3.40 ratio in 76 ? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

*Fast68Chevy* · 05-13-2001, 12:17 PM

Was there 3.40 ratio in 1976 12 bolt axles?

I tihnk its RPO# HE4

The 76 GMC has this, I think it says 3.40,hard to read the sticker, its 3. something.

Whats the url to SwervinErvins RPO code list ?

------------------
-'77 Electra 403/TH350
-'76 GMC C-1500 Sierra Classic 350ci/TH350(35th vehicle)
-'68 C-10 chassis
-'72 K-5 chassis

Note: Looking for an S-10, Nova, Malibu, Monza, or similar for sale for around $1200
5652 posts 5-10-01
http://communities.msn.com/RandyR72K5
Randy
Lincoln, IL
"life's gonna leave me in the dust, if I don't try and catch up to it soon"
r72k5@hotmail.com

**swervin ervin** · 05-13-2001, 01:40 PM

Fast,

yes, according to the info I can find, there was an HE4 code, 3.40 ratio axle. It is in years 76 - 81. I don't know anything about it other than it is for real. I have never seen any info to it being in a truck. From all the places I've seen the only 3.4x I've seen is 3.42. These were in both 10 bolts and 12 bolts.

Maybe someone else can help here. Now you have got me thinking. It doesn't matter if it's a GMC or Chevy BTW.

------------------
Mike

1985 Chevy C-10
Mike's 73-87 Chevy Pickup Site

*Fast68Chevy* · 05-13-2001, 07:16 PM

Well I have 3.40 in this one

It gets up and goes pretty good too, I like it. Gotta fix that water burning on the drivers side though, hmm....

I found your site url like 2 minutes after I posted, heh.

Oh, and old swingset pipe dual exhaust is the best, its looking good under there.

------------------
-'77 Electra 403/TH350
-'76 GMC C-1500 Sierra Classic 350ci/TH350(35th vehicle)
-'68 C-10 chassis
-'72 K-5 chassis

Note: Looking for an S-10, Nova, Malibu, Monza, or similar for sale for around $1200
5652 posts 5-10-01
http://communities.msn.com/RandyR72K5
Randy
Lincoln, IL
"life's gonna leave me in the dust, if I don't try and catch up to it soon"
r72k5@hotmail.com

[This message has been edited by Fast68Chevy (edited 05-13-2001).]

[This message has been edited by Fast68Chevy (edited 05-13-2001).]

**crossy** · 05-14-2001, 02:53 AM

yes, if you do the math the ratio comes out to 3.40 I think it commonly gets called 3.42 because there are so many other rears that came with that ratio. the 3.40's are aperfect street ratio and i have bought several complete rears and even have an extra set of gears . 12 bolt only . if you have 4WD and have 3.42 i the front you can put a stronger 12 bolt 3.40 in the back. that tiny difference in numbers [.02] makes no difference at all. poppinp a 3.40 under those 81-87 305's really made a difference in the way they move and mileage [after speedo correction] only dropped 1 MPG .mainly found in 75-76 trucks. I just hung one under my 85 thats for sale and it made the truck much mre enjoyable to drive .The stinking stock converter in this one is the tightest one I have ever owned and is still hurting off line perf.

------------------
with all the rocks that I turn over I should be finding more than slugs!

**swervin ervin** · 05-14-2001, 10:24 PM

The math works out to 41/12 = 3.4167 so how do they get 3.40. I still can't figure out why they have a 3.40 and a 3.42.

It just flat don't make any sense to me. You can look in all the catalogs and never see any 3.40 gear sets for sale, only 3.42 in either 10 or 12 bolt. I can see a 3.07 or 3.08 because of 40/13 = 3.0769. This could go either way, although I never see 3.07 gear sets for sale either.

I guess it's one of them GM quirks. I think they did stuff like this to keep us confused.

------------------
Mike

1985 Chevy C-10
Mike's 73-87 Chevy Pickup Site

*Fast68Chevy* · 05-15-2001, 06:40 AM

lol yeah, guess so.

Yeah, 3.40 and 3.42 were both used, and are not the same Crossy.

3.42 is a whole different gear set, 3.42 was also used in the semifloat 14 bolt 9.5" axles.

3.40is the line drawn between a series 3 and a series 4 carrier, in 12 bolt axles.

I'm not sure when Im gonna get to inspect the rear axle gearset, as I ran into head problems, up front that I have to deal with.Once I get the engine deal figured out, and done, I'll move back to the trans and axle,and look at the tooth count stamped on the ring gear.

