upgrade for 4l80e maybe?

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tayto

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one thing i've observed in this thread is you need to take into account rpm AFTER lockup, this is good for 100-300 rpm drop.
 

99xcss4

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one thing i've observed in this thread is you need to take into account rpm AFTER lockup, this is good for 100-300 rpm drop.
yes that is right this stuff is very new to me and I would say that I understand some of what is going on the lockup thing I do not understand and I struggle with the number of tire rotations at given engine rpm. I could plug in numbers for ever but if I do not fully understand it the info that gets spit out it may as well be useless or be in jiberish
 

L31MaxExpress

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If you think your rpms might be too high for your comfort just remember how much more power it takes to push those taller/wider/heavier tires down the road.



I get trucks in every week with 35s and 3.42s with 4l60s and they have put too big of a cam in and want it tuned. Then complain it doesn't make any more power.

I suggest 4.56s for 35s to get the final ratio back a little better than stock. Got buddys that went from 3.42/35s to 3.90 or 4.10 and 35s and regret it. Eventually they went to 4.56 or 4.88s and finally were happy.
Don't fear the gear.

Absolutely agree with you. I had a Hemi Ram with 3.55s and factory ~33" tall P275/60R20s. I put shorter P305/50R20s on it that were ~32" tall on it when it needed tires which helped it a bit. I then had it regeared to 4.56s. That truck was a BLAST to drive with 4.56s.
 

L31MaxExpress

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yes that is right this stuff is very new to me and I would say that I understand some of what is going on the lockup thing I do not understand and I struggle with the number of tire rotations at given engine rpm. I could plug in numbers for ever but if I do not fully understand it the info that gets spit out it may as well be useless or be in jiberish

Many tires have revolutions per mile included from the tire manufacturer. At 60 mph that would be the tire RPM. Then again, I am not sure why you would need the tire RPM if you put an accurate tire height into a gearing calculator.
 

99xcss4

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Many tires have revolutions per mile included from the tire manufacturer. At 60 mph that would be the tire RPM. Then again, I am not sure why you would need the tire RPM if you put an accurate tire height into a gearing calculator.
can you explain what tayto is talking about with the lockup rpm drop and what do the numbers represent in the 1000 to 6500 rpm range on the carts is have post that is what is going over my head
 

df2x4

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can you explain what@ tayto is talking about with the lockup rpm drop and what do the numbers represent in the 1000 to 6500 rpm range on the carts is have post that is what is going over my head

The numbers in the charts you posted are speed in MPH. They signify how fast you'll be going at that RPM in that gear with the choice of transmission and differential gearing that you've selected.

What tayto is saying is regarding torque converter lockup. When the converter locks in 4th, you'll see another 2-300RPM drop, so you'll actually be running a little bit lower RPM than what the charts say cruising in top gear at part throttle.
 

yevgenievich

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Would it not be the other way with the charts regarding lock up. The chart shows rpm for specific gear ratio, which would be with torque converter locked. Before torque converter lock up, rpm wold be higher by a 200-300rpm?
 
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df2x4

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Would it not be the other way with the charts regarding lock up. The chart shows rpm for specific gear ratio, which would be with torque converter locked. Before torque converter lock up, rpm wold be higher by a 200-300rpm?

Could be, I'm honestly not sure how most of these calculators account for lock up.
 

OutlawDrifter

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Would it not be the other way with the charts regarding lock up. The chart shows rpm for specific gear ratio, which would be with torque converter locked. Before torque converter lock up, rpm wold be higher by a 200-300rpm?

This is correct.

The math is based on the inputs, with no underlying "slip" calculated in. That's why it works for manual and automatic transmissions.
 

Supercharged111

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My truck with 33s and a 4.10 hits 2000 RPM at 62mph. This is the same as your calculation with 37s and a 4.88. You're still giving up more than I am swinging all that meat around, so I wouldn't go any less than a 4.88 to try and breathe some life back into that thing.
 
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