Turbo Gear 3.40, 3.50, 3.60 or 3.70 ?
02-03-2012, 10:06 AM
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Turbo Gear 3.40, 3.50, 3.60 or 3.70 ? 364" 220* cam 4L80e 2.48 low gear, 258mm (9.92ish") 3500-4000 stall, transbrake, 3200 lbs twin 6262sp precision's w/ .82 exhausts. Well not sure what gear to pick. Never had a Drag race Turbo car w/brake, not sure what gear. What I've researched is taller gear loads engine and convertor spooling turbos faster.
Car will see lots of low highway miles too, Drag Week
Car will see lots of low highway miles too, Drag Week
02-03-2012, 10:42 AM
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Gear it like any other car. Match rpms at the 1/4 mile mark with the gear/tire based on your trap speed.
For more street, you can gear down abit more to save rpms at cruise speeds.
Say you got a 140mph setup there, and you should easily with that low weight and power in the 650whp range. Say you make peak at 6200 rpm. If you want to cross the line at 140mph and 6200 rpm then that will require a 3.4 gear with 26" tire assuming locked converter (6153 rpm) If you leave it open, its gonna slip a few % so say 5% slip that puts you at 6460 rpm. Not bad if power hangs on past peak.
28" tire would need more gear. Same 140mph with 3.4 gear would cross at 5714 rpm locked. 5% slip would be 6000 rpm. A 3.5's gear would perhaps be alittle better.
Then again that combo should be capable of 800whp and possibly high 150's mph at that light weight. Gear changes so you need to figure out how fast its gonna go, where the peak power is gonna be and gear/tire to match.
FWIW my 89 uses 2.73 gears and i love it for cruise but I dont have a lock up converter, just a TH400 with 4000 stall and it works well on the highway. If I had overdrive and lockup, it would drive like stock. It matches my old combo pretty well but the new setup would like 3.23's or so to be optimal.
For more street, you can gear down abit more to save rpms at cruise speeds.
Say you got a 140mph setup there, and you should easily with that low weight and power in the 650whp range. Say you make peak at 6200 rpm. If you want to cross the line at 140mph and 6200 rpm then that will require a 3.4 gear with 26" tire assuming locked converter (6153 rpm) If you leave it open, its gonna slip a few % so say 5% slip that puts you at 6460 rpm. Not bad if power hangs on past peak.
28" tire would need more gear. Same 140mph with 3.4 gear would cross at 5714 rpm locked. 5% slip would be 6000 rpm. A 3.5's gear would perhaps be alittle better.
Then again that combo should be capable of 800whp and possibly high 150's mph at that light weight. Gear changes so you need to figure out how fast its gonna go, where the peak power is gonna be and gear/tire to match.
FWIW my 89 uses 2.73 gears and i love it for cruise but I dont have a lock up converter, just a TH400 with 4000 stall and it works well on the highway. If I had overdrive and lockup, it would drive like stock. It matches my old combo pretty well but the new setup would like 3.23's or so to be optimal.
02-03-2012, 11:24 AM
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364" 220* cam 4L80e 2.48 low gear, 258mm (9.92ish") 3500-4000 stall, transbrake, 3200 lbs twin 6262sp precision's w/ .82 exhausts. Well not sure what gear to pick. Never had a Drag race Turbo car w/brake, not sure what gear. What I've researched is taller gear loads engine and convertor spooling turbos faster.
Car will see lots of low highway miles too, Drag Week
Car will see lots of low highway miles too, Drag Week
well having an overdrive will help out with the long cruising but i think what dschmittie said, something aroud there will be a great starting point. what et mph are you shooting for?
02-03-2012, 11:52 AM
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Ultimate goal is to run 8.50's with forged bottom end and get 25+ mpg. Will probably give standing mile a shot too. This is in a 62 ChevyII w/strut front end, split monos and assassin bars.
