Ordering New Transmission, but What Gears ?

[henrys57wagon]

Aubrey, SLR= starting line ratio. Here is a calculator.
When we raced I was one of the cars to increase count, did get into 2nd round the odd time at division meets.

http://www.wallaceracing.com/calc-slr.php

Go with at least a 3.19 or higher. The lower the first gear, the lower you can go starting line rpm and use the tq of that engine to get it moving. The higher you leave, the better the chance of not hooking that car. The slower wheel speed, with give the tires a better chance of hooking. IMHO

[james schaechter]

Consider a 3.19. The 3.29 is a 34/15 gear and is not as strong as the 33/15 that the 3.19 has. Could be a concern with yout torque and weight combo. Plus the 3.19 can easily be converted to a 3.08. Stay away from the 3.17 also. It is a 34/16. The 34 tooth mdg is not as strong. Same diameter gear only one more tooth crammed in.

[Aubrey N Bruneau]

This is fantastic info, people... no wonder I come in here !
My combination had a 14.52 SLR. Yes, I did use to leave at pretty high RPM... about 6200.
Never did really hook up.

Have to make a decision pretty soon, so I can get the transmission under way.

[Sean Marconette]

The statement on what is considered a good SLR being 9,10, or 11 for the Walace Racing calculator might be fine for automatics but is completely wrong for a stick car. We do not have a torque multiplier. So our SLR will be higher. Sorry I did not elaborate on SLR earlier.

So what clutch did you get? The dual 7" is very user friendly and extremely predictable.

Sean

[Aubrey N Bruneau]

No, not quite that exotic, Sean. Still just single disk. Rob set it up so it has a "soft hit".

[BRIAN SEATE]

You also have to look at the strongest column with regard to gear selection. We have a 3.08 Jerico in our Vette, but the car is light at 3000 pounds . The old Doug Nash was a 3.25. I would try to talk to Richard Feldman if possible. I don't know him but hes been at it for a long time with the big car and stick. Good luck my friend.

[Adger Smith]

Aubrey a little math:
3.19 1st gear to a 1.91 second is a 40% drop 7,000 - 40% =drop to 4,200
3.08 1st gear to a 1.91 second is a 38% drop 7,000-38% = drop to 4,340
after you get past the first gear:
1.91 second to a 1.32 3rd is a 30% drop 7,000 - 30% =drop to 4,900
1.32 3rd to a1 to 1 is a 24% drop 7,000-24% = drop to 5,320
you always want the % drop less as the gears go up. The 1.91 may have just a little too much drop with either the 3.19 or the 3.08 with your high torque engine it migh not. Either way I would try to work it from peak Tq to peak HP since it is not an RPM combination. This ain't your Dad's Small Block Chevy! That low gear will have to be determined by testing just how much "Hook" you really have.
When I ran a stick I kept 2 low gear ratios and 2 different weight flywheels to tune to track conditions and available "Hook"
Keep in mind that if you are crossing too high at the finish line you can always take a little rear gear out and add the starting line ratio back with low gear in the tranny.
More Math: pick your poison!
2.83 X 5.13 = 14.52 That you had trouble hooking @ 6,200 leave
3.19 X 5.13 = 16.37 Proably too low leaving at a high RPM
3.08 X 5.13 = 15.80 leave at just above peak Tq 4,300
3.19 X 4.88= 15.57
3.08 X 4.88 = 15.03
That is the beauty of using a stick. You can vary the leave RPM, clutch and gearing combos and do like Todd said, Drive it off the line!!
just my .02 for free!
Good luck.