what rear end gear in 1977 c10 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

samstheman · 05-25-2012, 01:18 PM

I have a 12 bolt rear 6 cylinder 250 trying to calculate speedometer swap I put in a t5 5 speed and have 20s but dont know what rear end setup I have does anyone know Thanks

Keith Seymore · 05-25-2012, 03:58 PM

Nope. Nobody knows. And nobody is gonna know until you pull the cover and count teeth - or roll the tires and count driveshaft revs.

K

Keith Seymore · 05-25-2012, 04:02 PM

Now - if you are asking what was available, well - that is known.

RPO HE4 3.40 was standard, and GT4 3.73 was optional, so you'd have to find your SPID label and see if either of those are noted.

Regardless, that would assume that no one has changed it in the interim, so really the only way to know is check the parts as mentioned above.

K

Mrknowitall · 05-25-2012, 04:03 PM

Quote:

Originally Posted by Keith Seymore

Now - if you are asking what was available, well - that is known.

RPO HE4 3.40 was standard, and GT4 3.73 was optional, so you'd have to find your SPID label and see if either of those are noted.

Regardless, that would assume that no one has changed it in the interim, so really the only way to know is check the parts as mentioned above.

K

YOU THE MAN!!!

D13 · 05-27-2012, 05:20 AM

My 1977 1/2 ton strippo 250/3spd has a 12 bolt with 2.73's. Appears to be stock. My 1982, 84, and 87's all have 3.08's 10 bolts.

Buy a cover gasket and 2 qts lube, pull the cover, and count. It probably could use clean fluid anyway.

**hatzie** · 05-27-2012, 09:04 AM

If you're lucky you'll find a part number or tooth count stamped on the ring gear as you spin it.

samstheman · 05-31-2012, 01:24 AM

I pulled cover and counted 34 ring gear 10 pinion gear so I guess its a 3.40
I think id like that 3.73 more low end. What are you guys running I have 5 speed and inline six once the motor is done up I may like the 3.40.

cory d · 05-31-2012, 01:55 AM

with the 5 speed i think 3.73 would be pretty good. its a commen gears to pair up with the 700r4 and they have about the ame final gear right?

05-25-2012, 01:18 PM	#1
samstheman Registered User Join Date: Nov 2010 Location: whittier calif Posts: 160	what rear end gear in 1977 c10 I have a 12 bolt rear 6 cylinder 250 trying to calculate speedometer swap I put in a t5 5 speed and have 20s but dont know what rear end setup I have does anyone know Thanks

05-25-2012, 03:58 PM	#2
Keith Seymore Registered User Join Date: May 2009 Location: Motor City Posts: 9,237	Re: what rear end gear in 1977 c10 Nope. Nobody knows. And nobody is gonna know until you pull the cover and count teeth - or roll the tires and count driveshaft revs. K __________________ Chevrolet Flint Assembly 1979-1986 GM Full Size Truck Engineering 1986 - 2019 Intro from an Old Assembly Guy: http://67-72chevytrucks.com/vboard/s...d.php?t=342926 My Pontiac story: http://forums.maxperformanceinc.com/...d.php?t=560524 Chevelle intro: http://www.superchevy.com/features/s...hevy-chevelle/

05-25-2012, 04:02 PM	#3
Keith Seymore Registered User Join Date: May 2009 Location: Motor City Posts: 9,237	Re: what rear end gear in 1977 c10 Now - if you are asking what was available, well - that is known. RPO HE4 3.40 was standard, and GT4 3.73 was optional, so you'd have to find your SPID label and see if either of those are noted. Regardless, that would assume that no one has changed it in the interim, so really the only way to know is check the parts as mentioned above. K __________________ Chevrolet Flint Assembly 1979-1986 GM Full Size Truck Engineering 1986 - 2019 Intro from an Old Assembly Guy: http://67-72chevytrucks.com/vboard/s...d.php?t=342926 My Pontiac story: http://forums.maxperformanceinc.com/...d.php?t=560524 Chevelle intro: http://www.superchevy.com/features/s...hevy-chevelle/

05-27-2012, 05:20 AM	#5
D13 Registered User Join Date: Feb 2007 Location: Memphis MI Posts: 1,851	Re: what rear end gear in 1977 c10 My 1977 1/2 ton strippo 250/3spd has a 12 bolt with 2.73's. Appears to be stock. My 1982, 84, and 87's all have 3.08's 10 bolts. Buy a cover gasket and 2 qts lube, pull the cover, and count. It probably could use clean fluid anyway. __________________ 1987 2 ton 1982 250/TH350 beater in progress Dad's 1981 3/4 L6 3 on tree posi and no options, awaiting restoration or scrapping Plus a mess o' tractors

05-27-2012, 09:04 AM	#6
hatzie Moderator Join Date: Oct 2008 Location: Wentworth, NH Posts: 5,014	Re: what rear end gear in 1977 c10 If you're lucky you'll find a part number or tooth count stamped on the ring gear as you spin it. __________________ 1959 M35A2 LDT465-1D SOLD 1967 Dodge W200 B383, NP420/NP201 SOLD 1969 Dodge Polara 500 B383, A833 SOLD 1972 Ford F250 FE390, NP435/NP205 SOLD 1976 Chevy K20, 6.5L, NV4500/NP208 SOLD 1986 M1008 CUCV SOLD 2000 GMC C2500, TD6.5L, NV4500 2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263 2009 Impala SS LS4 V8 RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials... 1973-1991 GM Light Truck Service, Unit/Overhaul, Wiring Manuals, Parts Books and Some 1968-1999 GM Service Training textbooks in PDF 1988-1998 GMT400 CK service manual project 1988-1993 GMT400 CK parts books. 1967-1972 GM Light, Medium, & Heavy Truck Service Manuals in PDF Please include at least the year and model in your threads. It'll be easier to answer your questions. And please let us know if and how your repairs were successful.

05-31-2012, 01:24 AM	#7
samstheman Registered User Join Date: Nov 2010 Location: whittier calif Posts: 160	Re: what rear end gear in 1977 c10 I pulled cover and counted 34 ring gear 10 pinion gear so I guess its a 3.40 I think id like that 3.73 more low end. What are you guys running I have 5 speed and inline six once the motor is done up I may like the 3.40.

05-31-2012, 01:55 AM	#8
cory d Registered User Join Date: Dec 2011 Location: Arlington WA Posts: 1,728	Re: what rear end gear in 1977 c10 with the 5 speed i think 3.73 would be pretty good. its a commen gears to pair up with the 700r4 and they have about the ame final gear right? __________________ GMC C15 355 SM465 3.73 80 C10 cruiser build thread 79 short stepside crew cab. big and ugly. build thread

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