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Want to build a (gasoline) stump puller

Reprise

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Location
N. IL
Hello everyone...

I have an '03 Envoy XL that I've started using as a tow vehicle, after buying it / putting it back in shape the past couple of years (including a built 4L60e). Truck came from the factory with the 5.3L, and it runs great, especially after I turned down the torque mgmt while getting rid of the fan codes for the electro-viscous fan clutch that I converted over to a thermal. Looks great for its age, too - no rust to speak of, thanks to the big-@ssed running boards GM equipped it with. :D

Discovered after I crossed the Divide and headed for Glacier NP a few weeks ago that I might need a little more 'oomph', as I found myself in the 40mph 'blinker club' when climbing long / steep grades. My residence is in IL--we don't have 'hills', much less 'mountains'.

Now, I know I could get a 2500 w/ a Dmax, and be set for the rest of my life...but I just wrote a PIF check for the trailer - and maintenance on a diesel does scare me a bit, being so different than gassers. But I know it would be a torque monster.

Drove a 2500 w/ a 6.0L yesterday, and it was in rougher shape than I'd like. The motor was the best thing about the truck.

Since GM actually put LS2 motors into the Trailblazer SS back in the day, I know that putting a 6.0L into the Voy should be fairly painless (relatively speaking).

Found a 6.0L from a 2000 Silverado that I can rebuild (it was running, but the owner removed the motor from the truck, took it down to the short block, and decided he wanted to do something else. So it's going to need a good honing on the cylinders, as well as a new crank, as the early ones had a longer crank ('long tail') that would only fit a 4L80 (or a TH400) - and if I can avoid swapping out my newer beefed-up 4L60, I will.

Planning on building some extra TQ/HP into the motor. I don't want / need to 'go fast'...I just want to get 'up the hill'. So I've been researching along the lines of what's needed for extra TQ / longevity, vs. 'extra HP'

The dedicated forum I normally hang out on for the GMT360 platform is great for that platform, but hardly any user base for the GMT900-up trucks. So I figured I'd join here, and see what I could find out applicable to my project.

Hopefully I can find some build threads / advice - although it looks from first glance that most of the 'motor' action concerns the diesel owners. I respect the heck outta y'all - but I'm gonna stay w/ gasoline for the time being. I may regret that, later. :facepalm:

As for me - lifelong IL resident, mid-fifties, currently live at the northern edge of the state. Came 'back' to GM, as it were, with the Envoy. Until a year ago, I worked in IT. Now I'm...let's call it semi-retired. Eventually, I'll head back to work, but for now, I plan on visiting the parts of US / Canada that I haven't seen yet.
 
Welcome To the Truck Stop neighbor. Yes the 6.0 LS is a puller motor. I had one in a 2000 truck and liked it. I have not looked back though since I've driven a Duramax for the last 400k or so
..
 
Welcome. Ive owend a few 6.0 rigs. Currently one in the wife’s 05 Escalade.

How big of torque numbers are you looking for?

A friend did one couple years back still naturally aspirated and pulled 425 iirc. He did cam, ported heads (had to find right ones to do), injectors, and a new computer for the tune.
 
Step over to TBSSOwners.com for info on the LS2 and the "grenade" the transmission is. Thicker radiator, and block the return airflow paths aka the big one GM hid with plastic over the top of the radiator. The Obsolete fan you dropped in to replace the EV fan was a mistake. Cheap, yes, but when programmed the EV fan is light years ahead to get the dammed fan on NOW to cool the AC down and stop ECT runaway on grades. Electric fans for towing IMO are a waste, but, on a thick Ron Davis radiator a maybe. The TBSS fan is capable of 10,000 CFM in place with the radiators and hood closed. The thin OEM radiator can't use all 10,000 CFM. Electrics (2 fans) struggle to get 5,000 CFM freestanding : without any restrictions.

First off I would just dump the Trailblazer platform for towing. I dumped a TBSS for 1/2 the HP and same TQ in a 3/4 ton pickup. One week of towing grades and the TBSS transmission was toast. TBSS Brakes stop good but eat rotors as fast or faster than the pads. 3/4 ton truck brakes are night and day better than the CAFE strangled undersized TB brakes.

