34,000lb rears

[Hay Dude]

Would you be comfortable with a tandem axle flatbed truck with 34,000lb rears?
Im used to 40,000lb rears being pretty much the “industry standard”.
As long as the rear tandems arent overloaded, I dont see a problem, but wondered if there were any inherent issues, problems? Axles snapping? Again, overloading wouldnt be an issue.
Never ran a set of “light tandems” like that.
BTW suspension is 40,000lb, but rears are 17K each, 34K total.

 

[Ferg52]

As long as the axle ratings/GVWR aren't exceeded, I don't really see an issue. The axles were rated as such for a reason. Only thing is they won't hold up as well as 40 or 46k rears.

 

[RickB]

Trans type and drive ratios have more to do with snapping axles and shelling out differentials than axle weight ratings so long as load limits are observed.

 

[RickB]

As long as the axle ratings/GVWR aren't exceeded, I don't really see an issue. The axles were rated as such for a reason. Only thing is they won't hold up as well as 40 or 46k rears.

Kind of contradictory. You might have meant 34k rears carrying 46k won't hold up as well as 46k rears carrying 46k.

 

[Ferg52]

Kind of contradictory. You might have meant 34k rears carrying 46k won't hold up as well as 46k rears carrying 46k.

Sometimes things make better sense in my head. Assuming the 34k rears are within their load rating and carrying the same weight as 46k rears (let's say, they both are carrying 25,000lbs), 34k rears will not last quite as long, because the heavier axles are built with heavier components/housings. Which, I suppose is irrelevant here.

Sorry, it's been a tiring day. My brain is ready for bed...

 

[Hay Dude]

Sometimes things make better sense in my head. Assuming the 34k rears are within their load rating and carrying the same weight as 46k rears (let's say, they both are carrying 25,000lbs), 34k rears will not last quite as long, because the heavier axles are built with heavier components/housings. Which, I suppose is irrelevant here.

Sorry, it's been a tiring day. My brain is ready for bed...

I know what you mean.
What I am driving at is this:
Will a set of 34,000lb rears wear out faster than a set of 40,000lb rears if both sets are operated within their limits and treated & driven the same way and properly operated?

I think not, but I’m trying to understand if 34Ks were susceptible to any greater level of failure than 40K’s. What I thought may be more vulnerable was locking rear action or power divider lock operation breaking something

 

[4570Man]

How much actual difference is there in the build construction?

 

[Hay Dude]

How much actual difference is there in the build construction?

Enough difference to rate each 17,000lb axle 3,000lbs less than a 20,000lb axle.
That’s all I know.
I would guess the axle shafts themselves are smaller in diameter, along with smaller bearings, hubs, seals, or ring & pinions, carriers, axle tubes, etc., but that’s guessing.

 

[BravoXray]

They shouldn't wear out any faster if not overloaded, the gearing is about the same. The axles and wheel bearings are smaller and will give you problems if continously overloaded.
In the 70s we ran a fleet of IHC F2000Ds with RA351 differentials and rarely had problems as long as they were not seriously overloaded or tried to pull heavy loads through soft material. Had a few snapped axles on trucks that got stuck and the drivers didn't dive up and get pulled out. Never broke a gear set though.
We also had some with Eaton 3 speed tandems too. Was basically two air shifted 2 speed rears in a tandem setup. Worked like a 3 speed auxiliary transmission. You could have both in low, front in high,rear in low, or both in high, power divider allowed the difference in ratios. Low ratio was 4.10 and high ratio was 3.55.

 

[4570Man]

Enough difference to rate each 17,000lb axle 3,000lbs less than a 20,000lb axle.
That’s all I know.
I would guess the axle shafts themselves are smaller in diameter, along with smaller bearings, hubs, seals, or ring & pinions, carriers, axle tubes, etc., but that’s guessing.

Or potentially they just rated them at 34 because that’s all they’re legal to run and it’s the same set of axels.

 

[Hay Dude]

Or potentially they just rated them at 34 because that’s all they’re legal to run and it’s the same set of axels.

I have the build sheet. Theyre 34k

 

[Paystar]

It's all in the driver. I was in the bush and off road for 10 years with a 1978 IH S2674 that only had 38,000 rears and they were fine.

I think you will be good for a flatbed. What are you doing with it? Only way the light ratings will hurt you is giving you a light allowable gross weight in the eyes of the DOT.

 

[Hay Dude]

It's all in the driver. I was in the bush and off road for 10 years with a 1978 IH S2674 that only had 38,000 rears and they were fine.

I think you will be good for a flatbed. What are you doing with it? Only way the light ratings will hurt you is giving you a light allowable gross weight in the eyes of the DOT.

Looking to get back into a stand alone hay truck for some of my more difficult entry/exit fields. Found perfect truck, but 34k rears made me pause. It would have 20’ flatbed and haul large square bale hay.
BTW: truck‘s GVWR is 46,0000. Current owner and I think truck will have EW of 18-19,000lbs. So max payload is ~27-28,000lbs.
I probably wouldnt carry more than 20,000lbs, but might pull a trailer behind it with hay on it, too. Don’t know how much stress it would put on the rear-rear axle pulling an additional 15,000lbs (total GCWR at that point would be ~54,000, which is probably at or above it’s max GCWR). It has an older Allison automatic.


I even though of buying a set of cut off 40k tandems with 5.38 gears and replacing the 34’s, but there goes my money….

 

[Hay Dude]

I was looking at single axle, 33,000GVWR 4x4 trucks with an automatic, but thought a tandem would give good traction and increase GVWR.
I think this truck is what I would call a “light tandem”. Most of the newer versions are 54,00–60,000. This one is 46,000.
Considerably more than a single axle, but not what today’s newer tandems are.

 

[Paystar]

What make is the truck Hay Dude? What's it got for engine, trans and axle ratio?

 

[Hay Dude]

What make is the truck Hay Dude? What's it got for engine, trans and axle ratio?

IH4900 6x6. DT466@250/660 Allison MT643 5.38s
Has power divider box lock (air) and both rears are Detroit lockers
Front axle is 12k (air shift)
Has low range for field crawling (Air shift)

The 34k rears are my hang up, but it could be a needless concern

 

[Paystar]

If it hasn't been abused that will be a good reliable truck. I don't think you need to change anything on it for what you are going to do.
Are those 34's the IH branded axles? If so they were made by Dana Spicer. They were decent rears.

 

[Hay Dude]

If it hasn't been abused that will be a good reliable truck. I don't think you need to change anything on it for what you are going to do.
Are those 34's the IH branded axles? If so they were made by Dana Spicer. They were decent rears.

Yes they are IH RA34’s if my memory serves me

Edit: they are N-340 34,000lb axles

 

[Hay Dude]

Little more info: Hendrickson RT-403 walking beam suspension, 40,000lbs capacity, with 52” axle spacing with rubber center bushings.

 

[BravoXray]

Those old Hendrickson's are tough, but ride like a log wagon.

Here's a REAL 6X6 chassis for you, kinda spendy though.

6x6 Diesel Chassis - heavy equipment - by dealer - sale