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39.5's stock axles....How long will it last

howdiy

howdiy

1/2 ton status
Joined
Jan 28, 2004
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I have a 73 1/2 ton stepside

I don't really feel like upgrading anything just yet.

Should I just go with chromoly axles? But I think it's cheaper just to put a 14 bolt in the rear then though.

I don't really spin the tires much.

The diffs are open and stock geared. I think with the stock gears I should be fine.

My wheeling is mostly dirt hills and mud.

Edit: I did put a np205 after I grenaded the stock transfer case
 
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better have a hell of a motor to spin 39.5s with even 3.73 gears. First time you go offroad I bet you'll snap a shaft.

!4 bolt is definetally a cheaper and must stronger option than sticking chromo's in a 12 bolt. Also the 44 won't be too happy. I think you need to figure on doing a lot more than just slapping those tires on.

One truck I was suppossed to work on snapped a shaft in his 9" on 39.5" TSLs last night. Got the truck all finished up, 3 hours later its sitting on blocks needing an axle.
 
stepside says 1/2 ton to me. That and the fact that he asked whether he should upgrade to the 14 bolt or chromos....

73 wouldn't have a Dana 60 under the front even if it were a 1 ton. Not even sure there were 1 ton 4x4s in 73. Think only 2wd.
 
Depending on where you live, 14b are cheap. I got mine complete with 4.56 gears for $150 from the local junkyard. Almost completely unbolted from the truck too when I found it. I wouldnt want to have stock gearing (depending on what it is, I'm guessing 3.73) with 39.5"s. I wouldnt want to have 3.73 gearing with my 35"s for that matter
 
fixed it's a 1/2 ton obviously. I wouldn't be worried if it was a 1 ton. I have after market drive shafts also. I'm not really spinning the tires but It does have enough pep. I have to use a bit of momentum to get started. The axles are open also :eek1:. I think this is going to be the lifesaver. Although I just recently grenaded a 12 bolt with a 350 and 33 inch tires. I was beating it on very hard though. only having 1st gear and hitting 40 milesand hour across a mud field. A donut onto dry mulch is what put it in though.


The truck is already done BTW. It's was just sitting in the garage for a few years. I'm lowering it with 4 TC springs in the front and maybe 64's in the rear plus the shackle flip I'll have to put a fuel cell in also as the sattle tank is in the way and seems dangerous to be off roading with it in it's current position.
 
sled_dog said:
stepside says 1/2 ton to me. That and the fact that he asked whether he should upgrade to the 14 bolt or chromos....

73 wouldn't have a Dana 60 under the front even if it were a 1 ton. Not even sure there were 1 ton 4x4s in 73. Think only 2wd.
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Nope it was a 4x4 orginally
 
lochenjons said:
Depending on where you live, 14b are cheap. I got mine complete with 4.56 gears for $150 from the local junkyard. Almost completely unbolted from the truck too when I found it. I wouldnt want to have stock gearing (depending on what it is, I'm guessing 3.73) with 39.5"s. I wouldnt want to have 3.73 gearing with my 35"s for that matter
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Yeah they are in my junkyard also. I'm just too lazy to go get them lol. I guess I'll just go get one becuase it seems like a pretty seriously needed upgrade. I'll just weld them up also. Any repercussions to this? I know on a spool in a drag car it's a bit hard to turn but I think it should be fine on the street.
 
howdiy said:
I'll just weld them up also. Any repercussions to this? I know on a spool in a drag car it's a bit hard to turn but I think it should be fine on the street.
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It will eat your tires on the street. Every sharp turn you make (think turning into a parking spot or turning at a red light) and you will hear the tires chirping. A 14ff should hold up fine...but your tires might not like it.
-Harrison
 
eh its manageable on the street. Did it in my DD for a while. Welding the front makes it VERY difficult to steer. Add in 39.5" tires, and if you are running the stock push pull style steering, its going to be a nightmare/bear to steer the thing.

I understood your truck was 4x4, I was commenting on 1 tons of that era.
 
87BrnRsd said:
It will eat your tires on the street. Every sharp turn you make (think turning into a parking spot or turning at a red light) and you will hear the tires chirping. A 14ff should hold up fine...but your tires might not like it.
-Harrison
Click to expand...

It would just be down the street to the mud hole and the ocassional stopat the gas station
 
howdiy said:
I don't really spin the tires much.
Click to expand...

every axle shaft I broke was right before the tires would spin. I would be easing into the throttle from a stop to climb something and one would let go and then the other three would spin.

for the rest of the day it would be easier to turn, but 25% less traction.:doah:
 
stock gear ratios also wont help the axles live longer either, they will just be loaded down more when driving around.
 
guz71 said:
stock gear ratios also wont help the axles live longer either, they will just be loaded down more when driving around.
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I am trying to figure out how that makes sense. And it doesn't.

Gear ratio multiplies engine torque. Thats the basic function of it. Lower gearing(higher numerical) will in fact increase the stress on axleshafts, just make the engine work less to move the vehicle.

Driving around, either way the axles are still transmiting torque, just more so with a lower gear ratio.

Thus why portal axles are strong. The majority of the gear reduction is outboard of the axle shafts. Means the maximum torque is transfered through the minimum distance.
 
I guess, but no matter what gear ratio you have, the same amount of power is being placed on the ring and pinion. Yes with lower gear ratio your are going to transmit more torque to the wheels/axle shafts but if you have a really high ratio your really putting a burden on the ring a pinion because it takes so much more to get it turning. Maybe what I was told is incorrect but it just seems like if your having to load the gears up so much to just get it to move vs. with a lower gear ratio, it would stress the gears more. For the axle shafts, its totally different i understand that completely.
 
stresses ening and transmission more than anything. Higher gearings(lower numerical) usually have more material to the R&P due to the less teeth being cut in them. Usually makes them stronger in general.

Its not like you are spring loading the R&P to move the truck. All the lugging is occuring in the engine and trans. In an automatic trans it could burn up clutches from overworking the trans all the time. In a manual, burn up the clutch when you have to ride it off the line. And of course, lugging an engine isn't usually good for it. Not to mention making it work harder through the power band is actually going to hurt fuel mileage(even though its got the "mileage" ratios going).

This is how stuff works out in my mind. I am always welcome to someone proving me wrong. Can't learn if it never happens.
 
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