS manifolds don't clear the particular combo I have either. The DT headers would have worked too, but I was being cheap.

Re: LSx Lessons Learned.
 

Your frame should be the same as mine in the front, and my 6.o with TBSS mani's fit around the 4l80e and inside the frame, just a tiny bit of clearancing on the frame is needed if you want to be able to get a wrench on the top of the collector hardware.

Re: LSx Lessons Learned.
 

So putting the MAF too close to the throttle body screws with the readings? My MAF is right in front of my throttle body and it's been giving some low/weird readings...

Re: LSx Lessons Learned.
 

Bookmarked and now subscribed!

Re: LSx Lessons Learned.
 

The area right before the tb is subject to fast changes in air velocity from the turbulence and opening and closing of the throttle blade. It can make for some wacky readings.

The maf should be 8-14" away from the tb, mounted between the 10 and 2 oclock positions on the pipe, with no pinching of its electrical leads, no immediate obstructions like a nitrous nozzle or external IAT, and not mounted directly after a sharp bend in the path.

Re: LSx Lessons Learned.
 

Bingo!

Re: LSx Lessons Learned.
 

Words of wisdom!!! Most of the retrofit problems that I have found in my research had to do with mismatched ECM/TCM pairs.....

Re: LSx Lessons Learned.
 

The issue wasn't the frame - it was that part of the engine stands that sticks up. I had been using the 3" set-forward mount style, and pulled the engine stands back to the six cylinder spot - that gives pretty limited clearance at the front of the manifolds.