Original configuration of a 72 K20 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

The Blue Pig · 10-25-2012, 02:08 PM

Hey guys, just had a quick question. What would have been the standard differential type/gear ration configuration on a 72 K20? Are the 72's more or less desirable than other years? Not much of a 4x4 guy...

b454rat · 10-25-2012, 06:06 PM

44 front Eaton rear, could be a Dana 60, don't know why one over the other....ratios, just guessing but 3.73 up to 4.56s...

**Stocker** · 10-26-2012, 01:09 AM

Also just guessing, 4.10 ratio may be the most common on a '72 K20. I personally prefer '71 or '72 over earlier trucks because they came with front disc brakes. Not a huge deal because obviously those could be upgraded on an earlier truck. Also, I think frames were different on '67s so replacement springs are harder to come by.

**special-K** · 10-26-2012, 10:36 PM

I believe the automatic K/20s got 4.10 and 4spds got 4.57s. Front axle was Dana44 and rear was HO52 (Corporate). GMCs came with Dana60 rears and were 4.11 automatic/4.56 4spd. I think 71 & 72s are equally most desirable due to having the most improved drivetrain

rsmarr1982 · 10-27-2012, 11:12 PM

i just bought a rolling frame from a guy that he said had a eaton 72 rear which he said is one ton. any truth to this?

rsmarr1982 · 10-27-2012, 11:21 PM

its a 4x4 so would that make it a k30?

RPIcka · 10-27-2012, 11:49 PM

I believe the Eatons were 1 ton rated

**Stocker** · 10-27-2012, 11:50 PM

There were no K30s built in 1972. It may be a K20 frame with an HO52 differential, which is same as an HO72 except for brakes. There *might* be a difference in axles, but the pumpkins are the same. Some HO52s had the load bolt and some did not, while all HO72s had it.

Edit: IF it's a 2wd frame converted to 4x4..... I'm pretty sure C30 frames had larger (taller) c-channels than C/K10s or C/K20s, so you could measure & compare to a known frame.

SS Tim · 10-28-2012, 07:46 AM

Here is the powertrain chart.

**special-K** · 10-30-2012, 08:32 PM

No 30-series trucks were built with 127" wheel base. The only Fleetsides were Longhorns.

coopdog · 12-14-2014, 08:57 PM

My original browsher says the ratios

10-25-2012, 02:08 PM	#1
The Blue Pig Thread Wizard Since 2002 Join Date: Apr 2002 Location: Fairbanks, AK Posts: 102	Original configuration of a 72 K20 Hey guys, just had a quick question. What would have been the standard differential type/gear ration configuration on a 72 K20? Are the 72's more or less desirable than other years? Not much of a 4x4 guy... __________________ --70 C-10 Longbed --71 C-10 Longbed --72 K-20 Longbed --74 C-10 Shortbed --86 Toyota Tercel (His Driver) --05 Chevy Trailblazer (Her Driver)

10-25-2012, 06:06 PM	#2
b454rat Senior Member Join Date: May 2004 Location: Binghamton, NY Posts: 3,469	Re: Original configuration of a 72 K20 44 front Eaton rear, could be a Dana 60, don't know why one over the other....ratios, just guessing but 3.73 up to 4.56s... __________________ 2000 GMC CCSB 454/4L80 6” lift SAS 1999 Chevy CCSB 454/NV4500 4” SAS 1999 GMC Yukon 350/4L60 6" SAS

10-26-2012, 01:09 AM	#3
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,722	Re: Original configuration of a 72 K20 Also just guessing, 4.10 ratio may be the most common on a '72 K20. I personally prefer '71 or '72 over earlier trucks because they came with front disc brakes. Not a huge deal because obviously those could be upgraded on an earlier truck. Also, I think frames were different on '67s so replacement springs are harder to come by. __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

10-26-2012, 10:36 PM	#4
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,851	Re: Original configuration of a 72 K20 I believe the automatic K/20s got 4.10 and 4spds got 4.57s. Front axle was Dana44 and rear was HO52 (Corporate). GMCs came with Dana60 rears and were 4.11 automatic/4.56 4spd. I think 71 & 72s are equally most desirable due to having the most improved drivetrain __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

10-27-2012, 11:12 PM	#5
rsmarr1982 Registered User Join Date: Jul 2010 Location: mogadore ohio Posts: 867	Re: Original configuration of a 72 K20 i just bought a rolling frame from a guy that he said had a eaton 72 rear which he said is one ton. any truth to this? __________________ 1969 chevy c10 lwb stepside 250 6 3 ott 1971 chevy c10 lwb 250 6 with power steering 3 ott 1972 chevy k20 4x4 350/TH350 automatic 1978 chevy Malibu 4dr 305 2bbl (all original) 1979 chevy k10 Scottsdale 350/th350 full-time 4wd(daily driver)

10-27-2012, 11:21 PM	#6
rsmarr1982 Registered User Join Date: Jul 2010 Location: mogadore ohio Posts: 867	Re: Original configuration of a 72 K20 its a 4x4 so would that make it a k30? __________________ 1969 chevy c10 lwb stepside 250 6 3 ott 1971 chevy c10 lwb 250 6 with power steering 3 ott 1972 chevy k20 4x4 350/TH350 automatic 1978 chevy Malibu 4dr 305 2bbl (all original) 1979 chevy k10 Scottsdale 350/th350 full-time 4wd(daily driver)

10-27-2012, 11:49 PM	#7
RPIcka Registered User Join Date: Aug 2011 Location: Powell River, BC Posts: 229	Re: Original configuration of a 72 K20 I believe the Eatons were 1 ton rated

10-27-2012, 11:50 PM	#8
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,722	Re: Original configuration of a 72 K20 There were no K30s built in 1972. It may be a K20 frame with an HO52 differential, which is same as an HO72 except for brakes. There might be a difference in axles, but the pumpkins are the same. Some HO52s had the load bolt and some did not, while all HO72s had it. Edit: IF it's a 2wd frame converted to 4x4..... I'm pretty sure C30 frames had larger (taller) c-channels than C/K10s or C/K20s, so you could measure & compare to a known frame. __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay Last edited by Stocker; 10-27-2012 at 11:57 PM.

10-28-2012, 07:46 AM	#9
SS Tim Registered User Join Date: Aug 2010 Location: Edwards, CA Posts: 7,503	Re: Original configuration of a 72 K20 Here is the powertrain chart. Attached Images __________________ Thanks, Tim * VIN/Model Decoders * Power Team Charts (engine/transmission/gear ratio) * Post Your Pickup SPID Blazer SPID Suburban/Panel SPID * RTFM ... Read The Factory Manuals... download 'em here Highlanders Do you have a 1972 Plaid Pickup? Plaid Blazer ** Plaid Suburban

10-30-2012, 08:32 PM	#10
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,851	Re: Original configuration of a 72 K20 No 30-series trucks were built with 127" wheel base. The only Fleetsides were Longhorns. __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

12-14-2014, 08:57 PM	#11
coopdog Registered User Join Date: Nov 2012 Location: NYC Posts: 429	Re: Original configuration of a 72 K20 My original browsher says the ratios Attached Images



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