Square Driveline Mod

Does your front driveline keep coming apart cuz of lack of having enough slip?
Don’t feel like spending $120 for a 9” slip joint.

Well here's a trick that will give more then enough slip and a stronger driveline at the same time.

Things needed:

Tools:

1. Set of wrenches (for driveline)
   
2. Metal cutting saw or sawsall (optional)
   
3. Grinder w/ grinding and cut off wheels
   
4. Welder
   

Materials:

1. .25”X2” ID tube steel **
   
2. .25”X1.5” ID tube steel**
   
3. 4 zerk fittings – optional ($5)
   
4. Existing CV and universal joint from front driveline
   

** Use standard hitch and receiver size tubing cuz the seam is not raised. For a single T-case about 12” long ($20), for dual T-case about 18” long ($26). Actual length may vary depending on your preference and amount of suspension lift on your truck.


Reasons for a square driveline:

I decided to make my driveline square for a few good reasons.

1. Slip: With the stock slip joint I had about 2 inches of compression, and 3 inches of extension in the slip joint before the driveline would pull apart. With the square driveline I now have 7 inches of compression and 11 inches of extension.
   
   I do have a dual T-case plus my axle is set 2 inches forward so my driveline is longer. For a single T- case you could get something like 3 inches of compression and 9 inches of extension.
   

2. Strength: The square driveline is very strong and the odds of the tube shearing or the corners being rounded off are very unlikely. The fact that the lower tube extends so far up into the upper tube adds lots of strength to the assembly.
   

3. Cheap: This is a very cheap mod cuz all you need to get is the tubing and some zerk fitting (optional).
   

4. Easy construction:
   

The square driveline is very easy to make and can be done in a few hours.
Ready to go square?

The first thing you need to do is remove your existing driveline and cut the CV and the universal joint off.



(Click either side of the above image to see it larger)

I cut mine so that I had about a 1/2 inch from the weld on the CV side and about 3/4 of an inch from where the slip joint tube goes into the yoke on the other end for where the square tubing is going to slip over.

On the yoke side you could cut the tubing off right where the tubing goes into the yoke and butt the square tubing all the way up to the flange surface of the yoke. This would be a preference thing, either way is good. However you decide to do it you want to give yourself an inch of tube for the square tube to side over.

Now since the yoke and the CV are to big to fit into the square tubing you’ll need to cut and grind them down to fit. This will also make them square so it will make them fit better and also give you more welding area.

To do this I cut a 1/2 inch long scrap piece of the smaller square tubing and centered it on the circular end of the CV and yoke. I use a maker to trace the outside of the square tubing for the CV end and for the yoke end I traced the inside of the square tubing. I then used a cut off wheel (and grinding wheel as needed) to remove the unwanted sections. Remember when cutting, that on the yoke end to leave the line where as on the CV end you want to remove the line. Also try to get a slightly tight fit for more bite between the two pieces. I got mine to fit just tight enough that I needed to lightly tap the tubing on with a hammer.



Notice the notch on the yoke in the area where the square tube will slip over it. This is for the weld on the inside for the tubing to slide in. You could also use a die grinder on the square tubing and just remove the weld as needed. I just found it quicker and easier to make a notch.

After getting them to fit together I then welded them together. If the joints are good and you don’t feel like removing them; what I did was wrapped the joints with a wet towel being careful not to get water in the welding area. Also to help from heating up the joints I welded one side on yoke end then one side of the CV end. Then I welded the opposite side of both ends. I then let them cool down before welding the rest in the same manner.

The next thing is to drill and tread a hole for the zerk fittings on each side of the large tube. The holes should be at about the middle point of the two tube ends of where the tubes will sit at rest on your truck. This can be optional. I still have not yet got around to doing mine yet. The pros and cons of this would be that the zerk fittings would make it easier for re-greasing, yet if you hit your driveline a lot it wouldn’t take much to break them off. Have thought about the idea of after greasing up the driveline removing the zerk fittings and inserting a small (allen wrench) plug to keep dirt out. Just need to make sure the plug doesn’t go in far enough that it hits the inner tube. Also some lock tight might be good to keep them from backing out on the trail.

The last thing to do is to paint it, grease it, install it, and go play.





Miscellaneous notes:

Even though I’ve heard people say that they think that doing a square tube driveline puts to much weight on the joints, I have not had a problem with mine yet in the past five years since doing this mod.

Weight wise my existing driveline was 25 lbs. and the square driveline came to 35 lbs.

The square tubing does have a little slop in it and makes a little noise after a while on trail, but it is nothing to worry about. If you would like to make it tighter then welding a 1/32 inch shim (1 inch by the length of tube over lap) on each side of the smaller tube will work for this. Drill an 1/8-1/4 inch holes in sets of two with the holes near the outer end sides of the shims and about 3-4 inches apart along the length of the shims. Then use the holes to spot-weld the shims to the tube. Then grind any welds down smooth as needed.

The only drawback I see with a square driveline is that if you happen to set it down on something while wheeling it will hop some instead of spin on the shaft. But good wheeling and enough clearance will eliminate this.

As for balancing… Unless you plan on doing some high speed wheeling then I say who cares. There really is no reason for the front driveline to be balanced. I have had mine up to about 45-50 mph with very little vibration coming from it.