I know a few of you have 600-900hp cars.
How did you come about to final gear selection for something like this?
I have read all the posts I can take on gear selection.
What are the few who make enough TQ and top end HP to double/triple the stock power numbers doing to decide what to run?
I"m on the lower end of this comparison, but I'm running a 3.73 with a 25.5" tire. It's way too much gear. I need to switch to a 28" tire at the drags but I like the sleeper look. I thnk that 3.54 would be perfect with me along with a a higher 1st gear in my 700r4. The stock first gear is over in a blur. In addition, I don't have enough gear to get though the quarter with this setup. With my short tire and 3.73's, I run out of rpm in 3rd at about 110 mph or so.
The 3.73's were in the car when I bought it. I guess the guy like to peel out and go nowhere.
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Basically to keep traction and to keep from shifting every half second you want a smaller gear ratio with higher power. Allowing those big torque/hp numbers to play themselves out is helpful.
If you are running a stick I would say stick with the stock 3.45:1 rear end. This puts you at the top of 4th gear at the drag strip when you are trapping in 130-140mph.
I would have to do the math for an auto, but basically you want a little lower than a stick.
I'll give an answer that is probably off the path reltive to most drag racers.
My car is somewhere near 500 at the crank, probably a little lower.
I have a 2.59 gear. Yes really wimpy and would not even think of a gear like this in a non forced induction setup. I was considering changing it but have decided ultimately not to.
The reason is on street tires I cant hook this thing out of the hole anyway and I spin all of 1st gear and into second. I will not put a sticky tire on it or I am prone to blow up the D36. I have a high stall converter that makes up for the off the line.
Other nice thing is at 60 - 70MPH I can hammer it and it jumps down to 2nd gear at about 4000 RPM right into boost and the car launches forward unbelievably.
In general on my oher cars I preferred the perfromance 3.07 axle when naturally aspirated.
I am sure this will differ from most people but my baseline setup will be with street tires due to reasons above and I am not sure off the line a deeper gear would really buy anything but tire spin on street tires.
I'll give an answer that is probably off the path reltive to most drag racers.
My car is somewhere near 500 at the crank, probably a little lower.
I have a 2.59 gear. Yes really wimpy and would not even think of a gear like this in a non forced induction setup. I was considering changing it but have decided ultimately not to.
The reason is on street tires I cant hook this thing out of the hole anyway and I spin all of 1st gear and into second. I will not put a sticky tire on it or I am prone to blow up the D36. I have a high stall converter that makes up for the off the line.
Other nice thing is at 60 - 70MPH I can hammer it and it jumps down to 2nd gear at about 4000 RPM right into boost and the car launches forward unbelievably.
In general on my oher cars I preferred the perfromance 3.07 axle when naturally aspirated.
I am sure this will differ from most people but my baseline setup will be with street tires due to reasons above and I am not sure off the line a deeper gear would really buy anything but tire spin on street tires.
I agree entirely.
My view is put in as low a ratio as you can while still having a hard time getting traction in first gear while the car is below it's power band. If you can't go WOT until you are into the meat of the power band then you probably you have the perfect ratio.
In general I would recommend that anyone looking at buying deeper gears instead invest the money in some more torque to fix the problem
I did run a 2.59 in my NA/auto setup back in the day. I was able to wind up the motor and trap in at 112mph while just topping out second gear.
I guess the way to look at is to multiply your transmission gear by your rear end gear to get your overall drive ratio. You'll want to make that number as big as possible while keeping the number of shifts as small as possible and still giving you good cruising rpm. That is of course until you start messing with your tire diameter, then you need to throw that calculation in there too.
Thanks for the replies, this turned out different then I had thought.
I kind of had the feeling most people around here had 4.10/11 or 3.73 combos for what ever reason. (maybe they got them before going FI)
Now can a 2.56 or 3.07 fit in a D44? (I read some other posts about D36 maxing out at 3.75 and it clouded things up for me)
Do gears gain or lose strength with changing ratios? Would you be at more risk to kill some gears based on ratios?
Keep in mind the gear ratio is also the torque ratio. For example the half shafts, U-joints etc. on a 4:1 ratio gearset will experience twice torque as on a 2:1 ratio gearset (all other things being equal).
