ALL LSED OUT! PART 2
Making Sense of Wiring and Transmissions
So you’ve mentioned that a lot of the issues you see with LS swaps are related to wiring. You’d think that a lot of these things would have been figured out long ago, but what are some examples of common problems?
I’ve seen horrific things done with wiring—not only on the chassis side, but on the engine side—that aren’t very safe.
It’s really popular to rework the factory harness, but what people need to realize about a reworked harness is … wiring has a lifespan, a shelf life, especially when it’s been heat-cycled a thousand times underneath a hot hood. It’s lived a laborious life. It came from the factory after being made into a harness,
[was] installed on the chassis in an assembly line, it was driven around in the donor vehicle for X amount of time until you, the salvage yard or whoever removed it with the engine.
A lot of times [the harnesses] get cut, yanked on, damaged … The engines are moved around in the backs of trucks, dragged around people’s garages … The wiring harness becomes a liability at that point.
They get brittle, too, after being heat-cycled so much and from holding one shape for so long.
Yeah, they get brittle for sure. So you’re a DIY guy, or you send them to a shop to get reworked, and [the harnesses] can get butchered, [making] reliability suspect. A lot of people [think reusing the harness] is a cost-effective way to handle the wiring, but at Tilden we definitely try to get our customers to go with a new harness. They’re thinned down to the bare minimum, and only have what you need to operate the engine and the standalone operating system. There are no cut wires, no unused pigtails from stuff you’re not using, and you don’t have to worry about subsystems like headlight wiring or the AC system, or sensors that might not be applicable to your swap.
The big thing for us is in five years when you have to service the truck again, you’re not chasing your tail trying to figure out the wiring. Starting with a new harness like the ones we offer, which are labeled and set up specifically for swaps, you can put the computer behind the firewall, and it won’t be stuck up front by the battery like a stock vehicle, which doesn’t look as good.
Let’s say the engine wiring is decent. What should people look out for when tackling the chassis side of the equation?
The thing to keep in mind on the chassis side is that you want to keep things clean. One of the biggest mistakes we see with wiring is a lack of proper grounds from the block to the frame, from the frame to the battery, and from the frame to the body. The fuel injection really needs to have clean grounds. It’s as critical as clean, good power. That’s something that’s often overlooked and becomes a major challenge when you have to troubleshoot these swaps.
Also, finding good, clean, keyed power that’s hot while cranking … I can’t tell you how many times over the past 10 years I’ve seen swaps with keyed power that would try to start but couldn’t because the vehicle
would lose power during cranking. So, that’s just a function of trying to find the right source for that part of it.
Kind of along those lines are the computer and flashing. All computers for the LS series starting back in 1998 to 2014 have VATS, or Vehicle Antitheft systems, built into them. You can’t buy an engine and computer from a salvage yard without having to have the VATS flashed out of the system. You can’t bypass it; you can’t rewire around it.
You have to take or send it to someone to flash the computer with HP Tuners or some type of operating system software that can get rid of that function.
Is that something that people can do themselves?
It’s expensive to buy that stuff, so you’d probably be better off just having someone who already has the equipment do it. When we sell engine packages, we take care of it for you by providing a new harness with a pre-flashed computer, and the engine is ready to go with a warranty so you don’t have to worry about anything. It’s kind of tough to beat that when you compare it to buying a junkyard engine with a regular harness, and then you still have to reflash the computer.
As far as tuning, if you’re not using rear oxygen sensors, if you’re not using emissions or EVAP stuff, having a reputable shop that can understand the needs of your application and flash the computer so it’s ready to go and you’re not going to have a bunch of error codes and drivability issues popping up on you is vital.
What are the key points of actually buying an engine set? The truck-based 4.8s and 5.3s seem cheap enough on their own, so is it wise to piece everything together to keep costs down?
When you’re buying an engine, you actually have to be careful not to mismatch components on the operating system side. So, you really want to try to get everything from the same donor vehicle when possible so that your computer, your fly-by-wire pedal and your tach module all match the same VIN.
A lot of times if you buy from a salvage yard or you try to piece things together from different sources, you’re going to end up with mismatched parts. They’re not all compatible, not even on the Gen III side or the Gen IV side. There are a dozen different computers, a dozen different pedals, different tach modules and different throttle bodies.
So the short answer is no?
It’ll probably end up costing you a lot more money and a lot of heartache if you don’t buy everything as a complete package, but on the bright side, you’ll become very educated on the subject [laughs]. I’d say that once or twice a month, we’ll get a customer vehicle from another swap shop or someone who DIYED it, and they’re scratching their head wondering what’s wrong with their swap. It’s not that much easier for us when we have to play detective and try to figure out where everything came from and how to fix it. A lot of people don’t realize it, so they buy parts from random places and think that they’ll all work together, but they don’t.
Talk us through transmissions for a bit. We’ve seen practically everything behind an LS, but is there any magic behind what works best?
GM’S been really great, unlike Ford and Dodge, at keeping the bell housings consistent. You can run a ’40s manual transmission on the back of most any GM engine from the late ’40s to current day. They share the same bell housing, with only a couple of variations in spacing, but they all pretty much fit. However, you can’t take a Gen III truck engine and put a 6L80 on it from a
2012 or 2014 because the Gen III engine can’t run the operating system side of things. It wasn’t invented when the engine came out. On the flip side, you can run an SM465 from a ’70 Chevy truck behind your 6.0L truck engine. There are conversion parts to make everything work, clutches, flywheels, etc., but they just happen to drive terribly because the engine is so modern. It revs up so quickly and it’s precise, so that trans is clunky and old in comparison. It just makes for a very unpleasant driving experience.
So, basically the engine has more than the tranny knows what to do with?
Yeah, exactly. If you have to have a manual in your truck with an LS swap, I’d say stick with a T-56 six-speed or a
T-5 five-speed, or for heavyduty truck applications, an NV4500 or NV5600. You know, their synchros are a lot better, and they do better in that environment. So, trans
compatibility is a big thing that people overlook, but there are a lot of possibilities.
Back to the engines for a bit. When fitting an LS into something older, are clearance issues just a matter of finding the right oil pan?
Really, there’s an oil pan out there for pretty much every application. In some very rare cases, you might have to modify or fabricate a pan depending on steering and cross member clearance. There are a lot of oil pan choices, and we offer a rear sump pan that fits a lot of different applications. If there’s no room for whatever reason, you can always convert to a dry sump. It’s not costeffective, but it’s an option.
Are there any other major mistakes you see coming into the shop?
One of the common mistakes we see is related to exhaust size. I don’t know how many times I’ve seen people take an Ls3—you know, a 6.2-liter engine with 450 horsepower—and put it in a truck with like a 2-inch exhaust. These things need to have 2 ½-inch exhausts minimum. I mean, 3-inch is factory on a lot of these engines, so it’s critical to make sure that it’s the right size for the application.
When you get a donor engine, it most likely hasn’t been started in weeks, months or even years, and it isn’t like an old small-block Chevy where you take your distributor out and put an oil pump in to start it up. You’re limited with the LS as far as prelubing the engine. It’s critical to pull out all of the spark plugs, disconnect the coil packs, and crank the engine with the starter until you can see oil pressure on your oil gauge. That’ll ensure that you’re not doing a dry start on an engine that’s sat for a long time, or a new engine for that matter.
Those seem to be the ones that pop up again and again. There are probably a lot more, but we’d be here for days.
Thanks again to Kevin for his wealth of knowledge regarding all things LS. If you have any specific questions or would like to get more information on Tilden Motorsports’ products, use the info provided in the source box.