Rear differential - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jonnymel · 04-12-2021, 11:38 PM

I have a 1960 gmc step side it has a 4:10 gear ratio in it . I would like to change the ratio . I’m thinking 3:55 .
Would still like a good start of the line but need a highway gear too.
Also does anyone have a suggestion for a supplier. Don’t want to change the axle just the differential.

SkinnyG · 04-13-2021, 12:36 AM

Is this the HO32 rear end (removable center section AND removable rear cover)? I don't think you will find -any- gears for it.

jonnymel · 04-13-2021, 08:01 AM

Ok
Thanks
Obviously I need to identify exactly what I have first. Possibly not as easy as I’d hoped. So what does everyone do ? Drive around with 4:10 gears or is there a rear axle swap that’s relatively simple .
I have a 454 with a 400 turbo 3 speed and I need to improve my highway rpms

jonnymel · 04-13-2021, 08:08 AM

Hey SkinnyG
I looked at your Apache project.......great job , I love it.

SkinnyG · 04-13-2021, 10:50 AM

Thanks!

You could swap just about any axle relatively easily. You'd need to weld on axle mounts. 60-62 is a different width than 63+, so even swapping a later axle requires welding mounts. I'd go 63+ 12-bolt or even a Ford 8.8. Keep in mind bolt pattern and such.

You could swap in a 5-speed. Be gentle though, a 454 has a lot of torque.

You could find a 4L80E for the overdrive and get a trans controller for it.

jbgroby · 04-13-2021, 03:52 PM

I have a '60 with the DANA 44, called Precision Gear and bought a 3.23 (stock was 3.92), I changed all the inner and outer bearings while I was at it too.

AcampoDave · 04-13-2021, 07:55 PM

I'm thinking going to a 3.55 still isn't a big enough change to get you what you're looking for. I feel a 454 has plenty enough torque that it should still smoke the tire with a 3.08

**vetnat** · 04-14-2021, 02:06 AM

If it is an HO32, Yukon has a 3.38 ring and pinion.
https://www.yukongear.com/partslist....nion+Gear+Sets

jonnymel · 04-14-2021, 09:04 AM

Thanks , I was wondering about that.

jonnymel · 04-14-2021, 09:25 AM

Thanks everyone for your input .......I really appreciate it.
I think I will go with the 3:38 Yukon Ring and Pinion.
Next question other than a new diff gasket and cover what other parts would I buy as well.
I’m relatively sure nothing has been done to the rear end previously.
I’m a rookie at this. I will purchase parts but have some qualified help for the install.

SkinnyG · 04-14-2021, 10:35 AM

Oh cool!

I've previously run Yukon gears - they are very good.

**60short** · 04-14-2021, 05:32 PM

from my experience / while you are in there ....

The bearings are R1502EL - available from several manufacturers including Timkin and National

The seals are : SKF 18695 - also interchangeable and available from several manufacturers / vendors.

(the best prices I found was on RockAuto, searching by PN).

Somebody else made a good point - above parts are for the Eaton HO 32/33

61K10 · 04-15-2021, 01:47 PM

take a pic of the rear cover and post it. Most GMC's had a Dana rear axle.

Killer Bee · 04-15-2021, 03:12 PM

lucky you! most of us just tool around in our 4.57s day dreaming about 4:10s

cross your fingers you've got a dana under there and good luck finding a suitable gear swap!

04-12-2021, 11:38 PM	#1
jonnymel Registered User Join Date: May 2013 Location: Carp Ontario Posts: 15	Rear differential I have a 1960 gmc step side it has a 4:10 gear ratio in it . I would like to change the ratio . I’m thinking 3:55 . Would still like a good start of the line but need a highway gear too. Also does anyone have a suggestion for a supplier. Don’t want to change the axle just the differential.

04-13-2021, 12:36 AM	#2
SkinnyG Registered User Join Date: Feb 2012 Location: Beautiful BC, Canada, eh?! Posts: 2,306	Re: Rear differential Is this the HO32 rear end (removable center section AND removable rear cover)? I don't think you will find -any- gears for it. __________________ 1961 Apache: "Grabber Orange" Shortboxed, pancake, step-notch, air-ride, turbo, LS 1977 Silverado: Shortboxed & dropped, potato-potato V8 Pontiac Firefly (Chevy Sprint): The ultimate engine swap: 5.7L in a 1.0L bag Lotus Super 7 Replica: Scratch-built street-legal rollerskate

04-13-2021, 08:01 AM	#3
jonnymel Registered User Join Date: May 2013 Location: Carp Ontario Posts: 15	Re: Rear differential Ok Thanks Obviously I need to identify exactly what I have first. Possibly not as easy as I’d hoped. So what does everyone do ? Drive around with 4:10 gears or is there a rear axle swap that’s relatively simple . I have a 454 with a 400 turbo 3 speed and I need to improve my highway rpms

04-13-2021, 08:08 AM	#4
jonnymel Registered User Join Date: May 2013 Location: Carp Ontario Posts: 15	Re: Rear differential Hey SkinnyG I looked at your Apache project.......great job , I love it.

