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-   Drag Racing Discussion (http://www.ramforumz.com/forumdisplay.php?f=135)
-   -   2nd prime (http://www.ramforumz.com/showthread.php?t=100219)

blue beast 12-31-2011 08:39 PM

2nd prime
 
ok why is the third called 2nd prime, to me its just a short third? just wondering thanks.

Dodge891 01-02-2012 03:04 AM

thats how i always heard of it as well if anyone does know that would be a nice topic and why is it caleld that

brad12kx 01-02-2012 11:18 AM

'2nd Prime' sounds better than 'Short 3rd' :4-dontknow:

Although it's a small step from 2nd, it is usable and under certain circumstances, useful.
Because of this small step, I'm sure they were reluctant to include it in the step sequence as a 'real' gear until pressure came from the Marketing departing to have a 6 speed trans.

Personally, I find it rather amazing that in this day and age we have a transmission with 6 speeds and the bottom 4 gears are not spaced better. May be this the result of a new breed of engineers that have come from the early 'video game for entertainment' era......but that is such a cynical thought. :D

FrostKing 01-02-2012 01:55 PM

Our truck transmissions are still a 40 yr old 3-speed automatic with two over-drives, hence the poor gear spacing.

sprintertech 01-02-2012 02:14 PM

2nd prime is utilized as a passing gear....in most cases your trans wont downshift to 2nd for passing....to shift to 2nd it would be letting go of 2 clutches and grabbing 2 new clutches resulting in a rpm flare up...for 2nd prime it only needs to let something go at most speeds....its also available in tow haul mode if load demands or if manually shifted you will go into 2nd prime before 3rd.....in the 2012 models it will also 2nd prime at wot upshifts also....6spd technically.....marketing ploy definitely! they should build a real 6spd where 4th or 5th is 1:1......

brad12kx 01-02-2012 02:50 PM

How about an 8 speed....;)
4 on the bottom, 1 direct and 3 OD; all spaced to keep the Hemi in the prime power range at WOT.

In my dreams, this is offered in 2013.... :D

TNC 01-03-2012 11:50 AM

While transmission gearing can be a little bit preferential, I found just the 4 speeds in my old '89 GM 700-R4 to be more than adequate when mated behind a decently powerful, torquey engine. I did some serious 4-wheeling and towing with that setup, and it did just fine. The tranny has a low 1st and well spaced gearing up to the 4th which was an overdrive. While the gearing performed well, that model of tranny needed some good mods to make it work well and live long, and I had those done to mine.

I know that closer spacing with more gears maintains keeping the engine in its rpm-to-power sweet spot. On a truck with a decently wide torque and power band, is this as critical? Now we're talking about 8 speeds and such, and while I agree there's benefit, is perhaps some of this being driven by marketing hoopla a bit? And I realize why semi's have many gear selections to optimize their hauling capacity and economy, but that may be a stretch of a comparison for a 1/2 ton pickup. Still, I know there's some application even then. I'm thinking sometimes that 4 or 5 gears max, designed in a more robust and stouter package would be better than 8 gears in a package where they're trying to cut weight and increase fuel economy...at least on a pickup. All the money saved in fuel economy can quickly evaporate when you get the $1500-$3000 repair bill on your whizbang 12-speed auto...LOL!

And please don't take my comments as argumentative on this issue. I just wonder sometimes...are we overdoing it? And don't get me wrong. I love more, more, and even some more when it comes to power, bells-and-whistles, and hoopla as much as anyone...LOL!

One other question, because I'm new to Dodge. I'm sure I could research this one, but the comment made here about this tranny being based on a 40 year old design...if that's true, does this mean this tranny is just a redesigned Torqueflite?

AllUCIsTailLights 01-05-2012 04:47 PM

Quote:

Originally Posted by brad12kx (Post 686055)
How about an 8 speed....;)
4 on the bottom, 1 direct and 3 OD; all spaced to keep the Hemi in the prime power range at WOT.

In my dreams, this is offered in 2013.... :D

That would be a dream come true if so it would be the perfect time to get a 2013! ill be done paying for the one i have this year.:smiley_thumbs_up:

2011lilred 01-06-2012 07:22 AM

Quote:

Originally Posted by FrostKing (Post 686020)
Our truck transmissions are still a 40 yr old 3-speed automatic with two over-drives, hence the poor gear spacing.

Quote:

Originally Posted by TNC (Post 686617)
One other question, because I'm new to Dodge. I'm sure I could research this one, but the comment made here about this tranny being based on a 40 year old design...if that's true, does this mean this tranny is just a redesigned Torqueflite?





While the 545RFE came from the 45RFE and one could argue the 45RFE is based on the Torqueflight family with additional planetary gears, the gear spacing issue is has nothing to do with it since the 727 uses 2.45:1 in first, 1.45 in second, and 1.00 in third while the 545RFE uses:
  • 1st 3.00:1
  • 2nd 1.67:1
  • 2nd Prime 1.50:1
  • 3rd 1.00:1
  • 4th 0.75:1
  • 5th 0.67:1
(Note the similarity to the 700R4 ratios of 3.06, 1.63, 1.00, 0.70)

If you take 2nd Prime out of the upshift sequence, the gear spacing is just fine. The whole 2nd Prime gear came about simply as a taller passing gear to avoid downshifting all the way down to the 1.67 gear when you stomp on it on the highway. As you would likely be in an overdriven gear at the time, jumping all the way down into the traditional 2nd gear causes rpms to skyrocket - again, note the similarity to the 700R4.

2nd Prime was not originally intended as an upshift gear, it just morphed into one.

TNC 01-06-2012 10:37 AM

Quote:

Originally Posted by 2011lilred (Post 688722)
While the 545RFE came from the 45RFE and one could argue the 45RFE is based on the Torqueflight family with additional planetary gears, the gear spacing issue is has nothing to do with it since the 727 uses 2.45:1 in first, 1.45 in second, and 1.00 in third while the 545RFE uses:
  • 1st 3.00:1
  • 2nd 1.67:1
  • 2nd Prime 1.50:1
  • 3rd 1.00:1
  • 4th 0.75:1
  • 5th 0.67:1
(Note the similarity to the 700R4 ratios of 3.06, 1.63, 1.00, 0.70)

If you take 2nd Prime out of the upshift sequence, the gear spacing is just fine. The whole 2nd Prime gear came about simply as a taller passing gear to avoid downshifting all the way down to the 1.67 gear when you stomp on it on the highway. As you would likely be in an overdriven gear at the time, jumping all the way down into the traditional 2nd gear causes rpms to skyrocket - again, note the similarity to the 700R4.

2nd Prime was not originally intended as an upshift gear, it just morphed into one.

Thanks for that info on the trans background and ratios. I realize that this is the drag racing forum segment, and more gear selections usually relate to better performance times/numbers.


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