Hello, I have a question that I did search on, and found no good answers. I have an 86 F250 4x4, and I just did a 4" suspension lift and it previously had a 3 inch body lift for a total of 7" of lift. Right now it has 36" tires on it, and I just bought a set of 15/38.5/16.5 Ground Hawgs used, they are about a quarter tread or so. Now, my question is not on fitment because they have plenty of room to clear, but the question is on IFS. From what I found on my search, with new shocks, springs, an alignment and a tight front end that the IFS is not that bad. I have new springs, shocks and the front end is tight, and I just got the alignment done. Do you think that I will have any issues with this size tire on IFS? I really do not do any HARD four wheeling, I basically use four wheel drive when I start spinning and then just take it out. I really only use it when I have to. If I do go out four wheeling,I know I'll just have to take it easy on her. Has anyone had any experience with this size on IFS? Any forseen problems? Thanks for the help!

 

35's are about the limit for stock axles. Anything bigger and you are going to need a solid Dana 60.

Run them until it breaks, and then do an SAS.

 

I'd love to do an SAS but not in the budget right now lol. I figure ill just run it until it breaks. What is the weak point? I can replace the shafts or u-joints easily.

 

I also found this post, which kind of answered my question. It was originally posted by Jim Allen about a year ago, i just wanted to give him the credit for it. It basically states that the Dana 50 IFS does not fall very far from the 60. It appears that, from Dana, the 50 IFS can take some power, far more than I would ever give it.


For what it's worth, here are the output torque ratings for the 44/50/60 as listed in the 1982 and 1999 Dana axle systems specification catalog:

Dana 44IFS- 3,450 lbs-ft (max short duration). 1,100 lbs-ft (continuous)
Dana 50IFS- 5,000 lbs ft (max short duration). 1,200 lbs-ft (continuous)
Dana 60F- 5,500 lbs-ft (max short duration). 1,500 lbs-ft (continuous)

Output torque is essentially the amount of traction torque, or tire grip, that the axle can hold before something breaks. The engine torque, multiplied by the gearing (500 lbs-ft x 3.0:1 first gear x 4.10:1 axle ratio= 6,150 lbs-ft ) is pitted against the traction torque. If you can generate enough grip to hold the 6,100 lbs-ft your engine is generating and your axle is only rated for 5,500, then snap-crackle-or-pop (and it ain't Rice Crispies). Fortunately, seldom can tires generate that much grip, but using Dave's snowplow example, you see there are exceptions. You put a bunch of weight (a big plow up front) onto two big, sticky tires (weight x coefficient of friction= grip) and downstream of a torque-monster engine and some gearing multiplication... wham-o!

Note: The Dana 60F rating would be much higher but for it's small 30-spline outer shafts and the relatively weak hubs. A Dana 70 front, which is very similar and uses the same inner shafts and u-joints, is rated for 8,000/2,000 lbs-ft. The major difference, besides a bigger ring gear, (that doesn't contibute all that much to a high maximum torque rating if the gear ratios are inside the test envelope, though a bigger ring and pinion does add a lot to the continuous rating) is the 35-spline outer shafts and stronger hubs. I was told by a Dana engineer that at least 1,000 lbs-ft (and maybe 1,500) of that maximum rating difference between the D60F and D70F was the outer shafts and hubs. Those numbers hold up on paper too if you work the axle strength formulae.

FYI, Ford (Visteon) rated the 10.25 rear axle at 8,300/2,000 lbs-ft. The later 10.50 is even higher, at 10,660/2,900. Those rating have a lot to do with the 1050 high carbon steel alloy axle shafts that Ford has used for many years.

 

The D50 is essentially a D44 center section with D60 outers on it. I'm not too surprised it compared so well to the D60. The IFS just has more moving parts to wear out and break. Those tires will probably be a heck of a pain on your steering components though and your tight front end may not be tight for very long.

 

im running 38s on a d44 solid front with no problems yet. 38s arent too much bigger than 35s. just leave the front open and if something breaks look into a sas

 

Chromoly axles will also give you a little more breathing room. But like I sad, 35's are about the limit (still kind of reliable) with the stock TTB.

You can run bigger tires, but you are taking a risk and something WILL eventually break. Only question is when and where.

IMO - D60 for anything bigger than 35's.

 

You will want to make sure that it is a d50 too. I don't know about the 86. But I have a 80 f250 and I was told by a mechanic at the shop that it was a d50. After doing some research on here and other places I found out that it was a d44 with 8 lug rims. In the early 80s the d50 only came with the snow fighter package or on extended cab trucks. Just something you might want to make sure about.

 

Thanks, now you have me thinking lol. I've read that one way to tell if it is a 44 or 50 is by the size of the hub. Is this true? My truck has an 8600 GVW and a sterling 10.25 full floating rear. I do not have the vin number on hand. I know this topic has been beat to death, but what can I look for to make sure? Is there a front axle code in the door jamb? Also from what i found is that the Sterling 10.25 full floater (which I am 100% sure I have) is a sign of the truck being a F250HD. This would correspond with the info about the Dana 50 being equipped in HD trucks, so thus I should have a Dana 50? Am i wrong or am i right? I am confused lol

 

If you have the FF rear, then most likely it's a HD.

D50's come with 1 1/16 lug nuts and 9/16 studs as opposed to 1/2 inch studs on D44's.

Plus the much larger hubs.

 

Ya if you have the Sterling then you probably have a D50. I was just giving you something to think about, didn't want you to kill your front end just yet.