Trans low gear set.

greg fulk · 11-19-2013, 02:55 AM

Alan I have 2.75 low gear in my car with 5.13 & 94" slicks....

Adger Smith · 11-22-2013, 12:23 PM

Another thing to be aware of is the way a lower gear causes your converter to work like it is tighter. It won't be the same converter when you go lower on gears. The same converter issues happen with rear gear, but not as bad as when you do a low gear tranny set. Some times the converter issues are a good thing and is what actually makes for the combination to be quicker. The lower gear may really help, but the change it causes in the converter may take away any gains. What I'm saying is: Monitor the way your converter works when you change gears. There is more to look at than just an ET Slip!!! That is why it is called getting the most out of your "Combination"

Mike Taylor 3601 · 11-22-2013, 02:44 PM

When I had auto in my F/PS ran 8.30's 1/8 went from 2.45 (stock 350th 1st.?) to 2.75 low car ran the same,only differences I could measure was RT was quicker had to drop about 5-8 lbsfront tire. to hit the tree the same spot and right rear tire started getting roughed up,changed spring and fixed that.
I think converter was slightly tight before,see if this is correct? Car would run .20 faster in 1/8 off dead idle about 1000 rpm but could'nt find tree would be -.020/-.040 or +.120 could'nt hit between, bring up to 2000 rpm could hit tree good but slow down .20 in 1/8 then could get trans fluid up to 200-210 would pick up .07-.09 in 1/8
By leaving @ idle converter flashed a little more and when trans temp got 200-210 fluid thinned and raised flash also is that correct theory? Did it need a little more stall?

Found I could run 4 speed in my combo so did'nt make anymore changes to converter and went to stick

Adger Smith · 11-22-2013, 03:02 PM

I would say your conclusions about the converter were correct. It was telling you it was too tight. It was probably on the verge of too tight with the other trans ratio.
The gear ratio made nothing, but tree/lite problems. You fixed it with a variable stall controled by "The Left Leg" Now it is loose any time you want or need it!! :~) But now: how about that gear ratio??

Mike Taylor 3601 · 11-23-2013, 10:00 AM

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 · 11-23-2013, 10:34 AM

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 · 11-23-2013, 01:26 PM

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'

11-19-2013, 02:55 AM	#1
greg fulk VIP Member Join Date: Jan 2003 Location: jackson Posts: 1,165 Likes: 0 Liked 5 Times in 3 Posts	Re: Trans low gear set. Alan I have 2.75 low gear in my car with 5.13 & 94" slicks.... __________________ Greg Fulk 308 308X P/SA "ALL AMERICAN"

11-22-2013, 12:23 PM	#2
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: Trans low gear set. Another thing to be aware of is the way a lower gear causes your converter to work like it is tighter. It won't be the same converter when you go lower on gears. The same converter issues happen with rear gear, but not as bad as when you do a low gear tranny set. Some times the converter issues are a good thing and is what actually makes for the combination to be quicker. The lower gear may really help, but the change it causes in the converter may take away any gains. What I'm saying is: Monitor the way your converter works when you change gears. There is more to look at than just an ET Slip!!! That is why it is called getting the most out of your "Combination" __________________ Adger Smith (Former SS) Last edited by Adger Smith; 11-22-2013 at 12:24 PM. Reason: sp

11-22-2013, 02:44 PM	#3
Mike Taylor 3601 VIP Member Join Date: Oct 2008 Location: Somerset,Ky Posts: 1,374 Likes: 358 Liked 308 Times in 103 Posts	Re: Trans low gear set. When I had auto in my F/PS ran 8.30's 1/8 went from 2.45 (stock 350th 1st.?) to 2.75 low car ran the same,only differences I could measure was RT was quicker had to drop about 5-8 lbsfront tire. to hit the tree the same spot and right rear tire started getting roughed up,changed spring and fixed that. I think converter was slightly tight before,see if this is correct? Car would run .20 faster in 1/8 off dead idle about 1000 rpm but could'nt find tree would be -.020/-.040 or +.120 could'nt hit between, bring up to 2000 rpm could hit tree good but slow down .20 in 1/8 then could get trans fluid up to 200-210 would pick up .07-.09 in 1/8 By leaving @ idle converter flashed a little more and when trans temp got 200-210 fluid thinned and raised flash also is that correct theory? Did it need a little more stall? Found I could run 4 speed in my combo so did'nt make anymore changes to converter and went to stick

11-22-2013, 03:02 PM	#4
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: Trans low gear set. I would say your conclusions about the converter were correct. It was telling you it was too tight. It was probably on the verge of too tight with the other trans ratio. The gear ratio made nothing, but tree/lite problems. You fixed it with a variable stall controled by "The Left Leg" Now it is loose any time you want or need it!! :~) But now: how about that gear ratio?? __________________ Adger Smith (Former SS)

11-23-2013, 10:00 AM	#5
Mike Taylor 3601 VIP Member Join Date: Oct 2008 Location: Somerset,Ky Posts: 1,374 Likes: 358 Liked 308 Times in 103 Posts	Re: Trans low gear set. 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

11-23-2013, 10:34 AM	#6
jcw31 Junior Member Join Date: Jan 2013 Posts: 94 Likes: 0 Liked 6 Times in 6 Posts	Re: Trans low gear set. 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

11-23-2013, 01:26 PM	#7
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: Trans low gear set. 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' __________________ Adger Smith (Former SS)