4spd first gear choice.

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cudaman51

cudaman51

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Im puting together a streat and strip 69 barracuda with a 340 indy rhs x heads 3.91 25 or 6 inch tires and comp cam xe275hl cam. i have parts to build either the 2.5 or 3 to one first gear mopar 4 spd. whats the opinions out their on witch is best choice.
 
Mighty short tire. I would do the 2.5 either way.
 
i always thought the only ratios available were 2.45 in the close ratio, 2.66, and the 3.09
 
I you're talking about the 3?? to one first in the factory A833's used in the /6's and 273, those boxes are not nearly as strong as the others. Mainshaft is smaller because of the low first gear.
 
The 3.09 first gear trannies are just as strong as any other 833. The gear sets in the low gear trans ( made from 64 to 66 in /6 and 273 a bodys and again from 73 to 75 in Dart Sports and Dusters with 318 and 2.76 rearend gear) are innerchangable with all 23 spline trans. as a complete gear set. The only gear sets that where not innerchangable are the ones from the overdrive 833's
 
the /6 gear set from the early abodies is fine.
the difference was some had the small, 904 output shaft size and some smaller bearings on the mainshaft.
as far as gears go they interchange with the larger mainshafts that accept the 727 size output, totally interchangable.
As far as your gearing question, 3.09 and 3.54 (10.93 overall 1st) with 27" tire is about right for me.
2.66 1st with 3.54 (9.41 overall 1st) not enough gear for me.
but 2.66 with 3.91 (10.4 overall 1st) may be fine.
depends what you like.
Do the math.
 
theclutcher said:
...............the difference was some had the small, 904 output shaft size and some smaller bearings on the mainshaft.........................
as far as gears go they interchange with the larger mainshafts that accept the 727 size output, totally interchangable........................
Click to expand...

I want to be sure I understand you----you are saying that even though you have a box with the small shaft, all the gearing would fit a large shaft?

'S been awhile, I don't remember that
 
Why not phone Passon or Brewers and talk to a tech that does this for a living?
It might be worth a shot to get their opinions too.
Phone both of them and compare with what everyone has to say here.
Food for thought.
 
I ran an O.D in my 340 Dart and it worked great ! launched @ 5k with 1.6 60ft times running 4.10's and cruised at 75 mph somewhere around 2800 rpms . You'll lose a tenth or so on your ET , but if you want a true dual purpose car and you're on a budget .

Race with 1-2-3 and cruise with 4th . Besides the aluminum case saves some lbs....
 
I said 2.5 and 3 not knowing the exact numbers. I have one with a 2.45. and one that had the 3.09 put in it.I was thinking the 2.45 wouldnt be low enough and the 3.09 would be a large jump from 1st to second. I wised i had the 2.66 one. I would be using it.
 
cudaman51 said:
I said 2.5 and 3 not knowing the exact numbers. I have one with a 2.45. and one that had the 3.09 put in it.I was thinking the 2.45 wouldnt be low enough and the 3.09 would be a large jump from 1st to second. I wised i had the 2.66 one. I would be using it.
Click to expand...

from what i know, those 2.45 close ratio boxes can fetch a pretty penny, especially with guys doing challenger T/A or AAR cuda restos/recreations...if you sell it you should have more than enough for a 2.66 box
 
Really you want a minimum a 10.1 start ratio for drag racing,to figure out your start ratio you divide the first gear ratio by the rear ratio.My car has a 3.09 first gear trans and 3.23s and I have a 9.98 ratio,basicly my car will launch the same as if I had a std gear auto and 4.10s (10.04).
 
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