Re: Swap a 3.55 on a rear end 8-3/4 to 2.93 need advice please
[Re: SunnyMopar]
#2551436
09/18/18 11:37 AM
09/18/18 11:37 AM
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Joined: Sep 2007
Posts: 14,889 up yours
Supercuda
About to go away
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About to go away
Joined: Sep 2007
Posts: 14,889
up yours
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I'm just curious as to how you came to the decision that this forum was the best place to ask this question. Near as I can figure it has nothing to do with handling.
Maybe you should decide what RPM you want to run at and then do the math to figure which gear would be closest.
They say there are no such thing as a stupid question. They say there is always the exception that proves the rule. Don't be the exception.
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Re: Swap a 3.55 on a rear end 8-3/4 to 2.93 need advice please
[Re: krautrock]
#2551495
09/18/18 01:53 PM
09/18/18 01:53 PM
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Joined: Dec 2003
Posts: 22,696 Bitopia
jcc
If you can't dazzle em with diamonds..
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If you can't dazzle em with diamonds..
Joined: Dec 2003
Posts: 22,696
Bitopia
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Assuming you are in the handling section for a reason, that also likely means a shorter tire, then you may actually might as well look for a more common 2.76 ratio and be done with it, you spend a lot more time cruising then accelerating, if you are on the street.
Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
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Re: Swap a 3.55 on a rear end 8-3/4 to 2.93 need advice please
[Re: SunnyMopar]
#2551570
09/18/18 04:38 PM
09/18/18 04:38 PM
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Joined: Jan 2010
Posts: 1,442 NW Chicago suburban area
Mopar Mitch
pro stock
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pro stock
Joined: Jan 2010
Posts: 1,442
NW Chicago suburban area
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I've highway driven with 4.30, 3.91, 3.55, 3.23... and loooong time ago 2.76. The car was typically going to an autocross, or road race track (and occasional car show or cruising).
Currently I'm running the 3.23.. excellent gear for hwy cruising and HHPDE/HSAX and pylon AX... you'll learn the gears (1-2-3, 727) to run whatever event your involved in.
With the 3.23 I can run 1st gear in most pylon autocross events; briefly 2nd, then back to 1st.
With the 3.55 I found it necessary to be 2nd gear more often (slower AX times).
The 3.91 was great; the 4.30 was also great (although too much 1st gear tire spinning and used 2nd more often).
At track lapping events (HPDE/HSAX) the 3.23 is good.. lots of 2nd gear then 3rd gear. The 3.55 needed 3rd gear more often but lost top end mph. The 3.91/4.3 track lapping required 3rd gear dominantly and limited top end mph.
I also have a 2.9 ring/pinion that I'm eventually going to try; I know the 2.9 will reduce the hwy rpms by about 450-500 depending on typical hwy cruising speed (~65-75).
My thoughts with the 2.9 is longer stretches in 2nd and higher mph with 3rd gear... as well as dropping the hwy cruising rpms by 450-500 for long drives (short drives doesn't matter as much).
My engine (340-6) likes to cruise at ~3200-3500 ~65/75.
Look up one the available rpm/mph charts on the web and you can play with that to determine what you'll like. Tire diameters matter; as well as your transmission gears (727 vs stick).
Mopar Mitch
"Road racers and autocrossers go in deeper and come out harder!"... and rain never stops us from having fun with our cars... in fact, it makes us better drivers!
Check out MOPAR ACTION MAGAZINE, August 2006 issue for feature article and specs on my autocross T/A!
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Re: Swap a 3.55 on a rear end 8-3/4 to 2.93 need advice please
[Re: BigBlockMopar]
#2551574
09/18/18 04:49 PM
09/18/18 04:49 PM
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Joined: Jan 2010
Posts: 1,442 NW Chicago suburban area
Mopar Mitch
pro stock
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pro stock
Joined: Jan 2010
Posts: 1,442
NW Chicago suburban area
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O/D is the next step... which one... but major $$.
Mopar Mitch
"Road racers and autocrossers go in deeper and come out harder!"... and rain never stops us from having fun with our cars... in fact, it makes us better drivers!
Check out MOPAR ACTION MAGAZINE, August 2006 issue for feature article and specs on my autocross T/A!
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Re: Swap a 3.55 on a rear end 8-3/4 to 2.93 need advice please
[Re: RM23U0A]
#2551576
09/18/18 04:54 PM
09/18/18 04:54 PM
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Joined: Nov 2007
Posts: 21,819 Kirkland, Washington
Pacnorthcuda
Too Many Posts
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Too Many Posts
Joined: Nov 2007
Posts: 21,819
Kirkland, Washington
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Yes, It has been done went from 3.91 to 2.76 on an AAR auto. and 3.23 on another 340 car. The rpm`s dropped to 2600 at 60 with the 2.76. I used a short tire. Drag racing performance changed little; just had to manually shift once in the quarter. Did not need third. Good luck, Wayne I'm having a bit of trouble processing a change from 3.91 to 2.76 having "little" change on drag racing performance. In fact, I'm having a LOT of trouble with that....
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