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#1 |
Registered User
Join Date: Jul 2008
Location: Lawrenceville
Posts: 32
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**Help**Having trouble figuring out how to change rear Differential
I have a 1968 c10 that was once a police two truck. The rear end is at a extremely high gear. If I am driving down a hill and let go of the gas the truck slows down a lot. About three years ago I put a New 350 V8 four barrel engine and feel that I am not get the top performance from it due to the rear end. I just added disc brakes so I am looking for a cheap way to fix this...Any Ideas from the great minds?
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#2 |
Recovering 67-72 Addict
![]() Join Date: Oct 2000
Location: North Bend, WA
Posts: 1,788
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Re: **Help**Having trouble figuring out how to change rear Differential
Cheapest route would be to find a complete rear axle from a donor truck that has a numerically lower gear set.
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68 Short Fleet 4x4; 427; BTO Level 3 700R4; NP205; Dana 60 front and rear; 4" lift with 35's; Disc brakes; AGR variable ratio steering; factory bucket seats; factory tach and tilt. "Friends call me cruzer cuz I like fast cars and fast women" |
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#3 |
Registered User
Join Date: Jul 2008
Location: Lawrenceville
Posts: 32
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Re: **Help**Having trouble figuring out how to change rear Differential
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#4 |
Recovering 67-72 Addict
![]() Join Date: Oct 2000
Location: North Bend, WA
Posts: 1,788
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Re: **Help**Having trouble figuring out how to change rear Differential
If you don't want to have to change your wheels then you will need to find a 67-70 axle. You should have a 6 lug rear. In 71 the General went to 5 lugs on the 1/2 tons.
__________________
68 Short Fleet 4x4; 427; BTO Level 3 700R4; NP205; Dana 60 front and rear; 4" lift with 35's; Disc brakes; AGR variable ratio steering; factory bucket seats; factory tach and tilt. "Friends call me cruzer cuz I like fast cars and fast women" |
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#5 |
Recovering 67-72 Addict
![]() Join Date: Oct 2000
Location: North Bend, WA
Posts: 1,788
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Re: **Help**Having trouble figuring out how to change rear Differential
If you were closer, I would give you one...
__________________
68 Short Fleet 4x4; 427; BTO Level 3 700R4; NP205; Dana 60 front and rear; 4" lift with 35's; Disc brakes; AGR variable ratio steering; factory bucket seats; factory tach and tilt. "Friends call me cruzer cuz I like fast cars and fast women" |
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#6 |
Registered User
Join Date: Jul 2008
Location: Lawrenceville
Posts: 32
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Re: **Help**Having trouble figuring out how to change rear Differential
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#7 |
Registered User
Join Date: Jul 2007
Location: Portland, OR
Posts: 35
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Re: **Help**Having trouble figuring out how to change rear Differential
I was able to pick up a used third member from my local 67-72 wrecking yard. It only cost my $150 and installed in about an hour. Although that thing is a heavy pumpkin.
I'm not sure if all the axles came with a removable third member though. Mine is a 1967 C-20. But if you have bolts on the driveshaft side of your rear axle you might consider this option. |
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#8 |
Registered User
Join Date: Mar 2002
Location: Forney TX
Posts: 4,512
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Re: **Help**Having trouble figuring out how to change rear Differential
If you were closer again I have a 3.73 I want to get rid off for something taller...
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Troy 1965 Chevy Bagged,361 sbc,voodoo cam,1.5 full roller rockers,patriot 185cc vortec heads 2.02-1.60,vortec weiand polished intake,demon carb my truckhttp://67-72chevytrucks.com/vboard/s...d.php?t=332884 Big Red Dog build http://67-72chevytrucks.com/vboard/s...d.php?t=572274 |
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#9 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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Re: **Help**Having trouble figuring out how to change rear Differential
Lionc68c10... do you have a C/10, or C/20? You say tow truck, I am assuming it is a 20 or even a 30 series truck.
