« previous next »
Pages: [1]   Go Down

Author Topic: K20 diff question, need quick answer!  (Read 3287 times)

Offline Elpresidente

  • Registered Users
  • *
  • Posts: 212
K20 diff question, need quick answer!
« on: April 27, 2014, 05:10:28 PM »
Will the ring & pinions from factory 3/4 ton 73-87 diffs be the same size as those from a 67-72 style truck? I'm buying differentials from a '79 and was wondering if I could swap the gears over for my '70 3/4 ton.
Logged
'82 Chev Scottsdale
Proud to be Canadian \m/

Offline Irish_Alley

  • Tim
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 13319
  • Family is not an important thing. It's everything.
Re: K20 diff question, need quick answer!
« Reply #1 on: April 27, 2014, 07:20:58 PM »
the 14 bolt ff didnt come out till 73. the sf did come out in 64
Logged
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline bake74

  • Senior Member
  • ****
  • Posts: 5871
    • Build Thread
Re: K20 diff question, need quick answer!
« Reply #2 on: April 27, 2014, 11:19:53 PM »
     It depends on if you are comparing the same style axle to axle, kinda like apples to apples and not apples to oranges.  I have seen 70'ish 3/4 ton trucks with different rear axles, especially if they were 2wd.
Logged
#1: The easiest and most obvious solution to any problem is 99% of the time correct.
#2: There is no such thing as impossible, it just takes longer.
  74 k10, 77k10    Tom

Offline Elpresidente

  • Registered Users
  • *
  • Posts: 212
Re: K20 diff question, need quick answer!
« Reply #3 on: April 29, 2014, 04:23:06 PM »
Right on, thanks. I assume stock K20 diffs from a '79 would have something like a 4.10 gear ratio?
Logged
'82 Chev Scottsdale
Proud to be Canadian \m/

Offline bake74

  • Senior Member
  • ****
  • Posts: 5871
    • Build Thread
Re: K20 diff question, need quick answer!
« Reply #4 on: April 29, 2014, 06:28:07 PM »
Quote from: Elpresidente on April 29, 2014, 04:23:06 PM
Right on, thanks. I assume stock K20 diffs from a '79 would have something like a 4.10 gear ratio?

     I wouldn't think that a lot of them were ordered with 4.10 gears, but could be wrong.  I guess it depends really on what part of the country the truck was ordered for and what it was used for mainly.
Logged
#1: The easiest and most obvious solution to any problem is 99% of the time correct.
#2: There is no such thing as impossible, it just takes longer.
  74 k10, 77k10    Tom

Offline Irish_Alley

  • Tim
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 13319
  • Family is not an important thing. It's everything.
Re: K20 diff question, need quick answer!
« Reply #5 on: April 30, 2014, 11:10:02 PM »
Quote from: bake74 on April 29, 2014, 06:28:07 PM
Quote from: Elpresidente on April 29, 2014, 04:23:06 PM
Right on, thanks. I assume stock K20 diffs from a '79 would have something like a 4.10 gear ratio?

     I wouldn't think that a lot of them were ordered with 4.10 gears, but could be wrong.  I guess it depends really on what part of the country the truck was ordered for and what it was used for mainly.
all the k20s that i have touched all had 4.10s. now thats not saying most are like that just saying the handful i have opened up had that ratio
Logged
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline The dream

  • Registered Users
  • *
  • Posts: 147
Re: K20 diff question, need quick answer!
« Reply #6 on: May 02, 2014, 02:26:32 PM »
Mine had 3.73's.  78 K20.  14 bolt FF
Logged
Never give up.

Offline LeftysRodandCustom

  • Newbie
  • Posts: 72
  • Newbie
Re: K20 diff question, need quick answer!
« Reply #7 on: May 02, 2014, 04:48:30 PM »
It depends on the axle housing and carrier. There are 3 carrier sizes for the 10 bolt and just as many for the 12 bolt I belive. The 10 bolt has an 8.5" ring gear, the 12 bolt uses an 8.75" one. They share axle widths, axle bearing size, and carrier bearing size. While the 10 bolt has a 28 spline axle and the 12 has a 30 spline. You'd be far better off switching out the whole unit than trying two switch gears. These break in to a wear pattern with time and wont like having the pinion depth or the backlash change. Keep em complete unless you're installing new gears altogether.
Logged
Pages: [1]   Go Up
« previous next »