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Username Post: '64 3/4 Ton rear end gears        (Topic#235019)
cactusbud 
Forum Newbie
Posts: 34
cactusbud
Loc: Kansas City
Reg: 04-11-08
02-05-10 12:13 PM - Post#1856953    

Hello all, Quick question about the rear end gears for a '64 C20 with coil spring rear end. My understanding is that this is an Eaton unit(Has round rear cover and removable 3rd member) and was told it was a HO52 and am looking at local vendors for Ring and Pinion Sets in 3.55 or 3.73. So far, I have had no luck as everyone is telling me they are NA. Can anyone tell me if this info is correct for this rear end and if there is a vendor who has ring and pinion sets for my truck. Thanks, Bud
1966 C10 Shortbed Fleetside w/ Big Window
455 Olds Rocket/ M-20 trans

1965 C20 LWB Beater "Ranch Truck"
250 L-6 SM-420

1956 GMC 350 Series Grain Truck
316 Pontiac V-8 SM-420

http://www.flickr.com/photos/66511554@N00/


 
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LGriffin 
Contributor
Posts: 436

Age: 68
Loc: Gateway to Yosemite
Reg: 04-16-04
02-05-10 05:41 PM - Post#1857116    
    In response to cactusbud

All the information you've given is correct. The best you are going to be able to do is 4.10. IIRC you'll find these gears in Suburbans with automatics up to 1972. I believe the HO72 third member will swap into the HO52, but there maybe an issue with axle splines. If I'm wrong we will hear about it. 8^)

Larry
I don't own a vehicle that isn't old enough to drink.


 
christopherlutz 
Bronze Member
Posts: 431

Loc: Flower Mound, Texas
Reg: 11-10-06
02-06-10 04:02 PM - Post#1857585    
    In response to LGriffin

There is a vendor - I'll check and get back to you - unfortunately, your only gear choices on this full floater are:

4:56 (stock)
4:10

I have a 65 C20 - swapped the rear end for a 69 12 bolt.
Lutzy

1965 C20 (completely dismantled)
2008 Chevy Silverado 1500 (5.3l V8)
2006 Honda Pilot EX


 
cactusbud 
Forum Newbie
Posts: 34
cactusbud
Loc: Kansas City
Reg: 04-11-08
02-06-10 04:26 PM - Post#1857604    
    In response to christopherlutz

I think that 4.10 gears would be a definite improvement in drive ability over the 4.56 gears, i will be anxious to hear back, Thanks to both, Andrew
1966 C10 Shortbed Fleetside w/ Big Window
455 Olds Rocket/ M-20 trans

1965 C20 LWB Beater "Ranch Truck"
250 L-6 SM-420

1956 GMC 350 Series Grain Truck
316 Pontiac V-8 SM-420

http://www.flickr.com/photos/66511554@N00/


 
LGriffin 
Contributor
Posts: 436

Age: 68
Loc: Gateway to Yosemite
Reg: 04-16-04
02-06-10 06:22 PM - Post#1857645    
    In response to cactusbud

Hate to disappoint you, but I wouldn't get excited about 4.10 over 4.56. The reason I say that is that I went from 4.56 to 3.73 in 68 C20 with a sm465. That allowed me to get out of the intersection with second gear, before I was shifting to third before the crosswalks. I would still like to have 3.30 to 3.55 gears, so I could be under 2500 RPM at 65 mph.

Find an RPM calculator and run some numbers. I think you'd find that larger tires might make the difference between 4.56 and 4.10. I went with an OD in my 63 C20 that bumped my mpg from 12 to 16, and dropped my RPM from about 3300 to 2500.

Larry
I don't own a vehicle that isn't old enough to drink.


Edited by LGriffin on 02-06-10 06:32 PM. Reason for edit: No reason given.

 
Vaughn 
"12th Year" Gold Supporting Member
Posts: 15397

Loc: Colorado Springs, CO
Reg: 08-08-04
02-06-10 08:24 PM - Post#1857720    
    In response to LGriffin

The last known supplier that I know of was Patrick's trucks, who had a number of 3.73 gears made up for the Eaton axle that came stock in 47-72 3/4 ton trucks (the HO52 axle). The 1 ton axle was the HO72 eaton, which was similar (had larger axleshafts, apparently).

http://www.patricksantiquecars.com/index.htm

They aren't giving the gears away, in case you were wondering. Expect prices above $750, and a fair amount for professional setup (which you HAVE TO HAVE).

You would be MUCH better off swapping a later 14 bolt single axle rear in, you can get examples for $200-300 in the 3.73 range. They are a bit of a squeeze to get under a 64, but you can do it with wheels that have a bit more offset than stock.



 
hilandr451 
9th Year Platinum Supporting Member and Moderator
Posts: 3671
hilandr451
Loc: Bakersfield, Ca.
Reg: 01-02-02
02-07-10 11:36 AM - Post#1857976    
    In response to Vaughn

Larry,

what size tires did you end up going with to achieve that kind of performance?

