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| | | | Joined: Feb 2007 Posts: 31 Shop Shark | | Shop Shark Joined: Feb 2007 Posts: 31 | I have a 1951 Chevrolet 1/2 ton Pickup. I have a 350 with a Muncie (M-21) 4-speed. And the rear end is out of a 1970 GMC, with a 6-bolt wheel pattern. I think the rear end gearing is 3.73's.
When I'm driving 60-MPH, my tach says 3400 RPM. (My speedo has been recalibrated to spec's) What I'm trying to find out is what ring & pinion gearing would work best if I was to change it, using the same rear end?
And if so...what good supplier would have them? And how hard is it to change?
I'd like to lower the RPM's in 4th-gear, going 60-MPH. Could somebody please help me with information that I need on this subject?
Thankyou...Jeff
Last edited by diditanole; 09/29/2009 12:37 AM.
| | | | | Joined: Mar 2002 Posts: 9,115 'Bolter | | 'Bolter Joined: Mar 2002 Posts: 9,115 | That is a very high RPM figure that you have there. What size of tires are you running?
Last edited by truckernix; 09/29/2009 11:40 AM.
| | | | | Joined: Jan 2008 Posts: 502 Shop Shark | | Shop Shark Joined: Jan 2008 Posts: 502 | Jeff, Ya, that does sound like low "R,s " for a 373 gear and I say that cause I've got a car with a 3.36 gear,15in. tires and it turns 3500 RPM at 70 mph, so a 3.73 should be turning even faster unless you have some tall tires on the rear.
Ya better check the ratio on that rear again.
No dis-credit intended but to hear you asks how much work is involved with a gear swap says maybe you ought to have it done.
I've been a wrench for 40 years and even though I could do the mechanical part of changing the gears I lack the neat tools which make setting up the gear easy. Backlash and tooth contact pattern have to be right or the gear may howl.
Randy's Ring and Pinion in Everett, Wa. has about everything you might ever want for your rear-end.
He can tell you, given the tire size you need to run ,what ratio will be needed to turn what ever RPM you would like to be at when doing 70 MPH or whatever speed.
Dan
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| | | | | Joined: Apr 2009 Posts: 431 Shop Shark | | Shop Shark Joined: Apr 2009 Posts: 431 | glas - 3500 at 70mph with 3.36s? what size/type engine? | | | | | Joined: Feb 2007 Posts: 31 Shop Shark | | Shop Shark Joined: Feb 2007 Posts: 31 | *My tire sizes are: 215/70R15.
*Engine: 1970 Chev Impala 350 4-bolt main
*Trans: 1968 El Camino Muncie 4-speed (M21)
Thanks...Jeff
Last edited by diditanole; 09/29/2009 11:38 PM.
| | | | | Joined: Feb 2006 Posts: 549 Shop Shark | | Shop Shark Joined: Feb 2006 Posts: 549 | Sounds a bit high to me as well.
I'm running a 350 & saginaw 4 speed (70ish Nova).
I changed from 4:10 to 3:35 and changed RPM's from about 3300 to 2800 at 70 MPH.
| | | | | Joined: Mar 2002 Posts: 9,115 'Bolter | | 'Bolter Joined: Mar 2002 Posts: 9,115 | OK, your tire size gives you a revs per mile of 777 which is the wheel RPM at 60 mph. If you have 3.73 gears in the rear end your engine will be turning 777 x 3.73 which is 2898 RPM. That is why I was surprized at your stated RPM. | | | | | Joined: Feb 2007 Posts: 31 Shop Shark | | Shop Shark Joined: Feb 2007 Posts: 31 | I think that I was probably going 65 MPH and my tach read 3400 RPM. Would like to change the gears a bit higher though. Thanks for all your reply help! ...Jeff
Last edited by diditanole; 10/10/2009 11:32 PM.
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