Hi all, longtime member, I used to have a fun little toy that I posted about here, 2002 RCSB 2WD 4.8 I called "Project Stepslide". Fun truck, but parted ways with it in 2019. Done a few other LS builds over the years too...LQ4 E39 BMW, L92 C5 Vette, LQ4 turbo Crown Vic, and my current LQ4 turbo Jaguar "XJ6.0".

I'm brainstorming on towing with a turbo LS. I have a 2016 BMW X5 with the turbo 6, probably makes a bit north of 300 whp with a tune. Most I have towed with it is my E92 M3 on a Uhaul trailer, probably close to 6500lbs all loaded up with tools and tires, but being physically smaller and with a short wheelbase, I am looking to get something a little more secure. Since we are planning on buying a travel trailer this year (6-7K lbs) the X5 doesn't seem fit for the job. Got my eye set on finding a rust free '01-'06 Suburban/Yukon XL 2500 from down south (stock 6.0 and 80E). I thought about getting a 1500 Burb since they are easier to find but only 5.3/60E, wimpier frame/brakes, etc...

My thought is 6.0 with stock cam for good response down low, upgrade valvesprings to handle boost
1.25A/R 7875, 2.25" hotside using truck manifolds, ebay cast log
Stock exhaust with 3" boost activated cutout (I love these things)
93 pump with some E85 splashed in for good measure, bigger pump and injectors naturally
3" A2A, 8-10 lbs boost
Freshened up 80E, add HD2 kit.
Converter - have had good luck with Circle D's 3200 - it has no issue spooling the 7875 in my Jag despite 2.88 gears. My understanding is that too high of a stall, while helping spool, will heat the trans quickly.

Regarding trans cooling - any reason one couldn't run a couple of stacked Trucool 40k coolers behind the grille as long as there's space? Combine that with the end tank cooler to keep it from overcooling?

How does the IFS on the GMT800 stand up to boost when towing a lot?

 

You can probably fit the Trucool in front of the radiator stack, between an intercooler. I'm pretty sure it's been done many many times. They work great, so I doubt you will need 2 of them. My single cooler "overcools" in the winter, and it's plumbed into the radiator and I have a 160 degree thermostat on the transmission lines. They are super efficient...

I don't see how the IFS matters in towing or boost, unless you are going to be doing 4WD boosted launches... with a trailer?

You really should look for a 2500 suburban if it is really going to be a dedicated tow rig.

As far as the converter, you may want to go a bit tighter? There will be plenty of "load" in the weight of the vehicle alone, plus any trailer you may have. Someone else can give you a better answer, but the suburbans are heavy, the 3/4 ton truck/suburban are even heavier. Typically you want a fairly tight converter for towing to keep the heat down in the transmission, now with a turbo you should have lots of power and it's probably going to stay in lockup most of the time so heat will be less of an issue.

 

I think one Trucool 40k will be just fine.

The IFS won't care about towing or boost

 

Rear coil springs vs leaf springs would be the biggest differences on the suspension. One rides smoother and the other is stiffer and generally better for towing or payload.

I really don't know the difference on the fronts though, except 8.25 vs 9.25 IFS.

Today I saw a fancy Ram 1500 crew cab, the latest generation towing an extended cab GMT800 2wd. I don't know how much weight that was, maybe 5500 to 6000 lbs including the trailer? Or maybe closer to 6500? It looked like a standard trailer everyone uses. Anyways, the poor truck's rear end was all pushed into the wheel wells. I believe those have coil springs (?) It looked kinda sad, especially because the truck on the trailer didn't even look all that nice.

 

The HuronSpeed V4 kit provides mounts to hang Tru-Cool 40KBtu directly below Air to Air Aftercooler.
Leaves the ports very close to existing Trans cooler hardlines.
Seems like a pretty tidy install.
A single cooler of that size is more than plenty.

 

So, I've acquired a victim for this project. '05 2500 LT, 6.0/4WD from AZ. I spent a few days after it arrived changing the oil in the engine, trans, and differentials. Still need to do the transfer case.

Slapped on a 41930 hitch and put it to the test towing my M3 300 miles round trip down to Watkins Glen for an HPDE weekend. I slept in the truck for 3 nights at the track with plenty of room for all my overnight and cooking stuff. The rig was comfortable and towed great, no doubt due to the long wheelbase and heavy weight.





My only gripe was that I wished for a bit more power up the hills. Which brings me to my next thoughts regarding the turbo build...

Definitely going to stick with a stock cam, but will be upgrading valvesprings. I've had good luck with the PAC1218s in my turbo 6.0 Jaguar but may use a high quality dual spring from BTR for extreme reliability.

The two big things I'm still pondering are the turbo choice and torque converter.

I am brainstorming for the turbo build and still need to talk with Viren at VSR, but I'm thinking a cast 6673 or 7875 would be good. I don't plan to exceed 10-12 lbs or 5500 rpm as this is a towing rig, so I think the 7875 might be overkill. The goal is reliablity and instant boost response at a low RPM (2000 or so). Don't think I want or need more than 500 whp.

Regarding the converter - research has told me that sticking with a stock converter for towing is the way to go. I agree with this on the premise that a low stall will heat the trans fluid less, but my concern is that towing up long hills under boost with the stock converter clutch locked may chew up the clutch and trash the trans.

On the other hand, a looser converter like I have in my 6.0 turbo Jag is amazing for getting up to 3000rpm quickly and lighting off the turbo rather than lagging off the line. A triple disc will also allow me to lock the converter under boost up hills, although I'm not sure even that will survive under boost with 6000 lbs of truck and 7000 lbs of trailer behind it.

Other random thoughts...
-HD2 kit in 80E, Trucool 40K mounted low up front
-The 4.10 gears in it will help get the big girl moving
-Cast china log, small 2.25/2.5" crossover and 3" DP into a straight through muffler
-Enable Flex fuel with sensor, run blend of 93 and E85 depending on availability and need
-Suggestions on injector? I like the Deka 80s.
-Wally 450 in tank in the stock basket
3" A2A I/C

Open to suggestions on turbo and converter.

 

I’d go triple disk on the converter at stock stall if this is a tow pig. The added power will make it stall higher but that wouldn’t be terrible to help get on boost.

 

out of curiostiy what kinda MPG did you see? What are you expecting to see with the turbo? Are you gonna run it on 87 fuel? Im looking at soing something similar but in a 3500 truck.

 

You can Just use Stock LS3 valve springs with the stock cam and they will be plenty for some boost.
Turbo choice, i would look hard at this one. TDI Billet S464/83 https://tdi.forcedinductions.com/tdi-s400
You dont need a large compressor at all. But the larger the turbine the lower the drive pressure so it can make more power with less boost. Also go with the .90 Exhaust housing.
You dont want instant boost either. A smooth boost curve helps with fuel mileage. Instant boost will need more fuel.

Stock torque converter is plenty fine. The clutch is plenty strong for towing. Just make sure your tune is spot on.
I would suggest running the largest intercooler possible. Towing up long hills with that much weight is going to heat up the air. I use a large 1200HP Water/Air intercooler and it does great. Then added Water/Meth injection and the higher temps dont bother it.
Tru Cool 40k Is one the best trans coolers.

Another thing is i would go with 3.5" downpipe.

Never liked the Deka Injectors. Especially now with all the import copies.

https://fuelinjectorconnection.com/p...r-550-48-14-14
You would be fine with a 340 pump