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Author Topic:   Driving... what gear ?
PB II
Member
posted January 04, 2002 03:26 PM
I am new to racing cars and I am confused about what gear everyone is using during a race. I understand that there are many variables that determine the correct answer, however I was reading some of the earlier posts and people were talking about, final drive and the gear ratios for first and second gear. I was under the impression that the car should be set up to run in one or the other without shifting during the race. Is this correct? For example: if the track is longer would you set up the rear end with a taller gear so that the transmission would be run in second constantly? I am planning to run a T350 and unfortunately do not know what the ratios for any of the gears are. Can any of you all help get me straightened out.


AC156
Member
posted January 04, 2002 03:29 PM
You are correct, the car should be run in one gear without shifting. If possible, you should run the final ration in the rear end and the tranny in high (1:1), this will increase horsepower as opposed to running a tranny in low or 2nd. However, if you need to run a tranny in second or low you can calculate the final gear ratio as the previous responder explained.


racer17j
Member
posted January 04, 2002 07:20 PM
what size track are you running tire size weight of the car are all things you should consider when figuring what gear you run. i also run a t350 i have to run mine in 2nd gear 1.52 because i have to run a stock 7.5 rear end and they don't make a gear big enought to run in drive but if you can run a ford 9 in rear end then you will be able to run drive as for shifting youi shouldn't need to my friends dad always shifts on restarts but i wouldn't recomend it i tried it in his car one nite in a crew race and lost 4 spots cause i missed the mark lol

[This message has been edited by racer17j (edited January 04, 2002).]

DirtDobber
Member
posted January 29, 2002 12:38 PM
K Newbe here. Street mechanics under my belt and this dirt stuff fascinates me. I have been playing with the toolbox and your suggestions and the information my buddy gave me about his car I just purchased.
He put a 2.73 rear end in it and said it was the best for the high-banked ¼ mile hard clay track I would be running on. “Throw it in low and go” he says “turn left and have fun!” He also said the engine would handle anything my foot could put into it but he is not sure of what RPM he was turning. Listening to him I would guess 5k to 6k. Low gear in the 350 Turbo calcs a 6.88. Respectable gear but why would he set the car up for low gear and not high gear like 49mtmod suggest? Where does the extra HP come from?


racer17j
Member
posted January 29, 2002 01:10 PM
gm does not make a gear big enought to run high gear as i stated above thats the reason for setting it up for low the lowest you can get is a 557 in a 10 bolt and a 614 in a 12 bolt. tthats part of the reason why ford rear ends are so popular they have gears that you can run in high gear i see they are up to 7.0 ratio now in the ford 9in


45cent
unregistered
posted January 30, 2002 11:23 PM           
Also the reason people live by 9 inch rear end is because they are strong and you will not lose an axle as easy as if you used and 10 bolt plus the 9 inch is like an tank


canadian racer
Member
posted February 04, 2002 12:32 AM
When running the final ratio in the rear end...tranny(1-1,as versus any other combination,where does the extra hp come from?Does the tranny doing the extra work make that much of a difference?


PB II
Member
posted February 04, 2002 09:09 AM
racer17J,
when you are putting your car in 2nd gear does it stay in second gear through out the whole race? Does it automatically shift down if you slow down for a caution. I guess what I am getting at is if you are at a dead stop and you put the t350 tranny in 2nd will it start out in second gear or will it start from first and go to second but not to exceeded. Anyway I am sure I will figure it out as soon as I get this car up and running. What final drive ratio do you recommend if I plan to run in second gear on a 3/8 mile low bank, red clay track? Thank you for all the help.


racer17j
Member
posted February 04, 2002 10:10 AM
the way i do it is i block off the vacume mod at the back or the tranny i just put a vacume cap over it that way it wil not shift you also drive it like a manual i start out in low then up into 2nd after we pull out. i also do that if we have to stop for a red flag anytime i come to a complete stop i will downshift and start over again but as long as you keep rollong it will not have any problems


racer17j
Member
posted February 04, 2002 10:18 AM
as for a gear i'm going to run the same as i run on my 1/2 with smaller tires on the rear on the 3/8 depending on tyour tire size you could run anywhere from a 3.23-4.11 depending on what roll you have on your tires


PB II
Member
posted February 04, 2002 01:20 PM
Thank's again for the help.


redneck bubbas racing
Member
posted February 04, 2002 09:07 PM
Not trying to go against the grain here but.. If you are still going to have to run in second you will probably be cheaper running in first. You can find 2.56 and 2.73 gears very easily (the 2.56 the easiest) in most any wrecking yard. If you have a motor that you dont want to turn up much the 2.56 works real good on a 3/8. If you like it to sing just a little then the 2.73 is the one. On a med bank 3/8 with the 2.73 the most I have ever turned is 6300 rpm. These gears work out to 645 and 686 final. If you can gear deep enough and have the money then by all means run the tranny in high. If you are still comprimising and broke like me, run it in low with factory gears.


YAZ
Member
posted February 04, 2002 10:01 PM
BECAUSE OF ARE RULES ON REAR END GEARS,
I RUN MY T350 IN 1ST GEAR WITH 2.73 GEARS
IN THE REAR ON A 1/3 MILE TRACK. RPM WAS
AROUND 5700. I STAYED CLOSE TO THE FRONT
MOST OF THE TIME. ONE THING I AM GOING TO
CHANGE IS PUTTING A FLOOR SHIFTER IN BECAUSE
IT POPPED INTO SECOND A FEW TIMES DURING THE RACE.


racer17j
Member
posted February 05, 2002 01:12 AM
bubba if you look in the junk yards you can find stock gears that will work that where i got my from was a v6 cutlass i also have one that came out of a v6 lesabre they are 3.23 some astro vans have 342s and some s-10s have 3.73 so it is just as ez to find the gears that will work to run 2nd as it is to run first i have a 273 and a 256 sitting around but don't ever plan on useing them unless i go to a 1/4 i may run the 273


Machinah
Member
posted February 05, 2002 04:49 AM
I'm a real dummy on gears and rely on the opinions of good people like these here. As for your tranny shiftin', you will need to experiment with what feels comfortable to you. Most tracks have a couple of practice sessions before the points season starts up, and you can always try a few different things durring hot-lap. Whatever you do, don't change your mind in the middle of the real race, unless your comfortable with it, or you may miss a gear and wind up a few positions back like Racer17j.


redneck bubbas racing
Member
posted February 05, 2002 05:18 PM
racer17j, Your right. The 3.42 and 3.73 are common in the astros and the s-10's. You wouldn't happen to know where I could find these gears for the 8.5 axles though would you? In these parts about all you will find is 2.41,2.56,2.73. The 2.73 are pretty rare. Sometimes you will find a 3.08 but thats real rare. I wasn't thinking of the metric rears, only the 8.5's.


racer17j
Member
posted February 06, 2002 01:41 AM
i have never realy looked for any 8.5so not sure where you might look for if you want a 3.o8 you can look in a nova thats what i used to run in mine till i sold the rear end because i was planning on moving up and running a 9inch but that never panned out.but other than that i'm not sure what came in what in 8'5s


dirtracer50
Member
posted February 06, 2002 06:47 PM
In my digging around I have come up with some 3.42's in late seventies Z28's and full size trucks especially the four wheel drives of the 70's and 80's you should be able to find some decent gears. I am talking about the 8.5 inch gears. Don't know if this will help or not but thought I'd throw it out here. Good luck


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