ALL LSED OUT! PART 2

Mak­ing Sense of Wir­ing and Trans­mis­sions

Street Trucks - - CONTENTS - IN­TER­VIEW BY MIKE SELF PHOTOS BY MIKE SELF AND TILDEN MO­TOR­SPORTS

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.

TILDEN MO­TOR­SPORTS’ LS HAR­NESSES ARE PARED DOWN TO THE BARE MIN­I­MUM, WHAT­EVER THAT MIGHT BE FOR YOUR AP­PLI­CA­TION. THE COM­PANY BUILDS HAR­NESSES TO OR­DER TO AC­COM­MO­DATE ONLY THOSE OP­TIONS YOU NEED. NO MORE RAT’S NEST WIR­ING HAR­NESSES.

THERE ARE SEV­ERAL COM­PO­NENTS THAT AREN’T INTERCHANGEABLE FROM ONE LS EN­GINE TO ANOTHER. AS YOU CAN SEE, EVEN THE DRIVE-BY-WIRE PED­ALS COME IN MANY DIF­FER­ENT VER­SIONS.

IT’S RE­ALLY SAT­IS­FY­ING TO SEE DE­TAILS LIKE THIS. HAV­ING EACH PLUG LA­BELED HELPS MAKE QUICK AND CLEAN WORK OF ANY LS SWAP.

THE OWNER OF THIS C-10 HAD A RUN OF BAD LUCK THROUGH­OUT THE BUILD, IN­CLUD­ING A BLOWN HEADGASKET DUE TO BLOCKED OFF STEAM PORTS, BE­FORE BRING­ING IT TO TILDEN MO­TOR­SPORTS. HE’D PUR­CHASED MIS­MATCHED PARTS, WHICH HAD TO BE SWAPPED OUT FOR THE COR­RECT VER­SIONS. LUCK­ILY, THE EX­PEN­SIVE 6L80E TRANNY WAS UNDAMAGED.

BELOW. TH­ESE ARE ONLY SOME OF THE LS EN­GINES THAT GET SHIPPED OUT OF TILDEN MO­TOR­SPORTS DAILY, ALL WITH PRE-FLASHED COM­PUT­ERS AND NEW, CUS­TOM WIR­ING HAR­NESSES. THEY DEF­I­NITELY HAVE TH­ESE SWAPS DOWN TO A SCIENCE.

ABOVE. THIS SQUARE-BODY SUB­UR­BAN IS MID-SWAP (IT’S GET­TING A SU­PER­CHARGED 6.2L LSA EN­GINE). THE 6L90E TRANS­MIS­SION WILL FIT NICELY BUT RE­QUIRES A NEW, CUS­TOM CROSS MEM­BER. NO, THE BLUE STRAP IS NOT THE NEW CROSS MEM­BER.

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