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Old 08-28-2017, 01:34 PM
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Default Looking for advice

Hi folks,

it's been a good while since I had last posted here, kids and life have a way of reprioritizing ones life. Anyway, I'm trying to make my truck plans for the future and could use some advice, especially since I'm not really current with the GMT900 community.

A bit of background, I bought my 2010 Sierra Denali in the fall of 2010. Starting some time in early spring of 2011, I purchased the Whipple 140ax kit and installed it myself. I was impressed with the quality of the parts but not impressed with the results. I had already owned a copy of HPTuners so I set out to teach myself how to tune my truck. That opened up a can of worms for me and the mods continued, wideband O2/boost gauges, Kooks LT's, E-cutout, 8psi then 11.5psi pulleys, bigger injectors, ZR1 MAP sensor and relocated IAT sensor, Yank 2800 stall converter. In the summer of 2013, I went to Norwalk and proceeded to get my trans a little too hot, it started slipping badly on my drive home to western PA. Up to that point my personal best was [email protected] I knew my trans was fried so I sent it to Gearstar for a rebuild/upgrade. They did their best but I was literally their first 6L80e customer and we had several issues. Their chosen tuner was a dipsh*t for one. MY TCM was found faulty so they replaced it, they don't even DO 6l80's anymore. I used Zippy to help me get the trans tune correct and all was doing pretty well, just a few minor driving issues. Oh, during the Gearstar upgrade, my single disk Yank was switched for a billet triple disk unit. My final addition was Alky Control system set to activate via MAF frequency. I got pretty busy with life but did manage a single run at a TnT with a best of [email protected] I felt there was an 11 second pass in there if I just had more time to tune and practice launches. My best 60' was 1.72 and on that run it was like 1.90.

Now comes the WTF part...it's my DD and I drive it ALL over the country for work. I have about 155k miles on it now (I put over 20k mile a year on my DD's). Even though it's never burned oil, I had plans to replace the engine and upgrade to a 175ax charger this summer. I had Thompson Motorsports build me an engine (boostzilla stage 3) this spring, but by the time it arrived, I was already experiencing the dreaded 2-3 slip. So now my confounded 6l80 is in need of a rebuild again. Though the frame has been diligently rust treated twice a year since I've owned it, there are rusty bits on the tailgate, front bumper and hood. It has hail damage (mild) from a few years ago on the hood and roof. It would probably take about $4k to get the body back up to snuff, plus at least another $3-4k for the trans (which has all but lost my confidence) all on a 7 year old truck with 155k miles on the clock. It has forced me to think of other options, and I would greatly appreciate honest opinions on these:

1) stick with the old gal and fix her up, rebuild the 6l80 myself (I guess I'd need a crap-ton of custom tools), put in the new engine, fix up the body panels, eventually upgrade to the 2.9L Whipple and drive her another 6-8 years.
1A) send out the trans for a rebuild to one of the reputable shops (Circle D, PATC but haven't heard the greatest feedback on them though) to the tune of $6-7k in trans when all is said and done

1B) ditch the 6l80 and go 4L80 with everything else being the same. I've tried to read up on this and I know it's not a small project to tackle. probably $6-8k in trans work with all of the crap and built 4l80.

2) get her ready to sell (with Whipple still on it) and take the hit on a low sale price for miles and mods. Use that money on finding a regular cab 4x4 GMT900 truck (I prefer smaller trucks) with the 4l60 or 65, a better overall body and do a bad a$$ed build with my engine, 4l80 swap and either 2.9L Whipple or big turbo system. shoot for 900-1,000hp and have fun.

3) say to Hell with it all, sell the Denali, get something cheap to last me about a year and pick up a slightly used Colorado ZR2 next summer and leave that b$%#@ STOCK!
3A) I guess I could still look for a reg cab GMT900 truck and drive it for a while to see if it will suit my needs.

I have loved my truck, it's been the best vehicle I've ever owned, despite the transmission. I am a speed freak to the core and have great difficulty leaving sh%t alone, I am aware that it makes my life more complicated but I'm willing to sacrifice that for the joy I get out of it. I forgot to mention that I must have a truck for my DD as I haul equipment with me, and I've already got other toys so I don't really NEED a fast truck but I sure do enjoy it!

Sorry for the long post.
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Old 08-28-2017, 05:47 PM
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Sooo is the new motor already in? Myself, I am a 4l80e fan but everyone has their own take on that.
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Old 08-28-2017, 06:10 PM
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Yes. I've actually got it for sale on eBay but I'm heavily leaning toward keeping it.


spec sheet (I know I'm inviting trouble):


Last edited by Boober; 08-28-2017 at 06:17 PM.
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Old 08-28-2017, 07:26 PM
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I have a gauge for that
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900-1000hp trucks do not make good work trucks or DDs....if you are serious about that being your goal, you need another vehicle as a toy and either sell this one and get something nicer as your DD, or keep it as your project but not both.
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Old 08-28-2017, 08:56 PM
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I hear you. A more realistic track tune would be around 800, with a lower boost for daily use maybe 700 or less. I put 100k miles on a truck with at least 500whp, it's not like I go ***** to the wall too often (which begs the question why the heck should I even bother?). The stock motor wasn't even the weak link, my trans failed me first. I kept up with the engine tune and it never failed me.

My kids are getting older and I want to get back to the track more, and take my oldest with me. My other "toys" are cruisers and I would never consider taking them.
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Old 08-29-2017, 11:19 AM
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A reconditioned 6l80 is available from our GM for 2755 or so. That way you could keep it or sell it especially if you get paintless hail repair. That trans would probably hold up to 600 hp at that weight since you don't really beat on it all the time. I sure wouldn't spend all that on upgrades on a truck that heavy. Get something lighter for that engine and a 4l80.

Last edited by ZO6Ted; 08-29-2017 at 09:08 PM. Reason: price correction
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Old 08-30-2017, 01:51 PM
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I think I remember seeing $2,500 price for a 6L80 from one of the GM parts places, that would possibly be an option but I've honestly lost confidence in the 6L80 for big power, especially a stock one.
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Old 08-30-2017, 03:06 PM
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I have a gauge for that
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Most guys above 700hp or so tend to swap to an 80e from what I have seen.
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