Dana 70HD - Spring Perches and Gears - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Mattman2010 · 12-01-2010, 01:42 PM

I have a 85 C30 crew cab that I am converting to a single wheel 4x4 truck. As we all know the 14b out of a k20 and the Dana 70HD out of the c30 have the spring perches at different spaces. I swapped k20 spring brackets onto the c30 frame to compensate for the difference in the spring spaces. Well now that I did that and I looked at pictures of the truck before I started to do the swap, I kinda think I want to go back to a dually, it just looks cool.

So what I am asking is, how hard would it be to move the spring perches on the Dana 70HD axle to fit the same width as the 14b? I ask this because the k20 spring hangers are a lot taller than the c30 spring hangers giving me more of the 4x4 look, and should make it about the right height to be a little taller or level with the front after I get the front converted to 4x4.

Also how hard is it to swap gears in the Dana 70HD rear end? I have a Dana 44 front axle that I plan on using till I can find a Dana 60 front end for a dually and it has 3.73 gears I want to go with 3.73 gears for more of a highway friendly gear ratio. I do not plan on towing with the truck that often, so 3.73s will still allow me to tow, but also allow me to get better gas mileage.

I also want to point out that this is the first axle swap I have ever done, and I have never moved spring perches or changed out gears before.

Thanks, Matt

gloriavoxdei · 12-01-2010, 02:26 PM

My D70 came with a 3.73 gear from the factory sothey are out there if you just want a new dif. As far as changing gears the D70 came in a lot of differant applications and configurations so make sure you have casting numbers and application info when you go to buy the parts. As far as the gear instal it self I've been told the D70 is basically a beefier D60 so it should be pretty straitforward.

Mattman2010 · 12-01-2010, 02:30 PM

Thanks for the info. I have heard that you have to "stretch" the diff to get the shims out of the diff so that you can get the gears out. Im not sure if this is true or not, a guy told me this one time when I was talking to him about my truck.

1985-GMC · 12-01-2010, 10:29 PM

Removing the old spring perches wont be to hard, it'll just take a little time washing out the welds with a torch then some grinding.

Ive heard you have to use a case spreader on D60's so I assume the D70's are the same way.

78customdeluxe · 12-02-2010, 11:00 PM

Dont hold me to it, but I think you can get dually hubs for the 14bolt. I had a set around here for a while, but I sold the axle. I dont know it was a cab and chassie axle or not, I never measured the width of it though. I do have a cab and chassie axle that is a 14 bolt

jltait · 01-16-2011, 10:40 PM

Mattmann,
I have read on the Ck5 site that the dually and srw hubs interchange between a D70HD and 14bolt. Keep in mind though that the D70hd housing is wider than a 14bolt housing. About 67.5" WMS-WMS for a 14bolt with srw hubs and about 72" for a D70HD with DRW hubs. The DRW hubs will be 2" narrower per side vs. SRW hubs on the same axle. Check out the 14 bolt bible link

http://www.pirate4x4.com/tech/billav...ble/index.html

Good information.
JLT

78gmc4by · 01-17-2011, 04:12 AM

I was told that you had to use a case spreader with any dana axle when we did the gears in my dana 44 we opted to try it without a spreader it was a pain but we did it
Posted via Mobile Device

12-01-2010, 01:42 PM	#1
Mattman2010 Registered User Join Date: Jun 2010 Location: Pittsburg, KS Posts: 953	Dana 70HD - Spring Perches and Gears I have a 85 C30 crew cab that I am converting to a single wheel 4x4 truck. As we all know the 14b out of a k20 and the Dana 70HD out of the c30 have the spring perches at different spaces. I swapped k20 spring brackets onto the c30 frame to compensate for the difference in the spring spaces. Well now that I did that and I looked at pictures of the truck before I started to do the swap, I kinda think I want to go back to a dually, it just looks cool. So what I am asking is, how hard would it be to move the spring perches on the Dana 70HD axle to fit the same width as the 14b? I ask this because the k20 spring hangers are a lot taller than the c30 spring hangers giving me more of the 4x4 look, and should make it about the right height to be a little taller or level with the front after I get the front converted to 4x4. Also how hard is it to swap gears in the Dana 70HD rear end? I have a Dana 44 front axle that I plan on using till I can find a Dana 60 front end for a dually and it has 3.73 gears I want to go with 3.73 gears for more of a highway friendly gear ratio. I do not plan on towing with the truck that often, so 3.73s will still allow me to tow, but also allow me to get better gas mileage. I also want to point out that this is the first axle swap I have ever done, and I have never moved spring perches or changed out gears before. Thanks, Matt __________________ 1980 K10 - 6.2L Diesel/SM465/NP205 Build Thread 1984 K30 CC Dually - "The Tank" 12V Cummins/Nv4500/Np205/D60/D70HD 4" lift & 37's Build Thread 1960 C-60 Dump Truck Make it road worthy! Thread