I also have an Eaton from a '64 donor truck in my '66. I am hoping that my buddy's '66 C20 with a factory powerglyde has a 4:10 in it. He's converting to 1/2 ton running gear for tires & rim selection and I've got dibs on the diff.

I am currently running a 1991-ish 5.7L V8 in front of a TH700R4.
-The Hilander.
'06 Impala LT, '66 C20 Custom Camper, '65 Airstream "Overlander"
Project Pics
hilanders6066chevytruck.com


 
persh 
Frequent Contributor
Posts: 1462
persh
Loc: Tucson, Arizona
Reg: 07-19-00
02-07-10 03:55 PM - Post#1858099    
    In response to hilandr451

I ended up with a Dana 60 axle (I had the mounting pads removed and redone for the coil spring setup) and put 3.52 gears in it. With 235/85-16 tires (350/700R4) it cruises down the freeway very nicely and gets away from stop lights with plenty of zest......
'60-'66 Idea Page or Corvair Stuff


Edited by persh on 02-07-10 03:55 PM. Reason for edit: No reason given.

 
LGriffin 
Contributor
Posts: 436

Age: 68
Loc: Gateway to Yosemite
Reg: 04-16-04
02-08-10 08:01 AM - Post#1858438    
    In response to hilandr451

  • hilandr451 Said:
Larry,

what size tires did you end up going with to achieve that kind of performance?

I also have an Eaton from a '64 donor truck in my '66. I am hoping that my buddy's '66 C20 with a factory powerglyde has a 4:10 in it. He's converting to 1/2 ton running gear for tires & rim selection and I've got dibs on the diff.

I am currently running a 1991-ish 5.7L V8 in front of a TH700R4.



The tire size is 235/75 16, but I didn't change tire size, I changed transmissions. I pulled the sm420 and replaced it with NP A833(RPO MY6). The A833 has a 26% overdrive for fourth.

Larry
I don't own a vehicle that isn't old enough to drink.


 
ccpanel 
Forum Newbie
Posts: 2

Loc: nor-cal
Reg: 04-05-09
12-29-10 11:28 PM - Post#2024319    
    In response to LGriffin

I know old post but there is another option-late 60's vans used the HO72 and commonly came with 3.73 gears.

Im told also that the internals are virtually identical to the later model 14 bolt axles.(not verified)

gear calculator;
http://www.grimmjeeper.com/gears.html
http://customclassics.org
- -
Suppose you were an idiot. And suppose you were a member of Congress. But I repeat myself.
- Mark Twain
- -


 
MKline 
Contributor
Posts: 109
MKline
Loc: Pawnee, Oklahoma
Reg: 08-17-06
12-30-10 12:05 AM - Post#2024324    
    In response to ccpanel

I know these are out there... 'cause I found one. Some 67-72 C20s and GMC 2500s with coil spring rears have Dana 60 differentials. I am having mine worked up with 3.54 gears and a positrac. I was probably lucky to find mine... Good Luck!
1966 C20 Custom Camper
1966 K20 Flatbed


 
LGriffin 
Contributor
Posts: 436

Age: 68
Loc: Gateway to Yosemite
Reg: 04-16-04
12-30-10 09:48 AM - Post#2024441    
    In response to MKline

There was also a rumor that 3.90 gears were available for the Eaton HO differentials. A couple of Stovebolters researched 3.90 gears, and many have looked for them, not to be found. This is the first I've heard of 3.73 gears.

The Eaton HO diffs and the GM 14 bolt do share some parts albeit it's a one way swap. IIRC you put the HO carrier in a 14 bolt, but the reverse is not true.

Larry
I don't own a vehicle that isn't old enough to drink.


 
kieth 
Forum Newbie
Posts: 87

Loc: Tulsa, Oklahoma
Reg: 08-05-10
12-30-10 10:07 AM - Post#2024450    
    In response to cactusbud

Give these guys a call they are knowledgable

Axles, Transmission, and transfers 918-425-7725 ask for richard he knows and has some older units. Kieth

 
Vaughn 
"12th Year" Gold Supporting Member
Posts: 15397

Loc: Colorado Springs, CO
Reg: 08-08-04
12-30-10 02:31 PM - Post#2024552    
    In response to kieth

The parts in the Eaton HO axles are not interchangeable with the later 14 bolts. The only similarities that they share is that they will nearly bolt in place of each other.

There was a place that used to have Eaton gears, and they used to advertise on the Stovebolt site. I believe it was Patricks, but am not sure since it has been a while. They weren't giving those gearsets away either - they were charging upwards of $800 for the privilege of supplying people that gearset - and because of that price most people just swapped in a different rear with more reasonable gears and posi availability.

 
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