3/4 ton axle swap???

['71k-10]

I am thinking about swapping out my 1/2 ton running gear in favor for 3/4 ton. Can the running gear from 73-87 trucks be swapped underneath my 71? are there any adverse complications behind this swap and any advice for the swap? i plan on ordering ORD's 4" shackle flip and 1" zero rate add a leaf to complete the swap, should i order the 73-87 springs or the 67-72 springs.
Thanks,
Tom

[JIMs70GMC]

Can't use the 73 and up springs. They are 3" longer and would require some mods to the spring hangers.
As far as the 3/4 ton gear, the front will bolt in and you can use the 1/2 ton calipers. In the rear you will need to move spring perches and shock mounts on the axle, unless you can find a 3/4 ton rear from a pre 73 truck.

[4x4Poet]

A 14bFF from a GM 1 ton pickup will have the same spring perch width as your 71 because the 1 tons used dualies which required the spring perches to be more inward for the springs to clear the inner dual wheel. Measure to be sure before purchase. So it comes down to the advantages of a 14bFF vs. an Eaton H052 rear axle:

14bFF advantages:
1. More ring & pinion gearing choices.
2. More locker choices.
3. Reasonably priced diff rebuild kits. Hub bearings no more costly than Eaton.
4. Drum brakes are superior size to Eaton's 2" wide shoes.
5. Strong, 30-spine axles. Can handle BB torque with aplomb.
14bFF disadvantages:
A. Heavy sucka! You'll feel that massive unsprung weight as a poor ride in back. Axle is tubes pressed into heavy cast pumpkin.
B. A bit expensive to buy, but can be found cheap ($1-200 not refurbished)
C. Shop R&P labor costs more to rebuild unless axle is off vehicle because of integral carrier.
D. IIRC, only GM 1 tons had 67-72 spring perch width.

Eaton H052 advantages:
1. Lightweight axle in comparison to 14bFF. Eaton housing is all welded mild steel. Retains reasonable ride characteristics.
2. Carrier housing is removeable. Makes R&P repair labor cheaper. Makes swaps easy.
3. Avaiable for a pittance thru most wrecking yards. This great axle is ignored by most 4 wheelers looking to upgrade their 1/2 ton.
4. IIRC, all pre-73 Eaton H052s' wms and spring perch width fit 67-72 K10/20s.
5. Axles have only 17-spline, but they are arguably as strong as 14bFF axles. Can handle BB torque with aplomb.
Eaton disadvantages:
A. Few ring & pinon choices, mostly thru used/wrecking yard market.
B. Diff rebuild kits costly. Main carrier bearings are expensive. Hub bearings comparable cost.
C. IIRC, only one locker choice: Detroit locker.
D. Drum shoes only 2" wide but within 12" drums. Drums are no longer available new, but I took D60 12" drums and had a brake shop turn the outer lip down to clear the Eaton's drum backing plate. Presto! New drums.

Eaton axles can use the 14bFF disc brake conversion brackets. Also, one can swap the side gears in an Eaton's Detroit locker with a 14bFF's Detroit locker side gears to run 14bFF axles in an Eaton.

Between the two, I'd go with an Eaton for the lighter weight as long as the R&P gearing matched your needs. Go with the 14bFF if you want a selectable locker (ARB, etc.) or need R&P gearing not available w/Eaton axle.

Another option is to use a D60 out of a 67-72 K20 pickup. Less weight than the 14bFF, plethora of gear & locker choices, can also be converted to disc brakes, axles can be upraded to 35-spline ($$), prolly more expensive to source, less common in wrecking yards. Ring gear size (9.5")[*Edit:9.75" Thanks JIMs70GMC & 1969 GMC) is inferior to Eaton & 14bFF (10.5")

For the front axle, use only a D44, if not a D60, for the superior parts & locker selection over a 10-bolt front. You can find front D44s with a 71's wms & spring perch width. Enjoy.

['71k-10]

wow, thanks for all the great info. this really clears up a alot.

4x4poet- you stated that a 14bff could be used out of a Gm 1 ton. Is that year specific. also what are the differences between a 1/2 ton d44 and a 3/4 d44? and what does wms stand for?
Thanks alot for answering all my questions.
Tom

[JIMs70GMC]

wms-wheel mounting surface

4x4 poet, are you positive about the eaton being able to use the 14bff caliper bracket? If so, I might get the brackets from diy4x4 and put disc on the rear of my 71's H052.

Another rear to consider is a dana 60. GMCs used them. Lighter than the eaton or 14BFF and lots of gearing options. They were also found in 2wd big block 3/4 tons.

[4x4Poet]

Originally Posted by '71k-10

...4x4poet- you stated that a 14bff could be used out of a Gm 1 ton. Is that year specific.

IIRC, GM 1 tons from their start in '77 till at least '87. Just measure your wms and spring perch width (center to center) and then take your tape measurer to the wrecking yard. I expect most wrecking yard folks would know this swap possibility for 67-72 K10/20s.

Originally Posted by '71k-10

...also what are the differences between a 1/2 ton d44 and a 3/4 d44??...

3/4 ton D44s have 8 lug hubs with larger bearings. Should be the same Cs and knuckles. The R&P is the same across all years. I've read that 3/4 ton front D44 axle tubes have greater wall thickness than 1/2 ton D44s, but I haven't been able to verify this or measure. I believe this version is called the heavy duty D44, or HD44. This week I'm tearing down my K10s D44, so I'll have half the comparison info. As an aside, for all GM installed D44s, the inner/outer axles were smaller in 67-72 than 73/4up, but 73/4up axles fit in 67-72 front D44s.

