08 Gmc 2500hd , Auto 6spd, 6.0

[rayjc33]

Ok, so I am very interested in this truck, I have a couple questions, first it is a six speed auto but has the option to put in Manual and shift with a but on the Gear Selector. What are your opinions on this tranny and motor combo. Looking to pull 8,000-10,000 pounds with it. Also what kind of mileage empty and towing is normal out of these. Anything else I should know about these trucks, thanks for any and all info.

[shocktrp]

Ok, so I am very interested in this truck, I have a couple questions, first it is a six speed auto but has the option to put in Manual and shift with a but on the Gear Selector. What are your opinions on this tranny and motor combo. Looking to pull 8,000-10,000 pounds with it. Also what kind of mileage empty and towing is normal out of these. Anything else I should know about these trucks, thanks for any and all info.

 

It shifts a lot more than an A4 - you will get used to it.

 

You don't need to shift manually - put it in tow/haul mode and go. If you don't want it to go into the second overdrive because you're towing a heavy load then you put it in M5 and leave it there.

 

All the button does is replace the P-R-N-OD-D-2-1 on an A4 with P-R-N-D-M_1 for the A6 (otherwise your gear shift would be P-R-N-6-5-4-3-2-1).

 

Try to get one with 4.10's instead of 3.73's if you can.

 

It will easily pull 10k with either gear set.

 

You will get about 12MPG empty.

 

Make sure it has the HD trailering equipment option & brake controller option.

 

Don't keep 80PSI in the rear tires if you're not towing (unless you like replacing tires every 30k).

[Ridgerunner30]

I have an 09 GMC 2500 6.0 3.73 4X4. I have been very happy with the truck.

 

There is wide variation on gas mileage reported. Probably the variation has much to do with where you routinely drive. I live in a rural area and seldom drive in urban areas. My overall average when driving lightly loaded is 15 mpg. I typically get 17 mpg on the interstate (lightly loaded) at 70 mph on the 1000 mile round trip to my daughter's house (I have made this trip six times in this truck). I get about 9.5 mpg pulling a travel trailer at 60 to 65 on the interstate.

 

I really like the engine and transmission combination. The functionality of the transmission seems to be very similiar to the Allison transmission. When you put the transmission into M (range select mode), you limit the top gear to the gear you select. For example if you select 4, the tranmission can shift from 1 up to 4 but won't shift up to 5 &6. The manual shift is not intended to be used to manually shift gears, it is used to limit how many gears you have available. As shocktrp said, you may want to put the transmission in 5 to keep if from shifting into 6 when you are pulling a heavy trailer. However, I believe you do not have grade breaking when you put the transmission in M.

The transmission also has a "low traction mode" that limits torque to the rear wheels and prevents rear wheel slip. You get into "low traction mode" by stopping and placing the gear range select in "2".

 

You will be at your trailer weight limit at 10,000 lbs with the 3.73. The 4.10 will give you about 2500 lbs more trailer capacity.

 

Good luck in your search.

[rayjc33]

This particular truck has the hd Tow package. It has the built in brake controller, so when towing you reccomend tow haul mode and d, or tow haul mode and m5, I am new to this style transmission. Thanks for all feedback

[SS Crew]

This trans will also downshift when you slow down if you leave the tow/haul selector on. Scared the crap out of me the first time it happened since I wasn't expecting it to do that.

[TorkFaze]

Unless there's something you don't like about the way it acts when in D, just leave it there. Tow/haul makes 6th harder to get (only at highway speeds) and should be pretty decent for most driving other than maybe rolling hills at highway speeds.

 

If you put the trans in M5 or lower, you DO lose the grade-braking feature as mentioned in Ridgerunner's post.

[rayjc33]

So where do I look to see gear ratio??

[Ridgerunner30]

So where do I look to see gear ratio??

 

 

There is a sticker on the inside of the glove box door that has codes for your truck. A GT4 code means that it is a 3.73, I believe either a GT5 or GT8 means that it is a 4.10. G80 means that it has a limited slip rear end. I have attached a link for figuring out codes for this.

 

http://www.drivetrain.com/parts_catalog/ri..._chevrolet.html