------------------
-'77 Electra 403/TH350
-'76 GMC C-1500 Sierra Classic 350ci/TH350, now need a set of heads for it

-'68 C-10 chassis
-'72 K-5 chassis
The designer of the #333882 head castings needs shot !!!
5652 posts 5-10-01
http://communities.msn.com/RandyR72K5
Randy
Lincoln, IL
"life's gonna leave me in the dust, if I don't try and catch up to it soon"
r72k5@hotmail.com

[This message has been edited by Fast68Chevy (edited 05-15-2001).]

rick@its · 05-15-2001, 09:20 AM

I have a 77 that has 3.40

------------------
Rick
Broken Arrow, OK
72 cheyenne (in pieces)

**crossy** · 05-19-2001, 01:43 PM

I never meant that they were the "same" 10 and 12 bolts don't interchange,but they are the same amount of teeth . they are both 12/41 gearsets as I have a set of each 10 and 12 bolt lying here.GM quirk , mike was right.that's it !!!!!!. got a better one for ya.chevy 396 or 400 or 402 ????????????????and you thought they had us on rear ratios!!! DAVE

**72BBGMC** · 05-21-2001, 03:10 AM

The 3.40 gears have 10 teeth on the pinion and 34 teeth on the ring gear. I just picked up a 3.40 rear end, and the teeth numbers are stamped on the ring gear. This is the first one I've seen or heard of until I saw this post. If anyone is interested in one, I'll take $150(plus shipping) for the whole rear end or just the gears for easier shipping.

05-13-2001, 12:17 PM	#1
Fast68Chevy Account Suspended Join Date: May 2000 Location: IL Posts: 0	3.40 ratio in 76 ? Was there 3.40 ratio in 1976 12 bolt axles? I tihnk its RPO# HE4 The 76 GMC has this, I think it says 3.40,hard to read the sticker, its 3. something. Whats the url to SwervinErvins RPO code list ? ------------------ -'77 Electra 403/TH350 -'76 GMC C-1500 Sierra Classic 350ci/TH350(35th vehicle) -'68 C-10 chassis -'72 K-5 chassis Note: Looking for an S-10, Nova, Malibu, Monza, or similar for sale for around $1200 5652 posts 5-10-01 http://communities.msn.com/RandyR72K5 Randy Lincoln, IL "life's gonna leave me in the dust, if I don't try and catch up to it soon" r72k5@hotmail.com

05-13-2001, 01:40 PM	#2
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	Fast, yes, according to the info I can find, there was an HE4 code, 3.40 ratio axle. It is in years 76 - 81. I don't know anything about it other than it is for real. I have never seen any info to it being in a truck. From all the places I've seen the only 3.4x I've seen is 3.42. These were in both 10 bolts and 12 bolts. Maybe someone else can help here. Now you have got me thinking. It doesn't matter if it's a GMC or Chevy BTW. ------------------ Mike 1985 Chevy C-10 Mike's 73-87 Chevy Pickup Site __________________ Mike 1985 Chevy C-10

05-14-2001, 02:53 AM	#4
crossy Oh,you can't buy that new Join Date: Apr 2000 Location: Pennsville,N.J. 08070, USA Posts: 2,039	yes, if you do the math the ratio comes out to 3.40 I think it commonly gets called 3.42 because there are so many other rears that came with that ratio. the 3.40's are aperfect street ratio and i have bought several complete rears and even have an extra set of gears . 12 bolt only . if you have 4WD and have 3.42 i the front you can put a stronger 12 bolt 3.40 in the back. that tiny difference in numbers [.02] makes no difference at all. poppinp a 3.40 under those 81-87 305's really made a difference in the way they move and mileage [after speedo correction] only dropped 1 MPG .mainly found in 75-76 trucks. I just hung one under my 85 thats for sale and it made the truck much mre enjoyable to drive .The stinking stock converter in this one is the tightest one I have ever owned and is still hurting off line perf. ------------------ with all the rocks that I turn over I should be finding more than slugs! __________________ "been there, done that, ruined the T-shirt". 2007 LBZ GMC Sierra, ECSB 2006 LM7 RCSB Silverado 98 Vortec project. 94,3500,6.5L 4L80 81 SWB GMC POS finally gone 73 Pinto, stock, w/CragarSS's-eww LOTS of Cummins trucks.

