: Anyone know the torque rating of the new 2006 Differential?



verbs
12-10-05, 01:55 AM
I think the old one was like 320tq.....what is this new one supposed to handle?

StealthV
12-10-05, 10:00 AM
The 320 rating that keeps getting tossed around is internet lore. The torque capacity of the Getrag in the '04 and '05 was one the topics of discussion we got pretty detailed on with John Heinricy. The LS6 delivers just under 1000 lb-ft to the rear axle assembly. One also needs to consider engineering safety factors in the rating.

The 2006 version was built to handle the 469 hp/439 lb-ft of the STS-V plus torque mulitplication and safety factors. That puts it well over 1000 lb-ft.

r_casino
12-10-05, 10:28 AM
StealthV,

Can you give an easy (?) explanation of how to get from the Getrag numbers to the numbers we should be using...

http://www.en.getrag.de/181

(I.e., how to go from the Getrag spec to knowing it can handle the just under 1000 lb-ft spec.)

StealthV
12-10-05, 11:15 AM
For delivered energy to the rear axle input shaft:

LS6 power delivery at peak = 395 lb-ft.

Torque multiplication (power delivery/acceleration force) is at its maximum in 1st gear with its ratio of 2.97:1.

Thus the power from the engine to the output shaft of the transmission is 395 lb-ft times the 2.97:1 ratio which results in a delivery of 1173.15 lb-ft.

Of course the energy transfer from the engine through the transmission has some losses. Assuming a 15% energy loss in the clutch/transmission, the delivery at the tailshaft of the transmission would be 1173.15 lb-ft times 85% which gives 997.18 lb-ft.

Since we don't have actual energy loss figures from the T-56 transmission, these calculations are ballpark figures. My gut would say the transmission energy loss is more on the order of 6-10%. For more accurate calculations, one also would need to consider the additional power losses from friction in the pinion and ring gear, as well as rotational losses of the rear axle assembly, half-shafts, brake discs, hubs, etc. This puts us into the 15-17% ballpark.

Bottom line, John Heinricy told our panel of V owners that the 2004 and 2005 CTS-V rear axle assembly was rated to handle the power delivery of the LS6. To do anything less doesn't make sense using simple engineering 101 rules.

Mr. Heinricy also mentioned that due to the increased power output of the STS-V, the Getrag rear was upgraded for 2006 and would be used as replacements for 2004 and 2005 CTS-Vs that experienced problems.

For an actual rating of the 2006 assembly, we'd need that straight from Getrag or GMPD.

lasstss
12-10-05, 11:54 AM
StealthV,

Can you give an easy (?) explanation of how to get from the Getrag numbers to the numbers we should be using...

http://www.en.getrag.de/181

(I.e., how to go from the Getrag spec to knowing it can handle the just under 1000 lb-ft spec.)

Keep in mind that Getrag simply added stiffeners to the case all around. So the 'box' is stronger. They did nothing with the gears, side carrier and pinion bearings. The rating at Getrag 420NM X 0.737 + 306 ft lbs is an internet spec on that model rear. There are so many versions that what ours is rated for isnt exactly known. The Pacifica uses the same diff up front! The CTS diff that I bought had a much lighter case than even the base 2004 V.So with the torque multiplication (gearing), the axles see some pretty high torque, which is why we have seen a few twisted axles and given the case splits, the added stiffeners. It was most definetly designed on the edge for the V. On the face of it, its pretty stought given its size and light weight. It would probably be bullit proof if the case was Iron. I have anout 500mi on my #2 diff and the pinion bearing went.

In the end, as long as you back out of a bad hop and dont visit the strip every week, it will probably last a long time. The 2006 diff will certainly help the situation.

urbanski
12-10-05, 12:25 PM
engineers are cool :cool:

StealthV
12-10-05, 01:41 PM
Gears aren't the problem with the assembly; they use the identical gears in the CTS-VR. Compared to the base CTS, the V gear set is shot peened for fatigue life improvement.

From all the failures on the forum, I've yet to see torn up gears. Cases split in half, half-shaft outputs sheared yes. The gears take the torque load and the case can't handle it; causing the case to deflect and deform. From this, the next thing one notices is the gear set is now making noise because the alignment between the pinion and ring gear is off.

As Marty mentioned, it's a case deflection issue. Aluminum is a horrid material when you look at it from a deformation and fatigue life standpoint. ANYTHING made from aluminum is guaranteed to have a fatigue failure, it is just a matter of time. Whether it is tomorrow or a thousdand years from now is all a matter of how much load is placed through the material. It will fail.

The same diff case made out of cast iron would be bullet proof. It exists. I want one.

ace996
12-10-05, 02:00 PM
On that phone call, John H. and anyone else who represented GM, would NEVER outright say that they used sub-par materials/parts. Never ever.
Can you imagine a car company sharing that type of info before making the "public" or service organization aware via "recall"?

The part was under-designed.

And to answer your question, Verbs, no...we don't know.
-ace

moldowan
12-10-05, 09:13 PM
sorry to thread jack,
But seeing R casino posting reminded me of this summer in chicago, I was in town for my wedding and was headed downtown and i see a V coming to the tool booth. I wait until it pulls up and it roars out of the toll booth- VERY COOL sounding.
Since this was the 1st time I heard a V outside of one It gave me chills. Turns out it was R casino with B&B cat-bak/ headers on his car!
Remember that R???? My wife though I was such a geek that day-LOL
-moldy

r_casino
12-11-05, 12:46 AM
sorry to thread jack,
But seeing R casino posting reminded me of this summer in chicago, I was in town for my wedding and was headed downtown and i see a V coming to the tool booth. I wait until it pulls up and it roars out of the toll booth- VERY COOL sounding.
Since this was the 1st time I heard a V outside of one It gave me chills. Turns out it was R casino with B&B cat-bak/ headers on his car!
Remember that R???? My wife though I was such a geek that day-LOL
-moldy
Sure do remember that! It was great meeting a fellow V owner. And I'm sure your wife has probably figured out your car fanatic side now! I remember her saying "he has a car like that" -- I suppose she was making sure that I didn't think there was some crazy guy pulling up along side of me and yelling out the window!! But it was all great and I enjoyed it!