Trans low gear set.

[Mike Taylor 3601]

Adger,
Had to drive the same way w/stock gear set also,I figure my low gear set did'nt help cause converter was already a little tight and w/ low gear set was tighter and took away any gains the low gear set made.Converter guy said 8'' I had was as loose as could be made w/o becoming inefficient,so I replied so then I need 7''? he said no 7 won't work in your application,could'nt get a answer that made any sense from him,was going to change companies but went back to stick.
You mean my stick gear ratio? if so 2.88 and wide open Ahhh so much more fun!!!!
I know 2.88 is a little higher first than common,but have to use stock type trans in pure stock and barely over 6K my experience has been you can get too low in first w/lower rpm combo,seems to me to work better if you can clear 60' in low gear.
I had 2 automatics,my 1st and last LOL
Mike Taylor 3601

[jcw31]

Not to hijack the posts but with a stick with a 2.52 low 1.62 second 1.24 third 327/300 4.88 rear. Would it be better with a 2.70s low with 1.62 second or stay where it is only because of shift recovery ? The spread just seems to great to recover and keep up rpms. Also what about a 396?

Thanks Joe

[Adger Smith]

Joe,
That first trans 1-2 ratio drop is 35%. The second Trans 1-2 drop was 40%.
When you had recovery problems on the shift could the engine combination get away with taking the 1-2 shift point higher? Say your best runs with the 2.52 were made @ a 1-2 shift point of 6500. Your 35% drop put you at or near 4225 RPM. (no clutch slip considered). To get to the same drop point your 1-2 shift with the 2.70 would have been 6,825. If you tried that and it didn't work I would suspect it was the engine "Going over" with the added 325 RPM. Could it have been the difference in your 12.30 Vs 13.18 final drive ratio in low gear causing a little too much tire slip on the hit?
Back in the early 70's I ran an F/S 302/290 combination and the 7" tires kept me from running the 2.70 all the time. When we got on a "Real Good" track I could take my heavy flywheel out and put the lightest wheel I could find in the bell housing and slide the clutch a little. It would haul it when I got it hooked. We worked out hind ends off working with wheel width, flywheels/clutches, tranny ratios & shift points back in those days.
(Hey Dwight, you remember those days?)
Back then it sure would have been easier if we had some data besides 60' and 1/8 mile (no 1/8 MPH) and quarter mile E.T (W/ MPH at the good tracks). A good computer in the car might have made life easier at the track. That computer would have been real easy to tell what was happening when we started a clutch control program.
We thought we had hit the jackpot when the LTM came out!! :~)
I'm glad my buddies and I were young when we were doing all that work.
I sure couldn't do it today like we did it then.
At this stage of life just getting a combination ready in the shop and going to the track, hoping it was right, is tough to do.
Well, so much for the Sat. morning 'Run Through the Memories'

[jcw31]

Adger the driver felt no problem on 1-2 shift with for recovery he said
2-3 and 3-4 was the worst on recovery . This makes no sense because of a smaller spread in ratio. He was told to go to a steeper low gear to keep
the motor happier . Also that the ratios were wrong. I just need an opinion
if its the gear spread or the motor isn't happy on the fallback. My idea is to up the shift point not the go to the 270s low.

thanks again Joe

[Adger Smith]

Those ratios 2-3, 3-4 are good ratios. 23% and 19% drops.
Is the driver an experienced Stick driver? Does he understand the difference he should feel? That low 19% fall back in 3-4 should keep the engine up and pulling in the curve. That is good only if that is what your combination likes. Is it a HP or TQ combination? Back in the day I made a hand written sheet and calculated my shift points and the drop back RPM. Now I do it with Excel.
I would move the shift points all over the place, in your case. find out if the engine is going over the Tq/power curve or running under it. If it is running under it it will take forever to recover on the shift and if it is going over it will feel like there is no pull or nothing after the shift. Do you have dyno sheets to work off of? Even if you do, you need to get on the track and have a test session with shift points. Before you go plan the test. Lay out a good outline of what you are going to do. It doesn't hurt to log the "expected results" in your outline. Remember to make at least 2 baseline runs. When at the track stick to the plan as you test, then digest the results after the session. Don't get lost "in the moment" when testing.
I've been with customers that think "They Find Something" and spend most of the test session "Chasing the Rabbit" and then realize they have wasted their time. If you make enough planned runs the car will show you trends and what makes it happy. OH, it is nice to have help and input from others, but only believe 100% what "you" see and hear the car doing. That help, as well as the driver, can get you off chasing rabbits. In this day and age of low cost electronics get some data aquisition and A good video with sound will help. If you can make your test runs as a single you will hear as well as see what the car is doing. If I'm at a track during time trials I always have a crew guy (biggest) request that the starter make it a single.
Good luck.

[jcw31]

Adger

thank you very much.

Joe