05-14-2001, 10:24 PM	#5
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	The math works out to 41/12 = 3.4167 so how do they get 3.40. I still can't figure out why they have a 3.40 and a 3.42. It just flat don't make any sense to me. You can look in all the catalogs and never see any 3.40 gear sets for sale, only 3.42 in either 10 or 12 bolt. I can see a 3.07 or 3.08 because of 40/13 = 3.0769. This could go either way, although I never see 3.07 gear sets for sale either. I guess it's one of them GM quirks. I think they did stuff like this to keep us confused. ------------------ Mike 1985 Chevy C-10 Mike's 73-87 Chevy Pickup Site __________________ Mike 1985 Chevy C-10

05-15-2001, 09:20 AM	#7
rick@its Registered User Join Date: Jan 2001 Location: Broken Arrow, OK Posts: 52	I have a 77 that has 3.40 ------------------ Rick Broken Arrow, OK 72 cheyenne (in pieces) __________________ Rick Broken Arrow, OK 72 cheyenne (in pieces)

05-13-2001, 07:16 PM	#3
Fast68Chevy Account Suspended Join Date: May 2000 Location: IL Posts: 0	Well I have 3.40 in this one It gets up and goes pretty good too, I like it. Gotta fix that water burning on the drivers side though, hmm.... I found your site url like 2 minutes after I posted, heh. Oh, and old swingset pipe dual exhaust is the best, its looking good under there. ------------------ -'77 Electra 403/TH350 -'76 GMC C-1500 Sierra Classic 350ci/TH350(35th vehicle) -'68 C-10 chassis -'72 K-5 chassis Note: Looking for an S-10, Nova, Malibu, Monza, or similar for sale for around $1200 5652 posts 5-10-01 http://communities.msn.com/RandyR72K5 Randy Lincoln, IL "life's gonna leave me in the dust, if I don't try and catch up to it soon" r72k5@hotmail.com [This message has been edited by Fast68Chevy (edited 05-13-2001).] [This message has been edited by Fast68Chevy (edited 05-13-2001).]

05-15-2001, 06:40 AM	#6
Fast68Chevy Account Suspended Join Date: May 2000 Location: IL Posts: 0	lol yeah, guess so. Yeah, 3.40 and 3.42 were both used, and are not the same Crossy. 3.42 is a whole different gear set, 3.42 was also used in the semifloat 14 bolt 9.5" axles. 3.40is the line drawn between a series 3 and a series 4 carrier, in 12 bolt axles. I'm not sure when Im gonna get to inspect the rear axle gearset, as I ran into head problems, up front that I have to deal with.Once I get the engine deal figured out, and done, I'll move back to the trans and axle,and look at the tooth count stamped on the ring gear. ------------------ -'77 Electra 403/TH350 -'76 GMC C-1500 Sierra Classic 350ci/TH350, now need a set of heads for it -'68 C-10 chassis -'72 K-5 chassis The designer of the #333882 head castings needs shot !!! 5652 posts 5-10-01 http://communities.msn.com/RandyR72K5 Randy Lincoln, IL "life's gonna leave me in the dust, if I don't try and catch up to it soon" r72k5@hotmail.com [This message has been edited by Fast68Chevy (edited 05-15-2001).]

05-19-2001, 01:43 PM	#8
crossy Oh,you can't buy that new Join Date: Apr 2000 Location: Pennsville,N.J. 08070, USA Posts: 2,039	I never meant that they were the "same" 10 and 12 bolts don't interchange,but they are the same amount of teeth . they are both 12/41 gearsets as I have a set of each 10 and 12 bolt lying here.GM quirk , mike was right.that's it !!!!!!. got a better one for ya.chevy 396 or 400 or 402 ????????????????and you thought they had us on rear ratios!!! DAVE __________________ "been there, done that, ruined the T-shirt". 2007 LBZ GMC Sierra, ECSB 2006 LM7 RCSB Silverado 98 Vortec project. 94,3500,6.5L 4L80 81 SWB GMC POS finally gone 73 Pinto, stock, w/CragarSS's-eww LOTS of Cummins trucks.

05-21-2001, 03:10 AM	#9
72BBGMC Senior Member Join Date: Jun 2000 Location: georgia Posts: 292	The 3.40 gears have 10 teeth on the pinion and 34 teeth on the ring gear. I just picked up a 3.40 rear end, and the teeth numbers are stamped on the ring gear. This is the first one I've seen or heard of until I saw this post. If anyone is interested in one, I'll take $150(plus shipping) for the whole rear end or just the gears for easier shipping.



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