cruising rpm with 3.73's?
12-30-2010, 07:04 PM
#12
Staging Lane
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funny thing is, it feels slow as hell. of course coming from a cammed stalled reg cab 2wd doesnt help lol. im deff happy to know it has 4.10's that means im set for larger tires which are in its NEAR future.
12-30-2010, 07:48 PM
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You are one of the fortunate ones to have gotten the half ton crew with 4.10s. In 2005 the half ton crew had two options, 3.42s and 4.10s, this is for 4wds mind you. My old man was used to the days of the 350 and just knew he wanted 3.42s to keep the rpms nice and low and get some mileage out of it and its running about 1650 at 65 mph. The thing is a slug and gets about 17 at best at 65 mph. Get the speed up towards 80 and it can do 18-19 mpg. He should have went with 4.10s. My 99 has 3.73s and 31.5 inch tall tires (about to change to 33s) and it runs right at 1850 at 65. I wish I had 4.10s but I prefer to be geared a little high and let it twist in the lower gears then be geared low and blow right through the gears. With 33s I will be near 1700 at 65 and near 2400 at 65 in 3rd so when I get into a lot of hills or a head wind I can run in 3rd and not be spinning too awful high.
12-31-2010, 07:42 PM
#15
RE cruising RPM w/ 3.73
I have the exact same setup and tire size. At 70 MPH my tach shows 2100.
either you don't have 3.73, or the converter is not locking up.
Have you noticed high trans temps after a long drive?
either you don't have 3.73, or the converter is not locking up.
Have you noticed high trans temps after a long drive?
12-31-2010, 08:58 PM
#17
Now that you know your gear ratio, you can easily check and make sure that your tcc is locking up...get on the highway and start a steady cruise. While maintaining speed with your right foot, tap your brake with the left...the RPM's should jump up a few hundred as the tcc disengages, if the tach doesn't show a change, your tcc is not functioning properly.
01-01-2011, 10:46 AM
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I really dont know if a set of 285's will make you economy any better. You city mileage will decrease with taller tires for sure.
I ran 4.10's with 27" and 28" tires for years. The fast cruising at like 80-85mph fuel economy certainly wasnt great, but 65-70 mph wasnt too bad.
RPM isnt the be all end all with regards to fuel economy. Whatever puts the less load with the least TPS% will be best.
A 3.08 gear with a 30" tire will lug an engine at 50 mph thus causing the throttle to be opened more to maintain speed, conversley a 5.13 gear with a 30" tire will cause less load, but will require more rpm which will also cause more throttle to be used.
I ran 3.08's with stock 235/75/15 stock tires with 3.08 gears and with cruise control on the TCC would unlock while climbing grades on the highway, I could feel the pedal being pulled away from my foot. With 4.10's the TCC would stay locked on the same grade at the same speed and the pedal would barely move.
I would think that a heavier GMT800 truck along with the heavier configuration of an crew cab coupled with a 5.3 would do better with 4.10's in all around driving with the current tires you are running.
I suppose that if you drive mostly highway, it might help you a mpg or 2, but certainly not worth the cost of tires, unless swapping when worn.
I guess my point is, 4.10's dont necessarily equal bad fuel economy, esp with todays OD transmissions, and for the taller and taller tires stock tire heights that GM has been placing on their trucks from the factory. When the GMT800 truck debuted in 1999, there was no more 3.08 option, it was upped to 3.23's due to the decreased low rpm torque and taller tire heights the new for 99 GEN 3 4.8/5.3 trucks were equipped with. This is the same reason there was never a 4.10 gear option in the 88-98 GMT400 <7200 lb GVRW 1/2 ton trucks, but there was a 4.10 available gear in the newer trucks.
When in closed loop, the PCM will always maintain stoich., so whatever you can do to reduce your MAF g/sec will be bettering your fuel economy. It would be interesting to see you log your MAF now and when you install taller tires.
Be sure to retune with the tires so that any comparison for fuel mileage is accurate.
peace
Hog
I ran 4.10's with 27" and 28" tires for years. The fast cruising at like 80-85mph fuel economy certainly wasnt great, but 65-70 mph wasnt too bad.
RPM isnt the be all end all with regards to fuel economy. Whatever puts the less load with the least TPS% will be best.
A 3.08 gear with a 30" tire will lug an engine at 50 mph thus causing the throttle to be opened more to maintain speed, conversley a 5.13 gear with a 30" tire will cause less load, but will require more rpm which will also cause more throttle to be used.
I ran 3.08's with stock 235/75/15 stock tires with 3.08 gears and with cruise control on the TCC would unlock while climbing grades on the highway, I could feel the pedal being pulled away from my foot. With 4.10's the TCC would stay locked on the same grade at the same speed and the pedal would barely move.
I would think that a heavier GMT800 truck along with the heavier configuration of an crew cab coupled with a 5.3 would do better with 4.10's in all around driving with the current tires you are running.