04-13-2021, 10:50 AM	#5
SkinnyG Registered User Join Date: Feb 2012 Location: Beautiful BC, Canada, eh?! Posts: 2,306	Re: Rear differential Thanks! You could swap just about any axle relatively easily. You'd need to weld on axle mounts. 60-62 is a different width than 63+, so even swapping a later axle requires welding mounts. I'd go 63+ 12-bolt or even a Ford 8.8. Keep in mind bolt pattern and such. You could swap in a 5-speed. Be gentle though, a 454 has a lot of torque. You could find a 4L80E for the overdrive and get a trans controller for it. __________________ 1961 Apache: "Grabber Orange" Shortboxed, pancake, step-notch, air-ride, turbo, LS 1977 Silverado: Shortboxed & dropped, potato-potato V8 Pontiac Firefly (Chevy Sprint): The ultimate engine swap: 5.7L in a 1.0L bag Lotus Super 7 Replica: Scratch-built street-legal rollerskate

04-13-2021, 03:52 PM	#6
jbgroby Registered User Join Date: Nov 2008 Location: Lacombe, LA Posts: 2,772	Re: Rear differential I have a '60 with the DANA 44, called Precision Gear and bought a 3.23 (stock was 3.92), I changed all the inner and outer bearings while I was at it too. __________________ http://s1299.photobucket.com/user/jb...23904108567829

04-13-2021, 07:55 PM	#7
AcampoDave Registered User Join Date: Feb 2013 Location: central California Posts: 2,801	Re: Rear differential I'm thinking going to a 3.55 still isn't a big enough change to get you what you're looking for. I feel a 454 has plenty enough torque that it should still smoke the tire with a 3.08 Last edited by AcampoDave; 04-13-2021 at 08:02 PM.

04-14-2021, 02:06 AM	#8
vetnat Senior Member Join Date: Jun 2015 Location: Moose Jaw, SK Posts: 511	Re: Rear differential If it is an HO32, Yukon has a 3.38 ring and pinion. https://www.yukongear.com/partslist....nion+Gear+Sets __________________ 1961 GMC half ton, short step, Canadian model. Just starting work on it.

04-14-2021, 09:04 AM	#9
jonnymel Registered User Join Date: May 2013 Location: Carp Ontario Posts: 15	Re: Rear differential Thanks , I was wondering about that.

04-14-2021, 09:25 AM	#10
jonnymel Registered User Join Date: May 2013 Location: Carp Ontario Posts: 15	Re: Rear differential Thanks everyone for your input .......I really appreciate it. I think I will go with the 3:38 Yukon Ring and Pinion. Next question other than a new diff gasket and cover what other parts would I buy as well. I’m relatively sure nothing has been done to the rear end previously. I’m a rookie at this. I will purchase parts but have some qualified help for the install.

04-14-2021, 10:35 AM	#11
SkinnyG Registered User Join Date: Feb 2012 Location: Beautiful BC, Canada, eh?! Posts: 2,306	Re: Rear differential Oh cool! I've previously run Yukon gears - they are very good. __________________ 1961 Apache: "Grabber Orange" Shortboxed, pancake, step-notch, air-ride, turbo, LS 1977 Silverado: Shortboxed & dropped, potato-potato V8 Pontiac Firefly (Chevy Sprint): The ultimate engine swap: 5.7L in a 1.0L bag Lotus Super 7 Replica: Scratch-built street-legal rollerskate

04-14-2021, 05:32 PM	#12
60short Revitalizing a 6T C10 Join Date: Aug 2017 Location: Santa Barbara, CA Posts: 224	Re: Rear differential from my experience / while you are in there .... The bearings are R1502EL - available from several manufacturers including Timkin and National The seals are : SKF 18695 - also interchangeable and available from several manufacturers / vendors. (the best prices I found was on RockAuto, searching by PN). Somebody else made a good point - above parts are for the Eaton HO 32/33 __________________ 1960 C-10 Apache- "Rusty the Redneck Reject" 1/2 Ton short bed step side. 350 crate motor, 3 speed manual (floor shifted) MKII - Buddy Buckets and Glass Packs 20+ year long term project in process Lots of Rust, more memories... Build Thread Last edited by 60short; 04-15-2021 at 10:39 PM.

04-15-2021, 01:47 PM	#13
61K10 Registered User Join Date: Feb 2012 Location: pleasant valley--placerville ca Posts: 3,039	Re: Rear differential take a pic of the rear cover and post it. Most GMC's had a Dana rear axle. __________________ 1961 chevy K10 my build is------------61K10 build

04-15-2021, 03:12 PM	#14
Killer Bee Registered User Join Date: Jan 2016 Location: Barber City, CA Posts: 4,829	Re: Rear differential lucky you! most of us just tool around in our 4.57s day dreaming about 4:10s cross your fingers you've got a dana under there and good luck finding a suitable gear swap! __________________ *I started out with nothing - and I still have most of it*



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