Hi George, glad you asked, gives me an opportunity to answer it once for everybody.

 

 If you mean 'what problem would it be for me' the answer is "No problem at all".  Except for scrapping every part of the current design, scrapping all the tooling developed for it,  scrapping all the production procedures (this is no small thing) and replacing all this with new stuff.

 

Obviously, there has to be a good reason to do this to make it worth while.  It has to solve an existing problem  (are there any?), significantly improve performance (would it?) or reduce cost enough to justify all the work and expense of changing (does it?).

 

I'm sure that Dodge gear set is a fine piece of hardware but what does it give us?  It has a smaller diameter ring gear (4.4" vs 5.0") narrower gears (about 3/4" vs 7/8") and one less planet.  On paper, this looks like a minus, not a plus.  The availability of straight cut gears is a possible bonus but on the other hand, I have not had any problem dealing with the helical gear thrust so far. 

 

The splined sun gear might be nice but so far we are paying a pretty high price for it.  A lot of other factors need to be considered.  For instance, How do you isolate the oil in the gear box when using that mating splined part?  Is there a place to put an oil seal?  There are literally hundreds of questions like this that must be answered during the course of designing a gear reduction drive. 

 

As far as the ratio goes, 2.85 : 1 is actually a bit higher than optimum for most applications.  Going even higher is the wrong direction.  Note that I said "most applications".  There will of course be some that would favor a higher one.  A detailed discussion of this would be interesting but is way more involved than I can detail in an email message.  But, to summarize, I believe fuel economy, engine life, and proper matching with a suitable prop would suffer with a higher ratio.

 

Anecdotal data from people in the auto transmission industry has been contradictory at best.  It's the Chevy vs Ford vs Mopar thing all over again.  I give the Ford guys as much credit as the Dodge boys -  Zero.

 

I know Paul L. pushes for more power at every turn (higher rpm (requiring higher ratios), P porting, etc) but I think this focus is counterproductive in too many other areas.  I'm more in tune with Richard Vangrunsvan's goal  -  Total Performance.

 

You also asked why I was previously opposed to changing from 2.17 to 2.85.  Note that I did not change.  The 2.85 is in addition to the 2.17 which is still in production.  There are plenty of applications where the 2.17 is clearly a better choice than the 2.85.  There are still times when I would prefer the 2.17 on my own plane.  Some of the reasons are subtle and not quantifiable.  I like the BMW better than the Chevy I drove but I couldn't give you any hard reasons for it.

 

Tracy (now stepping off soap box)