Chevrolet Suburban 3500 Questions

[Geotrash]

Thanks for the tow review! Glad to know it can tow more than 3k lbs lol.

I cannot believe you found a truck with such low mileage. Absolutely insane, but the issue sounds like most cars that sit for long periods of time.

I know. Finding one of these unicorns in the LT trim is hard enough, but finding a low mileage creampuff is another thing altogether. I just got really, really lucky.

 

[Bigburb3500]

With how these trucks are built, unless something else comes up in 10yrs that can match this truck I will probably start the mega upgrades. Not sure you saw the thread on here where someone dropped a new L8T into these trucks with a 6L90. We already have the 6L90 sooo would be pretty easy and a 10speed could also be used…

 

[Geotrash]

With how these trucks are built, unless something else comes up in 10yrs that can match this truck I will probably start the mega upgrades. Not sure you saw the thread on here where someone dropped a new L8T into these trucks with a 6L90. We already have the 6L90 sooo would be pretty easy and a 10speed could also be used…

Yup. I thought about that but I’m pretty happy with the power for my purposes - I have no problems keeping up with traffic while towing through the hills. If I make any engine changes in the next several years, it would likely be a cam since I have experience with that. I could see new wheels and tires in my nearer future, possibly a bull bar, and a class V hitch.

Part of the draw of this rig for me is how bulletproof the L96 is, so I’ll probably leave it alone - at least until I start having reliability concerns with it. One thing I will do for sure though is have a blackbear tune done since I already have their autocal device.

What else is on your wish list besides the L8T?

 

[Bigburb3500]

The L8T upgrade is a pipedream wish list. Right now the big items for upgrades are the shocks which I will order on Friday of this week, tow mirrors, and I also want new wheels. I love the BFG KO3s I put on when I bought the truck, and as much as I love the overall look of the suburban, my truck looks like a contractor special. It’s just plain white. Hoping to paint the black grill white to match + white tow mirrors and then throw a set of dark bronze 18” wheels on the truck. Few nice looking sets out there that would look good against the white.

what are your thoughts on blackbear tuning? Considering this truck does not have AFM or anything, what would the tune do?

 

[Marky Dissod]

... thoughts on blackbear tuning?
Considering this truck does not have AFM or anything, what would the tune do?

*It would net more power - not just over 5000RpM, but basically anywhere over 1500RpM, meaning that your MpGs may improve IFF you keep your foot out of it
*Your transmission has Normal and Tow / Haul shift maps available;
they can be more finely customized to suit your tastes AND improve durability / longevity at the same time
*(In your particular case the TCC behavior is likely superior to '1500' type vehicles;
generally when and how the TCC locks and unlocks improves MpG at the cost of longevity for '1500')
*There are engine coolant and ATF overheat mitigation protocols that GM tends to activate almost-too-late;
they can be adjusted to enable sooner for your benefit
(I've overheated ONE mid-90s LT1 engine myself, as a result,
all my LT1 tunes have GM's overheat mitigation protocols enabled sooner than GM OE, which has already saved two of them)
The tuners you consult will explain their menus better than I can, but the point is,
aftermarket tuning exists precisely because GM left them so much room for personalization and improvement.

 

[Bigburb3500]

*It would net more power - not just over 5000RpM, but basically anywhere over 1500RpM, meaning that your MpGs may improve IFF you keep your foot out of it
*Your transmission has Normal and Tow / Haul shift maps available;
they can be more finely customized to suit your tastes AND improve durability / longevity at the same time
*(In your particular case the TCC behavior is likely superior to '1500' type vehicles;
generally when and how the TCC locks and unlocks improves MpG at the cost of longevity for '1500')
*There are engine coolant and ATF overheat mitigation protocols that GM tends to activate almost-too-late;
they can be adjusted to enable sooner for your benefit
(I've overheated ONE mid-90s LT1 engine myself, as a result,
all my LT1 tunes have GM's overheat mitigation protocols enabled sooner than GM OE, which has already saved two of them)
The tuners you consult will explain their menus better than I can, but the point is,
aftermarket tuning exists precisely because GM left them so much room for personalization and improvement.

Thanks Marky! This is super helpful and detailed. Probably will add this to my growing list. Why is this called a Yukon/Tahoe forum… it’s really a forum to open up our wallets…

 

[Geotrash]

Thanks Marky! This is super helpful and detailed. Probably will add this to my growing list. Why is this called a Yukon/Tahoe forum… it’s really a forum to open up our wallets…

Truth!

