2 Month Grade Card

[Pat Grant]

I've had my truck for right at two months now and I just got back yesterday from a 2,100 mile trip to Buena Vista, CO. Total mileage now is 9,600 (yeah, I drive a LOT). In the end, I LOVE this truck, I drove 860 miles yesterday in 11.5 hours. I put the Diablo "Economy Tune" on it before the trip and averaged 18.8 mpg for the duration of the trip. Mind you, I AM a leadfoot. My best 400 mile leg was 21.4 and my best 25 mile was over 42! (love going down hill!). The driving comfort of this truck is incredible. There is zero fatigue from long distance driving, even in heavy cross winds.

 

Pluses:

• Grade Braking.....Awesome!
• Quite and comfortable....Still hard to believe it's a truck
• The overall brakes
• 18 to 21 mpg from 420hp? Comon!

Negative:

 

Now for the bad part.....I cancelled the speed limiter and while making time on US 87 across NM and the TX Panhandle I opened it up for the first time. Man, this thing pulls....HARD. BUT......At 100mph, there was an incredible driveline vibration and I mean BAD, to the point that the hood was flexing like a trampoline! At 105mph it went away. No vibration on the deceleration and checking it a couple more times, I narrowed it down that it only vibrated under a hard acceleration, if I creeped up on the speed, no vibration..........It is what I would describe as a higher frequency vibration and it is definitely the driveline.

 

Before any of you are ready to chastise me for driving so fast, please save it............

[nadrojcote]

In the tsb for vibration, they check the driveshaft as well as the ring gear. Could be either of these.

 

http://www.gm-trucks.com/forums/topic/153186-shake-or-vibration-issues/page-1

[ghgmi]

Pluses:

• The overall brakes

 

Very good to hear. Brakes seemed awful on the '99-'06 models (long stopping distance, low-frequency ABS that robbed the brakes of most their stopping power, ABS activated too easily). Never drove one of the '07-'13s.

[WendysOrBust]

I've had my truck for right at two months now and I just got back yesterday from a 2,100 mile trip to Buena Vista, CO. Total mileage now is 9,600 (yeah, I drive a LOT). In the end, I LOVE this truck, I drove 860 miles yesterday in 11.5 hours. I put the Diablo "Economy Tune" on it before the trip and averaged 18.8 mpg for the duration of the trip. Mind you, I AM a leadfoot. My best 400 mile leg was 21.4 and my best 25 mile was over 42! (love going down hill!). The driving comfort of this truck is incredible. There is zero fatigue from long distance driving, even in heavy cross winds.

 

Pluses:

• Grade Braking.....Awesome!
• Quite and comfortable....Still hard to believe it's a truck
• The overall brakes
• 18 to 21 mpg from 420hp? Comon!

Negative:

 

Now for the bad part.....I cancelled the speed limiter and while making time on US 87 across NM and the TX Panhandle I opened it up for the first time. Man, this thing pulls....HARD. BUT......At 100mph, there was an incredible driveline vibration and I mean BAD, to the point that the hood was flexing like a trampoline! At 105mph it went away. No vibration on the deceleration and checking it a couple more times, I narrowed it down that it only vibrated under a hard acceleration, if I creeped up on the speed, no vibration..........It is what I would describe as a higher frequency vibration and it is definitely the driveline.

 

Before any of you are ready to chastise me for driving so fast, please save it............

From what I've read the drive shaft is not balanced to be driven at those speeds. Chuck, a tuner who specialized in GM's down in Houston replaced the drive shaft on his 2014 Silverado to be able to achieve 115mph +

 

 

 

At $1,600 its not a cheap upgrade but if you are going to be spending allot of time at that speed it would be a solid investment.

 

Btw; I don't know how you were able to open it up that much. All the roads in New Mexico/Colorado had that annoying, "Safety Enforcement Zone - Fines Doubled" shit.

[Pat Grant]

From what I've read the drive shaft is not balanced to be driven at those speeds. Chuck, a tuner who specialized in GM's down in Houston replaced the drive shaft on his 2014 Silverado to be able to achieve 115mph +

 

 

 

At $1,600 its not a cheap upgrade but if you are going to be spending allot of time at that speed it would be a solid investment.

 

Btw; I don't know how you were able to open it up that much. All the roads in New Mexico/Colorado had that annoying, "Safety Enforcement Zone - Fines Doubled" shit.

 

Thanks for the heads up....I seldom get that fast for any length of time at all, unless I'm in West Texas....Mojave, Wyoming, Montana etc. It's kind of tough to mention this issue to GM when it has a 97mph limiter...lol. But as you can see by my drive yesterday, I like to make time when I can.

[newdude]

They do put speed limiters on these for a reason you know. Tires, driveshafts, etc are rated to run certain speeds and what not. Do you have the limiter disabled or something to hit that fast?

 

 

 

 

 

This is why there are speed limiters in place on things. Want to go faster? Gotta pay to play.

[ghgmi]

Good point about tires. What's the speed rating on yours? Hopefully not Q.

[Pat Grant]

Here we go.....Please don't hijack my thread....

[tnchevy]

You opened it up by talking about how fast you went.

[fpdsniper]

Regardless of whether or not he should be going that fast, there appears to be an issue that should be addressed.

[bdbake01]

Not every truck left the factory w/ a 97 mph limiter.

 

That said, no vibe here at 100+

[ghgmi]

Regardless of whether or not he should be going that fast, there appears to be an issue that should be addressed.

 

Apparently no issue at 97. Perhaps the vibration is why GM limited the truck to 97 instead of a more typical 120--that is, they did address the issue. Cheaper than manufacturing drivetrain components to tighter tolerances.

[tnchevy]

GM has been cutting off trucks at 97 for a very long time now, so that is not the reason.

[bdbake01]

GM has been cutting off trucks at 97 for a very long time now, so that is not the reason.

Some, not all.

[Pat Grant]

You opened it up by talking about how fast you went.

 

Okay....I will play.

 

Since you want to focus on the speed I was driving at and not the real subject of this thread, I will also let you know that I took it on up to 122 mph. I survived, you survived and no unicorns or kittens were put in harm's way Do you feel safer now? .