So figure on a 4L80E for your build. Yes the TBSS owners got tired of literally blowing up the beefed up transmission GM gave us (beefed up 4L60E) and figured out how to shove a 4L80E in it. A beefed up or aftermarket built 4L60 is still a s#it transmission for towing let alone the 1/4 mile. Blow a sprag and the input drum spins at 2x engine RPM. With a Corvette LS2 6500 RPM redline the input drum explodes at 13,000 RPM with a blown sprag clutch. You have a scatter shield on the built transmission, right?

The Intake manifold cost 5HP to be shorter and clear the hood on the corvette LS2.

End of the day your money is better spent on a 3/4 ton pickup than an endless project that takes years to prefect before you can enjoy it. RV season is NOW. Project for winter and then you got to shake it down nearly forever. MPG will be better with a diesel, but, gasoline is cheap esp. if you go with a 6.0L or 8.0L V8. 3/4 tons are way more stable while towing.
 
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Wow...appreciate the speedy replies & well-wishes. (Mods: if this now needs to be out of the 'introductions' section, feel free to move it--although I don't know how 'busy' this thread will get, TBH)

How big of torque numbers are you looking for?

A friend did one couple years back still naturally aspirated and pulled 425 iirc. He did cam, ported heads (had to find right ones to do), injectors, and a new computer for the tune.

Nothing like a Dmax, for sure. I just want to maximize the NA potential. I have a TBSS intake / throttle body I'd been intending to use on the 5.3, which can also be used on the 6.0. Keeping the 317 iron heads from the LQ4 (larger valves than the ones on my LM4, and greater stability WRT coolant temps, vs. the later aluminum heads), but will have them massaged a bit. Going to add a Texas Speed 'towing' cam / lifter kit; it's a milder grind that's not lope-y. The stock crank s/b strong enough, but I'll add forged rods. May go with the LQ9 pistons / pins, but haven't decided on doing a stroker motor, yet. Looking at @WarWagon 's post, maybe I should rethink doing a swap entirely - ?


Step over to TBSSOwners.com for info on the LS2 and the "grenade" the transmission is. Thicker radiator, and block the return airflow paths aka the big one GM hid with plastic over the top of the radiator. The Obsolete fan you dropped in to replace the EV fan was a mistake. Cheap, yes, but when programmed the EV fan is light years ahead to get the dammed fan on NOW to cool the AC down and stop ECT runaway on grades. Electric fans for towing IMO are a waste, but, on a thick Ron Davis radiator a maybe. The TBSS fan is capable of 10,000 CFM in place with the radiators and hood closed. The thin OEM radiator can't use all 10,000 CFM. Electrics (2 fans) struggle to get 5,000 CFM freestanding : without any restrictions.

First off I would just dump the Trailblazer platform for towing. I dumped a TBSS for 1/2 the HP and same TQ in a 3/4 ton pickup. One week of towing grades and the TBSS transmission was toast. TBSS Brakes stop good but eat rotors as fast or faster than the pads. 3/4 ton truck brakes are night and day better than the CAFE strangled undersized TB brakes.

So figure on a 4L80E for your build. Yes the TBSS owners got tired of literally blowing up the beefed up transmission GM gave us (beefed up 4L60E) and figured out how to shove a 4L80E in it. A beefed up or aftermarket built 4L60 is still a s#it transmission for towing let alone the 1/4 mile. Blow a sprag and the input drum spins at 2x engine RPM. With a Corvette LS2 6500 RPM redline the input drum explodes at 13,000 RPM with a blown sprag clutch. You have a scatter shield on the built transmission, right?

The Intake manifold cost 5HP to be shorter and clear the hood on the corvette LS2.

End of the day your money is better spent on a 3/4 ton pickup than an endless project that takes years to prefect before you can enjoy it. RV season is NOW. Project for winter and then you got to shake it down nearly forever. MPG will be better with a diesel, but, gasoline is cheap esp. if you go with a 6.0L or 8.0L V8. 3/4 tons are way more stable while towing.

Lots to go over here, but I like your volume of input--even though I may not agree with every bit of it. Your prior ownership of a TBSS adds credence to your arguments, to be sure.

I know I'll need to upgrade the radiator; the stocker is barely adequate for the 5.3L It's about the only underhood component of the cooling system I didn't replace, when I did the fan clutch.