12-01-2010, 02:26 PM	#2
gloriavoxdei Registered User Join Date: May 2010 Location: Florissant, CO Posts: 97	Re: Dana 70HD - Spring Perches and Gears My D70 came with a 3.73 gear from the factory sothey are out there if you just want a new dif. As far as changing gears the D70 came in a lot of differant applications and configurations so make sure you have casting numbers and application info when you go to buy the parts. As far as the gear instal it self I've been told the D70 is basically a beefier D60 so it should be pretty straitforward. __________________ 1978 GMC Jimmy, 400, th350, np203 with part time conversion, Fibrecraft popup camper, soon to get a 14 bolt/d44 swap 2001 Yukon XL2500, 6.0, 4L85E, 4x4, family truckster

12-01-2010, 02:30 PM	#3
Mattman2010 Registered User Join Date: Jun 2010 Location: Pittsburg, KS Posts: 953	Re: Dana 70HD - Spring Perches and Gears Thanks for the info. I have heard that you have to "stretch" the diff to get the shims out of the diff so that you can get the gears out. Im not sure if this is true or not, a guy told me this one time when I was talking to him about my truck. __________________ 1980 K10 - 6.2L Diesel/SM465/NP205 Build Thread 1984 K30 CC Dually - "The Tank" 12V Cummins/Nv4500/Np205/D60/D70HD 4" lift & 37's Build Thread 1960 C-60 Dump Truck Make it road worthy! Thread

12-01-2010, 10:29 PM	#4
1985-GMC Chevy Enthusiast Join Date: Jul 2009 Location: Canyon Lake Texas Posts: 2,024	Re: Dana 70HD - Spring Perches and Gears Removing the old spring perches wont be to hard, it'll just take a little time washing out the welds with a torch then some grinding. Ive heard you have to use a case spreader on D60's so I assume the D70's are the same way. __________________ Tony 1985 GMC K2500 restoration Project: Rust, White & Blue 1989 Chevy R3500 CC Cummins & 4X4 swap some day... 1989 Burb (D60, 14BFF, 12V, NV4500, NP205, 37" tires in progress) Last edited by 1985-GMC; 12-01-2010 at 10:29 PM.

12-02-2010, 11:00 PM	#5
78customdeluxe Registered User Join Date: Dec 2002 Location: Upper Sandusky Ohio Posts: 72	Re: Dana 70HD - Spring Perches and Gears Dont hold me to it, but I think you can get dually hubs for the 14bolt. I had a set around here for a while, but I sold the axle. I dont know it was a cab and chassie axle or not, I never measured the width of it though. I do have a cab and chassie axle that is a 14 bolt __________________ 88 Crewcab Dually 5.9 Cummins, 5306 Eaton 6-speed, converted 4x4 w/52's up front, 90 front clip(parting out) 1986 ElCamino (needs motor) 1970 C30(future service truck for my ag-equipment repair business) 1970 CST10(parting out and partial donor for the '70 C30) 2000 GMC 1500 ext cab sb, z71, 5.3 loaded auto

01-16-2011, 10:40 PM	#6
jltait Registered User Join Date: Mar 2010 Location: Eaton Rapids, MI Posts: 97	Re: Dana 70HD - Spring Perches and Gears Mattmann, I have read on the Ck5 site that the dually and srw hubs interchange between a D70HD and 14bolt. Keep in mind though that the D70hd housing is wider than a 14bolt housing. About 67.5" WMS-WMS for a 14bolt with srw hubs and about 72" for a D70HD with DRW hubs. The DRW hubs will be 2" narrower per side vs. SRW hubs on the same axle. Check out the 14 bolt bible link http://www.pirate4x4.com/tech/billav...ble/index.html Good information. JLT

01-17-2011, 04:12 AM	#7
78gmc4by Registered User Join Date: Jan 2011 Location: Lamar Missouri Posts: 14	Re: Dana 70HD - Spring Perches and Gears I was told that you had to use a case spreader with any dana axle when we did the gears in my dana 44 we opted to try it without a spreader it was a pain but we did it Posted via Mobile Device



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