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looking to buy 14 (6.2/6sp) or 15 (6.2/8sp)

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Chets LS3

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I have researched and researched until my head hurts trying to figure out the 8 speed trans with the new 15+ 6.2's. I know some people have had issues with TC/shudder/etc. Is it a very common problem or just a select few vehicles. Im looking at buying a used 14 or 15 between 20-40k miles. Should I stay away from the 2015's?

 

Also the truck will be used primarily for towing a race car (total with trailer 5k lbs) and a truck to drive to town and back. Not really DD duty. but my trips with the car can range from 150 miles to 800 miles to different tracks.

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michigan2500hd Senior Enthusiast

michigan2500hd

Posted
Posted

If I could do it all over I would get the '14 6.2 as it came with the six speed. Only because it's a tick quicker then the '15 and the 8 speed is just plain bipolar. That said, my 2015 6.2 tows like a beast! So for just daily driver duty the six speed is best and towing the eight speed rocks.

I'm getting ready to to a trailer about 2000 miles round trip so I'll have a better opinion on young after that.

 

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Justin101714 Enthusiast

Justin101714

Posted
Posted

Definitely 6 speed! They've been out longer and most bugs are worked out with them. The 8 speed I'm sure will be fine with some time, but that's time I don't have

 

 

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dgirouard39 Enthusiast

dgirouard39

Posted
Posted

Ill be honest, i don't mind my 8 speed. I have only felt it a handful of times where it will shake or something but I love the fuel mileage on the 8 and if i want the power through the gears i keep tow mode on.

 

mine is 15' 6.2 8 speed.

Mark Diedrich Enthusiast

Mark Diedrich

Posted
Posted

I think you will be happy with either one. The 8 speed is supposed to be built stronger ( higher hp capacity) so it should hold up better long term if you get a good one.

Both of them have had shifting issues.

I have an 8 speed in my 17 and brother has a 6 speed in his 14 both with 6.2 motor, I would say they pull our enclosed trailer very similar to one another.

Good luck

JimCost2014 Senior Enthusiast

JimCost2014

Posted
Posted

I have researched and researched until my head hurts trying to figure out the 8 speed trans with the new 15+ 6.2's. I know some people have had issues with TC/shudder/etc. Is it a very common problem or just a select few vehicles. Im looking at buying a used 14 or 15 between 20-40k miles. Should I stay away from the 2015's?

 

Also the truck will be used primarily for towing a race car (total with trailer 5k lbs) and a truck to drive to town and back. Not really DD duty. but my trips with the car can range from 150 miles to 800 miles to different tracks.

So to make your head hurt more, are you looking at a max tow package or just a normal truck? 6 speed will give you options of 3.42 or 3.73, 8 speed will give you 3.23 or 3.42 rear ends depending on tow package (normal, max tow).

JimCost2014 Senior Enthusiast

JimCost2014

Posted
Posted

I'm looking at 14-15 Denalis. I don't believe they have max tow (don't those have the bigger mirrors)

They do, along with a few more heavy duty towing options. Good call on the Denali, good looking trucks.

newdude Senior Enthusiast

newdude

Posted
Posted

I'd go 8 speed. Stronger unit over the 6L80, and makes better use of the powerband.

 

They do, along with a few more heavy duty towing options. Good call on the Denali, good looking trucks.

 

Denali does not have Max Trailer NHT.

amxguy1970 Senior Enthusiast

amxguy1970

Posted
Posted

I've had a 6.2 6spd, the 8spd blows it away towing.

 

If that isn't an over exaggeration I don't know what is. 4.03 and 3.42 vs 4.56 and 3.23 with a slightly tighter spread does not equal "blows it away". It will "blow away" a NA V6 or other smaller less powered trucks but the same motor with a slight gear change is not that big of a difference. Helps yes but big difference, not at all...

 

Tyler

TheGovernment Enthusiast

TheGovernment

Posted
Posted

I have researched and researched until my head hurts trying to figure out the 8 speed trans with the new 15+ 6.2's. I know some people have had issues with TC/shudder/etc. Is it a very common problem or just a select few vehicles. Im looking at buying a used 14 or 15 between 20-40k miles. Should I stay away from the 2015's?

 

Also the truck will be used primarily for towing a race car (total with trailer 5k lbs) and a truck to drive to town and back. Not really DD duty. but my trips with the car can range from 150 miles to 800 miles to different tracks.

It's a select few vehicles for the shutter. Even then, some people are blowing it way out of proportion. There are for sure some people with legit issues but then there are the typical forum lemmings that have convinced themselves they have the same issue, when they probably don't.

Justin101714 Enthusiast

Justin101714

Posted
Posted

It's a select few vehicles for the shutter. Even then, some people are blowing it way out of proportion. There are for sure some people with legit issues but then there are the typical forum lemmings that have convinced themselves they have the same issue, when they probably don't.

I agree on the forum lemmings [emoji23][emoji23]

 

Personally I have corrected at least 30 vehicles with the shudder problem in just my dealership. I work on the transmissions. These 30 vehicles would include the Escalade, Silverado, Camaro and Corvette.

 

This being a isolated problem to a limited few? I don't think so. I'm curious to see how it'll be when some get some real miles on them. Why do you think GM worked on lowering that power train warranty? It saves them money. GM introduced software into the ECM's of many vehicles beginning in 2013 called "Torque Management" . That's why our throttle response sucks as well. It's made to open the throttle slowly so the drivetrain doesn't take harsh abuse from constant wide open throttle or moderate throttle. They are so confident in this that the software was the beginnings of warranty adjustments.

 

 

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Jon A Senior Enthusiast

Jon A

Posted
Posted

 

If that isn't an over exaggeration I don't know what is. 4.03 and 3.42 vs 4.56 and 3.23 with a slightly tighter spread does not equal "blows it away". It will "blow away" a NA V6 or other smaller less powered trucks but the same motor with a slight gear change is not that big of a difference. Helps yes but big difference, not at all...

 

It's not an exaggeration at all under certain circumstances. The 6-Speed has a huge gap between 2nd and 3rd gear. If you're towing something heavy enough up a hill steep enough that you can't pull 3rd gear it will hunt back and forth between 3rd and 2nd. It goes from bogging to screaming because of the distance between the gears. In addition, the shift programming in tow-haul mode sucks so the truck will not maintain highway speed while this is happening.

 

A tune can fix that last part--mine will grab 2nd much more quickly and hold it all the way to redline so I can maintain speed, but it's still far from ideal. The engine is screaming unnecessarily and fluids heat up more quickly in 2nd so it's best to avoid it at highway speeds. With a few engine mods and 4.10 gears you should be able to pull 3rd with any remotely legal load up pretty much any hill but as far as I know they don't yet make 4.10's for the 9.76" forcing you do downgrade to the smaller gears if you want the ratio.

 

The 8-Speed has a gear effectively right between those two gears so it's not an issue--it can always find the right gear. No need for 4.10's.

 

Of course this is a much bigger issue/more common with the 5.3 but it can still happen with the 6.2 if you tow heavy through the mountains. In the OP's case, if he stays with a 5000 lb trailer it shouldn't be an issue as the 6.2 can pull 3rd with that much weight up pretty much anything.

 

The one plus the 6-speed has is tests seem to show it has more aggressive programming for the grade braking than the 8-speed. The 6-speed can hold some big loads down some steep hills without needing the brakes, the 8-speed doesn't seem to do as well in the tests I've seen so you may need to use manual mode more often going downhill. I don't think a tune can change the grade braking. Even so, I'd still choose the 8-speed for its advantages going up the hills.

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