LFD2037

Have any of you put some decent power into your truck that have the factory 6 speed auto yet? I was wondering how durable/dependable that tranny is. TIA

LFD2037

Nobody has put it to the test yet?

Lil Dog

I have some reports that the new 6.7Smarty can put the hurt on it with low levels of input. Maybe 100 Hp? Patiently waiting for that little toy to hit the market.

LFD2037

Man, ya'll need to get on the ball!!! Unless there just isn't any power acc. out yet.

no_6_oh_no

I'd worry more about the engine than the trans. The 6.7 has a limited ability to handle additional power. It looks like the typical mods, pressure & TC , will suffice but not a lot of them out yet.

ChrisM55

Not sure where you are seeing your info but there are guys on another site running huge numbers. These engines can handle the power but most of them are running manuals for pulling. I know that one guy is running twins and a few with big HP stacked and water/meth kits.

I have been seeing a few little quirks with my 68rfe lateley with my Edge on 5 but I am thinking it is more of a program issue than with the trans. It can't make up it's mind of where it wants to be and down and upshifts really quick and kinda jerks ya

Chris

no_6_oh_no

Never said they couldn't make power, power is only fuel after all.

The block design is going to interfere with a 6.7 making big HP and keeping its integrity. Push big power too long and the 6.7 will eat itself up. Just not seeing it yet. The longevity of the 6.7 will be much more effected by power than the 5.9 ever was.

LFD2037

I was refering to the strength of the 6 SPEED AUTO.

Ace

Because why?

txfiremedic

Just curious as to where you are getting your info?

no_6_oh_no

Well, your not adding power by bombing the trans. As with any 3 pinion band centric auto trans they will be stronger to a point then become problematic. Once you hit a certain power level or need shifting capability, well, there is a reason a lot of D-Max powered trucks are using 48RE's to handle the duties.


Thats easy, siamesed cylinders. Previous attempts at using this type of design and diesle engines have met with very limited success. Realtively cool gas applications work a lot better than the high compression high temp applications.

With the cylinder design there is now a pretty large area on each bore that is not directly water cooled. There is the potential at some point to have some radically different expansion\cooling changes in a cylinder that needs to stay pretty close to round at all times. Taking a cylinder frm round to oval, even by a few thousandths, is going to cause some strange wear patterns on rings and bores. Aside from the creep in the head gasket is several directions and varying degrees, there is a more of a danger of the pistons expanding from too much heat and scoring the cylinders.

Second problem is the harmonics generated in the engine with the high compression combustion. No there is even more of a channel for harmonics to travel back and forth and possibly build on each other. Literally, at some point the block is going to ring like a bell from the harmonics. That can lead to metal fatigue in certain areas and the possibility of amplifying existing flaws. In the cylinders you now have the equivalent of pressure waves starting pistons oscillating in the bores and once that hits critical they start bouncing off the sides of the bores.

The big question is when will it happen. Cummins has obviously done a lot of testing and implemented measures (up to 5 injection events, different materials in the block, EGR, etc) to reduce the possibilities, but, once you step beyond the OEM settings its a crap shoot.

Its not that they can't\won't make big power but rather the range of power they can make without catastrophic failure has been narrowed, some will say considerably. All the engineers that know way more than I know about this stuff agree there is potential for problems and all agree there are many factors that will drive it.

Time will tell how good the engineering, metal casting, etc, is at addressing the potential problems. There is just not enough info yet to say one way or another what the reality will be.

LFD2037

I wasn't saying a bombed tranny. I was saying a bombed truck(engine). I was wanting to know if anyone has made some serious power w/the 6.7 & still had the 6 speed auto that is bone stock. Sorry for the confusion.

DR3500

I have seen a Power Pup kill a 68rfe. 4WD boosted launches on 35" tires @ the dragstrip is what did that one in.
I have the same programmer/engine/trans combo but with 37" tires so I am justifiably worried about mine. I can promise I WILL not be doing any boosted launches with mine! I will probably invest in the full Suncoast setup when I can afford it.

Lil Dog

Do we have any data on the MNF (Mechanical Natural Frequency) of the block with water and all recip/rotating parts installed to be sure that it is going to be coincident with any run speed or harmonic from combustion? Stiffening of the block will result in higher MNF and possibley less likely to coincide with combustion harmonics in the 2.5Khz to 10Khz range.

I would like to see this data...