Re: thermal vs. EV clutch... I did that swap b/c the EV clutches are notoriously unreliable (regardless of vendor) - some 360 owners are on their 3rd / 4th EV clutch. Meanwhile, even GM swapped to a thermal for the last year of the 360 run. I'm certainly not the only one of my group to do so, nor the first. 1 or 2 of the 360 owners have e-fans, but most stick w/ the belt-driven. As an aside, the site I frequent is GMTNation, not TBSSOwners, although I've visited it. OffroadTB.com is also one I've spent some time on, if only for their front disconnect rebuild info.

I actually drove a 2500 yesterday, figuring that for what I'd probably spend on rebuilding a 6.0, I could spend a little more and have the whole enchilada, as it were. Besides the one I was looking at being too rough, even for me, I'd have to bring a stepladder to get in the cab / work under the hood; IIRC, I had to stand tiptoe to see down into the engine bay. Not sure if it was lifted, but I'll admit to the fact that I'm 5'8". Not Peter Dinklage short, but short. For that reason alone, the LWB Envoy is a better fit 'for me' (and it's a 4WD as well - w/ 3.73 gears)

BTW - I googled 'ETC runaway' but didn't find anything specific. I monitored my coolant / trans temps like a hawk; while the coolant never climbed past 218 or so (non-tow is 195F), I did experience a thermal breakout (ETC runaway - ?) issue with the trans temps twice in the 2700 mi trip - and that fluid bypasses the rad now, cooled by a stacked plate Derale (which probably needs to be swapped for a bigger sized one, in retrospect).

Once I figured out to keep speed to 65 max (which I needed to do for the China Bombs, anyway) & keep the trans from kicking down to second (4K rpm), I was able to keep the fluid mostly between 164-215F, w/o issue (non-tow never gets past 165F, even in summer heat). Didn't burn the fluid (or the clutches), and she shifts fine, no differently than before I took the trip. All I'd have to do to lower the temp after a climb was to keep the tach under 2900, and the fluid would cool back down in short order. Maybe I was just lucky, and I've only been back a short while, too.

Re: scatter shield... my 4L60 is 'built'...but for towing, not racing. It does have a 3200 stall (stock is 2800, IIRC), Vette servo, hi-energy band, Alto clutches, a corrective shift kit (including the TCC fixes), and a Beast shell, to cover the major items. It doesn't have the 5-pinion f/r planetaries; that's about the only thing I chose to skip. When I'm not towing, I admittedly drive like grandpa - the tach never sees north of 2500 unless I'm on the interstate. So, no scatter shield (and I think you'd agree, given the circumstances). Oh - and I actually *like* the 4L60e (although I thought a couple of times during the trip how I'd benefit from having a couple of extra gears). To fit a 4L80 into the Envoy, I'd have to have driveshaft work done. But if I need to eventually go there, I will. BTW, while the 360s never came with a tow/haul mode, it can be activated via the PCM, via pin J-71, a couple of resistors, a relay, and a momentary switch - the shift tables are contained within the PCM. That being said, I tow in 3rd, currently.

Brakes - I did a complete brake job at all 4 corners before starting out, with new rotors, fluid, and even e-brake shoes. Pads were NRS-certified, and I bedded them per guidelines. Although I had a Prodigy P3, there were a couple of times during the trip when I forgot to plug it back in - and I barely noticed the difference with / without it. IOW, I had no issues with fade, etc., no matter how steep or long the descents were. Also, FWIW, the LWB Envoy / TB has 11" rotors up front - and I had new-ish tires all around (probably on the order of 10/32"), before I started the trip.

I think that covers everything except the 'stable towing' statement. For the others following along... I have the XL / LWB, which is on a 119" WB (16" longer than the 5-passenger version, and at 207", it's actually longer than the same-gen Tahoe / Yukon). With the 5.3L and 3.73 gear, mine is rated for 7000# tow. I was pulling about 5K on a 25' double axle, with a weight-distribution hitch, and I have to say - it was a very easy tow (till I hit the aforementioned mountains).