This can chainge things a LOT. |
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#10 |
Registered User
Join Date: Jul 2008
Location: Lawrenceville
Posts: 32
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#11 |
Registered User
Join Date: Jul 2008
Location: Lawrenceville
Posts: 32
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Re: **Help**Having trouble figuring out how to change rear Differential
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#12 | |
Registered User
Join Date: Jul 2008
Location: Lawrenceville
Posts: 32
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Re: **Help**Having trouble figuring out how to change rear Differential
Quote:
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#13 |
Registered User
Join Date: Jul 2008
Location: Lawrenceville
Posts: 32
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Re: **Help**Having trouble figuring out how to change rear Differential
Also, I have heard stories of people using parts from Cj jeeps on the old chevy trucks. The reason I ask is bc i found a dana35 rear axle from 95 wrangler with 3.73 gears. Is this possible?
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#14 |
Registered User
Join Date: Oct 2005
Location: Northern Arkansas
Posts: 1,136
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Re: **Help**Having trouble figuring out how to change rear Differential
If you are going down hill and the truck slows down when you let off the gas, you already have 3:73 or lower. I think you are wanting higher gears like 3:50 or 3:08.
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#15 |
Registered User
Join Date: Jul 2008
Location: Lawrenceville
Posts: 32
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Re: **Help**Having trouble figuring out how to change rear Differential
I believe you are right, because I just got off the phone with a guy that recommended I get a 3.41 or higher.
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#16 |
Account Suspended
Join Date: Mar 2007
Location: san bernardino ca. everywhere
Posts: 3,938
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Re: **Help**Having trouble figuring out how to change rear Differential
sorry had to do it
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#17 |
I'm a poor spectator
Join Date: Aug 2006
Location: San Antonio, Tx
Posts: 2,287
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Re: **Help**Having trouble figuring out how to change rear Differential
You don't have a drop out third member. You need either a whole rear axle or regear it.
3.42 is a good choice, I'd probably go with a 3.07 but that's just me. I would bet that you have a 3.90 or so right now. A dana 35 out of a Jeep is very weak and very narrow ( about 60 inches wide) so would not be a good candidate for a heavy truck with V8 power. BTW, if you still plan on using it for towing the 3.42 is probably a better choice than the 3.07's I said earlier but I think the 3.07's would be great for a non OD cruiser with V8.
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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!!! |
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#18 |
1970 Daily Driver
Join Date: Jun 2007
Location: Glenns Ferry IDAHO
Posts: 1,037
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Re: **Help**Having trouble figuring out how to change rear Differential
Jtrux, I have a 3.07 posi rearend in my 70 chevy. I put an NV3500 tranny in her and It makes my OD kind of worthless unless I am doing 85mph or more. In your post you said regearing was an option. Have you done it? Is it hard? I was going to swap out for a 71-72 with a lower gear but couldn't find any in my area. I would like to keep my posi and I already have 5lug hardened axles that make my rearend basicaly a 71-72 5lug posi 3.07. So I like every thing about my set up, it works great I just wish I had more grunt in lower gears and the OD was more usable. Any advice would be great.
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It's not truly yours if you didn't build it yourself or if you don't do your own maintenance. Last edited by lts70; 01-07-2009 at 04:14 PM. |
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#19 | |
I'm a poor spectator
Join Date: Aug 2006
Location: San Antonio, Tx
Posts: 2,287
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Re: **Help**Having trouble figuring out how to change rear Differential
Quote:
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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!!! |
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#20 |
1970 Daily Driver
Join Date: Jun 2007
Location: Glenns Ferry IDAHO
Posts: 1,037
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Re: **Help**Having trouble figuring out how to change rear Differential
sweet! Where did you get the gear? Can I get a gear out of a non posi used rearend? How much did it cost you if you don't mind? Did you have to buy any other parts besides the gear? What gear ratio would you recomend? Sorry about all of the questions.
