What gears do I probably have? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

mcne2026 · 11-02-2007, 09:38 PM

I have a '72 Blazer and it was mostly stock when I got it. Was 3.07 the common 4x4 gearing used stock? I just lifted 6" and put on 35's and it goes really slow up any type of grade now. I am guessing gearing is the issue. I don't have $1,500 to re-gear right now so will have to live with it.

1969k10stepside · 11-02-2007, 09:43 PM

The motor,and tranny play a role in the gears it had..I believe with a 350 and a auto it had 3.07s unless other wise ordered.I don't know for sure but with a 4spd I think it had 3.73s standard..I'm not for sure though.Pull the cover,get the numbers off the ring gear and find out...Is that what it will cost to swap gears out front and rear,$1500? I'm glad I can do this stuff myself..it only cost me the ring & pinion,and new bearings,and a few gaskets--I had $200 total in swapping to 3.73s..Then I spent a little more on parts to redo the axles completly since they were already apart..

Critter · 11-02-2007, 10:00 PM

Quote:

Originally Posted by 1969k10stepside

The motor,and tranny play a role in the gears it had..I believe with a 350 and a auto it had 3.07s unless other wise ordered.I don't know for sure but with a 4spd I think it had 3.73s standard..I'm not for sure though.

I believe you got them swapped. A 4x4 with a 350 engine and a 350 auto should have 3.73 gears(mine is that way), but a 350 v8 with a floor shift manual would probably be 3.07s. As far as 2wd or a three speed on the column, or a 6 cylinder...someone else will have to give you that info

Jtrux · 11-02-2007, 11:41 PM

Mine is a factory 4 speed with factory 3.07's.

bouncytruck · 11-03-2007, 12:34 AM

Mines a factory 350/TH350 with 3.07's. My understanding was that the 3.07s were standard, but a huge portion were shipped/sold with 3.73's.

35's are a bit tall for 3.73's. 4.10's are much better suited for 35's. Save your money and swap up to 4.10's. You'll get better gas mileage and better pickup off the line.

**Yukon Jack** · 11-03-2007, 10:03 AM

My GM restoration pack for 1970 K5's shows for the 4wd K5, 3.73's were standard with all engines except for the 350 V8 which it shows only got 3.07's.

For whatever reason it doesn't show any optional gear ratios for the 4wd K5's.

For the 2wd 1970 K5 it shows:

3.73 was standard for the 250 six regardless of transmission and standard with the 307 V8 with a three speed.

3.07's were standard for the 307 V8 and 4 speed manual or auto, along with any 350 V8 combo.

4.11's were optional for all and if it had the 3.73's then 3.07 was an option and if it had 3.07's then 3.73's were also optional.

Critter · 11-03-2007, 10:30 AM

Quote:

Originally Posted by Yukon Jack

My GM restoration pack for 1970 K5's shows for the 4wd K5, 3.73's were standard with all engines except for the 350 V8 which it shows only got 3.07's.

For whatever reason it doesn't show any optional gear ratios for the 4wd K5's.

350 V8 4X4s ONLY got 3.07s??? Interesting, were the options in 70 different from 72? I know for a fact there are ALOT of 72 4x4 K5 with 3.73 gears out there...my CST is one of them.

**Yukon Jack** · 11-03-2007, 12:05 PM

I wouldn't take that restoration packet as gospel, but that is what it states.

**1970cstblazer** · 11-03-2007, 02:08 PM

Quote:

Originally Posted by Yukon Jack

I wouldn't take that restoration packet as gospel, but that is what it states.

The packet is incorrect.. My '70 is equipped with 3.73 gears.

bouncytruck · 11-03-2007, 12:51 PM

My first 72 CST had 3.73's with a 350/TH350. I don't think consistency was one the most common practice back then.

Chris27 · 11-03-2007, 02:10 PM

My '72 had 350/th350 and 3.07's stock.

11-02-2007, 09:38 PM	#1
mcne2026 Registered User Join Date: Oct 2007 Location: Buellton, CA Posts: 27	What gears do I probably have? I have a '72 Blazer and it was mostly stock when I got it. Was 3.07 the common 4x4 gearing used stock? I just lifted 6" and put on 35's and it goes really slow up any type of grade now. I am guessing gearing is the issue. I don't have $1,500 to re-gear right now so will have to live with it.

