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Old 03-11-2009, 10:44 PM   #1
westofb
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Question Any idea's on what rear end gear I have?

I have a 69 chevy with 327 and newly rebuilt th350 and the tire size is 255/70R15. Running down highway at speeds of 65 mph, motor is turn 3200 rpms, making me a little uncomfortable to take it very far. I can find no markings on my rear end and the glovebox decal is unreadable. Any ideas? Am thinking it must have 3.73's or higher. By the way great site here!
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Old 03-11-2009, 10:54 PM   #2
68gmsee
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Re: Any idea's on what rear end gear I have?

Unless your axle was changed there should be a number stamped on the passenger side on top of the axle. It may take some sand paper or wire brush to make it out. If you do happen to locate it, go to GMC Pauls site below.

Scroll down to locate your info.
http://www.gmcpauls.com/67-72_chevy.htm
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Old 03-11-2009, 11:00 PM   #3
1LoC10
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Re: Any idea's on what rear end gear I have?

I have the same size tires with 4:56 gears and its running about the same RPM's as you
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Old 03-11-2009, 11:13 PM   #4
67 cst swb
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Re: Any idea's on what rear end gear I have?

tire size is 255/70R15 (= 29 inch tall)
speed of 65 mph
motor is turn 3200 rpms

Well that figures out to be about a 4.25 gear (probably not)
But...

I figured out a few because tire sizes vary brand to brand:

tire size is 255/70R15 (= 29 inch tall)
speed of 65 mph
motor is turn 3096 rpms

rear gear = 4.11 ratio

OR

tire size is 255/70R15 (= 28.5 inch tall)
speed of 65 mph
motor is turn 3150 rpms

rear gear = 4.11 ratio

OR

tire size is 255/70R15 (= 28 inch tall)
speed of 65 mph
motor is turn 3200 rpms

rear gear = 4.11 ratio

Hope that helps...
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My Trucks:
1967 Chevrolet Short Wide Box 327 TH350 9" w/3.90 gears paint will be White - Current Project
1967 Chevrolet Custom LWB 283 TH400 3.73 Posi, no-AC, no-PS, no-PB, bench-seat, small-window - mostly orig driver
1967 Chevrolet CST LWB originally a 327 TH400 3.73 Posi AC PS PB, had Buddy Buckets, Small Window - parts truck
1967 Chevrolet CST LWB, 283 MT 3.73 had Buddy Buckets, Panoramic Window - parts truck
2001 Chevrolet 3500 2WD Crew Cab Dually 8.1L Allison White

Last edited by 67 cst swb; 03-11-2009 at 11:15 PM.
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Old 03-12-2009, 03:31 AM   #5
westofb
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Re: Any idea's on what rear end gear I have?

thanks everyone for the info!
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Old 03-12-2009, 06:12 AM   #6
jbristo67
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Re: Any idea's on what rear end gear I have?

get you a 700 no more worries
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Old 03-12-2009, 11:43 PM   #7
westofb
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Re: Any idea's on what rear end gear I have?

Yeah I know, but just put in a fresh 350 and it will not be daily driven so fuel mileage not that big an issue. Was more concerned about destroying my engine....lol, thanks all for the help!
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