Gear Ratio Help

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P

peats

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TotalyHucked said:
It's the cam. A rowdy cam doesn't like to be lugged and basically won't do anything at low speed in 4th. My daily's like that, anything below 1800-1900 and I've gotta make it downshift to get it to go anywhere
Click to expand...
I would change the cam to something more low end torque friendly. The trans and gears are not the problem IMHO.
 
xm20k

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I'm turning 2800-3000k at 55 with a 4.56 with a cam that has .600 lift and 252 @50 with a 28" tire and no overdrive a 4.56 or 4.88 with OD would allow it to still have power with the higher final drive at a more reasonable rpm.

However, if you're getting on it a lot that 700r4 may not be long for this world.
 
Craig Nedrow

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I would never swap from a OD trans to a 3hree speed, makes on since. My 489 cam duration is right at 300, 33" tire, 4:11 rear gear. It ran right @ 2800 to 3000 on the freeway with the 350, did fine, just made me tense and a bit noisy. The OD(4l80e) trans will help with that.
 
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Craig Nedrow said:
I would never swap from a OD trans to a 3hree speed, makes on since. My 489 cam duration is right at 300, 33" tire, 4:11 rear gear. It ran right @ 2800 to 3000 on the freeway with the 350, did fine, just made me tense and a bit noisy. The OD(4l80e) trans will help with that.
Click to expand...
300 duration? Got to be advertised and not @50 because 300 @50 is mechanical roller, race gas, and 13:1 or higher territory.

My advertised is 315 but is 252 @50 most people only ever use the @50 numbers.

My issue with his trans is a stock 700r4 will take around 350HP, if memory serves with a bunch of aftermarket parts will handle around 1K but I've never messed with one so have no idea what all would be involved with that. If his trans is stock, it probably won't last long behind that engine and a heavy foot. The TH400 might be the better option.
 
Craig Nedrow

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xm20k

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Craig Nedrow said:
I had 350 after I installed the 454, broke fairly soon, rebuilt is myself, did untold burnouts, sitting in the shop, as I am going 4l80e. Could look at my build, I have it documented.
Post start, 98. Buy an ATSG book, there great. Good luck.
Cam here, as well as the 489 build, https://www.gmsquarebody.com/threads/bbc-489-build.45389/page-4
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My bad I read that wrong and thought you were saying the cam in the 350 was 300, but that's in the 489.
 
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Cblaho81 said:
I am looking for suggestions on what gear ration do swap to. My current set up is a 1983 Chevy C10 with a built 355 small block, 3200 rpm torque converter, 700r4 trans and 3.73 posi rear. With the current engine/cam combo i can not use 4th gear unless I am running above 70 mph. The cam was originally specked for my 1975 Chevelle with a 3500 rpm converter, TH400 and 4.11 gears. Cam specs are as follows; Comp Cams 284H Hydraulic Flat Tappet, .507/.510 Lift, Duration @ .050 - 240/246, RPM Range 2300-6500. I do not want to change cams as this one sounds and runs great. I am pondering two options:

Option 1: Swap trans to a TH400 and change to 4.11 gears

Option 2: Swap the rear gears to either 4.56 or 4.88 so that I can use 4th gear in the current set up.

I am looking for information if anyone else has had this problem and what the best solution would be.

Thank you
Curtis
Click to expand...
Either change to 4:56 gears, or change to a milder cam that will give you more low-end and switch to 4:11 gears. Your's is pretty aggressive for a truck.

J. B.
 
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