11-02-2007, 09:43 PM	#2
1969k10stepside Registered User Join Date: Mar 2006 Location: USA Posts: 21,019	Re: What gears do I probably have? The motor,and tranny play a role in the gears it had..I believe with a 350 and a auto it had 3.07s unless other wise ordered.I don't know for sure but with a 4spd I think it had 3.73s standard..I'm not for sure though.Pull the cover,get the numbers off the ring gear and find out...Is that what it will cost to swap gears out front and rear,$1500? I'm glad I can do this stuff myself..it only cost me the ring & pinion,and new bearings,and a few gaskets--I had $200 total in swapping to 3.73s..Then I spent a little more on parts to redo the axles completly since they were already apart.. Last edited by 1969k10stepside; 11-02-2007 at 09:45 PM.

11-02-2007, 11:41 PM	#4
Jtrux I'm a poor spectator Join Date: Aug 2006 Location: San Antonio, Tx Posts: 2,287	Re: What gears do I probably have? Mine is a factory 4 speed with factory 3.07's. __________________ 2006 Jeep Unlimited IMPACT ORANGE 1993 Chevy 2500 4x4 ExCab LWB 454/NV4500 Tow rig 1977 Ford F100 2x4 LWB 1st truck I owned, still have it!!! 1979 Ford F150 4x4 SWB Built Ford Tough!!! 1971 Chevy Blazer 350 / SM465 / NP205 UNDER CONSTRUCTION Soon to have a LQ4 6.0!!!

11-03-2007, 12:34 AM	#5
bouncytruck SKINNY TIRES RULE! Join Date: Sep 2001 Location: Bothell, WA Posts: 11,038	Re: What gears do I probably have? Mines a factory 350/TH350 with 3.07's. My understanding was that the 3.07s were standard, but a huge portion were shipped/sold with 3.73's. 35's are a bit tall for 3.73's. 4.10's are much better suited for 35's. Save your money and swap up to 4.10's. You'll get better gas mileage and better pickup off the line. __________________ bouncytruck 1972 K5 The Hauler 1994 K1500 Suburban The Daily2010 Kia Soul Wife's Ride2014 Fiat 500L

11-03-2007, 10:03 AM	#6
Yukon Jack Post Whore Join Date: Feb 2000 Location: Rose Hill, KS, USA Posts: 12,686	Re: What gears do I probably have? My GM restoration pack for 1970 K5's shows for the 4wd K5, 3.73's were standard with all engines except for the 350 V8 which it shows only got 3.07's. For whatever reason it doesn't show any optional gear ratios for the 4wd K5's. For the 2wd 1970 K5 it shows: 3.73 was standard for the 250 six regardless of transmission and standard with the 307 V8 with a three speed. 3.07's were standard for the 307 V8 and 4 speed manual or auto, along with any 350 V8 combo. 4.11's were optional for all and if it had the 3.73's then 3.07 was an option and if it had 3.07's then 3.73's were also optional. __________________ 1970 Blazer with a 400 sbc and 4" lift 1980 Pontiac Trans Am, 455 Oldsmobile 2012 Kawasaki Concours 14

11-03-2007, 12:05 PM	#8
Yukon Jack Post Whore Join Date: Feb 2000 Location: Rose Hill, KS, USA Posts: 12,686	Re: What gears do I probably have? I wouldn't take that restoration packet as gospel, but that is what it states. __________________ 1970 Blazer with a 400 sbc and 4" lift 1980 Pontiac Trans Am, 455 Oldsmobile 2012 Kawasaki Concours 14

11-03-2007, 12:51 PM	#10
bouncytruck SKINNY TIRES RULE! Join Date: Sep 2001 Location: Bothell, WA Posts: 11,038	Re: What gears do I probably have? My first 72 CST had 3.73's with a 350/TH350. I don't think consistency was one the most common practice back then. __________________ bouncytruck 1972 K5 The Hauler 1994 K1500 Suburban The Daily2010 Kia Soul Wife's Ride2014 Fiat 500L

11-03-2007, 02:10 PM	#11
Chris27 Blazerless Join Date: Nov 2006 Location: Kelowna, BC, Canada Posts: 274	Re: What gears do I probably have? My '72 had 350/th350 and 3.07's stock. __________________ 72' K5 Blazer 4x4 350TBI/700R4/NP205 3/4 ton diffs. Daily driver. SOLD 69' Beaumont 388/700R4 11.70@116 77' Bronco, Wife's mall cruiser/poser 4x4. Capable but too pretty to go offroad.



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