Another way to describe what a Blackbear tune does is that it 'wakes up' the vehicle. Throttle response improves, shift points are tuned for better drivability (the factory tune prioritizes economy), shifts are quicker with less TCC slip, and they can also tune for premium fuel if you wish, which increases power output a bit. In my case, one of the reasons I bought a truck with the L96 is because of the lower compression ratio that makes running 87 gas okay, so I'll ask them to focus on their usual suite of drivability and towing-related improvements, while making sure it will still be safe to run 87.

They tuned both of my Yukon XL Denali's and I've been thrilled with the results.

 

[Marky Dissod]

Another way to describe what a Blackbear tune does is that it 'wakes up' the vehicle.
*Throttle response improves -
*shift points are tuned for better drivability (the factory tune prioritizes economy),
*shifts are quicker with less TCC slip ...

Other tuners besides BlackBear SHOULD be able to accomplish the above.
*Electronic-signal-throttle vehicles NEVER open or close the throttle as quickly as your foot can - unless you have your ecm tuned.
*GM OE transmission shift pattern not only prioritizes economy, it either encourages conservative driving, punishes enthusiastic driving, or both.
If you're a hypermiler, you might even ask your tuner to prioritize MpGs EVEN more.
The rest of us likely would want something less lazy than GM provides, though.
Since we have TWO shift tables, how do you want the 2nd one?
Since I'll likely NEVER tow anything, my Tow / Haul mode is more like a 'try as best you can to chase that TrailBlazer SS' mode,
which is why my normal mode prioritizes neither MpGs, nor lazy driving - it simply protects the 4L60E as best as possible.
Maybe you want your Tow / Haul mode to entirely avoid 6th, or 5th & 6th? You'll never get what you want if you don't ask.
*GM OE TCC behavior for '1500' type vehicles prioritizes NVH over durability/longevity.
Your 3500 may not have this particular problem, but most of us do ...

 

[Geotrash]

*GM OE TCC behavior for '1500' type vehicles prioritizes NVH over durability/longevity.
Your 3500 may not have this particular problem, but most of us do ...

I suspect it does because there is lots of slip in the shifts. It's built to be armored and carry around dignitaries who would likely be quite cross if a harsh shift caused them to spill their Scotch while fleeing enraged proletariat.

 

[Bigburb3500]

I suspect it does because there is lots of slip in the shifts. It's built to be armored and carry around dignitaries who would likely be quite cross if a harsh shift caused them to spill their Scotch while fleeing enraged proletariat.

hahahaha no further comment needed

 

[Marky Dissod]

*GM OE TCC behavior for '1500' type vehicles prioritizes NVH over durability/longevity.

I suspect it does because there is lots of slip in the shifts.

With the slip left in the shifts and the TCC LockUps, the driver may only notice the slight changes in RpMs, but will feel almost nothing at the seat of the pants.
Aunt Tique and Aunt Cester might appreciate these barely detectable transitions, but
they are a significant cause of cumulative wear on shift clutches and torque converter clutches.
When the slip is taken out of the shifts and the TCC LockUps, these are positively felt in the form of a gently noticeable thump.

It's built to be armored and carry around dignitaries who would likely be quite cross if a harsh shift caused them to spill their Scotch while fleeing enraged proletariat.

Made me spill a wee bit of me Tullamore Dew ...

 

[Bigburb3500]

Lucky for me, my aunties didn’t buy the truck and it wasn’t for their comfort! Hahaha

@Geotrash - add Blackbear to my list of wants/needs. When my wife asks I will blame @Marky Dissod ….

 

[Marky Dissod]

@Bigburb3500, if I owned a 3500 with intent to Tow / Haul over 12,000lb,
I'd get Tow / Haul mode rewritten as follows:
*avoid 6th entirely (... or only allow 6th @ or over a road speed you'd NEVER achieve while towing)
*only use 5th with the TCC Locked at the VERY light throttle angles associated with cruising / coasting / decelerating.
*late upshifts so that the engine never gets under, say, 2125RpM (if not even higher?) after the upshift is complete
(Minimum 1Up2 @ 21MpH, 2Up3 @ 32MpH, 3Up4 @ 42MpH, 4Up5 @ 57MpH
*the downshifts should be responsive to the throttle so long as the RpMs aren't too high AFTER the downshift, to protect the powertrain

I know the 6L90 has engine grade braking, but I do not know if those specific values can be enhanced with a tcm tune.
If they can, you'll be even more pleased.

