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

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

Re: Ordering New Transmission, but What Gears ?
 

My thought would be to go to a 3.25 first

Re: Ordering New Transmission, but What Gears ?
 

I would go with 3.19 first

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.

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......

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

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

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.

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.

Re: Ordering New Transmission, but What Gears ?
 

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

Re: Ordering New Transmission, but What Gears ?
 

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

Re: Ordering New Transmission, but What Gears ?
 

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.

Re: Ordering New Transmission, but What Gears ?
 

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.

Re: Ordering New Transmission, but What Gears ?
 

I don't want to steal the thread but; I have always done(and read) finish line RPM,shift RPM and launch RPM calculations off of engine max HP not max torque.
May be I've been looking at this wrong!?

Re: Ordering New Transmission, but What Gears ?
 

Terry,
You are right, but he has no real RPM HP he has a torque engine. A 409 will not RPM like a SBC. You have to "work" the engine differently. If you have ever seen a 409 piston and pin you don't want to RPM one of those. Just the sheer weight will take things apart. Right Aubrey? I feel 7,000 is really pushing it. BTY you aren't stealing the thread, you are adding to the discussion.. :~)
If I was gearing a good RPM engine I would go for 8-10% RPM over peak Hp as a shift point and then figure the % gear pull back based on that to keep the engine right around peak HP. I would also work the ratios to get it in high gear somewhere around the 330' on the track.
Sean added a good point about stick cars not having the TQ multiplier of a TQ converter. The old rule of thumb that we used was add at least 20% to the low gear ratio of a stick over an automatic.
My 330 ft mark may be a little early for a stick, but a good automatic will respond to that. It would be interesting to watch a stick Comp car with about the same power to weight ratio as he has and see where it goes to high. On second thought that may not be the real deal because most all Comp cars are 5 speeds. Hummm, might be interesting just to watch!! :~)

Re: Ordering New Transmission, but What Gears ?
 

Thanks Adger. No, Terry, you're not stealing the thread.
Just looked at my old dyno chart. Same cam, using stock stamped rockers.
Here's what I have: ( stupid printout wasn't legible in places... or maybe I'm over 50 ? )

4000 450 350
4100 465 361
4200 467 373
4300 473 384
4400 475 398
4500 481 410
4600 479 420
4700 482 429
4800 479 438
4900 479 444
5000 478 456
5100 477 461
5200 477 472
5300 477 478
5400 476 481
5500 465 485
5600 461 491
5700 459 495
5800 446 493
5900 443 496
6000 437 500
6100 439 508
6200 429 507
6300 423 505
6400 419 511
6500 ??? 512.6
6600 407 510
6700 ??? 509
6800 384 501
6900 ??? 497
7000 372 497
7100 ??? 490
7200 357 486

You're right, need to be careful about RPM, but Adger, the failures have never been pistons !... it's the damn "super duper" race car parts on the uncontrollable intake lobe... shattering retainers !
Have a toned down intake lobe now.

I've used the "average horsepower" system.

Re: Ordering New Transmission, but What Gears ?
 

Scott at Jerico talked me into 3.08 first (1.93, 1.34, 1.00) and said it could be changed to about 3.19 later if needed. His argument was that I would have no time in first with 3.19. I have found with the right clutch slippage, I am OK, but still wonder if 3.19 would be better. If I do decide to change, I will discuss gear strengths with Scott.
I also have a torque type engine that I don't want to over-rev and gear the diff for the top end, then take what I can get in terms of first gear.

Re: Ordering New Transmission, but What Gears ?
 

Aubrey,
I think the 3.19 is too steep a gear for you combination. It will have too much 1-2 drop and with the 5.13 rear gear you have you will never hook it. IF I tried it I would use 4.88's in the rear. I think you have the shift point just about right. You might want to pull it 200 early in low to second with all that new gear ratio. then string it out in 2-3 & 3-4.
One thing about it is all the thinking and planning needs to be verified by testing.
Do Not shove what you want at the car.
Let the car tell you what it wants.

Re: Ordering New Transmission, but What Gears ?
 

Lots of good information, give us an update when you do some testing.

Re: Ordering New Transmission, but What Gears ?
 

40+ years ago on 7" slicks I learned that the steeper first gear Muncie transmission would only run fast when the traction was very, very good.

Even in a small block hydraulic cam rpm limited 3200lb car.

A 2.5 trans with a 4.88 rear gear and a steel flywheel dug holes in the starting line sometimes......

Basically we needed an aluminum flywheel at the minimum to adjust to the track conditions. Going from a 2.5 to a 2.20 first was a huge change and we threw that at the car in desperation at one race. A bog was faster than a spin........by a lot...We were racing on asphalt then and hot summer was way less traction than cooler conditions by a mile....Smoking the tires on the launch was normal....but only a little....

The fastest car in our class ran less gear in the trans and upped the TQ as much as possible with long collectors and other tricks....

Back in the traction limited days of 7" slicks...

Basically I think you have to pick something that is not as aggressive as you might like or think it could use. A happy medium so to speak.....

I don't miss those days one bit.....LOL

Re: Ordering New Transmission, but What Gears ?
 

Rich,
I think we walkd in the same shoes. I cut my teeth racing with a 69 Z-28 as a stocker. I raced it while I was in college. We carried 2.52 and 2.70 gear set trannys with us,as well as a 14 lb alum flywheel and a 34 lb Flywheel
I also had an alum hat with a Schiefer alum plate I had a lot of trouble with the heat shield. Back in the day it was fun, but today it would be hard work.

