View Poll Results: What sould I do?
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4.56s or Not ?!?!?
12-11-2005, 12:00 PM
#1
4.56s or Not ?!?!?
OK, if you don't know my truck, it is a RCSB 2wd 5.3L T56 3.73s (look in sig for website for the full run down)! Cool, right? It is very fun to drive since the T56 swap! I actually went from 14.4s to 14.0 with the swap! I am at the top of 3rd gear at the end of the 1/4 mile and have about ~285 rwhp about ~310 rwtq. I run about 1550 rpms at 70mph in 6th gear, but i rarely put it in 6th, only when I am really lazy. I calculated that if I put my 4.56s gears in it would run about 1950rpms in 6th going 70mph. I guess what I am trying to ask should I do it or not? Do I have enough power to use the 4.56 in the 1/4 mile or will i just have a burn out machine and run out of power on the top end? I realize that if I do put them, 1st gear at the track will just not work. Might need to launch in 2nd. What should I do?
1. Stay with 3.73s
2. Go for the 4.56s
2. Go with 4.10s
4. Go with something else
Please post why you voted the way you did!
1. Stay with 3.73s
2. Go for the 4.56s
2. Go with 4.10s
4. Go with something else
Please post why you voted the way you did!
Last edited by 1TRUESS; 12-11-2005 at 12:27 PM.
12-11-2005, 12:10 PM
#2
TECH Junkie
4.10s will give you more usable gears.With the 4.56s you'd be wanting to start in 2nd gear and with the 3.73s 6th gear would be so far below the engines powerband you wouldn't tolerate using it.
12-11-2005, 12:22 PM
#4
Originally Posted by 02BlueStepside
I remember reading in some mustang mag a while back that whatever gears they suggested for an auto, the manual used the next set up. Hopefully this helps some.
12-11-2005, 12:37 PM
#5
How's traction launching now? If you already have to work at it to keep the tires from going up in smoke then I would say a gear change won't help. If it ended up that you had to launch in second with the 4.56 gears, then all the gear swap would do is essentially take away sixth gear.
Also, keep driveline RPM in mind. If your tires are about 30" in diameter you're looking at 4300 driveshaft RPM at 85 mph, 5100 at 100mph, and 6100 at 120mph! I have this same problem with my truck. I have been over 120mph only a few times with the 4.56 gears because I know how dangerous and destructive it would be if the driveshaft came undone. It makes me too nervous to spin it that fast.
The additional driveshaft RPM robs power on accelleration too. Doesn't hurt cruising but it does take extra power to spin it up and extra braking to slow it down.
One more consideration:
The 10-bolt is not a good recipient of high-ratio gears because the ring gear is so small. With any gear set the ring gear diameter remains constant (8.5 or 8.6" for a 10-bolt) and the pinion changes in diameter with ratio. The pinion gear in a 4.56:1 set for the 10-bolt is tiny. The small diameter minimizes overall contact between the ring and pinion teeth concentrating forces. The extra torque multiplication will have to be handled by the differential, assuming you can make traction. A manual transmission launch is harder on a drivetrain than an automatic - torque peaks are greater. It's especially for that reason that you definately do not want to try to increase traction over what you've got right now, it'll break.
Some experience from own situation:
When I first had the rear end custom built with the 4.56:1 gears in it I was not making sufficient power to spin the tires on launch. Years later I have more than 100 foot-pounds more than I did back then and have traction problems with even 285 tires and a stock torque converter. The drivetrain could handle a set of slicks but I would not want to drive around on them - I want it set up for street trim.
That in addition to the driveshaft RPM scenario described earlier, I am considering going back to 3.73 gears for this truck. I could then put in a higher-stalling torque converter too. Unfortunately, in a 10.5" 14-bolt there are two different carriers, one for 4.10 and smaller, one for 4.56 and higher. I'd have to buy a whole new Eaton Posi to do the swap. It's a $1000 decision I'm in no hurry to make. Luckily, 10-bolts don't have that issue.
Also, keep driveline RPM in mind. If your tires are about 30" in diameter you're looking at 4300 driveshaft RPM at 85 mph, 5100 at 100mph, and 6100 at 120mph! I have this same problem with my truck. I have been over 120mph only a few times with the 4.56 gears because I know how dangerous and destructive it would be if the driveshaft came undone. It makes me too nervous to spin it that fast.
The additional driveshaft RPM robs power on accelleration too. Doesn't hurt cruising but it does take extra power to spin it up and extra braking to slow it down.
One more consideration:
The 10-bolt is not a good recipient of high-ratio gears because the ring gear is so small. With any gear set the ring gear diameter remains constant (8.5 or 8.6" for a 10-bolt) and the pinion changes in diameter with ratio. The pinion gear in a 4.56:1 set for the 10-bolt is tiny. The small diameter minimizes overall contact between the ring and pinion teeth concentrating forces. The extra torque multiplication will have to be handled by the differential, assuming you can make traction. A manual transmission launch is harder on a drivetrain than an automatic - torque peaks are greater. It's especially for that reason that you definately do not want to try to increase traction over what you've got right now, it'll break.
Some experience from own situation:
When I first had the rear end custom built with the 4.56:1 gears in it I was not making sufficient power to spin the tires on launch. Years later I have more than 100 foot-pounds more than I did back then and have traction problems with even 285 tires and a stock torque converter. The drivetrain could handle a set of slicks but I would not want to drive around on them - I want it set up for street trim.
That in addition to the driveshaft RPM scenario described earlier, I am considering going back to 3.73 gears for this truck. I could then put in a higher-stalling torque converter too. Unfortunately, in a 10.5" 14-bolt there are two different carriers, one for 4.10 and smaller, one for 4.56 and higher. I'd have to buy a whole new Eaton Posi to do the swap. It's a $1000 decision I'm in no hurry to make. Luckily, 10-bolts don't have that issue.
12-11-2005, 12:44 PM
#6
Traction?! I can spin my slicks if I want too! I just need to get the launch rpm down.
My 60' are ~2.0 with slicks!
Video of T56 and 3.73 launches
My 60' are ~2.0 with slicks!
Video of T56 and 3.73 launches
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12-12-2005, 10:19 PM
#10
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go ahead with the 4.10's, the 3.73's are good, i think the 4.10's would be better, and 4.56 is just over kill, what good is having 1st gear if u don't ever use it.