 

[Bigburb3500]

@Bigburb3500, if I owned a 3500 with intent to Tow / Haul over 12,000lb,
I'd get Tow / Haul mode rewritten as follows:
*avoid 6th entirely (... or only allow 6th @ or over a road speed you'd NEVER achieve while towing)
*only use 5th with the TCC Locked at the VERY light throttle angles associated with cruising / coasting / decelerating.
*late upshifts so that the engine never gets under, say, 2125RpM (if not even higher?) after the upshift is complete
(Minimum 1Up2 @ 21MpH, 2Up3 @ 32MpH, 3Up4 @ 42MpH, 4Up5 @ 57MpH
*the downshifts should be responsive to the throttle so long as the RpMs aren't too high AFTER the downshift, to protect the powertrain

I know the 6L90 has engine grade braking, but I do not know if those specific values can be enhanced with a tcm tune.
If they can, you'll be even more pleased.

This is super helpful! I’m beginning to think, like Geo, that a reprogram is in my future. Hopefully he can go first and figure out what he likes or thinks towing with this truck needs. I’m about a yr or so out from my big boy toys… depends on markets tho… stocks go up and prices come down, does this ever happen?

 

[Geotrash]

Doing a little wheel shopping and have landed on these as a good complement for the Tungsten Gray paint color of the truck. Probably won't order until the spring so I can start the 2025 towing season with a fresh set of tires. Amazingly, the tires that came on it have zero dry rot or blemishes of any kind, despite having mid-2017 date codes. I credit the climate controlled storage the truck was in. For tires, I will likely go with the Michelin Defender LTX M/S 2 in the LT265/70R18 size. It's about 1" bigger in diameter than the factory tires, but should still clear without issue. There are way more options than in the 265/65R18 size.

 

[Bigburb3500]

Doing a little wheel shopping and have landed on these as a good complement for the Tungsten Gray paint color of the truck. Probably won't order until the spring so I can start the 2025 towing season with a fresh set of tires. Amazingly, the tires that came on it have zero dry rot or blemishes of any kind, despite having mid-2017 date codes. I credit the climate controlled storage the truck was in. For tires, I will likely go with the Michelin Defender LTX M/S 2 in the LT265/70R18 size. It's about 1" bigger in diameter than the factory tires, but should still clear without issue. There are way more options than in the 265/65R18 size.

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Those will look great! I will be the first to tell you tho please be careful when towing in those tires. I have a small fleet of vehicles and most sit in climate controlled garage but a few yrs back one of them was needing some love and I put a fresh set of tires on it (I think they were about 6yrs old) and the difference was night and day. The old compound was extremely hard and brittle even tho it visually looked fine.

The Michs are good tires. I have run them before.

 

[Geotrash]

Those will look great! I will be the first to tell you tho please be careful when towing in those tires. I have a small fleet of vehicles and most sit in climate controlled garage but a few yrs back one of them was needing some love and I put a fresh set of tires on it (I think they were about 6yrs old) and the difference was night and day. The old compound was extremely hard and brittle even tho it visually looked fine.

The Michs are good tires. I have run them before.

Good call. Thanks for sharing your experience with it. I’ll get them changed out.

 

[Bigburb3500]

Parts fairy came the other day (love the FedEx guy) and new shocks were delivered. Rears were an absolute BREEZE, both sides done within an hr. I did cheat a bit and have been hitting the bolts with PB Blaster a couple times last week so everything came apart super easily.
Front new shocks had to be returned. Neither rebounded after compressed and no resistance when compressed either. The rear OEM shocks were completely gone, very stiff to compress and no rebound at all. Nearly impossible to physically rebound them once compressed so not sure how much they were doing except just being there.

 

[Geotrash]

Parts fairy came the other day (love the FedEx guy) and new shocks were delivered. Rears were an absolute BREEZE, both sides done within an hr. I did cheat a bit and have been hitting the bolts with PB Blaster a couple times last week so everything came apart super easily.
Front new shocks had to be returned. Neither rebounded after compressed and no resistance when compressed either. The rear OEM shocks were completely gone, very stiff to compress and no rebound at all. Nearly impossible to physically rebound them once compressed so not sure how much they were doing except just being there.

Wow, that's good to know! Maybe partly why your passengers were making comments. Bummer about the new fronts - seems like a pretty good strike against their quality control. Which ones did you settle on?

 

[Bigburb3500]

Wow, that's good to know! Maybe partly why your passengers were making comments. Bummer about the new fronts - seems like a pretty good strike against their quality control. Which ones did you settle on?

It rides so much better now and a lot more planted. Crazy how much a difference they make.
I went with the RS 9000XL. I was pretty shocked that both fronts would not rebound/extend at all. Wonder if both were old stock or something to that effect?