RPM at 60mph? - Moparts Forums

Register Log In Moparts Forums Moparts Question and Answer RPM at 60mph?

Print Thread

RPM at 60mph? #2784872 06/13/20 10:21 AM 06/13/20 10:21 AM
Joined: Jan 2003 Posts: 670 Third rock from the sun. B busboy OP mopar
busboy OP mopar B Joined: Jan 2003 Posts: 670 Third rock from the sun.	70’ b-body, 440 with an 833 (1967), 3:55 and a 28” tall tire. The online calculators show I should be turning 2500-2600 rpm at 60mph, I’m turning 3000rpm. I’ve confirmed the cars speed with a gps so not sure what’s up with my combination. What rpm are you folks turning using a similar set up? Last edited by busboy; 06/13/20 10:24 AM. Oh yeah, it's a hybrid.....it burns gas and tires!

Re: RPM at 60mph? [Re: busboy] #2784882 06/13/20 10:36 AM 06/13/20 10:36 AM
Joined: Jul 2010 Posts: 374 Alberta, Canada 300rag enthusiast
300rag enthusiast Joined: Jul 2010 Posts: 374 Alberta, Canada	That's the RPM for a 4.10 with a 28" tire. Peter '65 300 'vert 413/4spd '18 Challenger R/T Shaker '19 Durango R/T

Re: RPM at 60mph? [Re: 300rag] #2784896 06/13/20 11:02 AM 06/13/20 11:02 AM
Joined: Dec 2012 Posts: 257 Alberta 4 440_Offroader enthusiast
440_Offroader enthusiast 4 Joined: Dec 2012 Posts: 257 Alberta	My Challenger with a 383/727/3.55 runs 3000rpm @ 60mph. I have 255/60/15 rear tires, not sure the diameter. I thought it kind of high myself. Not sure if the tach is not reading correctly, or torque converter slipping some? I verified my gears when I had the case out, thinking the gears may have been changed, but they were correct to the tag.

Re: RPM at 60mph? [Re: 440_Offroader] #2784899 06/13/20 11:06 AM 06/13/20 11:06 AM
Joined: Dec 2004 Posts: 10,551 Rittman Ohio fourgearsavoy I Live Here
fourgearsavoy I Live Here Joined: Dec 2004 Posts: 10,551 Rittman Ohio	My Savoy with 4.10 gears and an 833 4 speed and 28" tires runs 3300 at 60 MPH Gus 64 Plymouth Savoy 493 Indy EZ's by Nick at Compu-Flow 5-Speed Richmond faceplate Liberty box Dana 60

Re: RPM at 60mph? [Re: fourgearsavoy] #2784902 06/13/20 11:11 AM 06/13/20 11:11 AM
Joined: Jul 2008 Posts: 30,424 Florida STAYcation dOc ! The village idiot's idiot
dOc ! The village idiot's idiot Joined: Jul 2008 Posts: 30,424 Florida STAYcation	4g needs a 5g to keep the Rs down !

Re: RPM at 60mph? [Re: 440_Offroader] #2784930 06/13/20 12:14 PM 06/13/20 12:14 PM
Joined: Jul 2010 Posts: 374 Alberta, Canada 300rag enthusiast
300rag enthusiast Joined: Jul 2010 Posts: 374 Alberta, Canada	Originally Posted by 440_Offroader My Challenger with a 383/727/3.55 runs 3000rpm @ 60mph. I have 255/60/15 rear tires, not sure the diameter. I thought it kind of high myself. Not sure if the tach is not reading correctly, or torque converter slipping some? I verified my gears when I had the case out, thinking the gears may have been changed, but they were correct to the tag. 255/60 is a 27" diameter, giving 2660 RPM with no slip. Peter '65 300 'vert 413/4spd '18 Challenger R/T Shaker '19 Durango R/T

Re: RPM at 60mph? [Re: busboy] #2784933 06/13/20 12:21 PM 06/13/20 12:21 PM
Joined: May 2003 Posts: 6,557 Downtown Roebuck Ont Twostick Still wishing...
Twostick Still wishing... Joined: May 2003 Posts: 6,557 Downtown Roebuck Ont	Originally Posted by busboy 70’ b-body, 440 with an 833 (1967), 3:55 and a 28” tall tire. The online calculators show I should be turning 2500-2600 rpm at 60mph, I’m turning 3000rpm. I’ve confirmed the cars speed with a gps so not sure what’s up with my combination. What rpm are you folks turning using a similar set up? Verify the axle ratio if you didn't install them yourself. 275/60/15 tires? If the axle and tire diameter check out, it's time to check your tach calibration. Kevin