I suppose that if you drive mostly highway, it might help you a mpg or 2, but certainly not worth the cost of tires, unless swapping when worn.
I guess my point is, 4.10's dont necessarily equal bad fuel economy, esp with todays OD transmissions, and for the taller and taller tires stock tire heights that GM has been placing on their trucks from the factory. When the GMT800 truck debuted in 1999, there was no more 3.08 option, it was upped to 3.23's due to the decreased low rpm torque and taller tire heights the new for 99 GEN 3 4.8/5.3 trucks were equipped with. This is the same reason there was never a 4.10 gear option in the 88-98 GMT400 <7200 lb GVRW 1/2 ton trucks, but there was a 4.10 available gear in the newer trucks.
When in closed loop, the PCM will always maintain stoich., so whatever you can do to reduce your MAF g/sec will be bettering your fuel economy. It would be interesting to see you log your MAF now and when you install taller tires.
Be sure to retune with the tires so that any comparison for fuel mileage is accurate.
peace
Hog
01-01-2011, 11:25 PM
#19
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I really dont know if a set of 285's will make you economy any better. You city mileage will decrease with taller tires for sure.
I ran 4.10's with 27" and 28" tires for years. The fast cruising at like 80-85mph fuel economy certainly wasnt great, but 65-70 mph wasnt too bad.
RPM isnt the be all end all with regards to fuel economy. Whatever puts the less load with the least TPS% will be best.
A 3.08 gear with a 30" tire will lug an engine at 50 mph thus causing the throttle to be opened more to maintain speed, conversley a 5.13 gear with a 30" tire will cause less load, but will require more rpm which will also cause more throttle to be used.
I ran 3.08's with stock 235/75/15 stock tires with 3.08 gears and with cruise control on the TCC would unlock while climbing grades on the highway, I could feel the pedal being pulled away from my foot. With 4.10's the TCC would stay locked on the same grade at the same speed and the pedal would barely move.
I would think that a heavier GMT800 truck along with the heavier configuration of an crew cab coupled with a 5.3 would do better with 4.10's in all around driving with the current tires you are running.
I suppose that if you drive mostly highway, it might help you a mpg or 2, but certainly not worth the cost of tires, unless swapping when worn.
I guess my point is, 4.10's dont necessarily equal bad fuel economy, esp with todays OD transmissions, and for the taller and taller tires stock tire heights that GM has been placing on their trucks from the factory. When the GMT800 truck debuted in 1999, there was no more 3.08 option, it was upped to 3.23's due to the decreased low rpm torque and taller tire heights the new for 99 GEN 3 4.8/5.3 trucks were equipped with. This is the same reason there was never a 4.10 gear option in the 88-98 GMT400 <7200 lb GVRW 1/2 ton trucks, but there was a 4.10 available gear in the newer trucks.
When in closed loop, the PCM will always maintain stoich., so whatever you can do to reduce your MAF g/sec will be bettering your fuel economy. It would be interesting to see you log your MAF now and when you install taller tires.
Be sure to retune with the tires so that any comparison for fuel mileage is accurate.
peace
Hog
I ran 4.10's with 27" and 28" tires for years. The fast cruising at like 80-85mph fuel economy certainly wasnt great, but 65-70 mph wasnt too bad.
RPM isnt the be all end all with regards to fuel economy. Whatever puts the less load with the least TPS% will be best.
A 3.08 gear with a 30" tire will lug an engine at 50 mph thus causing the throttle to be opened more to maintain speed, conversley a 5.13 gear with a 30" tire will cause less load, but will require more rpm which will also cause more throttle to be used.
I ran 3.08's with stock 235/75/15 stock tires with 3.08 gears and with cruise control on the TCC would unlock while climbing grades on the highway, I could feel the pedal being pulled away from my foot. With 4.10's the TCC would stay locked on the same grade at the same speed and the pedal would barely move.
I would think that a heavier GMT800 truck along with the heavier configuration of an crew cab coupled with a 5.3 would do better with 4.10's in all around driving with the current tires you are running.
I suppose that if you drive mostly highway, it might help you a mpg or 2, but certainly not worth the cost of tires, unless swapping when worn.
I guess my point is, 4.10's dont necessarily equal bad fuel economy, esp with todays OD transmissions, and for the taller and taller tires stock tire heights that GM has been placing on their trucks from the factory. When the GMT800 truck debuted in 1999, there was no more 3.08 option, it was upped to 3.23's due to the decreased low rpm torque and taller tire heights the new for 99 GEN 3 4.8/5.3 trucks were equipped with. This is the same reason there was never a 4.10 gear option in the 88-98 GMT400 <7200 lb GVRW 1/2 ton trucks, but there was a 4.10 available gear in the newer trucks.
When in closed loop, the PCM will always maintain stoich., so whatever you can do to reduce your MAF g/sec will be bettering your fuel economy. It would be interesting to see you log your MAF now and when you install taller tires.
Be sure to retune with the tires so that any comparison for fuel mileage is accurate.
peace
Hog
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