Re: Ordering New Transmission, but What Gears ?
 

Yes we did Adger....

My race partner and I became friends with a man that had a '69 Z/28. It was nearly new but was a racecar running F/S at the time. He had fully prepped the car and it had a race engine I drove it a couple times.

I was convinced he should get that 2.20 first gear trans out and I installed a 2.5 first like we ran in our car.

I was used to the hydraulic cammed engine we ran....350/295

His 302 was nothing like the 350 and would spin the tach to the moon if it spun the tires which it did. Leaving at 6500-6800 and with not much traction at our local track.....well forget about it......LOL

I also learned that the 2.5 box would not shift anywhere near as good behind the 302 at the much higher rpm...

Broke some trans parts pretty quickly with it but man that car was great fun to get behind the wheel of....

Black with white panels on the hood and trunk....black and white houndstooth interior and the cold air hood with all the stuff to go with it....except he threw some of it away thinking it was no good for racing....

The car went 12.1's in F/S in 1969 or 1970

Re: Ordering New Transmission, but What Gears ?
 

I'm getting closer to settling on this. Thanks for ALL the "combinations".
Yes, it's more inclined to be a "torque engine", but it still does pull nice up at the big end.

Re: Ordering New Transmission, but What Gears ?
 

Aubrey...did you ever try launching it at 5000 rpm?

Re: Ordering New Transmission, but What Gears ?
 

I did in Medicine Hat... but traction wasn't dependable. When it did hook, it bogged.
I don't go there any more.

Hoping for Mission in early June, but we're going on a big trip in May, for our daughter's wedding. That may stifle that particular race.

Re: Ordering New Transmission, but What Gears ?
 

I hope you can pull it off, Aubrey. It would be great to see you and the car again at Mission. Its one of my "must do" trips every year at one of my favorite tracks. Take care.
Danny Durham

Re: Ordering New Transmission, but What Gears ?
 

Aubrey, I would not be afraid of the 3.19 first gear. The super light clutch-flywheel assembly will allow you to accelerate the car without wheelspin. I would go with a 2.00 second and 1.40 third with the 3.19. The faster you can accelerate the car in the first half of the track, the lower the ET. Race setups have you in high gear at the eighth mark and it's just the ride from that point on regardless.

Re: Ordering New Transmission, but What Gears ?
 

Yep...

Re: Ordering New Transmission, but What Gears ?
 

Quote:
Originally Posted by Dwight Southerland View Post
Aubrey, I would not be afraid of the 3.19 first gear. The super light clutch-flywheel assembly will allow you to accelerate the car without wheelspin. I would go with a 2.00 second and 1.40 third with the 3.19. The faster you can accelerate the car in the first half of the track, the lower the ET. Race setups have you in high gear at the eighth mark and it's just the ride from that point on regardless.

Yep...
__________________

X2.

Re: Ordering New Transmission, but What Gears ?
 

I like the 319,200,140 idea, but you and I have tractor motors that few stick guys have. I like the 308 in my 400/427 stocker. Your car is 400 lbs heavier, but you have the rear gear to offset that. Todd,s thought on leaving lower with more 1st gear is certainly a good one, and his combo is closer to what you have, worth trying, and easy to switch 308 to a 319

Re: Ordering New Transmission, but What Gears ?
 

I like the ratios that I got with the 3.08 first, and if I went to 3.19 first, I would still want about the same for second and third as I have now (1.93, 1.34). The engine seems to recover a lot easier in the lower gears, and a wide 3-4 seems to slow down the engine's building rpm. About the worst was the old M20 with its 1.48 or 1.46 third ratio.

Re: Ordering New Transmission, but What Gears ?
 

Yeah, that also fits in with the fact that he has changed to the correct theory on camshafts now, I'm betting he'll find more power and more RPM working with the correct lobe designs. That gearing combination will allow him to put the gains he'll make in the future to good use. Not breaking valvetrain components will allow him to race the car and learn, instead of trying to keep it in one piece and running. Racing is about to get much more fun!

Re: Ordering New Transmission, but What Gears ?
 

I like your optimism, Alan !
Thanks again, everybody.

I'm going to get back on the phone with Jerico, and come up with a combination based on what I'm hearing here. I DO want to stop breaking the engine because of the valve train... while not choosing a gear combination that will break the transmission !

My daughter is getting married on a cruise ship, touring between Italy and Spain.
HHHMMM....
May have to settle for on a row boat in our local pond.

Re: Ordering New Transmission, but What Gears ?
 

If I were you....
Take a wide path around those rocky shores(no short cuts) and find out the captians name. You might also ask him if he is kin to another well know boat captian that runs over rocks.:D
If you get the wrong answer I would settle for the row boat!!

Re: Ordering New Transmission, but What Gears ?
 

Oh, that's just great, Adger.... the flight is going to be bad enough !

just give me 4 wheels ... and a clutch pedal !

Re: Ordering New Transmission, but What Gears ?
 

Aubrey, I assume you will be going from a "DR4" to a "DR4 Rev 4".
Would like to know if you find any difference in the two.
Best of luck,
Terry K

Re: Ordering New Transmission, but What Gears ?
 

Absolutely, there's a difference...
about $2000.00
! ! !

Re: Ordering New Transmission, but What Gears ?
 

I would have to agree with the steeper first gear as well.. Also have you considered a Gforce. I have had great luck working with Bubba 1-717-202-8367. I hope you make it to mission its great to see you and your car..

Re: Ordering New Transmission, but What Gears ?
 

X2 on the Gforce. Top notch people to work with, and a great reliable product