Some of the previous replies talked about specific ratios used on auto setups. Because of the torque converter and other differences you can often get away with a lot lower ratio in an auto car than a manual. Not sure what you have but I wanted you to consider that before making a decision.
Regardless of your transmission much of the same advice applies. The benefit of a high ratio (ex: 4:1 or more) is to get your engine into the power band sooner. Of course you don't get anything for free, and the torque multiplication of a high ratio gearset comes at the cost of speed division, meaning you are shifting sooner and more often.
Now can a 2.56 or 3.07 fit in a D44? Do gears gain or lose strength with changing ratios? Would you be at more risk to kill some gears based on ratios?
3.07 was the factory ratio in 4+3 D44 cars and take out gear sets are cheap because everyone NA is going to lower gears.
Lower gears are weaker because the pinions head is smaller.
Quote:
Originally Posted by jsiddall
I can only speculate that the limits on really tall ratios are likely a result of the increasing diameter of the ring gear. I doubt there is a limit of how low you can go with a D44, but someone with experience will need to speak to that question.
The thickness of the crownwheel changes with ratio ; not the diameter.
3.07 was the tallest gear offered in a C4 D44. I have never seen a aftermarket D44-HD gearset taller than that .
2.59 and 2.73 were only offered in D36's
In any case if taller D44 gears were available ,it would be a custom job as the Corvette D44-HD carrier is unique to Corvettes/Vipers and is a "3" series carrier which only take 3.07 - 3.73 ratios (lower ratios like 4.11 are run by using special aftermarket "thick" gears )
I am pretty sure on the D36 rearends that a 2.59 has a thicker ring gear than a 3.07 and I think because of this a 2.59 or 2.73 will handle incrementally more power than a 3.07.
Most aftermarket gears for a D36 do not want the 3.07 case, they require a 2.7x or numerically lower case for example when going fpr a 3.5x or 3.7x (appologize, don't know the exact ratios off the top of my head)
I don't know about D44 specifically
Last edited by HighMileage; 09-26-2009 at 04:19 PM.
Most aftermarket gears for a D36 do not want the 3.07 case, they require a 2.7x or numerically lower case for example when going fpr a 3.5x or 3.7x (appologize, don't know the exact ratios off the top of my head)
In a OEM D36 you have a "2" series carrier which takes the 2.59 and 2.73 gearsets and a "3" series carrier which takes the 3.07 and lower gears.
To save having to change the carrier when going to lower gears from 2.59 ,you buy a aftermarket "thick" gearset which allows you to fit a 3 series gear on a 2 series carrier
I am not really sure why we are discussing a D36 rear when the OP has asked about gearing for a high HP car. One hook, and the D36 is gone. For that matter, a decent hook in a stock D44 with 4 digit HP and the D44 is likely to be history as well.
From my perspective, I want to run the tallest gear (highest numerically) that I can run while still hitting my MPH at the end of the 1/4 mile without hitting redline in 4th gear. That leaves me with the 3.45D44...
I ran 3.73 in he 10's for years and that was with 750hp and 680tq.
I ran 3.90 for about 2 years and had no big problems.I went to 4.10's and uped the motor to over 1000 hp and spit out the rear .I have a 12 bolt with 4.10's and I have to shift into 4 th gear 700r4 at the 1000 mark on the track to make it through the 1/4.If you are going to drive on the street the 3.73 is more gear than you need.I almost never take my car on the street now it rpm's out in a few feet and if I had 2 more gears I would use them.
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I ran 3.73 in he 10's for years and that was with 750hp and 680tq.
I ran 3.90 for about 2 years and had no big problems.I went to 4.10's and uped the motor to over 1000 hp and spit out the rear .I have a 12 bolt with 4.10's and I have to shift into 4 th gear 700r4 at the 1000 mark on the track to make it through the 1/4.If you are going to drive on the street the 3.73 is more gear than you need.I almost never take my car on the street now it rpm's out in a few feet and if I had 2 more gears I would use them.
Seriously? A 4.10 with 1000 HP? Did you even notice there was a first gear?
