2005 /6 Dmax exceeding 700 ftlbs.

[Spartus]

Hey guys, I work at AAM, the supplier for our rear axles. In talking with an engineer a few days ago he was telling me that GM has requested AAM to design for them a new rear axle that is capable of handling 750+ ft lbs of tq. This axle is for the Duramax platform..


Also, in talking with the engineer I told him I'm running a 90hp juice module, and he told me to be very careful about hard launches with my truck, because our axle is known to develop leaks near the outer axle bearings if too much torque over the factory rating is applied.

-Tom

[Burner]

ok.......

Did you ask him how to fix the leak prone problem?


Burner----> :D

[pinehill]

Another question:

For comparison purposes, what's the torque rating of the current Dmax rear axle?

[Burner]

Can someone explain to me the difference between launching and pulling "BIG" weight? If I were to hook up to a 20k load and stomp the stock go pedal, how much torque will the axel see? If I did the same thing empty would the torque be the same? With a load the tires cannot slip and the drivetrain must accept the load or move, either by twisting the tires or it's self. Of course if there is no load we contribute two nice black strips of rubber to the road. So, I'm guessing that instant acceleration is very hard on the axels because they have a loose bearing set for heat reduction while pulling heavy loads. Is there a "FIX" for this problem?

Burner------> : :D

[afp]

I have been thinking about this as well. As I visualize this, I see more torque putting a greater twisting moment on the axles-which could case failure--but I'm not seeing how the axle seals would get any more stress. All the axle seals are doing is keeping the oil from getting out by tightly fitting the axle next to the outer bearing. When I drag raced, we would replace stock axles with stronger aftermarket units, but we's still use the factory seals.

To quote O'Reilly here, where am I wrong? What am I missing here?

Blaine

[Spartus]

I was rather confused as to why he said the seals would go out myself. But on my Impala SS, I once blew out an axle seal while road racing, so go figure..

He just said it had to do with the torsional twisting of the axles vs the housing, and horizontal load.. He said the fix they came up with was a gasket. I'll talk to him a bit more about this if anyone is too concerned. As for stock ratings of our axles, I didn't ask about that either.

-Tom

[Burner]

Perhaps the problem lay in the axel. I don't know, but I would think that we would have more axel wrap from a launch. It could be a correlation of speed and twist. Maybe on a hard launch the axel wrap stretches the bearing and seal so slow that it creates an oblong or parabolic wave that allows the oil to permeate the gap, just slightly. After continued hard launches the bearing and seal become damaged. I'm guessing that the bearings are hardened, to an extent, and do not have much of a spring like return. .... Humm.... I have not heard of a 3500 having this problem. What is the difference between the 2500 and 3500 axel? I recall that the F250 and F350 had the same chunck with different setups.

Spartus, please let us know something. It would be nice just swapping bearings. ;) :D


Burner-----> :D

----Happy Easter----- :D :D :D

[TBC]

I had my truck in for some service a while back and the dealer found both rear axle seals leaking. They replaced the seals and brake pads. It apparently was not a big leak or I would have seen it. Glad they checked everything and got it fixed.

Tom

[Toroflow]

You couldn't shed any light on the straight front axle 4X4 for 2005 rumor, could you? I would figure if it is true, G.M. would probably souce it from AAM as well. Anyway, about the 700+ ft. lbs. requirement, remember that's after the transmission, actual maximum torque output of the engine would be quite a bit less (though still impressive!).

[ 04-22-2003: Message edited by: Toroflow ]</p>

[ZFMax]

700 ft/lbs sounds like an awfully light duty axle.

Look at it this way ... if the motor is making 520 ft/lbs of torque, and you're in first gear on a ZF (5.79 ratio), the driveline has 3011 ft/lbs of torque (520 x 5.79). More if you're in 4-low range.

[K1XV]

I also thought 700 lb ft sounded light. The Duramax puts out 520 lb ft at the flywheel. The transmission in lower gears multiplies that by the gear ratio. Even with losses, with a 2 to 1 gear ratio in a lower gear, wouldn't that result in an input torque to the rear axle in the neighborhood of 1000 lb ft?

[Colorado Kid]

American Axle's web site says our 11.5" rears are rated for 11,300 N*m of Torque input. Lindberg's Civil Engineering Reference Manual, which happens to be within reach of my desk, says if I have N*m and I want ft*lb(force) I should multiply by 0.7376, so 11,300 x 0.7376 = 8,335 ft*lbs maximum input torque for our current axels. Even in low range with the front axle disconnect disengaged (nobody would do that would they?) we have 3011 ft*lbs (thanks ZFMax) x 2.72 = 8,190 ft*lbs max input torque, so every thing is cool. The Dodge boys with their 555 ft*lbs had better keep the front axle engaged or refrain from developing peak torque in compund low. ;) It's pretty hard to imagine developing any boost with a 59:1 crawl ratio (5.79 x 2.72 x 3.73).

Those of us who lack low range have very substantial margins for increasing torque before worrying about our rear axles....Dual mass flywheels, clutches and tranys are another matter. ;)

[ 04-24-2003: Message edited by: Colorado Kid ]</p>

[Amianthus]

"It's pretty hard to imagine developing any boost with a 59:1 crawl ratio."

You should try it some time. Takes me almost 30 seconds just to cross the street. :D Four whole pounds of boost! Wooo Hooo!

[Burner]

What happens when you "booste-up" and take off in LOW 4X4? What if you're pulling someone out of a ditch? What happens if you must "rock" your truck to get out of a hole? What happens if you run bigger tires? I would think that the tires are the biggest detriment to the axel.


Burner----------&gt; :D

[Spartus]

I stand corrected on several things. The 2005 Dmax will only be up to around 550ftlbs... The 2007/2009 will at the 700ftlb range.

And yes, GM has asked us to develop a stronger rear axle to handle that torque.

I understand what Colorado kid is saying though.. It seems as though our current axles would be more than strong enough. But what the GENERAL wants, the General gets.

[afp]

You mean it's taking GM 6 years what it took Edge 6 months (probably a lot less than that) to do?

Blaine

[pinehill]

If GM hadn't had to comply with emissions regulations, they could have given us a lot more power in the first one off the assembly line. I don't think that any of us that use power chips are worried much about emissions.

[SoCalDMAX]

Amianthus said,

"You should try it some time. Takes me almost 30 seconds just to cross the street. Four whole pounds of boost! Wooo Hooo!"

I used to be scared of him, but I think I can beat him! He's not nearly as fast as I thought! :D

Regards, Steve

[Amianthus]

:D