I thought it was 4.11 but may be 4.56??? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Longhorn 70 · 11-15-2013, 02:59 PM

I have always been told and always thought that I had a 4.11 under the truck. I am not so sure now. I have been trying to calibrate the speedo with little luck.

I DLd an app for my phone that is a GPS speedo. I am indicating about 10% HIGH off with a 700R4. I have a GRAY drive gear and GRAY driven gear for the speedo drive with 30" tall tires. All of the speedo calculators I see say I should be dead on or SLOW.

Insights??

Thank you in advance

**Stocker** · 11-15-2013, 04:11 PM

Jack up the rear of the truck and rotate either tire two full turns. Count how many times the driveshaft rotates. That's your approximate gear ratio.

Or to be sure, remove the differential cover and count the teeth on the gears. Divide the number of teeth on the ring gear by the number of teeth on the pinion gear. Button it back up and fill with fresh gear oil, and you've just killed two birds with one stone.

Longhorn 70 · 11-15-2013, 04:51 PM

I did try the spin the wheel thing. I may have miscounted or did the procedure incorrectly. I counted the driveshaft turns to rotate the wheel one time.

I'll have to wait until I get the time to do the bird killing.

**LockDoc** · 11-15-2013, 08:45 PM

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Toward the bottom of this thread there is a picture of where the rear axle code is located on the housing, then look it up in the charts.

http://67-72chevytrucks.com/vboard/s...d.php?t=578793

LockDoc

11-15-2013, 02:59 PM	#1
Longhorn 70 Registered User Join Date: Dec 2012 Location: Chandler AZ Posts: 1,149	I thought it was 4.11 but may be 4.56??? I have always been told and always thought that I had a 4.11 under the truck. I am not so sure now. I have been trying to calibrate the speedo with little luck. I DLd an app for my phone that is a GPS speedo. I am indicating about 10% HIGH off with a 700R4. I have a GRAY drive gear and GRAY driven gear for the speedo drive with 30" tall tires. All of the speedo calculators I see say I should be dead on or SLOW. Insights?? Thank you in advance __________________ 1970 Longhorn, Front Disc, 350/4 bolt, 882 heads, HEI, Edelbrock, 700R4, HO-52/4.11. 1996 Corvette, Collector Roadster, LT4, 396, 450RWHP, 6sp, 4.11/Dana44/posi 5 point roll bar And let us not grow weary of doing good, for in due season we will reap, if we do not give up. Gal 6:9

11-15-2013, 04:11 PM	#2
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,499	Re: I thought it was 4.11 but may be 4.56??? Jack up the rear of the truck and rotate either tire two full turns. Count how many times the driveshaft rotates. That's your approximate gear ratio. Or to be sure, remove the differential cover and count the teeth on the gears. Divide the number of teeth on the ring gear by the number of teeth on the pinion gear. Button it back up and fill with fresh gear oil, and you've just killed two birds with one stone. __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

11-15-2013, 04:51 PM	#3
Longhorn 70 Registered User Join Date: Dec 2012 Location: Chandler AZ Posts: 1,149	Re: I thought it was 4.11 but may be 4.56??? I did try the spin the wheel thing. I may have miscounted or did the procedure incorrectly. I counted the driveshaft turns to rotate the wheel one time. I'll have to wait until I get the time to do the bird killing. __________________ 1970 Longhorn, Front Disc, 350/4 bolt, 882 heads, HEI, Edelbrock, 700R4, HO-52/4.11. 1996 Corvette, Collector Roadster, LT4, 396, 450RWHP, 6sp, 4.11/Dana44/posi 5 point roll bar And let us not grow weary of doing good, for in due season we will reap, if we do not give up. Gal 6:9

11-15-2013, 08:45 PM	#4
LockDoc The Older Generation Join Date: Aug 2006 Location: Montezuma, Iowa Posts: 25,332	Re: I thought it was 4.11 but may be 4.56??? - Toward the bottom of this thread there is a picture of where the rear axle code is located on the housing, then look it up in the charts. http://67-72chevytrucks.com/vboard/s...d.php?t=578793 LockDoc __________________ Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 -



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