Speedo/Rear End question... - The 1947 - Present Chevrolet & GMC Truck Message Board Network

firefighter736 · 09-22-2010, 04:05 PM

Hey guys... just found out that the leak I've been fighting for a week or so is the oh-so-famous Speedometer housing leak.

I had previously thought I had bought the truck with a TH350 in it only to find, after ordering a Speedo Bullet, that I have a Olds TH350 and share the same speedometer housing with the 700R4.

The speedometer has always been off on this truck so I figured that now would be the time to fix it. The big question is what kind of rear end do I have? I don't really have time to pull the cover off the rear end and count teeth (I would like to get the Speedo Gear/Housing/seals ordered tonight) so I was hoping someone would know the gear ratio for the average '66 C-10 with an inline-6 and 3 on the tree. I know this is probably asking for a lot (I'm sure there are many variables...) but it's worth a shot.

Edited to say I've heard most of these trucks with the I6 had 3.73s but it seems to be taching so high that it makes me wonder if 4.11s came in them, too...

61_FL_Apache · 09-22-2010, 05:07 PM

3.73 seems to be common ratio I am finding too.

1Bad62Pro/Street · 09-22-2010, 05:18 PM

1960-1966 Chevy/GMC Pickup Truck Specs & Engine/Trans/Axle ID's

http://67-72chevytrucks.com/vboard/s...d.php?t=327764

My '62 had a 3.90 in before the swap. 3 speed I6.
Posted via Mobile Device

**Captainfab** · 09-23-2010, 12:17 AM

IMO it doesn't take that long to pull the cover on the differential. The tooth count is stamped on the ring gear so you don't have to count the teeth. Even if you look up the code on the axle tube, there's a chance that the gears could have been changed sometme in the last 45 years. Plus the gear oil probably needs changed.

raycow · 09-23-2010, 05:35 AM

As already stated, 3.73 was the most common gear, but 4.11 was an option. You don't have to take off the cover to find out what you have.

Jack one rear wheel off the ground, put the transmission in neutral, and the parking brake off. Put matching marks on the pinion yoke and differential housing. Turn the wheel exactly TWO revolutions and count how many times the driveshaft turns, estimating any fractional turn as closely as possible. That number is your axle ratio.

If the wheel is difficult or impossible to turn, you may have posi. In that case, jack both rear wheels off the ground and turn either of them only ONE revolution. Count the driveshaft turns the same way as for an open rear.

Ray

09-22-2010, 04:05 PM	#1
firefighter736 Registered User Join Date: Aug 2010 Location: Floyd/Salem VA Posts: 148	Speedo/Rear End question... Hey guys... just found out that the leak I've been fighting for a week or so is the oh-so-famous Speedometer housing leak. I had previously thought I had bought the truck with a TH350 in it only to find, after ordering a Speedo Bullet, that I have a Olds TH350 and share the same speedometer housing with the 700R4. The speedometer has always been off on this truck so I figured that now would be the time to fix it. The big question is what kind of rear end do I have? I don't really have time to pull the cover off the rear end and count teeth (I would like to get the Speedo Gear/Housing/seals ordered tonight) so I was hoping someone would know the gear ratio for the average '66 C-10 with an inline-6 and 3 on the tree. I know this is probably asking for a lot (I'm sure there are many variables...) but it's worth a shot. Edited to say I've heard most of these trucks with the I6 had 3.73s but it seems to be taching so high that it makes me wonder if 4.11s came in them, too... Last edited by firefighter736; 09-22-2010 at 04:19 PM.

09-22-2010, 05:07 PM	#2
61_FL_Apache Who Me? Join Date: Sep 2010 Location: Royal Palm Beach, FL Posts: 4,067	Re: Speedo/Rear End question... 3.73 seems to be common ratio I am finding too. __________________ Steve 1997 Tahoe LT 4D 2WD (DD) 2001 Blazer 4D 2WD 1961 Apache 10 (sold) 1965 C10 Stepper (sold)

09-22-2010, 05:18 PM	#3
1Bad62Pro/Street "Where were you in '62?" Join Date: Jul 2004 Location: Cleveland County, North Cackalacky Posts: 5,013	Re: Speedo/Rear End question... 1960-1966 Chevy/GMC Pickup Truck Specs & Engine/Trans/Axle ID's http://67-72chevytrucks.com/vboard/s...d.php?t=327764 My '62 had a 3.90 in before the swap. 3 speed I6. Posted via Mobile Device __________________ PROJECT: "FULL METAL YELLOW JACKET" 1962 Chevy C-10 Stepside Shortbed Nostalgia Pro/Street Pickup Truck PROJECT: "FULL METAL YELLOW JACKET Build Thread What Are You Workin' On? - 1Bad62ChevyPickup PROJECT: "TYRANNORAMBLER REX" 1969 AMC Rambler American Nostalgia Pro/Street Youtube Channel: Father Son Projects Youtube Channel: 2TIMOTHY2FITHTEEN "North and South Carolina Folks Click Here!" (((( ~ I have Parts For Sale & Miscellaneous Stuff ~ )))) "Well being as there's no other place around the place, I reckon this must be the place, I reckon...Nyuk Nyuk Nyuk" -Curly Howard Ph.D.

09-23-2010, 12:17 AM	#4
Captainfab 60-66 Nut Join Date: Mar 2007 Location: Coeur d'Alene, Idaho Posts: 23,254	Re: Speedo/Rear End question... IMO it doesn't take that long to pull the cover on the differential. The tooth count is stamped on the ring gear so you don't have to count the teeth. Even if you look up the code on the axle tube, there's a chance that the gears could have been changed sometme in the last 45 years. Plus the gear oil probably needs changed. __________________ Power Steering Box Adapter Plates For Sale HERE Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE Hydroboost Mounting Plates HERE

09-23-2010, 05:35 AM	#5
raycow Registered User Join Date: Mar 2003 Location: San Francisco, CA USA Posts: 2,454	Re: Speedo/Rear End question... As already stated, 3.73 was the most common gear, but 4.11 was an option. You don't have to take off the cover to find out what you have. Jack one rear wheel off the ground, put the transmission in neutral, and the parking brake off. Put matching marks on the pinion yoke and differential housing. Turn the wheel exactly TWO revolutions and count how many times the driveshaft turns, estimating any fractional turn as closely as possible. That number is your axle ratio. If the wheel is difficult or impossible to turn, you may have posi. In that case, jack both rear wheels off the ground and turn either of them only ONE revolution. Count the driveshaft turns the same way as for an open rear. Ray



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