Ordering New Transmission, but What Gears ?

Aubrey N Bruneau · 03-30-2014, 12:02 PM

I sold my 2.83 1st gear Jerico DR4 a few months ago ( thanks to Class Racer ! ).
Time to order the replacement.
I have the new whizzy ( for me anyway ) Advanced Clutch system now.
Obviously, my previous selection of a 2.83 1st gear was a miss-match. Most guys have told me that I need like around a 3.20. When I spoke with the guy at Jerico, he recommended no more than 3.08. His reasoning being, that the engine doesn't rev high enough. Sounded logical. Engine makes peak torque at 4500/4600 RPM

Car scales at 3635
Shifted at 7000
Thru traps at 7200 / 7300
Best previous 60 ft was 1.59

Sean Marconette · 03-30-2014, 01:27 PM

What was your SLR with the other first gear? 3.08 seems like not enough. The higher numerical gear the more you can work the clutch and accelerate the car

Sean

mopacltd · 03-30-2014, 01:37 PM

My thought would be to go to a 3.25 first

Bill Belden · 03-30-2014, 03:18 PM

I would go with 3.19 first

Aubrey N Bruneau · 03-30-2014, 04:27 PM

SLR ?
HHMMM...
"single lens reflex" camera ? ? ! !
You have to remember who you're dealing with here... the guy who shows up to increase car count, and give the new guys somebody to beat in the first round !
really don't know what SLR stands for

Thanks, guys. That's what I keep hearing from everybody but Jerico.
torque is pretty good on this engine... 490 ft lb, so I'm thinking recovery might not be such a monumental obstacle.

Rory McNeil · 03-30-2014, 05:26 PM

SLR equals Starting Line Ratio. 1rst gear x rear axle ratio.
example, 2.88 x 4.88 is 14.06 SLR.
My Mustang with 3.19x5.13 is 16.36 SLR. I would like even more SLR, but with the steeper 1rst gear, and only a 4 speed, the ratio drops thru the gears get pretty wide. Not as much of a problem for a big engine with good torque, but then you are also pulling a lot more weight.
Also, don`t forget that an engine that doesn`t like a lot of RPM will have less rear end ratio, so to get the SLR more favorable, the only other choice is more low gear. Of course more SLR also increases the chance of wheelspin......

henrys57wagon · 03-30-2014, 05:31 PM

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

03-30-2014, 05:55 PM

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 · 03-30-2014, 07:09 PM

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 · 03-30-2014, 08:55 PM

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.

03-30-2014, 12:02 PM	#1
Aubrey N Bruneau Member Join Date: Sep 2003 Location: South Eastern Alberta, Canada Posts: 311 Likes: 6 Liked 7 Times in 3 Posts	Ordering New Transmission, but What Gears ? I sold my 2.83 1st gear Jerico DR4 a few months ago ( thanks to Class Racer ! ). Time to order the replacement. I have the new whizzy ( for me anyway ) Advanced Clutch system now. Obviously, my previous selection of a 2.83 1st gear was a miss-match. Most guys have told me that I need like around a 3.20. When I spoke with the guy at Jerico, he recommended no more than 3.08. His reasoning being, that the engine doesn't rev high enough. Sounded logical. Engine makes peak torque at 4500/4600 RPM Car scales at 3635 Shifted at 7000 Thru traps at 7200 / 7300 Best previous 60 ft was 1.59 __________________ Aubrey N Bruneau 6409 C/S 62 BelAir sport coupe, 409 HP 409

03-30-2014, 01:27 PM	#2
Sean Marconette Senior Member Join Date: Mar 2006 Posts: 976 Likes: 780 Liked 274 Times in 76 Posts	Re: Ordering New Transmission, but What Gears ? What was your SLR with the other first gear? 3.08 seems like not enough. The higher numerical gear the more you can work the clutch and accelerate the car Sean __________________ Sean Marconette 84 Mustang 5060 SS/N

03-30-2014, 01:37 PM	#3
mopacltd Member Join Date: Aug 2009 Location: yarnell,az Posts: 311 Likes: 387 Liked 119 Times in 43 Posts	Re: Ordering New Transmission, but What Gears ? My thought would be to go to a 3.25 first

03-30-2014, 03:18 PM	#4
Bill Belden Member Join Date: Jun 2002 Location: York, PA Posts: 241 Likes: 0 Liked 1 Time in 1 Post	Re: Ordering New Transmission, but What Gears ? I would go with 3.19 first __________________ Bill Belden Retired Stock Eliminator [emailSTK1100@comcast.net[/email]

03-30-2014, 04:27 PM	#5
Aubrey N Bruneau Member Join Date: Sep 2003 Location: South Eastern Alberta, Canada Posts: 311 Likes: 6 Liked 7 Times in 3 Posts	Re: Ordering New Transmission, but What Gears ? SLR ? HHMMM... "single lens reflex" camera ? ? ! ! You have to remember who you're dealing with here... the guy who shows up to increase car count, and give the new guys somebody to beat in the first round ! really don't know what SLR stands for Thanks, guys. That's what I keep hearing from everybody but Jerico. torque is pretty good on this engine... 490 ft lb, so I'm thinking recovery might not be such a monumental obstacle. __________________ Aubrey N Bruneau 6409 C/S 62 BelAir sport coupe, 409 HP 409

03-30-2014, 05:26 PM	#6
Rory McNeil VIP Member Join Date: Jun 2007 Location: from Vancouver BC Canada, now in Nova Scotia Posts: 1,291 Likes: 292 Liked 1,052 Times in 287 Posts	Re: Ordering New Transmission, but What Gears ? SLR equals Starting Line Ratio. 1rst gear x rear axle ratio. example, 2.88 x 4.88 is 14.06 SLR. My Mustang with 3.19x5.13 is 16.36 SLR. I would like even more SLR, but with the steeper 1rst gear, and only a 4 speed, the ratio drops thru the gears get pretty wide. Not as much of a problem for a big engine with good torque, but then you are also pulling a lot more weight. Also, don`t forget that an engine that doesn`t like a lot of RPM will have less rear end ratio, so to get the SLR more favorable, the only other choice is more low gear. Of course more SLR also increases the chance of wheelspin...... __________________ NHRA 6390 STK M/S 85 Mustang

03-30-2014, 05:31 PM	#7
henrys57wagon Member Join Date: Jan 2009 Location: Carleton Place, On. Canada Posts: 107 Likes: 5 Liked 0 Times in 0 Posts	Re: Ordering New Transmission, but What Gears ? 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 __________________ old 1608 stock racer

03-30-2014, 05:55 PM	#8
Todd Hoven Guest Posts: n/a	Re: Ordering New Transmission, but What Gears ? 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

03-30-2014, 07:09 PM	#9
james schaechter VIP Member Join Date: Dec 2004 Location: Cumming GA Posts: 1,976 Likes: 1,259 Liked 1,384 Times in 288 Posts	Re: Ordering New Transmission, but What Gears ? 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. __________________ James Schaechter 3163 STK

03-30-2014, 08:55 PM	#10
Aubrey N Bruneau Member Join Date: Sep 2003 Location: South Eastern Alberta, Canada Posts: 311 Likes: 6 Liked 7 Times in 3 Posts	Re: Ordering New Transmission, but What Gears ? 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. __________________ Aubrey N Bruneau 6409 C/S 62 BelAir sport coupe, 409 HP 409