Rear axle interchange? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jku72 · 11-29-2003, 08:16 PM

I have an HO72 with a 4.10 gear, and was wondering why any newer 3/4 ton axle wouldn't fit in it's place, and second, what is the highest 3/4 ton ratio available. Id love to have a 3.40 or so.
Is there width issues here?

**kwmech** · 11-29-2003, 08:49 PM

GM 14 bolt rear axles can go up to a 3.42 ratio and a Dana 60 can easily go to a 3.54 ratio.

padreisla · 11-30-2003, 01:50 AM

I have a 67 C20 with a corporate rear end and the gear ratio is way too high for highway travel. You mentioned the GM 14 bolt, is that the same as the corporate and if so where can I get the 3:43 gears or even something a little higher fot it. I really don't want to change out my rearend since I just bought new 8-lug wheels and tires for it.

Thanks....Joey

Longhorn Man · 11-30-2003, 03:12 AM

The 14 bolt is the 73 & up rear axle. It is a fairly common swap, but there is some welding incolved since the shocks don't mount the smae.
There are aftermarket gear sets for teh HO52 Eaton/corp diff...but they are not cheap.

1969 GMC · 11-30-2003, 04:26 AM

a dana 60 out of one of our trucks should work, but i forget all the differences in spring perch width.

the eaton HO, dana 60, and corporate 14bff all have the same 8 lug pattern.

highest gearset available for the HO is 3.90, but i think a while back someone on here said this was discontinued. might have to do some snooping.

Vince M · 11-30-2003, 10:22 AM

I put a 14 bolt in my 72 4x4 and the spring perches had to be cut off and relocated, along with the shock mounts. It wasn't hard to do if you have a few basic tools.
The Eaton rear only has a few options for gear ratios and as mentioned the 3.90:1 is the lowest available and this is an aftermarket unit. 4.10:1 is lowest available froom GM. Parts and prices for parts for the Eaton are expensive, hard to find, or just plain not available. This is why I switched to the 14 bolt. The 14 bolt is wider than the Eaton by about an 1.5". This didn't effect anything on my truck at all. The 14 bolt in my opinion is a much better rear and not as prone to leaking like the Eaton.

jku72 · 11-30-2003, 12:08 PM

Thanks for the input. I think I'll end up going with the 14.

11-29-2003, 08:16 PM	#1
jku72 Registered User Join Date: Jan 2002 Location: cornville, maine Posts: 659	Rear axle interchange? I have an HO72 with a 4.10 gear, and was wondering why any newer 3/4 ton axle wouldn't fit in it's place, and second, what is the highest 3/4 ton ratio available. Id love to have a 3.40 or so. Is there width issues here? __________________ jku Cornville, Maine 68 C10 burb 42 Willys MB 46 Dodge WF-32 1.5 ton 53 & 56 Olds' 60 Cadillac 22 Dodge Brothers

11-30-2003, 01:50 AM	#3
padreisla Registered User Join Date: Jan 2003 Location: Tampa, Florida Posts: 141	Rear Axle Ratios I have a 67 C20 with a corporate rear end and the gear ratio is way too high for highway travel. You mentioned the GM 14 bolt, is that the same as the corporate and if so where can I get the 3:43 gears or even something a little higher fot it. I really don't want to change out my rearend since I just bought new 8-lug wheels and tires for it. Thanks....Joey __________________ 67 C20 LWB 454 BB THD 400 97 Jeep Wrangler 4cyl 5sp

11-30-2003, 04:26 AM	#5
1969 GMC Registered User Join Date: Feb 2003 Location: The Rubber City Posts: 5,498	a dana 60 out of one of our trucks should work, but i forget all the differences in spring perch width. the eaton HO, dana 60, and corporate 14bff all have the same 8 lug pattern. highest gearset available for the HO is 3.90, but i think a while back someone on here said this was discontinued. might have to do some snooping. __________________ 1969 GMC K2500 1996 Honda Accord 2007 Kawasaki KLR 650

11-30-2003, 10:22 AM	#6
Vince M Senior Member Join Date: Apr 2000 Location: Orlando, FL Posts: 1,076	I put a 14 bolt in my 72 4x4 and the spring perches had to be cut off and relocated, along with the shock mounts. It wasn't hard to do if you have a few basic tools. The Eaton rear only has a few options for gear ratios and as mentioned the 3.90:1 is the lowest available and this is an aftermarket unit. 4.10:1 is lowest available froom GM. Parts and prices for parts for the Eaton are expensive, hard to find, or just plain not available. This is why I switched to the 14 bolt. The 14 bolt is wider than the Eaton by about an 1.5". This didn't effect anything on my truck at all. The 14 bolt in my opinion is a much better rear and not as prone to leaking like the Eaton. __________________ ............................................................ 68 Chevy CST SWB w/LS1, carb & 700r4. Golden Anniversary clone with a few improvements.

11-30-2003, 12:08 PM	#7
jku72 Registered User Join Date: Jan 2002 Location: cornville, maine Posts: 659	Thanks for the input. I think I'll end up going with the 14. __________________ jku Cornville, Maine 68 C10 burb 42 Willys MB 46 Dodge WF-32 1.5 ton 53 & 56 Olds' 60 Cadillac 22 Dodge Brothers

11-29-2003, 08:49 PM	#2
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,483	GM 14 bolt rear axles can go up to a 3.42 ratio and a Dana 60 can easily go to a 3.54 ratio.

11-30-2003, 03:12 AM	#4
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	The 14 bolt is the 73 & up rear axle. It is a fairly common swap, but there is some welding incolved since the shocks don't mount the smae. There are aftermarket gear sets for teh HO52 Eaton/corp diff...but they are not cheap.



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