Now...with all of that said - it wasn't written to argue with / refute you - only to relay my experiences / info, relative to your comments. I definitely learned a couple of things I didn't know (e.g.; the CFM airflow figures you mentioned), so feel free to share any additional insights re: GMT360s - they will be digested and welcome. In the meantime, I'll renew my search for a suitable 2500, even though I'm scheduled to pick up that LQ4 I mentioned, later tomorrow (today).

Not giving up on the Envoy just yet, but I'd be an idiot to suggest that my midsize, even being a BOF, had anywhere near the capability of a 3/4 ton.
 
X-2 on WarWagon's comments about starting with the properly scoped tow vehicle rather than make a project by trying to up-size something else. The 6.0L gas paired with a 6L90E is a nice platform. A friend has it in a small motorhome (converted pickup chasis) and is getting 12 mpg on the highway. Bumped into somebody pulling an Airstream with a 3/4 ton Burb and he also stated 12 mpg.

But . . . If the goal remains to make a project out of the Envoy . . . I would look into a 6L90E and ditch the 4 speed slushbox in any form. Life was a whole lot better when the Burb had the 4L80E removed and a NV4500 (5 speed manual) put in. Life would have been even better with a ZF6-S650 (6 speed manual), but that opportunity was missed and no longer realistic.


From experience, that class of vehicle (the long Envoy) is fine with pulling ~5K# from a stability perspective. Much heavier than that and the stability will drop quickly.
 
The ETC-actually ECT (engine coolant temperature) is the breakout- yes. Different terminology same issue.

On cooling trans, engine, etc- check out Twisted Steel Performance on the banner above. Thermal disperse coating the radiator- entire cooling stack will make an amazing difference. There is a Hummer owner that I have been working on his project with him a bit, Hummers have bad overheating issues fromthe angled cooling stack, and the 6.5 is a known overheat engine in the first place. The 2 together is a rough combo. This particular hummer couldn’t stay cool since he has more $ in the new engine than most pay for a used hummer. Once he coated his all new stack- it made all the difference. I went from understanding it should work well to having been proved without a doubt.

Twisted Steel did not do the coating on his hummer, but the same brand of product was used. The different vendor that did his does poor work imo. His shop is 45 minutes from my house, but I will ship from Vegas across country with my bearings, and other pieces/parts for my coating later this year.
 
I am hard on everything and tell it like it is with very little "tolerance" for the "bean counter" shortcuts OEM's took. As you have had a taste of "out west grades" you have an idea of where I come from. This is my POV and sharing my experience for what it's worth. I have spent an awful lot of time attempting to cool down the AC and engine on a TBSS working with the EV fan, HTuners, etc. All in 121 degree summers on grades that go for miles up to ~8000'. When I bought it I only asked that it tow a jet boat. Before I got rid of it I asked a 24' and 28' cargo trailer from it.

Fan clutches last 5 years period before they are "done". They loose 200 RPM per year and at 5 years are 1,000 RPM down from new. Running around the "anthills" out east you likely wouldn't notice because you don't need all the cooling system has and so-so AC performance isn't the end of the world. Same parts wear out on obsolete spring thermal fan clutches as the EV fan clutch. GM had lots of problems with EV Trailblazer fan clutches failing for reasons I am sure you are aware of like the rubber bump stop desegregating and plugging the passages up in them. Regardless your 2003 should be on it's 3rd fan clutch just from the age wear out alone. The current part number should have all the fixes in it and even then it's a 5 year part.

The advantage to the EV fan clutch is that it can come on with a cold engine to cool down the AC. Spring thermal fan clutches wait till the engine warms up to come on resulting in condenser overheating, high head pressures, and AC that frankly sucks for 30 min after a cold start. EV clutches have almost no delay to heat up the obsolete thermal spring when you hit a grade at WOT and engine temp starts climbing. This the ECT, engine coolant temp, spike isn't as high. (ETC is a typo. :facepalm: )

GM went bankrupt and cut costs while vendors went under. Several things were changed in 2008-2010 resulting in cheaper things being put on or omitted. 2008 Duramax engines were supposed to have a EV fan clutch, but, didn't. Continuing a long history of an engine power check the cooling system can't cash. This financial trouble is why GM threw a obsolete fan clutch at the last runs of the Trailblazers and didn't put it in other models as planned.

