100 mph Governor

redwngr · December 29, 2015

"I don't think you can call 3.23 'rare'.

It is the standard ratio used with the 8 speed /6.2L combination.

I was just curious which ratio you were towing with. My 15 was also a 6.2/8sp/3.23. It also towed like a champ, but my tow loads have been considerably smaller. "

Ok, I retract the word "rare". Does that make it all better now?

Sorry, wasn't intending to give you a hard time.

Snoringbear · December 29, 2015

Naw, no worries. I don't consider your comment as giving me a hard time. Actually, did a little research and you were right; the 3.23 rear end is indeed the standard ratio for the 6.2.

When I went to the Chevy dealer to buy a new truck I had intentions of replacing my 2008 Silverado 5.3/4 spd with another 5.3/8spd being it's hp and torque had been bumped up quite a bit. But, was informed that the 8 speed tranny was not yet being matched with the 5.3. Salesman suggested I drive an LTZ 6.2 with 8 speed. And, after test driving it I decided to buy it even though it was a fancier and more expensive truck than I had in mind. But, now having made three trips towing my camper with it I'm very glad I bought it. Nothing like having lots of horsepower and torque for sure. Makes road trips with camper a real pleasure especially bring my wife likes the plush interior, wifi and such. Happy wife - happy life

redwngr · December 30, 2015

5.3 didn't get the 8 speed til 2016. And still only on SLT/LTZ and above.

alloutJ4 · August 18, 2016

Well I live in germany, not many vehicles here go any slower then 90 on the highway lol, I'm tracking 98 is top speed with governor with it have hit but with cruise the max is 94

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Colossus · August 19, 2016

I'd go ahead and contact Black Bear tuning (they have a section on the forums too) and see if they can help. You won't be dissapointed. They are the best for these trucks.

pm26 · August 19, 2016

If you want to find out what GM does to properly design full size trucks and SUVs for sustained high speed operation, check out the components they installe on a pursuit rated 2WD police Tahoe. "Pursuit rated" means rated for continuous high speed operation, up to vehicle's maximum speed. This vehicle has no speed limiter and according to published top speed tests it can reach speeds of about 140 MPH, wind drag limited. This with a 5.3 liter AFM engine, 3.08 rear axle ratio, 6 speed automatic. The vehicle is equipped with handling suspension, so it sits lower than a regular 2WD Tahoe, it has high speed rated tires (V rated I think), and I am sure there are some other minor mods like more aggressive transmission shift tuning and engine tuning. Probably the driveshaft and U joints are also different. It is interesting to not that GM will not pursuit rate a 4WD Tahoe equipped with the same police package. This is mainly becuase a 4WD version has higher center of gravity and it would not be safe at high speeds.

Colossus · August 19, 2016

It also has a few extra coolers on it for the fluids. But pretty much spot on, PM.

Cubes Racing · March 3, 2017

You can get the same drive shaft RPM at 15mph as you can at 100mph..............

Its called "doing a burnout." or "roasting the tires" etc etc etc

There are basically 3 sources of load (force) that you care about on drive shaft / U-joint needle bearings:

Centrifugal

Torque (torsional)

Harmonics

Centrifugal

If you double the drive shaft RPM the centrifugal force on those needle bearings quadruples (RPM squared). When you are doing a burnout there is not much load (torque) going through the driveshaft, or it's bearings compared to hauling the vehicle itself, a trailer, or fighting wind. Corrosion may throw a steel, or aluminum drive shaft out of balance over time. A lighter drive shaft, or better balanced drive shaft will help the most here.

Torque

At high speed you are pushing at least a few hundred foot pounds of torque (possibly more than a thousand) through those bearings, while they also have to cope with the other stresses. More bearing area (higher load rated U-joint) will help the most here.

Harmonics

You want to stay away from the 'natural frequency' (resonant frequency) of a system that is transferring power, especially near its failure limit (or engineering safety limit) as hitting the natural frequency (or a harmonic of it) can increase the force (amplitude) significantly. The highest number I remember quoted is 18 times. Cam shafts are usually well under their natural frequency for this reason. Steel is generally 2x stiffer than Titanium, and 3x stiffer than Aluminum. The specific stiffness (stiffness to density ratio), and amount of force (total torque - centrifugal included), stretching (tensile), and compressive forces dictate the natural frequency of the drive shaft. So larger diameter, thinner wall, or higher specific stiffness materials such as Carbon Composites (stiffness varies widely with these), Metal Matrix Composites, Ceramics, or Beryllium (dust is cancer, tons of money), help you here. Possibly more applicable to the salt flats, but not to be discounted.