Re: RPM at 60mph? [Re: 300rag] #2785261 06/14/20 09:22 AM 06/14/20 09:22 AM
Joined: Jan 2003 Posts: 670 Third rock from the sun. B busboy OP mopar
busboy OP mopar B Joined: Jan 2003 Posts: 670 Third rock from the sun.	That’s sure what it sounds like 300rag! I assembled the 3:55 pig myself but the shop installed it, think I will jack it up and spin the wheel for a rough check. They could have put in the wrong one😳! Oh yeah, it's a hybrid.....it burns gas and tires!

Re: RPM at 60mph? [Re: Twostick] #2785265 06/14/20 09:25 AM 06/14/20 09:25 AM
Joined: Jan 2003 Posts: 670 Third rock from the sun. B busboy OP mopar
busboy OP mopar B Joined: Jan 2003 Posts: 670 Third rock from the sun.	Correct Kevin, 275/60 15 tires. Tach calibration is a good call, freshly restored dash/gauges but it sure sounds like it’s buzzing high. Last edited by busboy; 06/14/20 09:26 AM. Oh yeah, it's a hybrid.....it burns gas and tires!

Re: RPM at 60mph? [Re: busboy] #2785334 06/14/20 11:38 AM 06/14/20 11:38 AM
Joined: Mar 2007 Posts: 3,277 West Coast, USA jbc426 master
jbc426 master Joined: Mar 2007 Posts: 3,277 West Coast, USA	I checked yesterday to make sure where it is with my combo. '68 Barracuda convertible, 408 Magnum based EFI's motor ((382hp & 525 ft lbs of torque at the wheels)), Stage 2 Extreme Automatic's 2004R transmission with a 3800 rpm lock-up torque converter and 3.91's turning 28" tall 275/60-15 Nitto Drag Radials. It spins 1950 rpm at 60 mph and gets 17+ mpg with the top down. The 2004R is the best transmission I've ever had the pleasure of owning. With the lower 1st gear ratio, it's the equivalent of having 4.30 gear ratio out of the hole. The car only spins for 10 feet and then dead hooks before it goes through the rest of the gears. It gets up to 60 mph pretty quick too. 1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's 1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 4.30's (closest thing to an automatic 5 speed going)

Re: RPM at 60mph? [Re: jbc426] #2785612 06/15/20 09:45 AM 06/15/20 09:45 AM
Joined: Feb 2003 Posts: 16,121 Mesa, Arizona D dart4forte I Live Here
dart4forte I Live Here D Joined: Feb 2003 Posts: 16,121 Mesa, Arizona	Originally Posted by jbc426 I checked yesterday to make sure where it is with my combo. '68 Barracuda convertible, 408 Magnum based EFI's motor ((382hp & 525 ft lbs of torque at the wheels)), Stage 2 Extreme Automatic's 2004R transmission with a 3800 rpm lock-up torque converter and 3.91's turning 28" tall 275/60-15 Nitto Drag Radials. It spins 1950 rpm at 60 mph and gets 17+ mpg with the top down. The 2004R is the best transmission I've ever had the pleasure of owning. With the lower 1st gear ratio, it's the equivalent of having 4.30 gear ratio out of the hole. The car only spins for 10 feet and then dead hooks before it goes through the rest of the gears. It gets up to 60 mph pretty quick too. Man, I love that Cuda “So if it’s on the internet it must be true” Abe Lincoln

Re: RPM at 60mph? [Re: busboy] #2786171 06/16/20 10:49 PM 06/16/20 10:49 PM
Joined: Aug 2005 Posts: 5,998 Salem Grizzly Moparts Proctologist
Grizzly Moparts Proctologist Joined: Aug 2005 Posts: 5,998 Salem	I was turning 3100 rpm at 60mph with 3.91's, 26's and A833, so, I think you are in the ballpark. Life is better these days with overdrive and 3.23's: 1700 rpm and + 4 mpg. No loss of acceleration either. Not sure why a 426 needs Slant Six gears to perform? . Mo' Farts Moderated by "tbagger".

