2017 Duramax

Trippin

SoCal Diesel
Aug 10, 2006
663
2
0
I did a little CAD work this afternoon with what we know about the new crank. Pretty interesting stuff. A .200 increase in diameter (without any decrease in rod journal width) increases the cross section between the second main journal and the first rod journal by almost 7%.

A 7% increase in cross section is exactly what we ended up with when we reduced the rod journal width on our billet cranks at the beginning of this year.

Code name NR for narrow rod journal. Fundamentally we machine the excess width off the big end of the rod (.125) that is already wider than the stock rod bearing. The cranks are manufactured with rod journals that are .250 narrower than stock Dmax. The result is crankshaft counterweights that are .125 wider. This means much less weight has to be added to the damper and flywheel for balancing. In effect moving more towards an internally balanced crankshaft. :)

The only two drawbacks I see to the 2017 crank is an increase in bearing surface speed with the larger diameter. Which is not really a huge issue at our crank speeds. We rarely see problems with rod bearings. The second is weight. All things being equal, increasing the rod journal diameter has added weight to that side of the crank, (similar to adding weight to the big end of the rod) which means it needs to be counter-weighted for balance in some fashion. If GM wasn't able to add mass to the counterweights, they had to add it to the damper and flywheel. :(

I can't wait to get my hands on the new cam and cylinder heads to see what changes GM made there. :hug:
 

hntngkd

Member
Jun 24, 2013
162
5
18
Attica, Mi
I did a little CAD work this afternoon with what we know about the new crank. Pretty interesting stuff. A .200 increase in diameter (without any decrease in rod journal width) increases the cross section between the second main journal and the first rod journal by almost 7%.

A 7% increase in cross section is exactly what we ended up with when we reduced the rod journal width on our billet cranks at the beginning of this year.

Code name NR for narrow rod journal. Fundamentally we machine the excess width off the big end of the rod (.125) that is already wider than the stock rod bearing. The cranks are manufactured with rod journals that are .250 narrower than stock Dmax. The result is crankshaft counterweights that are .125 wider. This means much less weight has to be added to the damper and flywheel for balancing. In effect moving more towards an internally balanced crankshaft. :)

The only two drawbacks I see to the 2017 crank is an increase in bearing surface speed with the larger diameter. Which is not really a huge issue at our crank speeds. We rarely see problems with rod bearings. The second is weight. All things being equal, increasing the rod journal diameter has added weight to that side of the crank, (similar to adding weight to the big end of the rod) which means it needs to be counter-weighted for balance in some fashion. If GM wasn't able to add mass to the counterweights, they had to add it to the damper and flywheel. :(

I can't wait to get my hands on the new cam and cylinder heads to see what changes GM made there. :hug:

The heads are much more open, not rectangular ports cut into a flat surface. They definitely look like they flow much better than previous years heads.
 

lil bleur

Its all good until..BOOM!
Oct 6, 2015
151
0
0
York PA
I could be wrong, but that has to be a misprint. The Tier 3 QSB7 Cummins engines that we do here at work on our generators don't have any of that downwind exhaust stuff and they still are using the ancient HX35W turbos. We don't have any VGT/SCR stuff other than on our Tier 4 final units. I heard Tier 4 Final has to be standard across the board everywhere by the end of 2017. We are low enough production that they allowed us that long. I would have thought that the light duty diesel industry would have been tier 4 compliant for quite a while now like since 2011 or something.
I first will say I don't know all about the "emissions standards" That only says tier 3, what's the difference between that and 4? Jw I think it's odd that a highway engine is 3, but our OFF-ROAD ONLY cranes have tier 4 final Cummins already
 

NC-smokinlmm

<<<Future tuna killer
May 29, 2011
5,201
363
83
At Da Beach
Awesome!!! Some real improvements! Glad I didn't go buy a 16......

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Your willing to pay 10 grand more for an unproven platform? I use my truck to make money so it has to perform, I went with a proven setup. In a couple years when they get all the little bugs worked out and freshen up the front end I'll go buy one. Untill then I'll enjoy my LML...:D
 

IOWA LLY

Yes, its really me
Feb 23, 2007
2,275
4
0
Your willing to pay 10 grand more for an unproven platform? I use my truck to make money so it has to perform, I went with a proven setup. In a couple years when they get all the little bugs worked out and freshen up the front end I'll go buy one. Untill then I'll enjoy my LML...:D


Saving 10 grand is all fine and good. But paying 50K and suddenly it's outdated would just really upset me.

I know that everyone would ask, "Hey is that one of those new 17s"?.......... And of course it wouldn't be.

So 50K for old and obsolete. Or 60K (maybe) for the newest latest greatest. Or what, maybe $100 a month more. I'll bet most people would gladly pay that a month just to have a stronger crank in there current Truck.

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Mike L.

Got Sheep?
Staff member
Vendor/Sponsor
Aug 12, 2006
15,681
232
63
Fullerton CA
If the cutaway of the trans is correct, it still only has 4 c3's.

You are correct. The final sign off on the Allison was done in Oct 2014. The new engine was being tested at that time. There were some software changes to the TCM to increase pressure on the 4/5 shift that I observed with my pressure gauge on the 2016. They probably increased it for 2017.
 

IOWA LLY

Yes, its really me
Feb 23, 2007
2,275
4
0
You are correct. The final sign off on the Allison was done in Oct 2014. The new engine was being tested at that time. There were some software changes to the TCM to increase pressure on the 4/5 shift that I observed with my pressure gauge on the 2016. They probably increased it for 2017.
Wow.... Pressure increase or not over 900 ft lbs of torque seems like an awful lot for 4 C3 clutches.....

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Sparky21

New member
Jul 15, 2016
4
0
0
Pacific NW
Can someone clarify on the rods. It says "Forged Powdered Metal", another article said "Forged and Sintered with a durable powdered metal alloy". So hopefully this is translating into a forged rod, with some type of powdered metal coating?

The rod itself is made of metal alloy that has been "ground" (or otherwise prepared) into a fine powder. This powder is then molded into the shape of the part. The molded part is then heated in an oven to the sintering temperature-not quite to its melting point but high enough to bond the powder into one piece of metal. The part is then forged.
It is somewhat similar to injection molding of plastic-only with metal. Its a common manufacturing method and can yield some high quality parts with consistent properties through the "casting". Generally has a nearer neat shape than traditional casting-meaning that the part requires less post machining.
 

Ridin'GMC

I like red
May 20, 2010
638
20
18
MA
They won't hold the power.

Why would GM allow the new engine to make that much torque if the current Allison isn't going to handle that power? Is there a possibility that the Allison will be updated for 2018 after the possible issues that may happen in stock power with the transmission for the '17 model?