Need advice on gearing
Need advice on gearing I'm trying to figure out gearing right now. I have 3.73's with a 26" tall tire currently. I'm crossing the traps in third unlocked at 5,800-5,900 = 110mph.. It seems there is about a 10% slip as 110mph locked in third should be 5,350. This is in a 63 pick up LS1/4L80E so I have a real tall first. Right now best motor pass was a 12.33 @ 110 with a 1.87 60' I don't want to add more verter as I have a 2 stage 200 hit to put on it. Any suggestions?
This is assuming 4.56 gears..
Tire- MPH = RPM Unlocked = RPM locked - Max mph locked (7,200) - RPM @ 65mph locked 4rth gear
26" - 111 =====7,200 ======= 6,500 ------ 122mph ------------- 2,850
28" - 110 ==== 6,600 ======= 6,000 ------ 132mph ------------- 2,675
30" - 110 ==== 6,200 ======= 5,600 ------ 141mph ------------- 2,500
This is assuming 4.88
Tire- MPH = RPM Unlocked = RPM locked - Max mph locked (7,200) - RPM @ 65mph locked 4rth gear
26" - 111 ===too much ===== 6,950 ------- 114mph ------------- 3,100
28" - 110 ==== 7,100 ======= 6,450 ------ 123mph ------------- 2,900
30" - 110 ==== 6,600 ======= 6,000 ------ 132mph ------------- 2,700
And before this comes up (JROD) No, it is no longer a tow vehicle
But I still do drive it around.
This is assuming 4.56 gears..
Tire- MPH = RPM Unlocked = RPM locked - Max mph locked (7,200) - RPM @ 65mph locked 4rth gear
26" - 111 =====7,200 ======= 6,500 ------ 122mph ------------- 2,850
28" - 110 ==== 6,600 ======= 6,000 ------ 132mph ------------- 2,675
30" - 110 ==== 6,200 ======= 5,600 ------ 141mph ------------- 2,500
This is assuming 4.88
Tire- MPH = RPM Unlocked = RPM locked - Max mph locked (7,200) - RPM @ 65mph locked 4rth gear
26" - 111 ===too much ===== 6,950 ------- 114mph ------------- 3,100
28" - 110 ==== 7,100 ======= 6,450 ------ 123mph ------------- 2,900
30" - 110 ==== 6,600 ======= 6,000 ------ 132mph ------------- 2,700
And before this comes up (JROD) No, it is no longer a tow vehicle
But I still do drive it around. Because my set up is not optimized.. The current 3.73 gearing does not allow me to use all 3 gears fully. Even on the bottle I would not use all of third. There is no way I'll run 140+ mph. Add to that the 26" tire I don't think will hold the bottle out of the hole. Going to a 28" to aid traction makes my gearing even worse. I'm using 130mph as my guess mph on the bottle.
TECH Senior Member
Joined: Nov 2001
Posts: 10,341
Likes: 1
What converter are you running now?
I would leave the gear and try the spray on the existing combo and creep up on the jet size till you run out of gear/tire or hit your goal.
If you need a taller tire do that first before the gear and see how it responds. Change one thing at a time, test, repeat
I would leave the gear and try the spray on the existing combo and creep up on the jet size till you run out of gear/tire or hit your goal.
If you need a taller tire do that first before the gear and see how it responds. Change one thing at a time, test, repeat
Teching In
Joined: Oct 2007
Posts: 21
Likes: 0
..... according to my calculations, if you are content to buzz the motor through the lights, 7200 RPM in 3rd Gear (1:1, correct? ), unlocked, w/ 30" slicks & 4.56s would be about 127 MPH:
if you could find 4.33 gear-sets, it'd be just-under 135 MPH.
It's probable you'd need 30" slicks to hook-up all that power because the 1st Gear in your transmission is so-low that a street-legal tire might-not do it on spray off the line, 'specially with a 4-series gear back-there.....
if you could find 4.33 gear-sets, it'd be just-under 135 MPH.
It's probable you'd need 30" slicks to hook-up all that power because the 1st Gear in your transmission is so-low that a street-legal tire might-not do it on spray off the line, 'specially with a 4-series gear back-there.....
The truck dead hooks right now to a 1.87-1.9x with the 3.73's and 275/50/15 with 410rwhp just motor. The converter flashes to 3,200. The first in the 4L80E is 2.48 which is the same as a 400. I thought it was rather tall in comparison to others. I was also thinking of giving the 30" MT drag radial a try (315/60/15). I'm also going to be changing ride height and spring rates around to A) store more energy and B) get the truck a little more aero.
Wouldn't I be able to run the bottle / 4.88 / 30" combo if I locked the verter in 3rd on the big end? I could run the same 30" tire for both motor and jug, difference being locking the verter. Sure it won't be optimum NA as it will only be about 6,600 rpm unlocked. But I think I could live with that.
Wouldn't I be able to run the bottle / 4.88 / 30" combo if I locked the verter in 3rd on the big end? I could run the same 30" tire for both motor and jug, difference being locking the verter. Sure it won't be optimum NA as it will only be about 6,600 rpm unlocked. But I think I could live with that.
Teching In
Joined: Oct 2007
Posts: 21
Likes: 0
I'd been under the assumption that 1st Gear in those was 3.06:1, like a 700R4, but I'm not-knowledgeable about the 4L80E:
THM400 are 2.48:1, and THM350 are 2.52:1, almost identical to each-other.
If you can lock-up the converter in 3rd, and 'assuming' 10% slippage, yes, you could run about 10% more gear, or even 5.13s (4.56 x 1.1 = 5.01 )
THM400 are 2.48:1, and THM350 are 2.52:1, almost identical to each-other.
If you can lock-up the converter in 3rd, and 'assuming' 10% slippage, yes, you could run about 10% more gear, or even 5.13s (4.56 x 1.1 = 5.01 )
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TECH Fanatic
Joined: Oct 2007
Posts: 1,129
Likes: 0
From: Ventura County, California
You think you'll gain 20 mph from a 200 shot in a truck?
You're talking about going from 12.30's to bottom 10's.
Personally I would run the car on the bottle, see what gains you get and then you'll have a closer idea of what gear to go with.
You're talking about going from 12.30's to bottom 10's.
Personally I would run the car on the bottle, see what gains you get and then you'll have a closer idea of what gear to go with.
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