1/2 ton or 3/4 ton diffs???

[rscustomrods]

So I got a new front differential in great shape with 3.73 gears and part time locking hubs for my daughter's truck. However, my rear has 3.07 gears. I have a chance to pick up a matched set of 3/4 ton diffs with 3.73 gears in it for $300. I do not know much history on the diffs, other than they are out of a 1979. I am going to pick the owner's brain about them.

My question is, should I do it? I am not building a crawler, but merely a daily driver for my daughter, that can also be 4x4 capable for very mild use. Should I just have az diff put 3.73 gear in my half ton rear end for $600 (I do not have the skills to do it myself), or buy the 3/4 ton axles? What do I really gain in the 3/4 ton axles? I already have 6 lug wheels and tires too, so I will have to buy 8 lug wheels if I do the swap.

Comments welcome and greatly appreciated.

Rich

 

[rscustomrods]

sorry, this should have gone in the "Differential section". Moderators can you help? Sorry for the inconvenience. New guy here

 

[HotRodPC]

So I got a new front differential in great shape with 3.73 gears and part time locking hubs for my daughter's truck. However, my rear has 3.07 gears. I have a chance to pick up a matched set of 3/4 ton diffs with 3.73 gears in it for $300. I do not know much history on the diffs, other than they are out of a 1979. I am going to pick the owner's brain about them.

My question is, should I do it? I am not building a crawler, but merely a daily driver for my daughter, that can also be 4x4 capable for very mild use. Should I just have az diff put 3.73 gear in my half ton rear end for $600 (I do not have the skills to do it myself), or buy the 3/4 ton axles? What do I really gain in the 3/4 ton axles? I already have 6 lug wheels and tires too, so I will have to buy 8 lug wheels if I do the swap.

Comments welcome and greatly appreciated.

Rich

sorry, this should have gone in the "Differential section". Moderators can you help? Sorry for the inconvenience. New guy here

Welcome to GMSB !!! Got the thread moved.

I say no thinking about it, like white on rice, get those 3/4 ton axles. Much stronger than the 10 bolts for the rear end. Granted the front is still going to be a 10 bolt, but now you'll have a spare, cuz with some moderate use, it's possible to break an axle shaft or maybe even a carrier depending on how big of tires you running on it. Chances are the 3.73 Full Float is still in good shape. They are hard to kill. Maybe some outter axle bearings and seals, and some new gear oil but go ahead and rock that deal. You say you have a new or good from 3.73 now? So transfer the 8 lug hubs to the good 3.73 that's in it now, and keep the other 3.73 for for back up, and sell that rear 3.08 10 bolt for $100-$125 and get you some 8 lug used wheels with the cash. You won't need a back up for the 14b Full Float rear end cuz you'll never break it.
This is a very common thing to do and guys are always looking for 3/4 ton axles. I'm doing the same thing soon.

 

[oneluckypops]

If you could tell us a little more about the truck it would help. Like what size tires are you running, What transmission does it have, ect. ect...

 

[HotRodPC]

If you could tell us a little more about the truck it would help. Like what size tires are you running, What transmission does it have, ect. ect...

yeah, all that would be nice to know, but I don't think it matters much for $300 on a matching set of 8 lug axles. Guess maybe if he wants to run a 700r4 he might want a lower gear, but in a 78, I'd assume it's a Th350, and with 3.73's and some 33-35 inch tires, don't need an OD.

 

[oneluckypops]

yeah, all that would be nice to know, but I don't think it matters much for $300 on a matching set of 8 lug axles. Guess maybe if he wants to run a 700r4 he might want a lower gear, but in a 78, I'd assume it's a Th350, and with 3.73's and some 33-35 inch tires, don't need an OD.

no it mattters plenty, he said it was his daughters truck, so if she doesnt wheel the truck and isnt running bigger tires it would be pointless to change to 4.10 ratio, even thou its cheaper for the differentials it would NOT be cheaper in the long run. They already have 6 lug wheels and tires, if they buy the 3/4 ton they will have to buy new wheels AND tires which would be a hell of alot when its not needed.

 

[HotRodPC]

hahahaha, how many daughters you raised??? That's all the more reason to upgrade the axles. Girls don't realize things break. My bosses 16yo daughter has all but tore her truck up being rough with it. Got a new motor in it now, front driveshaft, exhaust she ripped out from under it. I agree on buying the new wheels, but for $300 to upgrade, I say suck it up and not have to worry about it later. JMO

But yep, lets here the plans for the truck, tires sizes, what trans is in it etc. I could change my mind, but doubtful.

 

[rscustomrods]

Thanks for the replies guys. It is currently sitting on a 4 inch lift with 33 inch tires. The motor is a 330hp 350 and the transmission is a 400. The front diff is really good and has 3.73 gears. The 3/4 set I am going to see tomorrow has 3.73 gears. I will have to buy 8 lug wheels, but should be able to mount the tires on the 8 lug wheels, so I think the move is to buy the 3/4 ton axles. Thanks again for the input. If others have opinions, please feel free to comment

 

[bucket]

I agree with HRPC

 

[HotRodPC]

I'd hope 10 bolts will hold up to 33 inch tires and 330hp but that's sure the max I'd feel comfy with. Do keep in mind, the 8 lug wheels you're likely to find will be 16in, so your 15in tires won't fit those. There are 15in 8 lug wheels to be found, but are rare, and usually in a wagon wheel. Also, you'll have to do a little grind work on the calipers to get the 15inch wheels to fit. I don't know how much use you have left on those 15 x 33's but you can still buy the axles, not install them just yet and wear on the 6 lug tires for a bit and have some time to come up with 8 lug wheels and tires. ALso watch Craigslist for used or trades. 33x12.50x15 is real common tire and should be easy for you to sale if priced right too if you don't want to wait. 6 lug wheels are usually easy to sell too if they are Rallys or the OEM Aluminums. I still think you're ahead of the game though over buying 3.73's for the rear axle and having them installed Turbo 400 is a plenty strong trans too, so you'd esentially have a 3/4 ton powertrain in the truck with those axles. And remember, you said the 3.73 front you have is newish, you can take the 8 lug hubs off the used front you buy for that front axle. They are interchangeable.