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It's not truly yours if you didn't build it yourself or if you don't do your own maintenance. |
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#21 | |
I'm a poor spectator
Join Date: Aug 2006
Location: San Antonio, Tx
Posts: 2,287
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Re: **Help**Having trouble figuring out how to change rear Differential
Quote:
With that being said a 3.73 would probably be perfect for you. Ask around though, there is probably someone else out there with the same or similar drivetrain combo who can offer personaly experience. My Jeep has 3.73's with stock tires (30") and it runs about 2450 down the highway at 70 with the same tranny but get the opinion of someone with a V8 and see what they say.
__________________
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!!! |
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#22 |
I wish I was a cowboy
![]() Join Date: Apr 2008
Location: Rohnert Park, CA
Posts: 409
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Re: **Help**Having trouble figuring out how to change rear Differential
First, so everyone is clear, when someone says "I have a high gear ratio, they mean numerically low (2.73 is a "high" rear gear ratio). "Low" gears are numerically high, i.e., 4.11.
Second, so everyone is straight, 67-72 C10s came with GM truck 12 bolts, which do not have a 3rd member. The ring, pinion, and diff carrier are removable of course, but the housing is all one piece. A 3rd member is a removable portion of the rear end housing that contains the ring/pinion/diff carrier (i.e., F*rd 9"). Third, If you're using near stock tire size (30" or so tall), and a 1:1 final gear tranny (th350/400), a 3.07 would give you good 60+ mph mileage but would not work well in towing heavy loads. A 4.11 (I just swapped mine out) would be fantastic for towing heavy loads, but puts you at about 3300 rpm at 65 with your 30" tires and 1:1 tranny. A 3.42 is a great compromise. A beefy 200R4 or 700R4 and 4.11's is much better, though. Fourthly (is that a word?), changing gears is easy but the backlash and spacing needs to be set by a professional before you drive it very far or you'll tear them up quickly. Fifth, there are 2 diff carriers in 12 bolts, 1 for 3.73 and numerically higher gears, and 1 for 3.42 and numerically lower gears. If you have a 4.11 now, and you buy 3.07 ring and pinion, your diff carrier will not bolt up. Eaton posi's for truck 12 bolt are about $450 new. This is why what breech said is right on: changing housings with another 67-70 C10 housing would be easiest. If you go with a newer housing, as I did recently, you have to change wheels (5 lug axles), change leaf pads to coil pads (cutting, grinding, and welding required), and come up with a panhard bar solution. Leaf rear end housings do not have a provision for panhard. Sorry for the long $.02. Maybe that was $.03?
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-Kris Met list: Cyclone,Wilson,TranzAm,extd56,hotrodhomi,mnky30,Rokcrln,Brad,JerryJones(well, his truck anyway). Last edited by kcjones; 01-07-2009 at 04:44 PM. |
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#23 |
I'm a poor spectator
Join Date: Aug 2006
Location: San Antonio, Tx
Posts: 2,287
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Re: **Help**Having trouble figuring out how to change rear Differential
I know the 12 bolt was common but wasn't there a different axle in the 67 and 68's. If i'm not mistaken wasn't there a Dana 44 rear axle in some of them???
Good info about the carriers, I didn't know that. I don't however think it takes a "professional" to set up gears. Everybody has to start some where.
__________________
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!!! |
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#24 | |
Registered User
Join Date: Feb 2004
Location: Albany, NY
Posts: 522
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Re: **Help**Having trouble figuring out how to change rear Differential
Quote:
My .02... It might not take a pro to put in new ring and pinion gears... but for the guy who doesn't know his way around a differential, it's probably not a good idea. Even with the really great help on the internet, I grenaded a 12 bolt under a '70. and if you are even THINKING about swapping gears while the axle is under the truck... ![]() EASIEST OPTION... BAR NONE: buy 3.42 ring and pinion gears and the right sized carrier from Randy's ring and pinion or eBay. Bring the gears to a shop and have them install them.
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RN U OVR |
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#25 |
Registered User
Join Date: Aug 2007
Location: West Hills, California
Posts: 679
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Re: **Help**Having trouble figuring out how to change rear Differential
Why are you guys saying it's hard to swap gears? It's not that hard. First rear I had to do twice but after that it's not that hard. I changed gears in my c-10 without taking the rear out.
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