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#1 |
Registered User
Join Date: Sep 2013
Location: holton, in
Posts: 28
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changing rear end gear
I have a 76 c30 auto with 410 gears.I was considering changing rear gear ratio to get a little better gas milage. Was not sure which rear end I have and what options would be available. I have the original build sheet. Anyone have any experience with this?
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#2 |
Registered User
Join Date: Dec 2012
Location: Batesville Indiana
Posts: 126
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Re: changing rear end gear
An easy way to tell is count the bolts holing the cover on. Most likely a 14 bolt. But there are 2 types of them. It could also be a 12 bolt. Idk exactly what the c30s came with
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#3 |
Registered User
Join Date: May 2010
Location: Rochester NY
Posts: 831
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Re: changing rear end gear
Its most likely a Dana 70, if I remember correctly
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1973 k20 Suburban 350 1974 Custom stepside c-10 250 1975 Chevy stepside 454 1986 K30 Crewcab SRW 350 R.I.P- glimmertwin01- board member and good friend, you will be missed |
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#4 |
Registered User
Join Date: Dec 2012
Location: Batesville Indiana
Posts: 126
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Re: changing rear end gear
Forgot all about Dana's
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#5 |
Registered User
Join Date: Sep 2013
Location: holton, in
Posts: 28
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Re: changing rear end gear
I will check that. Anyway to tell from the original build sheet and truck plant or did they just use what ever was available at the time?
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#6 |
Registered User
Join Date: Aug 2009
Location: S.C.
Posts: 1,593
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Re: changing rear end gear
Way I understand it.
14 bolt ff-srw 14 bolt -dual cab and chassis Dana 70 -dual wheel pick-up My understanding, may be wrong. By all means, check your build sheet, and/or post up a pic.
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'86 C-30 dually, 454/tbh400 '73 K-20 350/350/205 (sold ![]() I'm kinda like duct tape- no real purpose, but handy to have around. |
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#7 |
Registered User
Join Date: May 2010
Location: Rochester NY
Posts: 831
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Re: changing rear end gear
Donut is correct. I assumed, seeing c30, it was a Dually. So do you have a single axle or dual?
__________________
1973 k20 Suburban 350 1974 Custom stepside c-10 250 1975 Chevy stepside 454 1986 K30 Crewcab SRW 350 R.I.P- glimmertwin01- board member and good friend, you will be missed |
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#8 |
Registered User
Join Date: Sep 2013
Location: holton, in
Posts: 28
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Re: changing rear end gear
It is a cc dually i will try and post a pic. I am trying to decifer the build sheet I will try to post a pic of it also
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#9 |
Registered User
Join Date: Aug 2009
Location: S.C.
Posts: 1,593
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Re: changing rear end gear
Don't sweat the build sheet to much. iirc, it'll show gear ratio, not necessarily the rear-end.
How tall are your tires? Rpm at speed? Personally, On mine, the rpm range was about where I wanted it. In my case, the expense of OD or a gear change wasn't worth it.
__________________
'86 C-30 dually, 454/tbh400 '73 K-20 350/350/205 (sold ![]() I'm kinda like duct tape- no real purpose, but handy to have around. |
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#10 |
Registered User
Join Date: Sep 2013
Location: holton, in
Posts: 28
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Re: changing rear end gear
It has 235/85-r16 and 4:10 gears I have never put a tach in it. I figure on nver selling it and I do not forsee gas getting any cheaper. I am in a rural area would be nice to ba able to drive to the city if need be. I just got a line on a good 200r4 for $100.
The drive shaft is the only part fo the swap I would not be able to do myself. |
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#11 |
Registered User
Join Date: May 2009
Location: Motor City
Posts: 9,194
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Re: changing rear end gear
I would like to see the build sheet if you can post it up.
Thanks in advance - K
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Chevrolet Flint Assembly 1979-1986 GM Full Size Truck Engineering 1986 - 2019 Intro from an Old Assembly Guy: http://67-72chevytrucks.com/vboard/s...d.php?t=342926 My Pontiac story: http://forums.maxperformanceinc.com/...d.php?t=560524 Chevelle intro: http://www.superchevy.com/features/s...hevy-chevelle/ |
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#12 |
Registered User
Join Date: Dec 2012
Location: Batesville Indiana
Posts: 126
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Re: changing rear end gear
I live in Napoleon and just swapped a 200-4r into my 82 swb and now I'm switching the gears to 4.56s. There is a guy up the road towards greensburg has a farm shop on the left who can put a new tube in your driveshaft. What trans do you have?
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#13 |
Registered User
Join Date: Sep 2013
Location: holton, in
Posts: 28
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Re: changing rear end gear
I have a 350 now. Are you talking about Kunz farm repair? Is the 200r4 a decent trans? Seems most post are about swapping to a 700r4.
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#14 |
Registered User
Join Date: Dec 2012
Location: Batesville Indiana
Posts: 126
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Re: changing rear end gear
200 is a direct swap, just move your crossmember back to the 400 location. That is if its a 6 inch tail shaft. Yes kuntz is the place I think. The 200 has a taller first gear and od. I had 3.08s in there and it would cruise at 1300 rpms. I have a 383 200-4r will be 4.56s and 255/45/20s (29" tire) and my rpms at 60 will be right around 2000, your 4.10s would drop it lower. I like my 200 a lot. If you have any questions on the swap I'm just a message away. I'll tell you everything you need
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#15 |
Registered User
Join Date: Sep 2013
Location: holton, in
Posts: 28
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Re: changing rear end gear
I will keep that in mind thanks a lot
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#16 |
Registered User
Join Date: Dec 2012
Location: Batesville Indiana
Posts: 126
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Re: changing rear end gear
No problem, that's what this site is for
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