[4x4Poet]

Originally Posted by JIMs70GMC

...4x4 poet, are you positive about the eaton being able to use the 14bff caliper bracket? If so, I might get the brackets from diy4x4 and put disc on the rear of my 71's H052.

I have it on good report from several experts at Pirate4x4.com You must use the Eaton hubs. I believe 14bFF disc brake brackets work with Eaton H052s because both axle's end flanges have the same spindle bolt pattern. I'm going to try it. After all, if the brackets don't fit, they're returnable. Here's the Pirate thread titled, appropriately, 67-72 Question.

Originally Posted by JIMs70GMC

...Another rear to consider is a dana 60. GMCs used them. Lighter than the eaton or 14BFF and lots of gearing options. They were also found in 2wd big block 3/4 tons.

You didn't see my mention of D60s? Just pullin' your chain.

[JIMs70GMC]

I just did! Got too excited at the rear disc for the HO52. But isn't the ring gear 9.75"?

[1969 GMC]

yup, dana 60 is 9.75"
14 bolt is 10.5"
the eaton is closer to 10.25"

the one tons used the 14 bolt from 73+.

I am also building up a H052/72 for my truck. those 3rd members are heavy mutha's.

[4x4Poet]

I found a tidbit on HD44s (heavy duty D44 3/4ton 8-lug axle). If the manual locking hub bolts onto the wheel hub, it's an HD44. For instance, my K20 Sub's HD44 has Spicer locking hubs that each bolt on with 6 allen bolts. If the locking hub attaches to the wheel hub with a snap ring on the outer stub axle and studs with cone washers & nuts, it's not a heavy duty D44.

The HD44s have a spindle all their own that uses larger bearings than lesser D44s. All the better for load-bearing capability [pardon the engineering pun].

[sept987]

Originally Posted by JIMs70GMC

As far as the 3/4 ton gear, the front will bolt in and you can use the 1/2 ton calipers. In the rear you will need to move spring perches and shock mounts on the axle, unless you can find a 3/4 ton rear from a pre 73 truck.

It seemed like I measured my 3/4 ton out of a 79 axles was 3 inches shorter drum to drum than the 5 lug. Any ideas?

[LostMy65]

I had an interesting thought that I'm going to investigate.
I'm currently redoing my brakes on my eaton. I keep reading how much on the 14ff will work with the eaton.
Like the Backing Plate, and the disc conversion bracket.
Here's what I'm thinking; I wonder if after mounting the 14ff Backing plate, if now the 14ff drums will work, allowing the eaton floating axle to mount.
Posted via Mobile Device

[72longbed]

I have converted both the 14 Bolt FF and the Eaton HO72 to disk brakes. YES, these axles can use the same disk caliper support bracket. I did it with no problem at all.

My HO72 lost nearly 100 lbs by converting to disk brakes.

[swamp rat]

Originally Posted by 72longbed

I have converted both the 14 Bolt FF and the Eaton HO72 to disk brakes. YES, these axles can use the same disk caliper support bracket. I did it with no problem at all.

My HO72 lost nearly 100 lbs by converting to disk brakes.

UNsprung weight, better stopping power, and lack of eaton drum parts, sounds like a win win situation. Any links to a different disk porportioning valve and calipers too?

[72longbed]

What I did was go to the 1978? Corvette Disk/Disk master cylinder, CPP disk/disk prop valve, and 76-78 Eldorado Calipers. Worked Great!!

[swamp rat]

Thanks!

[1malo68]

I'm doing the same thing with my project. I have a 72 swb frame and 79 K20 running gear. The 79 14bff spring perches were 42.5" center to center. The 72 Perches need to be 39.75" center to center. No big deal! My biggest issue is the shock mounts. Some people will use the stock frame upper shock mount studs and weld 1/2 of the lower shock mounts on the driver side to the axle tube and the other 1/2 to the center section. I haven't done it yet, but I'm going to weld my lower brackets ( Blue Torch Fab Link Mounts ) on my axle just inside of the leaf springs @ a 60 degree angle and build a crossmember for the top shock brackets ( same link mounts ). It's going to be a good bit of fabrication, but I think I should get pretty good articulation and a fair ride. Here's what a 14bff looks like from the Transfer case crossmember.

[1malo68]

BTW you can't see it real well, but that's the ORD disc brake conversion

Dan

[Chevymaniac]

what kind of tank did you install and how r u doing your filler access for gas?

[1malo68]

I got my tank from Classic Industries. I thought about doing it a bunch of different ways, but I like the way that 71meangreenc10 did his. He put it in the wheel well. http://67-72chevytrucks.com/vboard/s...d.php?t=390845 If your willing to put it on the passenger side, it should be a pretty straight shot into the passenger side wheel well. I'm gonna box it in once it's run for some extra protection and I'll have to fill it from inside the bed. That's the plan anyway.

[LostMy65]

Instead of having to know all the parts needed, are there rebuild kits for rear differentials?
Things like all the bearings and seals - not the brakes.

[72longbed]

Don't know what rear you have but, I would check with Randy's Ring and Pinion. They used to carry rebuild kits for most rears.