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02-03-2012, 12:12 PM
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8.50's is 160mph +. Definately need more of a highway gear depending on how high you are turning the motor.
28" tire, 3.23 gear will put you at 6281 rpm at 162mph with no slip in the converter. 6600+ rpm with typical converter slip.
28" tire, 3.23 gear will put you at 6281 rpm at 162mph with no slip in the converter. 6600+ rpm with typical converter slip.
02-03-2012, 09:15 PM
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I have a 63 chevyII that I am putting a 370" with a pt88. I have 3.20 gears in it and with the v6 in the sig below @28PSI boost I have ran a 10.4's. I am leaving the same gears for the LQ4 and looking for an 8 sec pass as well
02-03-2012, 09:56 PM
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Gear it like any other car. Match rpms at the 1/4 mile mark with the gear/tire based on your trap speed.
For more street, you can gear down abit more to save rpms at cruise speeds.
Say you got a 140mph setup there, and you should easily with that low weight and power in the 650whp range. Say you make peak at 6200 rpm. If you want to cross the line at 140mph and 6200 rpm then that will require a 3.4 gear with 26" tire assuming locked converter (6153 rpm) If you leave it open, its gonna slip a few % so say 5% slip that puts you at 6460 rpm. Not bad if power hangs on past peak.
28" tire would need more gear. Same 140mph with 3.4 gear would cross at 5714 rpm locked. 5% slip would be 6000 rpm. A 3.5's gear would perhaps be alittle better.
Then again that combo should be capable of 800whp and possibly high 150's mph at that light weight. Gear changes so you need to figure out how fast its gonna go, where the peak power is gonna be and gear/tire to match.
FWIW my 89 uses 2.73 gears and i love it for cruise but I dont have a lock up converter, just a TH400 with 4000 stall and it works well on the highway. If I had overdrive and lockup, it would drive like stock. It matches my old combo pretty well but the new setup would like 3.23's or so to be optimal.
For more street, you can gear down abit more to save rpms at cruise speeds.
Say you got a 140mph setup there, and you should easily with that low weight and power in the 650whp range. Say you make peak at 6200 rpm. If you want to cross the line at 140mph and 6200 rpm then that will require a 3.4 gear with 26" tire assuming locked converter (6153 rpm) If you leave it open, its gonna slip a few % so say 5% slip that puts you at 6460 rpm. Not bad if power hangs on past peak.
28" tire would need more gear. Same 140mph with 3.4 gear would cross at 5714 rpm locked. 5% slip would be 6000 rpm. A 3.5's gear would perhaps be alittle better.
Then again that combo should be capable of 800whp and possibly high 150's mph at that light weight. Gear changes so you need to figure out how fast its gonna go, where the peak power is gonna be and gear/tire to match.
FWIW my 89 uses 2.73 gears and i love it for cruise but I dont have a lock up converter, just a TH400 with 4000 stall and it works well on the highway. If I had overdrive and lockup, it would drive like stock. It matches my old combo pretty well but the new setup would like 3.23's or so to be optimal.
In the real world you do NOT gear every car the same... A max effort N/A combo you want dead on the redline as its going through the traps...
A power adder car makes TORQUE. That's torque you can utilize to run faster ET's by not spinning it to the moon.
This is ALL relative to the combo, so I'm not going to say there is a hard and fast rule for every situation.
With a turbo car you may find that a taller gear than the above logic would indicate you "need" actually makes you faster, due to the increased load on the engine...
Dont take someones word for it, do some experimentation and talk to those who have been there and done that before you choose a gear.
P.S. get off ls1tech and go somewhere like yellow bullet and ask your question. You'd be amazed at the difference in quality of information.
.02
Greg
02-04-2012, 09:48 AM
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Gear it like any other car. Match rpms at the 1/4 mile mark with the gear/tire based on your trap speed.
For more street, you can gear down abit more to save rpms at cruise speeds.
