MPH = RPM's - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Andy4639 · 01-28-2016, 10:56 PM

Here are a few shots while running down the interstate in the truck today.
I had to make a trip down to Atlanta to pick up some parts. I ran pretty much around 80 the whole way.

Stock 6.0 with 4l80e and 4:10 gears. 29" tall tires

izzy_Britton · 01-29-2016, 12:44 AM

Very Nice!

I need to check my rear end gear ratio. Now i have an idea of what to expect. thanks!

BR3W CITY · 01-29-2016, 02:50 AM

This always throws me....I swear mine turns a slightly higher RPM than everyone else. I have a 4l80e also, 3:73's but a slightly smaller tire, and turns like 300-400rpm higher than you with the 4;10's.

Then again, my lockup converter might be smoked, so it might be the slip during lock.

**Hart_Rod** · 01-29-2016, 09:22 AM

Quote:

Originally Posted by BR3W CITY

This always throws me....I swear mine turns a slightly higher RPM than everyone else. I have a 4l80e also, 3:73's but a slightly smaller tire, and turns like 300-400rpm higher than you with the 4;10's.

Then again, my lockup converter might be smoked, so it might be the slip during lock.

Bingo!

slotard · 01-29-2016, 11:18 AM

I have 350/350/4.10 and 30" tires and don't enjoy high speed. I have a 3.73 rear end I have to throw in and sometime it'll get an LS and overdrive tranny. Then again, I don't have a tach so I'm going by ear.

Is your speedometer accurate?

72MARIO · 01-29-2016, 12:19 PM

No guess work

https://www.ringpinion.com/Calculators/Calc_RPM.aspx

ptc · 01-29-2016, 12:30 PM

Did you verify that speedo with GPS? its always good to check that.

there are apps on iPhone and Android that you can use right on your phone.

izzy_Britton · 01-29-2016, 12:41 PM

The speedo in the first photo is a GPS speedo.

ptc · 01-29-2016, 12:56 PM

Quote:

Originally Posted by izzy_Britton

The speedo in the first photo is a GPS speedo.

oops my bad! ---- improper photo analysis

crazy longhorn · 01-29-2016, 06:57 PM

My 02 Silverado, with 29 " tires will run 65 mph @ 2200, with a 3.73 gear...(speedo reads 70mph, but the thing was not recalibrated, after the gear swap). original gears were 3.42. My old longhorn, same tire size/taller gear, is a tick over the legal limit @ 2200....will cruise all day long @ 100 mph (3100 on the tach? specs in the signature...longhorn

Andy4639 · 01-29-2016, 07:38 PM

Everything is accurate as it can be. The speedo is GPS + my garmin and my Iphone are all the same. The Iphone is a little slower responding though!

01-28-2016, 10:56 PM	#1
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,945	MPH = RPM's Here are a few shots while running down the interstate in the truck today. I had to make a trip down to Atlanta to pick up some parts. I ran pretty much around 80 the whole way. Stock 6.0 with 4l80e and 4:10 gears. 29" tall tires Attached Images __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

01-29-2016, 12:44 AM	#2
izzy_Britton Registered User Join Date: Apr 2013 Location: Nor-Cal Posts: 632	Re: MPH = RPM's Very Nice! I need to check my rear end gear ratio. Now i have an idea of what to expect. thanks! __________________ WHO_DCTC - Wifes 05 Z-71 Build - Now defunct as she decided she wants an Escalade too Cream Puff - LS'd Square - Slow going on the back burner Tripple Threat - 3 Wrecks for the price of one build thread Project Delongdium - Step-Sons Plastic Clad 2003 Avalanche - DONE and Delivered.

01-29-2016, 02:50 AM	#3
BR3W CITY meowMEOWmeowMEOW Join Date: Sep 2009 Location: MKE WI Posts: 7,128	Re: MPH = RPM's This always throws me....I swear mine turns a slightly higher RPM than everyone else. I have a 4l80e also, 3:73's but a slightly smaller tire, and turns like 300-400rpm higher than you with the 4;10's. Then again, my lockup converter might be smoked, so it might be the slip during lock. __________________ *'66 Short Step / SD Tuned / Big Cam LQ4 / Backhalfed /Built 4l80e / #REBUILDEVERYTHING* MY BUILD THE H8RDCPTR //\\ MY YOUTUBE CHANNEL REV J HD

01-29-2016, 11:18 AM	#5
slotard Registered User Join Date: Nov 2014 Location: Alameda, CA Posts: 877	Re: MPH = RPM's I have 350/350/4.10 and 30" tires and don't enjoy high speed. I have a 3.73 rear end I have to throw in and sometime it'll get an LS and overdrive tranny. Then again, I don't have a tach so I'm going by ear. Is your speedometer accurate? __________________ 1973 C20, 350/350

01-29-2016, 12:19 PM	#6
72MARIO Registered User Join Date: Nov 2000 Location: Huntsville Ontario Canada Posts: 4,051	Re: MPH = RPM's No guess work https://www.ringpinion.com/Calculators/Calc_RPM.aspx __________________ 1968 Suburban numbers matching all original truck now equipped with 6.0/4L80 on Accuair http://67-72chevytrucks.com/vboard/s...d.php?t=625017 1967 C/20 6.0/4L80 Roofing Truck 1990 V2500 Suburban "Plow Truck" 2005 TAHOE DD

01-29-2016, 12:30 PM	#7
ptc Registered User Join Date: Mar 2015 Location: Morada, CA --- (Near Lodi) Posts: 1,443	Re: MPH = RPM's Did you verify that speedo with GPS? its always good to check that. there are apps on iPhone and Android that you can use right on your phone. __________________ My Build: 57 Chevy Pro-Street

01-29-2016, 12:41 PM	#8
izzy_Britton Registered User Join Date: Apr 2013 Location: Nor-Cal Posts: 632	Re: MPH = RPM's The speedo in the first photo is a GPS speedo. __________________ WHO_DCTC - Wifes 05 Z-71 Build - Now defunct as she decided she wants an Escalade too Cream Puff - LS'd Square - Slow going on the back burner Tripple Threat - 3 Wrecks for the price of one build thread Project Delongdium - Step-Sons Plastic Clad 2003 Avalanche - DONE and Delivered.

01-29-2016, 06:57 PM	#10
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,402	Re: MPH = RPM's My 02 Silverado, with 29 " tires will run 65 mph @ 2200, with a 3.73 gear...(speedo reads 70mph, but the thing was not recalibrated, after the gear swap). original gears were 3.42. My old longhorn, same tire size/taller gear, is a tick over the legal limit @ 2200....will cruise all day long @ 100 mph (3100 on the tach? specs in the signature...longhorn __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears....

01-29-2016, 07:38 PM	#11
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,945	Re: MPH = RPM's Everything is accurate as it can be. The speedo is GPS + my garmin and my Iphone are all the same. The Iphone is a little slower responding though! __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

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