Originally Posted by LantanaTX
I have been running the V6 trans behind my V8 for the last 20K miles and all is good. My engine has 330 ft lbs of torque which is more than a SRT. ""knock on wood". I talked to a shop that builds performance Nag-1/722.6 trans and was told the only difference was the clutch packs. The SRT trans is pretty much the same torque rating as most of the n/a V8's. The 55K had an even higher torque rating and the and the ones that were bolted to the twin turbo V12's had the highest rating. I am not sure how accurate the ratings are becasue the new 7 speed is rated hgher than the n/a V8 trans and has proven to be easier to break.
I would have thought I would have at least seen an "over toque" fault, but his has never happened. I haven't worried too much as replacement used trans are easy to find at resonable prices. I was also told that I could put my gearing into a V8 trans/case which would result in my excellent gearing with higher torque capability. One reason, my trans might be holding up is due to the fact that MB also put the V6 and V6 version trans in the big S class. Our cars weigh a lot less which helps the trans. Btw, my tans also has 93,000 miles on it. The only problem I ever had was the speed sensor which is part of the conductor plate going bad. I replaced this a couple of weeks ago and installed the blue tops at that time.
Let's dissect this shall we as there is so much more to this than meets the eye. First, to counter your fortunate situation, don't forget chucknorris and how he fried his tranny with a less torque than what you are putting down. Second, saying the only difference is the clutch packs is an oversimplification to the extreme. That "only difference" equates to a 180 ft/lb rating by a conservative OEM! Do you realize how close to double the rating of our tranny that is? Why didn't they just use the same in both?
IIRC the clutch packs are not only beefier but I want to say there was at least one more set. You can read about this "difference" over and over and it is most often exaggerated versus minimized.
That said, there are SEVERAL other real world factors that come into play (above and beyond ratings) as I have explained in pm's. Neither your situation, mine, nor that of chucknorris will be indicative of all. There are simply too many variables to consider.
First, driving style. How much do you baby your car compared to the next guy? How much do you or the next guy floor it from 5th on the highway to show off to a friend and risk turning your tranny into a hot tub of goo? How much do you use the tiptronic versus automatic?
Second, production quality, defects, etc. Did you get the luck of the draw or not? That is always a fun one to live with when pushing your car on the track!
Third, supporting modifications. Do you have the blue top solenoids or stock? Do you have increased cooling capacity or at a bare minimum a tranny temp gauge when pushing that hard on an under rated tranny?
Last but not least. Regardless of torque, it is often said that "traction" kills a tranny not torque. What kind of tires do you have? Crappy stock tires, widened rims and tires, drag radials, slicks? This kind of goes along with your lightweight argument but what happens when you truly "do" something with that torque? That is the gist of this comment, not that torque doesn't matter, but it is what you do with it that is of the greatest concern or impact.
Want to run street tires and show off how easy it is to light them up or let traction control be your friend? Well, in this case a tranny may very well be able to handle way more than rated for a very long time. In fact miles don't matter as much as the type of miles put on the car for sure. When you decide however to get serious about putting that power to the ground, that is when bad things typically start to happen and the dollar signs increase. I've seen more than one overly optimistic car owner add slicks to their bright and shiny FI kit and find themselves renting a trailer to make it home
on cars with much more margin than ours (factory output versus trans rating).
Personally, I'm making a well educated decision to swap trannys for one that is rated higher than what I need for longevity. At the same time, doing so prior to frying my old unit (which I consider inevitable). I'll be able to recoup some of that money by selling a perfectly good stock tranny. It is a good investment in peace of mind.
In fact, I would advise people considering the turbo kit in development to read what I've posted here. I'm not going to hijack your thread to speak to this but as I said in PM's, I hope you at least advise the first prototype cars to monitor their tranny temps for a while until they feel safe and/or get better educated on tranny temps. The typical turbo configuration makes a huge torque peak at their boost threshold. This can be a tranny killer in much better situations than ours. Especially for an aggressive driver that does multiple pulls back to back without letting the tranny cool down!