Said differently, everything that moves, rings. When the drive shaft snaps back from resonant / harmonic force at the natural frequency, dynamic forces can be much higher than the working load of the system, and cause failure quite quickly, and dramatically. The system will actually store energy, and build amplitude with every cycle. Like hitting something with a 36 lb sledge, instead of 2 lb.

Like a guitar string, the frequency changes with force (torsional, tensile, compressive) Corrosion can change the natural frequency as well. Generally you want to be so far underneath the natural frequency that it doesn't matter.

Overall if you just want to raise the limit, you can:

Balance the drive shaft to higher rpm to negate centrifugal affects

Get higher precision bearings, that will lose less energy to heat

Get higher temperature, grease, seals, or bearings (Ceramic)

Get a stiffer drive shaft to negate harmonic effects if you are anywhere near them.

Seal quality may be higher on an OEM bearing, than an aftermarket Ceramic (not designed for OEM vehicle use). So they may need to be changed more often, especially if driving through salt, or grit.

Nasa found that Silicon Nitride bearings could only tolerate around ~95% I think it was of the maximum load of a steel bearing, since the SiN material is so much stiffer than steel, it has a much higher force (less contact area), on the rolling elements, and races, since they deform less under load. Steel rolling elements actually 'squish' under load, noticeably enough to increase the 'contact area', and keep the bearing from breaking through the lubricant film.

Prolonged high temperature use that doesn't cause seal failure may still cause:

grease to oxidize, and become less of a lubricant (think tar)

grease to thin out too much, and cause lubricant starvation (insufficient film thickness for the load)

Seal failure will cause:

grease to leak out, or to be flung out

sand, water or salt to get in

High Force can cause the parts of the bearing to deform enough that they slide past each other, instead of roll over each other. This is where lubrication is critical to keep the bearing from destroying itself quickly.

corndog247 · March 4, 2017

Ah yes. Diablo Trinity T-1000 Tuner. Running 91' Octane Tune. Silly post, I should have just done my research to delete the limiter. Sonoma Raceway here I come! Or maybe Stockton...it's closer. Anybody here do the Wednesday night drags? That said, no more street/hwy smashing you guys...I promise! Safety first.

I cant even count how many times i have seen this topic of discussion on just this generation of trucks. GM has been using the same limiter speed for years. They have also been using the same tires for years. And as for the driveshaft, the shadt itself isnt the issue, it is the needle bearings in the universal joints. Very small and can not tolerate heat well. Increased RPMs on them will cause them to heat, distort, and eventually seize. Once that happens the driveshaft breaks free and becomes a hazard to you or other drivers.

The driveshaft is an issue. I had two fail at around 115+with no sign of u-joint damage. The length, large dia, and thin wall makes these shafts reach critical speed depending on gear ratio around 110-120.

j-ten-ner · March 4, 2017

We have speed limits of 85, so I need to get a tune to remove my 98 governor. Really sucks trying to pass a truck moving at 88 mph on a single lane and only having a couple mph over him.

Single lane in each direction with a 85 mph speed limit?

Wow.

so long

j-ten-ner

Criscone · March 4, 2017

my 15' 5.3 6spd, 373 gears (max towing) shut off at just about 100, however my 16' 5.3 6spd, 342? climbed past 100. did they change something?

DGibson · September 25, 2017

Hi all, I stopped by to get some info on adding a tuner of some sort to my 2014 6.0 2500HD. I mostly tow with it and it is not my daily driver. I added a chip that hooks up to the mass airflow sensor, but was informed that that could be hazardous to the engine, causing it to run lean. Do you guys concur? So, that said, I saw one person used a Diablo tuner and I have looked at them, but wanted to get the straight scoop from you guys first. I tow a little over 13k with this truck. Everything is stock right now. Thanks in advance for any good advice.