Hello..2009 Tahoe Z71

[iamdub]

downshifting is caused by the fuel used Rarely do i downshift on a freeway with 91oct unless passing with 87 octane it will search for gears between 3-4 AFM will loop of death and gobble up a lot of fuel... the difference between 87 and 91 is upwards of 12.6MPG..


so on 87 it will get a solid consistent 18.5MPG(city/hwy) on 91 it's 22/25mpg(constancy )

31.1MPG City and 27.6MPG Highway were my best ever(favorable weather conditions helped)

Huh?

The extra downshifting (and upshifting) in city driving is because the 6L80 is programmed to get to a higher gear as quickly as possible in efforts to reduce fuel consumption. If you're gradually accelerating, as you would when going from block to block/light to light or in stop and go traffic, the trans has a tendency to upshift too soon. Then you lose your power and have to push the pedal more to compensate, which makes the engine either lug or trans downshift. If the damned thing held it's gears just a little longer and upshifted only after seeing a steady throttle input for a set amount of time, it wouldn't be doing all that extra up- and downshifting, prematurely wearing out its components and creating extra heat. In my van, that 6.0 spent LOTS of time at 3,000 RPM and higher in city driving cuz I manually shifted it and just let the motor sing if I was gonna be decelerating or stopping again.

 

[HiHoeSilver]

Ive seen those. Im thinking about just sending my PCM into black bear or something and see what they can do with it.

You wont be sorry. Many of us here can promise that.

Welcome to the forum. We would be happy to help with tuning. Give us a call 877-809-4070, or email us [email protected], when you are ready, and we can go over our tuning options.

Johnny (or Justin or Jenna) on the spot!

 

[swathdiver]

Huh?

The extra downshifting (and upshifting) in city driving is because the 6L80 is programmed to get to a higher gear as quickly as possible in efforts to reduce fuel consumption.

Brent has a hybrid transmission and has noticed that his runs more efficient when the engine is burning higher octane fuel. I think he's trying to say that it has just enough extra power on good gas to improve shifts and hold gears longer.

As for your work truck, their ignorance costs money.

 

[iamdub]

Brent has a hybrid transmission and has noticed that his runs more efficient when the engine is burning higher octane fuel. I think he's trying to say that it has just enough extra power on good gas to improve shifts and hold gears longer.

I read it a couple of times and I think I figured that much out. The abrupt tangent to the subject was confusing. Mine has noticeably more power on 93 so I'd imagine it to downshift less in certain, very specific scenarios. It being the lowly 4-speed means I'm just gonna push the pedal until it downshifts (if not floor it) rather than try to gently apply more throttle to get just enough of a power increase. I pretty much only use three throttle positions: ~25%, 50% and 100%.

As for your work truck, their ignorance costs money.

I agree. Nothing I could do but make the best of it while I had it, and I'd say I did and it worked. They switched to Ford Transits in 2016. They're supposedly rated as a 2500 but with a NA 3.7 V-6. Also a 6-speed. Its shifting program is much better than that of the Express/6L80, but I manually shift that one as well to keep the revs up so it can have a chance at getting out of it's own way. It sounds like a crotch rocket with its ~7,000 RPM redline. So far, that powertrain has held up to my abuse for 197,000 miles. My hat's off to Ford for that engine.

 

[swathdiver]

I pretty much only use three throttle positions: ~25%, 50% and 100%.

They switched to Ford Transits in 2016. They're supposedly rated as a 2500 but with a NA 3.7 V-6. Also a 6-speed.

Mine is not dissimilar to driving the old Grand Nationals around town, you can barely get on the throttle before exceeding the speed limit. I would say most of the time my pedal pressure is below 25%!

The transit is so much smaller and FWD too right? I was once going to buy one but it was smaller than my Pontiac Montana which I was using for deliveries. Or is there a difference betwen transit and transit connect?

 

[iamdub]

Mine is not dissimilar to driving the old Grand Nationals around town, you can barely get on the throttle before exceeding the speed limit. I would say most of the time my pedal pressure is below 25%!

The transit is so much smaller and FWD too right? I was once going to buy one but it was smaller than my Pontiac Montana which I was using for deliveries. Or is there a difference betwen transit and transit connect?

Definite difference in the Transit and Transit Connect! The Transit I drive is like the Mercedes cargo vans that Amazon delivers with, except mine doesn't have the tall roof. The Connect is itty bitty! Actually, word has it that's what our next round of service vans will be.

 

[swathdiver]

Definite difference in the Transit and Transit Connect! The Transit I drive is like the Mercedes cargo vans that Amazon delivers with, except mine doesn't have the tall roof. The Connect is itty bitty! Actually, word has it that's what our next round of service vans will be.

Ok, yeah I've seen those sold under lots of different brands. Seem like good trucks. Wait, I drove one once for a couple of days! LOL It was a Freightliner and a dually. I think an old Grumman bread truck with a 4 cylinder Cummins would be simpler and more robust. Lower deck height at least. Yeah, it was the little Connect's that we considered and realized they were just too small. The transit would work but I wanted easier ingress at the back without killing my knees. Just kept the Montanas working in the end.

 

[BG1988]

Brent has a hybrid transmission and has noticed that his runs more efficient when the engine is burning higher octane fuel. I think he's trying to say that it has just enough extra power on good gas to improve shifts and hold gears longer.

As for your work truck, their ignorance costs money.

engine has to have VVT so the yukon 6.2l will benefit... other wise there may be no benefit on the non vvt as with the VVT the Timing can be advanced to upto 42+ degrees normally i see 32-35+ with 91oct..

 

[thedog52]

6.0 is fun to have in ur tahoe


<-- has 6.0L.. LS2 based engine with corvette variable oil pump

Has 80HP booooost.. massive amount of torque 472ft-lb

Alt,A/C,Power steering delete


downshifting is caused by the fuel used Rarely do i downshift on a freeway with 91oct unless passing with 87 octane it will search for gears between 3-4 AFM will loop of death and gobble up a lot of fuel... the difference between 87 and 91 is upwards of 12.6MPG..


so on 87 it will get a solid consistent 18.5MPG(city/hwy) on 91 it's 22/25mpg(constancy )

31.1MPG City and 27.6MPG Highway were my best ever(favorable weather conditions helped)

Are you running a turbo or supercharger? I have seen plenty of Tahoe turbo kits that'll cost me around $2k. Of course that doesnt include tuning, and whatever misc stuff I'll need. Finding a gen 4 6.0 is hard where I am, 5.3's are easy but I really want the added torque of the 6.0.

 

[swathdiver]

Are you running a turbo or supercharger? I have seen plenty of Tahoe turbo kits that'll cost me around $2k. Of course that doesnt include tuning, and whatever misc stuff I'll need. Finding a gen 4 6.0 is hard where I am, 5.3's are easy but I really want the added torque of the 6.0.

DART Sleeves, a **** crankshaft, 402 cubic inches...