Standard axle ratios? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**JJorgensen52** · 02-05-2010, 11:16 AM

I've been trying to figure out the axle ratio in my '69 K-10, without much luck. No tag on the diff and I can't see (too much rust scaling) the stamped code on the axle tubes.

That said, it's a pretty basic truck and doesn't have a SPID entry for rear end ratio.

So, what should be the standard rear end for my truck? It's an early '69 (Dec. 68 build date / motor code), 4x4, has a 307 2bbl, SM465, Rockwell T221 and the rear is a 12 bolt. Given the way it drives on the highway I'm guessing 4.10, but not sure I could tell between 4.10 and 3.73 by ear (no tach).

67chevtruck · 02-05-2010, 11:21 AM

you can take your diff cover off and on your ring gear there will be 2 numbers
you divide the big number by the little number and it will give you your ratio

Longhorn Man · 02-05-2010, 07:24 PM

I am not all that educated on the 4x4s, but I would think 3.73

haysonj · 02-05-2010, 08:55 PM

My 69 4x4 had 4.09 in front and 4.10 in back but I have no way of knowing if it came factory that way. I have since changed the rear to a 73 14 bolt.

**Dieselwrencher** · 02-05-2010, 10:09 PM

I have seen a lot of 4 speed K10's with 3.07's in this era for some reason.

factorystock · 02-05-2010, 10:33 PM

If no ratio on the SPID, it has the standard ratio of 3.73. The standard V8 should not be on the SPID either. The only powertrain option on your SPID should be the M20 4 speed.

Blazer1970 · 02-06-2010, 07:34 AM

If it came with a 350, it came with 3.07 gears. If it came with a 307 or a 250 it came with 3.73 gears.

**JJorgensen52** · 02-07-2010, 11:47 AM

Quote:

Originally Posted by factorystock

If no ratio on the SPID, it has the standard ratio of 3.73. The standard V8 should not be on the SPID either. The only powertrain option on your SPID should be the M20 4 speed.

You are correct about the SPID, sir

Thanks much for the information guys.

02-05-2010, 11:16 AM	#1
JJorgensen52 Simple? What's simple? Join Date: Apr 2007 Location: Southeast CT Posts: 1,472	Standard axle ratios? I've been trying to figure out the axle ratio in my '69 K-10, without much luck. No tag on the diff and I can't see (too much rust scaling) the stamped code on the axle tubes. That said, it's a pretty basic truck and doesn't have a SPID entry for rear end ratio. So, what should be the standard rear end for my truck? It's an early '69 (Dec. 68 build date / motor code), 4x4, has a 307 2bbl, SM465, Rockwell T221 and the rear is a 12 bolt. Given the way it drives on the highway I'm guessing 4.10, but not sure I could tell between 4.10 and 3.73 by ear (no tach). __________________ CURRENT '50 GMC 100 shortbed Gen IV 4.8 LS - 4L65E (Secret truck, Shhh!!!) Build '63 Buick Wildcat Coupe 401ci Nailhead (Very much in pieces) Photos '66 Impala SS convertible 327-QJet-glide (4 speed swap one of these days...) Photos '69 CST/10 4x4 SWB Stepper 350 2bbl - NV4500/NP241C (Broken Truck!) '72 Sierra Grande 2WD LWB fleetside 350-TH350 Refresh '99 K2500 Silverado RCLB 5.7 Vortec - NV4500/NP241C (Daily) '99 K2500 Suburban 7.4 Vortec - NV4500/NP246 (still working out the bugs) SOLD '71 Custom/10 2WD LWB fleetside - '72 GMC K/3500 Dually (Sold to redryder)

02-05-2010, 11:21 AM	#2
67chevtruck Registered User Join Date: Jan 2008 Location: west richland WA Posts: 61	Re: Standard axle ratios? you can take your diff cover off and on your ring gear there will be 2 numbers you divide the big number by the little number and it will give you your ratio __________________ 67' chevy k10 350 sm420

02-05-2010, 07:24 PM	#3
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Standard axle ratios? I am not all that educated on the 4x4s, but I would think 3.73

02-05-2010, 08:55 PM	#4
haysonj Registered User Join Date: Dec 2007 Location: Santa Maria, Ca. Posts: 1,423	Re: Standard axle ratios? My 69 4x4 had 4.09 in front and 4.10 in back but I have no way of knowing if it came factory that way. I have since changed the rear to a 73 14 bolt. __________________ 69 Chevy 4x4 383 Power

02-05-2010, 10:09 PM	#5
Dieselwrencher 6>8 Plugless........ Join Date: Sep 2007 Location: Prairie City, Ia Posts: 17,139	Re: Standard axle ratios? I have seen a lot of 4 speed K10's with 3.07's in this era for some reason. __________________ Ryan 1972 Chevy Longhorn K30 Cheyenne Super, 359 Inline 6 cylinder, Auto Trans, Tilt, Diesel Tach/Vach, Buckets, Rare Rear 4-link and air ride option Build Thread 1972 GMC Sierra Grande Longhorn 4x4 1972 Chevy Cheyenne Super K20 Long Step side tilt, tach, tow hooks, AC, 350 4 speed 1972 C10 Suburban Custom Deluxe 1969 Chevy milk truck 1971 Camaro RS 5.3 BTR STG3 Cam Super T10 1940 Ford 354 Hemi 46RH Ford 9" on air ride huge project *Tired of spark plugs? Check this out.*

02-05-2010, 10:33 PM	#6
factorystock Registered User Join Date: Feb 2007 Location: west coast Posts: 3,380	Re: Standard axle ratios? If no ratio on the SPID, it has the standard ratio of 3.73. The standard V8 should not be on the SPID either. The only powertrain option on your SPID should be the M20 4 speed.

02-06-2010, 07:34 AM	#7
Blazer1970 Registered User Join Date: Dec 1999 Location: Old Mission, MI, USA Posts: 2,510	Re: Standard axle ratios? If it came with a 350, it came with 3.07 gears. If it came with a 307 or a 250 it came with 3.73 gears. __________________ Tim



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