DirtFirst 4x4, Offroad, Jeep, Outdoor Recreation Site, Dana 60 front axle

A V8-Jeep Owner on:
Dana 60 front end for V-8 powered Jeeps:

Many would say that a Dana 60 front end for a Jeep is ridiculous, and over kill. I have heard this many times, but no one has provided the facts to prove it to be over kill. And, if you ask the guy with the broken 1350 u-joint on his Dana 44 front end what he should have purchased, he would reply "Should have bought a Dana 60!". The Dana 60 has the space to house a 1480 u-joint, the limit for the Dana 44 is a 1350 u-joint.

To find some u-joint load data, I sent an e-mail to Tom Wood of Six States Drive Lines. He sent the following table of minimum elastic limits for the most popular u-joints.

Data for Dana u-joints

1310=1,600 lbs. ft.
1330=1,850 lbs. ft.
1350=2,260 lbs. ft.
1410=2,700 lbs. ft.

I also found this nice formula to calculate the Net Drive shaft Torque (NDT) which can be adapted to calculate the torque on the u-joint at the axle.

NDT = T x TL x 0.85

T = net engine torque (or 95% of engine maximum torque)

TL = Transmission Lowest gear ratio

( include the T-case and differential to get out
to the axle u-joints)

For my Jeep, with the '95 LT1 V-8,

the NDT is calculated using:	Ring and Pinion = 4.10 Atlas II T-Case = 3.77 1st Gear = 3.06 Maximum Torque = 320 lbs. ft.
where:	T = 95% of 320 lbs. ft. TL = axle ratio x T-case low range x 1st gear

NDT = ( .95 x 320 ) x (4.10 x 3.77 x 3.06) x .85
= 12,200 lbs. ft. (roughly)

This is the load on the entire drive line, so it should be divided by 4 to get the load at one tire:

NDT per u-joint = 3000 lbs. ft. (roughly)

This means a 1350 u-joint on the axle is at high risk of breaking when you give it the juice in first gear, low range. Manual transmissions put it further at risk because the first gear is usually lower, between 4.0:1 to 6.4:1.

Tom didn't have the load rating for the 1480 u-joint, but assuming that the scale is some what linear, it should be near 3,700 lbs. ft. , which is a great match, keeping within the limits at all times for my drive line equipment.

The reason why smaller u-joints are used is due to space limitations and the fact that 95% of the time, the tire will slip before it reaches the maximum load. The problem is the other 5% of the time when the tire doesn't slip, then you risk breaking the u-joint. For a rock crawling trail rig, this slip factor will decrease, causing more u-joint breakage then the normal trail rig. But, when the engine and gearing combination can not exceed the maximum load rating of the u-joint, then axle u-joint failure should only occur if the u-joint is damaged or poorly maintained.

Now that the axle u-joint is solved, I need to check out the drive shaft u-joint load. This will be:

NDT (drive shaft)	= ( .95 x 320 ) x (3.77 x 3.06) x .85
	= 3,000 lbs. ft. (roughly)

As you can see, a 1350 u-joint on the drive shaft is not "bullet proof" when you add a combination of more power and gearing.



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