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drove the SLT, Denali and LTZ today

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crushNchowda Senior Enthusiast

crushNchowda

Posted
Posted

Why and how should that make a difference

 

HUGE difference...I actually swapped a super early '14 truck back to the dealer for a /14 w/ 3.42's because the original truck had the gutless 3.08 gears and neither I nor the dealer knew initially (much more noticeable in hilly areas or w/ multiple passengers/gear

 

A 5.3 truck w/ 6 speed regular cab and max tow (3.73 gears) that is flex/fuel capable guzzling E85 may actually be the "quickest" of all current GM trucks/SUV's due to the gearing and increased power of the E85

 

As others have mentioned, if E85 is plentiful and about 20% cheaper than 93 (which it should be and then some) you may be better off getting a truck/SUV w/ that option and saving some money.

 

Dyno results have proven the 5.3 V8 puts down 90% of the power/TQ of the 6.2 on E85

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crafferty Senior Enthusiast

crafferty

Posted
Posted

 

HUGE difference...I actually swapped a super early '14 truck back to the dealer for a /14 w/ 3.42's because the original truck had the gutless 3.08 gears and neither I nor the dealer knew initially (much more noticeable in hilly areas or w/ multiple passengers/gear

 

A 5.3 truck w/ 6 speed regular cab and max tow (3.73 gears) that is flex/fuel capable guzzling E85 may actually be the "quickest" of all current GM trucks/SUV's due to the gearing and increased power of the E85

 

As others have mentioned, if E85 is plentiful and about 20% cheaper than 93 (which it should be and then some) you may be better off getting a truck/SUV w/ that option and saving some money.

 

Dyno results have proven the 5.3 V8 puts down 90% of the power/TQ of the 6.2 on E85

 

Get the 6.2L and tune it for E85.

crushNchowda Senior Enthusiast

crushNchowda

Posted
Posted

Get the 6.2L and tune it for E85.

 

I have one, but either way you can't put e85 in the 6.2 without swapping fuel lines and stuff as I understand it the 6.2 trucks don't support e85 use....it'll probably corrode

crafferty Senior Enthusiast

crafferty

Posted
Posted

I have one, but either way you can't put e85 in the 6.2 without swapping fuel lines and stuff as I understand it the 6.2 trucks don't support e85 use....it'll probably corrode

Actually you are completely wrong, all you need to do is just tune for E85 and your good to go. There are several members running this setup and one of them actually did the tuning himself.

crushNchowda Senior Enthusiast

crushNchowda

Posted
Posted

Actually you are completely wrong, all you need to do is just tune for E85 and your good to go. There are several members running this setup and one of them actually did the tuning himself.

Assuming the fuel pump, fuel line, fuel rails, and all associated supporting gaskets and anything that maybe rubber or polymer is all the same across all trucks and designed to be compatible for E85 then I guess I would be wrong.

 

I was under the impression that this was not the case... BUT if it's simply a matter of GM leaving a table in the ECM for E85 fuel then why wouldn't it be an option/available for use across ALL trucks then? Why would they even make it an option? You don't think they're trying to save pennies using less durable hardware suitable only for regular petrol??

 

I'm well aware that you can get a custom tune that will allow you to run any number of octane/fuel types, but the question is whether or not the supporting associated hardware is designed to handle the much more corrosive quality of E85

crafferty Senior Enthusiast

crafferty

Posted
Posted

Assuming the fuel pump, fuel line, fuel rails, and all associated supporting gaskets and anything that maybe rubber or polymer is all the same across all trucks and designed to be compatible for E85 then I guess I would be wrong.

 

I was under the impression that this was not the case... BUT if it's simply a matter of GM leaving a table in the ECM for E85 fuel then why wouldn't it be an option/available for use across ALL trucks then? Why would they even make it an option? You don't think they're trying to save pennies using less durable hardware suitable only for regular petrol??

 

I'm well aware that you can get a custom tune that will allow you to run any number of octane/fuel types, but the question is whether or not the supporting associated hardware is designed to handle the much more corrosive quality of E85

 

I definitely understand all your concerns as we are not talking about cheap trucks here. I do not know all the particulars off the top of my head but send a PM to Higgs Boson as he has tuned his truck to run on E85. Cool thing about him is he is the gentleman I referred to earlier who actually tuned his own vehicle. So he will be able to give you some very in depth information as he has a LT1 Corvette and L86 Silverado that are both on E85.

2018GMC Senior Enthusiast

2018GMC

Posted
Posted

I apologize in advance for the long answer. One of the most important considerations for your vehicle selection is what type of differential ratio is selected.

 

Gears have many different types of jobs in a vehicle. For example, one of the important jobs of the rear differential is to convert the energy transmitted from the driveshaft to a 90 degree angle and apply that power to the axles. A secondary job of the rear differential is that it is a mathematical multiplier of torque that is delivered from the engine and tranmission. Gears have been created to re-direct engergy and also to multiply the effect of that energy. You can think of them almost like levers or "pulleys". They create mechanical advantage.

 

In Suburbans and GMC Yukons outfitted with 5.3l engines you have gearing selections of 3.08:1 and 3.42:1. Just how powerful are these gears? The 3.42 gearing selection increases the maximum towing capacity of a 2WD GMC Yukon by 1 ton. Believe me, this is power that you can feel and record when you hammer down that throttle. The gearing will provide faster acceleration and ultimately the additional towing capacity you may need, but, is there a cost? Unfortunately yes. Think of it like racing your friend on a bicycle. If he is running 3.08 gears and you are running 3.42 you generally will beat him off the line (he is really having to apply MORE energy to the pedals initially to try and keep up with you) but eventually your friend is going to blow past you in "top speed" (your legs are pedaing like crazy in that final 3.42 ratio, he is gliding along nicely with 3.08 as he waves bye-bye).

 

Tradeoffs: Acceleration, Top Speed, Towing Capacity, Fuel Efficiency, "Cruising RPM" range

 

The top speed is sort of a mute point because these vehicles have governors installed to keep us from doing silly things that might hurt us (and others). Denali's have a fixed final ratio of 3.23 with the 6.2l engine and you can't order another option. If you are towing anything near 50% of the towing limits of the vehicle I'd recommend investing in the max towing option (3.42 gears included). If you drive the 3.08 and don't ever tow anything (say, greater than 3-4K lbs) and you are pleased with off-line accelaration the 3.42 gears are useless and you'll get better gas mileage and a more comfortable RPM range at maximum highway speeds.

 

My last 2011 Suburban 4X4 was 3.08. I regularly towed 4-5K lbs and it worked OK, but it really needed the max tow package to tow that load comfortably. Towing that same load uphill it felt like the vehice was about to explode or kept my wife looking in the mirror for transmission parts or screaming "we aren't going to make it!!!!". The sad news is that given a heavy enough load (RV camper) on an extremely steep incline with the wrong gears (and it happens to be 95 degrees outside) you absolutely can get to a point where "you ain't gonna make it".

 

I never had a problem with 3.08 in town and mileage was improved. it was a great "around town" ratio.

Nice informative writeup

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