Re: RPM at 60mph? [Re: Grizzly] #2786200 06/17/20 12:21 AM 06/17/20 12:21 AM
Joined: May 2019 Posts: 6,206 nowhere S Sniper master
Sniper master S Joined: May 2019 Posts: 6,206 nowhere	Originally Posted by Grizzly Not sure why a 426 needs Slant Six gears to perform? Because the most affordable way to put an OD manual trans behind a Hemi is the A833. All other options are multiples in additional cost.

Re: RPM at 60mph? [Re: busboy] #2786202 06/17/20 12:55 AM 06/17/20 12:55 AM
Joined: Jan 2003 Posts: 30,983 Oregon A AndyF I Win
AndyF I Win A Joined: Jan 2003 Posts: 30,983 Oregon	Originally Posted by busboy 70’ b-body, 440 with an 833 (1967), 3:55 and a 28” tall tire. The online calculators show I should be turning 2500-2600 rpm at 60mph, I’m turning 3000rpm. I’ve confirmed the cars speed with a gps so not sure what’s up with my combination. What rpm are you folks turning using a similar set up? 3000 RPM with 3.55 gears and a 28 inch rear tire is a little over 70 mph. So one of your numbers is wrong. Not sure which but something in your equation is wrong. You were in fourth gear correct? 3000 rpm at 60 mph with a 28 inch tire requires more than a 4.10 gear. I have 4.56 gears in my Duster and it turns 3000 RPM at 60 mph with a 31 inch rear tire.

Re: RPM at 60mph? [Re: Sniper] #2786734 06/18/20 10:28 AM 06/18/20 10:28 AM
Joined: Aug 2005 Posts: 5,998 Salem Grizzly Moparts Proctologist
Grizzly Moparts Proctologist Joined: Aug 2005 Posts: 5,998 Salem	Originally Posted by Sniper Originally Posted by Grizzly Not sure why a 426 needs Slant Six gears to perform? Because the most affordable way to put an OD manual trans behind a Hemi is the A833. All other options are multiples in additional cost. I was talking about the "need" to have 4.10's with a Hemi. Mo' Farts Moderated by "tbagger".

Re: RPM at 60mph? [Re: AndyF] #2792203 07/03/20 09:00 AM 07/03/20 09:00 AM
Joined: Jan 2003 Posts: 670 Third rock from the sun. B busboy OP mopar
busboy OP mopar B Joined: Jan 2003 Posts: 670 Third rock from the sun.	Thanks Andy, here’s the update. Haven’t been driving much lately but was finally able to get out in the car. Tried the gps again, turns out at 60mph gps shows 65mph so speedo is under reading by 5mph. When I slow to 55mph (60mph gps) my revs are at 2800rpm, seems a little better. I’m using the yellow 33 tooth speedo gear which I thought was correct for 3:55 gears, may have to change that. Next thing to check would be the accuracy of the tach, anyone have any idea how to I would go about that?? Oh yeah, it's a hybrid.....it burns gas and tires!

Re: RPM at 60mph? [Re: busboy] #2792215 07/03/20 09:19 AM 07/03/20 09:19 AM
Joined: Jan 2003 Posts: 10,685 North Dakota 6PakBee I Live Here
6PakBee I Live Here Joined: Jan 2003 Posts: 10,685 North Dakota	Originally Posted by busboy Next thing to check would be the accuracy of the tach, anyone have any idea how to I would go about that?? The best way would be to use a square wave generator. Sometimes technical colleges have them for electrical classes. If you are handy electrically, there are gobs of articles on the web how to build one using an op-amp but I'd see if I could borrow or use one before I resorted to that. Last edited by 6PakBee; 07/03/20 09:19 AM. "We live in a time when intelligent people are being silenced so that stupid people won't be offended".

Re: RPM at 60mph? [Re: 6PakBee] #2792987 07/05/20 02:42 PM 07/05/20 02:42 PM
Joined: Dec 2007 Posts: 12,587 Great Neck,LI,new york hemi-itis I Live Here
hemi-itis I Live Here Joined: Dec 2007 Posts: 12,587 Great Neck,LI,new york	3000 rpm with 4.10 & 31 inch tall tires is 60 MPH. HEMI-ITIS has no cure. My condition is fully BLOWN!!

Moderated by Al_Alguire, Hotwheelsjr, moparts, not_a_charger, RangerDan440, tboomer

Hop To

Powered by UBB.threads™ PHP Forum Software 7.7.1