*wall of text warning!*
track stuff is addictive but sooo expensive and abusive on everything. I was just about to say I wish I was that close to a track, but then I'm like wait, cota is right up the road. oddly I've never even thought about going there. plus looks like abusive on brakes and tires haha. my buddy got a track day rental for his birthday and said I couldn't miss it. small track in Fl called the firm. but just about 8 cars, all friends and we didn't really have to worry to much about rules.
I drove down that time and back, but man it was ******* everything. I tossed a ac belt that took put the main belt and before I realized it, over heated it to full ecm panic mode. on top of having super high oil temps in just a lap or 2 pushing, like 300deg was easy to hit. over heating was end of the day last session. we had to push it off the track and get a belt on it so I could drive home. it made it, but it wasn't happy. small lifter tick ever since on a cold start if it's been sitting a few weeks between starts. probably bleeds down a lifter, but pre lube it by cranking it a bit, or drive it more often gagaeand it's good. oil sample came back OK ish, so I've sent it haha. did oil cooler mods before the next time.
the very next year one of the other guys that went loved it and rented it again, this time I borrowed a trailer haha. I'm more of a mountain road fun weekend trip kinda car guy. I get to competitive on a track day, just with myself and times. I'd end up with a full blown gutted up race car and even less money. mountains are fun at 60% pace. buddy of mine has a little gti with a ton of handling stuff, it's a nightmare in the mountains to chase on the tight stuff, but so much fun.
there's a guy on another board that has one of these hybrids but it's the pick up truck. he tows almost non stop thru the Canadian mountains it sounds like. I think it will tow you up the coast nicely with a fresh tranny. which reminds me. have you seen the tranny cooler in these things? got like 5/8s lines where a normal auto has 3/8 to a small cooler in the radiator. this has a big front mount cooler, from what I can tell half of it is for the hybrid cooling system. there's an electric pump for that side to keep an eye on too with high mileage and other part is tranny. they seem to run cold all the time. normal around town temp on 100deg days is like 140deg. max I've ever seen is 167deg. either long trips or towing, it must have some kinda thermal stat. because I always read you shouldn't run to cool of fluid Temps, but gm kinda of throws that logic out the window. someday this thing never sees more than 120deg on cool days around town. but of course like everything, the cooler seems to be a discontinued part. one post I've seen a guy had to find a junkyard one. they seem to be reliable, but can they be flushed is what I'm wondering for your rebuild? may want to take a peek at it.
is yours 4wd or 2wd. only odd thing I've noticed is in all the high end suvs like the Denali and Escalade, the normal ones have a all time awd. these seem to have the lower model range 4wd transfer case. not sure why really, just as a guess I'm thinking being able to switch to only 2wd is more efficient for mpg. but on that note, while auto would sound perfect for you towing the boat thru the mountains. there's a bit a disagreement on these boards if it's best to drive it daily in 2wd or if always being in auto is fine. the thinking is auto always has its cluches slightly engaged to keep at the ready for slip and it's wearing out not being used.
I don't know either way really, but my t case fluid came out like black water the first change after I bought it. the truck doesn't feel abused at all either. it's pretty clean for the mileage. so leads me to thinking 2wd till needing auto is the best. I've flushed it twice, since it's only a few qts to get it back looking red again. it seems to work thou.
for the fluid, you can't go wrong with the oem Delco stuff. I think you'll be fine, and probably after the rebuild hassle, if you keep it. probably more likely to change it sooner than 130k anyways.
so as for the engine, I only know what I've read really. but it's a little bit of an oddball there too. the base seems to be close to a ls2 block and Cathedral style intake port heads, but with a higher compression. they then put a hybrid specific cam in it, late exhaust valve closing time, I think it's called or late intake early exhe. I don't remember haha. allows a little bit of fresh air to flow out thru the chamber into the exhaust to clean out the charge better, but needed the higher static compression to compensate, but you still end up with less pumping losses at idle speed, and good mid range, which is said to play well with the tranny tuning and veritable ratios the motors allow for.
if you drive a non hybrid one stock tuning, they are always trying to use the lowest rpm possible for mpg, these let the engine spend a lot more time around 2k rpm where the cam works best at.
the 6.2 used is all aluminum as well, but it's more like the ls3. Rectangle Port heads. my understanding is rec port flows better up top for hp, but the Cathedral port keep the air speed up better at lower engine rpm being more efficient in these trucks.
ls1, ls2, ls6 in the performance side use Cathedral port, ls3, ls9 went rec port. the ls7 is a big offball head. then a bunch of different truck and car rpo codes I don't know, most using cathedral port beside 6.2L ones.
all suff I've read thou, I have no way to back up if any of they actually helps haha
afm stuff, I turned mine off on the highway trip home, it's said to use it even more efficiently with the battery pack on these, but afm failure rate is pretty much 100% unless you bought it day one and changed the oil every 3k miles with the best synthetic out there. if the 1st owner went by the dash oil life, it was closer to 10k mile changes and they all fail about 130-160k. by fail, the lifter gets suck down, horrible tapping sound, dead miss and slowly trashes everything. it's fixable but most shops just replaced engines, not fix stuff. so best to avoid that.
the normal and "correct route" is to change to a cam set. lifters, push rods and timing chain setup for a none afm setup and then have the ecm tuned to turn it off. funny thing is, we don't have a ecm they is really supported by the major tuners. hp tuners software will disable afm in the tune, but that leaves the cam, since we have a funny grind cam, I don't think there's a non afm cam off the shelf, so that would mean running a normal cam, but being you can't tune the VE table in our ecm's. I don't know how a standard cam will run with it.
so basically you drive it till a lifter gets stuck and it starts tapping, replacing the broken parts with new oem stuff, or there's a 3rd option that's kinda cross your fingers and hope this is better than nothing. which is what I did, use hp tuners to disable the afm. if it's never used, the hope is it's less likely to fail, but I've seen posts about them still failing on non hybrid that have been just turned off. so what you do is, make sure the internal oil supply can't make it to the afm lifter release pins, there's a cheap oil passage way block off, and then you cut a gasket out of another area so that even if oil pressure comes back up thru the lifter, it can vent that tiny amount. making sure that lifter is never allowed to go into afm collapsed mode by accident. the hope is it lives a long life as a slightly heavier standard lifter haha. Just about any ls based engine would go 300k miles with just some random maintenance if it wasn't for the afm crap on these gens.
wall of text I know.. just stuff I wish I could have found all in one place when I was researching the truck, not almost 2 years of searching later haha.
