Chevrolet Suburban 3500 Questions

[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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View attachment 437466

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?