Say you got a 140mph setup there, and you should easily with that low weight and power in the 650whp range. Say you make peak at 6200 rpm. If you want to cross the line at 140mph and 6200 rpm then that will require a 3.4 gear with 26" tire assuming locked converter (6153 rpm) If you leave it open, its gonna slip a few % so say 5% slip that puts you at 6460 rpm. Not bad if power hangs on past peak.
28" tire would need more gear. Same 140mph with 3.4 gear would cross at 5714 rpm locked. 5% slip would be 6000 rpm. A 3.5's gear would perhaps be alittle better.
Then again that combo should be capable of 800whp and possibly high 150's mph at that light weight. Gear changes so you need to figure out how fast its gonna go, where the peak power is gonna be and gear/tire to match.
FWIW my 89 uses 2.73 gears and i love it for cruise but I dont have a lock up converter, just a TH400 with 4000 stall and it works well on the highway. If I had overdrive and lockup, it would drive like stock. It matches my old combo pretty well but the new setup would like 3.23's or so to be optimal.
For more street, you can gear down abit more to save rpms at cruise speeds.
Say you got a 140mph setup there, and you should easily with that low weight and power in the 650whp range. Say you make peak at 6200 rpm. If you want to cross the line at 140mph and 6200 rpm then that will require a 3.4 gear with 26" tire assuming locked converter (6153 rpm) If you leave it open, its gonna slip a few % so say 5% slip that puts you at 6460 rpm. Not bad if power hangs on past peak.
28" tire would need more gear. Same 140mph with 3.4 gear would cross at 5714 rpm locked. 5% slip would be 6000 rpm. A 3.5's gear would perhaps be alittle better.
Then again that combo should be capable of 800whp and possibly high 150's mph at that light weight. Gear changes so you need to figure out how fast its gonna go, where the peak power is gonna be and gear/tire to match.
FWIW my 89 uses 2.73 gears and i love it for cruise but I dont have a lock up converter, just a TH400 with 4000 stall and it works well on the highway. If I had overdrive and lockup, it would drive like stock. It matches my old combo pretty well but the new setup would like 3.23's or so to be optimal.
02-04-2012, 11:48 AM
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This info is false. Lots of math and theory without the real world.
In the real world you do NOT gear every car the same... A max effort N/A combo you want dead on the redline as its going through the traps...
A power adder car makes TORQUE. That's torque you can utilize to run faster ET's by not spinning it to the moon.
This is ALL relative to the combo, so I'm not going to say there is a hard and fast rule for every situation.
With a turbo car you may find that a taller gear than the above logic would indicate you "need" actually makes you faster, due to the increased load on the engine...
Dont take someones word for it, do some experimentation and talk to those who have been there and done that before you choose a gear.
In the real world you do NOT gear every car the same... A max effort N/A combo you want dead on the redline as its going through the traps...
A power adder car makes TORQUE. That's torque you can utilize to run faster ET's by not spinning it to the moon.
This is ALL relative to the combo, so I'm not going to say there is a hard and fast rule for every situation.
With a turbo car you may find that a taller gear than the above logic would indicate you "need" actually makes you faster, due to the increased load on the engine...
Dont take someones word for it, do some experimentation and talk to those who have been there and done that before you choose a gear.
Turbos make torque yes, and you can use less gear and get away with it. But HP accelerates cars. If you dont believe that then you have no business posting.
Dont need load on the motor once you start using that transbrake. It will be spooled by the time you leave the line anyway so the gearing should just match the mph goals
You dont have to spin a turbo combo to the moon. Thats not what I'm saying to do. My car only sees 6000 rpm shifts! I geared somewhat close to mid 5000 rpm crossing the traps and its worked well for me.
Theory??? this is how it works man. Tires of a certain diameter with certain gearing produce rpms/mph. Its physics and true math. Not a hard concept to master.
Last edited by Orr89rocz; 02-04-2012 at 11:53 AM.