For the GMT 360... A quick and dirty way to get power is put a turbo on the 5.3L. Less of a project than an engine swap. The thicker radiator I helped develop that uses the mechanical fan may no longer be available, but, when I was done with it I helped put it into a rig that had a turbo charged 5.3L. The track would have said who was quicker the 6.0 LS2 or the turbo 5.3...

Cooling system upgrades including sealing up the stack. Biggest offender is here: https://tbssowners.com/forums/e-fan...d-better-cooling-fix-recirculation-issue.html

So for towing I would suggest going back to the EV fan or thicker Ron Davis Radiator with electric fans. Maybe see if Simple Engineering can still get the thicker radiator that will work with the EV fan we developed that Ron Davis makes. Towing and electric fans IMO are a bad combo due to lack of CFM.

Put a torque converter lockup override switch in so you can lock the TCC on long grades to keep trans temps down. Run the trans oil through the radiator as I have found radiator than air to oil cooler results in the best trans temps. No matter how big the air to oil cooler is the trans runs hotter without going through the radiator first - at least when I tried it and I have a 2400 RPM stall behind the antique turbo 6.2 of mine.
 
I am hard on everything and tell it like it is with very little "tolerance" for the "bean counter" shortcuts OEM's took. As you have had a taste of "out west grades" you have an idea of where I come from. This is my POV and sharing my experience for what it's worth.

No worries. I find value in it, and I wasn't offended at all.
Funny you mention a turbo... I had thought about that, given how well Ford's EcoBoost w/ the MaxTow has been received. Would kill two birds with one stone - more power via less O2 at altitude. I always wanted to put a Roots-type SC on something, but found out recently that a turbo would suit my current needs better. And cheaper, besides.

With that said, I've spent a good amount of time today chasing down viable 2500 candidates.
I will look for / start a new thread (if needed) re: "Diesel for Dummies"...LOL
I (think I) know some things about owning one, but there's a lot that I don't. Knowledge is Power. :)
 
Avoid 2005 Duramax LLY overheater engines, earlier Duramax engines ate injectors and 2007-2012 have emissions you don't want. Non-DEF Cummins you don't want.

Again a big gas engine is not a bad choice unless you got bit by the diesel bug.
 
I've always liked the 30% FE increase that diesel gives.
The fact that I could pass one down to my heirs before it would be EOL, and no matter what I upgraded to, trailer-wise, that the rig could pull it -- anywhere -- are nice bonuses.

It used to be that diesel was cheaper than gas, one reason being that it didn't require the level of refining that gasoline does. Now, that price delta has been reversed, and I saw recently that a lot of that has to do with the shale-based oil that now makes up the lion's share of the US transportation fuel supply. Apparently, diesel can't / is very difficult to produce from shale oil. So it has to be refined from the traditional feedstock (e.g; WTI, etc.), driving up the cost. That being said - it's a lot easier to pull into the diesel pumps on the road, and I'd love to be able to extend my tank range from the low-200 mi range that I have now. Stopping for gas 3-4 times a day is a pain in the ass, and is time lost.

I also don't like that it may as well be like learning Mandarin compared to a gasser, from both a planned / unplanned maintenance standpoint. This intimidates me, greatly--I travel alone, and being stuck in BFE w/ a heavy load and no way to limp to a garage is not my idea of fun.

I don't like being forced to use DEF, and I've read that pre-DEF engines run better w/o it, as well (the Cummins notwithstanding, as you mentioned). So I'd want something made before the mandated DEF controls came into play.

I prefer GM to Ford in general, and while Cummins makes a great product, I dislike what it's attached to.
It's been my understanding that of the three, the Dmax is the 'sweet spot' pick. Looking at your date ranges, it appears that my best choice is 2013-forward. But those will be more than I want to pay, for something I don't earn a living with, or even drive daily.

If the late-model Duramax is the best / only real choice, then it looks like I will be sticking w/ the 6.0L gasser. That, I can fix / maintain without trouble, and parts are plentiful / cheap (at least compared to a new set of Dmax injectors) LOL
 
Based on what you are saying a 2006 or 2007 "classic" with LBZ Duramax is what you would be best with. Not easy to find one that anybody wants to part with. Based on the knowledge you have about vehicles you've mentioned, you wouldn't have difficulty getting used to the particulars involved with a diesel.
 
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