Another rear end and front end Question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

teeitup · 12-25-2002, 07:44 PM

How can I tell what gears are in this 72 3/4 automatic 4x4 without taking off the cover? THANKS any help is appreciated! Randy

travis martin · 12-25-2002, 09:10 PM

Randy i've been told if you jack the rearend up and spin the wheel and count how many times the yoke spins verse the wheel then do math and you have it. For example if the wheel spins 1 time and the yoke turns 4 and assume it means it has 4:11 gears. Don't quote me i'm not sure if that is right or not. But thought i would try. Later Travis

JHickson6 · 12-25-2002, 09:16 PM

You could try to get the stamped code off of the axle, I'm not sure if its on the driverside or passenger side axle tube on the top. It's hard to find on an assembled truck, but then you can compare the code to the ones herewww.americanclassic.com/paint_test.asp

JimKshortstep4x4 · 12-25-2002, 10:10 PM

With the age of these trucks and what they go through, the for sure way is to pull the cover. You can usually tell if you leave both
wheels on the ground and roll the truck straight for one tire revolution. We mark the inner drum with a line and a line on the backing plate with a piece of chalk and on the pinion we mark the shield and the housing. Whatever the pinion turns in one rev of the tire is your ratio. Because of the differential gears in the rear end you cannot get an accurate turn of the pinion with only one wheel being rotated, so you need both wheels on the ground.

The more accurate you make the lines and the care in making sure of one rev of the tires, the closer you can come to your ratio.

Jim

**Joesjunk** · 12-27-2002, 12:53 AM

Randy, there was a tag on the front diff cover from the factory that has the ratio on it. It is bolted on with a diff cover bolt usually on the lower passenger side. It may be gone from 30+ years of servicing though?? I can send you a pic of what this looks like if you need one. If it was a factory 350 truck with an eaton rear end and no ratio on the glove box sheet it will be 4:10. There are numbers stamped on the top of the eaton third members (on the out side) but thet are very hard to see. I have a third member out that I could send you a pic of where the #'s are on them.
Joe

teeitup · 12-27-2002, 09:08 AM

Thanks EVERYONE, I'll check this weekend and see if I can figure it out but probably has 4.10's in it. THANKS Randy

Longhorn Man · 12-27-2002, 12:07 PM

Why not pull the covers?
When do you think that oil was chainged last?

12-25-2002, 07:44 PM	#1
teeitup Just like to part out trucks!! Join Date: Nov 2001 Location: Meriden, Ks-North of Topeka 10 miles Posts: 27,395	Another rear end and front end Question How can I tell what gears are in this 72 3/4 automatic 4x4 without taking off the cover? THANKS any help is appreciated! Randy __________________ 67 Chev swb stepside 4x4 283 4 speed SOLD 72 blazer 4x4 4 speed Cheyenne 72 GMC swb 4x4 fleet 4 speed, original paint 1958 Cameo (one of 1405 built, it was my dads) 2020 chevy Apex 4x4 crew cab 1969 Z28 with the 302 1980 chevy swb 4x4 1964 chevell Malibu SS 1976 K20, sold new originally out of my dads chevy dealership Members that I've met, over 200 probably closer to 300 in the 12 years I've been on this site, everyone I met "It was a pleasure"

12-25-2002, 09:10 PM	#2
travis martin CoonHunter Join Date: Aug 2002 Location: valley falls ks Posts: 346	Randy i've been told if you jack the rearend up and spin the wheel and count how many times the yoke spins verse the wheel then do math and you have it. For example if the wheel spins 1 time and the yoke turns 4 and assume it means it has 4:11 gears. Don't quote me i'm not sure if that is right or not. But thought i would try. Later Travis __________________ 72 Chevy 1/2 ton 4x4 4" inch lift. 2000 Chevy Malibu

12-25-2002, 09:16 PM	#3
JHickson6 I Love This Stuff! Join Date: May 2002 Location: Winnipeg, Manitoba, Canada Posts: 739	You could try to get the stamped code off of the axle, I'm not sure if its on the driverside or passenger side axle tube on the top. It's hard to find on an assembled truck, but then you can compare the code to the ones herewww.americanclassic.com/paint_test.asp __________________ My Rides 1967 C10 In Pieces for now 1985 Ford B700 SourPuss Bus - BIG BLUE 2003 Silverado CITY WORKER YELLOW!!

12-27-2002, 12:53 AM	#5
Joesjunk Senior Member Join Date: May 2001 Location: Independence MO. Posts: 7,715	Randy, there was a tag on the front diff cover from the factory that has the ratio on it. It is bolted on with a diff cover bolt usually on the lower passenger side. It may be gone from 30+ years of servicing though?? I can send you a pic of what this looks like if you need one. If it was a factory 350 truck with an eaton rear end and no ratio on the glove box sheet it will be 4:10. There are numbers stamped on the top of the eaton third members (on the out side) but thet are very hard to see. I have a third member out that I could send you a pic of where the #'s are on them. Joe __________________ 72 3/4t Custom Deluxe 402/auto 66k Original paint 71 3/4t 4x4 Custom Deluxe 10k original miles Original paint 71 3/4t Cheyenne 402 70k original paint 72 3/4t 4x4 Custom deluxe 72 3/4t 4x4 Custom deluxe 91k original paint 72 Cheyenne/30 Dually 69 Camaro SS396 4-speed 13 GMC 2500HD Duramax I bought new 05 Jeep Wrangler "Willys Edition" 12k miles (I bought new) 85 3/4 ton 4x4 Scottsdale 33k miles original paint 86 1 ton 4x4 SRW Silverado 454 restored 80 1 ton 4x4 SRW Silverado 9,434 original miles!! original paint 95 GMC 1 ton dually 4x4 my dad bought new 95 GMC 3/4 ton 4x4, regular cab 454, 31k original miles 2002 2500HD 4x4 regular cab 6.0L 67k miles 2002 2500HD 4x4 regular cab 8.1L 28k miles 2003 GMC 2500HD 4x4 regular cab Diesel 93k miles 67-72 Parts for sale

12-27-2002, 09:08 AM	#6
teeitup Just like to part out trucks!! Join Date: Nov 2001 Location: Meriden, Ks-North of Topeka 10 miles Posts: 27,395	Thanks EVERYONE, I'll check this weekend and see if I can figure it out but probably has 4.10's in it. THANKS Randy __________________ 67 Chev swb stepside 4x4 283 4 speed SOLD 72 blazer 4x4 4 speed Cheyenne 72 GMC swb 4x4 fleet 4 speed, original paint 1958 Cameo (one of 1405 built, it was my dads) 2020 chevy Apex 4x4 crew cab 1969 Z28 with the 302 1980 chevy swb 4x4 1964 chevell Malibu SS 1976 K20, sold new originally out of my dads chevy dealership Members that I've met, over 200 probably closer to 300 in the 12 years I've been on this site, everyone I met "It was a pleasure"

12-25-2002, 10:10 PM	#4
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	With the age of these trucks and what they go through, the for sure way is to pull the cover. You can usually tell if you leave both wheels on the ground and roll the truck straight for one tire revolution. We mark the inner drum with a line and a line on the backing plate with a piece of chalk and on the pinion we mark the shield and the housing. Whatever the pinion turns in one rev of the tire is your ratio. Because of the differential gears in the rear end you cannot get an accurate turn of the pinion with only one wheel being rotated, so you need both wheels on the ground. The more accurate you make the lines and the care in making sure of one rev of the tires, the closer you can come to your ratio. Jim

12-27-2002, 12:07 PM	#7
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Why not pull the covers? When do you think that oil was chainged last?



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