A bone stock car is done first in about 3 seconds. You are talking about 4X the power and 1.5X the gear ratio. That means first is over in about 500 milliseconds. Yikes!
I ran 3.73 in he 10's for years and that was with 750hp and 680tq.
I ran 3.90 for about 2 years and had no big problems.I went to 4.10's and uped the motor to over 1000 hp and spit out the rear .I have a 12 bolt with 4.10's and I have to shift into 4 th gear 700r4 at the 1000 mark on the track to make it through the 1/4.If you are going to drive on the street the 3.73 is more gear than you need.I almost never take my car on the street now it rpm's out in a few feet and if I had 2 more gears I would use them.
I hear what you are saying, but what RPM are you spinning the motor (what CID), and how tall are the tires?
My concern is that people read this post and think that 4.10 gears may be a great gear, but you may be running 28" or even 30" tall tires (which other's are not). Then if you went to 26" tall tires, you may have way to much gear.
I'm just impressed that the dana lived for a while with that power? So are you saying you replaced it with a 12 bolt once the dana died or that you had a 12 bolt the whole time?
I see I need to clear up some things.The D-44 was a car creations with a spool and Dennys nitrous ready drive shafts ,yes those drive shafts hold but the u-joints don't last very long.The tires are 28 and 29 in MT slicks 11.5 and 10.5 wide.Yes first gear is a real quick shift.The load of the car and the hooking of the tires slows the shift time and if the tires spin off the line that run is dead.The spin happens but not that often.
The motor spins to 7500 and it is a 434 ci.
I did run my drag radials on the car for S And G two races ago the tire shake was unreal and I aborted the run and changed tires.
The drag radials were 315x35x17.
A 4.10 gear is great for my 86 but I would never put those gears in a daily driver .I have 3.73's in my 94 and it works great.I do run 315x35x17 DR on the street that are around 26 in tall.275 on the front.I replaced the dana when I was blowing out the u-joints every 3 to 5 runs.I did not find a u-joint that could hold any power above 825 hp more than 3 runs.You also need to tork every bolt in the dana every 10 runs and keep an eye on the dog bones.All the bushings have to be up graded to the urthane.You also have to run a qa1 or adjustable shock ,I tried all kinds and they would blow out and start leaking oil.
Running high hp is expensive and the dana will not last.I can also tell you that everyone would watch the car go down the track.I did not figure out why until after I put the 12 bolt in,after that everyone at the track told me, they never knew where the car was going.For years they thought I was going to crash it sooner of later.
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Johnny Carson once said.A married man may live longer ,but is more willing to die.
I see I need to clear up some things.The D-44 was a car creations with a spool and Dennys nitrous ready drive shafts ,yes those drive shafts hold but the u-joints don't last very long.The tires are 28 and 29 in MT slicks 11.5 and 10.5 wide.Yes first gear is a real quick shift.The load of the car and the hooking of the tires slows the shift time and if the tires spin off the line that run is dead.The spin happens but not that often.
The motor spins to 7500 and it is a 434 ci.
I did run my drag radials on the car for S And G two races ago the tire shake was unreal and I aborted the run and changed tires.
The drag radials were 315x35x17.
A 4.10 gear is great for my 86 but I would never put those gears in a daily driver .I have 3.73's in my 94 and it works great.I do run 315x35x17 DR on the street that are around 26 in tall.275 on the front.I replaced the dana when I was blowing out the u-joints every 3 to 5 runs.I did not find a u-joint that could hold any power above 825 hp more than 3 runs.You also need to tork every bolt in the dana every 10 runs and keep an eye on the dog bones.All the bushings have to be up graded to the urthane.You also have to run a qa1 or adjustable shock ,I tried all kinds and they would blow out and start leaking oil.
Running high hp is expensive and the dana will not last.I can also tell you that everyone would watch the car go down the track.I did not figure out why until after I put the 12 bolt in,after that everyone at the track told me, they never knew where the car was going.For years they thought I was going to crash it sooner of later.
John,
Thank you for taking the time to clarify your combo and to put your combo into perspective vs the general public.
Corvette Store
big HP guys, what gears are you running?
