Hello all,

As promised, I told the guys over in the Discovery II subheading that I would explain how to measure for a custom drive shaft. In some cases, people will install lift kits on their trucks that are so tall that it necessitates a little longer than standard drive shaft. I don't own a Discovery II but I've measured for a good many custom drive shafts ranging from DII's to rock crawlers and the procedure is pretty standard for most applications. In this case, we're dealing with a drive shaft with flanges on either end so we'll be taking a flange-to-flange, running position measurement. If anybody has any pictures of this procedure and wants to volunteer some, it would be greatly appreciated.

Here's how to go about measuring:

1: Ensure that the truck is on level ground and not lifted up on a lift. It's important for the suspension to bear the full weight of the vehicle during this procedure so that our measurement will accurately reflect how far the drive shaft will be extended during normal driving.

2: With the drive shaft removed, place the flat of the tape measure against the flange mating surface at the transfer case. It's best to measure from the top of the flange.

3: Extend the tape measure out and measure to the similar flange mating surface at the differential. It's best to measure to the bottom of the flange.

4: Write this measurement down. You now have the flange-to-flange, running position measurement for your drive shaft.

The reason we measure from the top of one flange mating surface to the bottom of the other flange mating surface is to arrive at a sort of "average" measurement. When the drive shaft is built, the parts will be laid out on a table where the tech will first measure the parts (the slip yoke will be extended to the middle of its travel range to provide the optimal amount of collapse and extension) from the flange surface to the welding points. Then, he will subtract this measurement from the flange-to-flange, running position measurement you've given him to determine how much tubing will be needed to build the correct length drive shaft. Thanks so much for reading, and if you have any questions, fire away!

Best,

Justin

 

It sounds like, in your last paragraph, that you're allowing for shaft compression when the suspension is at full compression. True? Or should people provide that measurement also?
I don't know how long the splines are on the shafts you sell so don't know if it's a possible issue or not.

 

Anti,

When you say full compression, are you referring to the amount of compression that is at play when the truck is just sitting on level ground or when, say, you're driving over an obstacle? Either way, it is possible to install a longer slip and stub setup to allow for even more compression and collapse. Thanks again, Anti!

Justin


edit: Upon further thought, for a truck needing a longer drive shaft, it would only make sense to install the longer slip setup. As opposed to the standard 2-3-8001 KX, we could install the longer 2-3-8021KX with accompanying stub at very little, if any, extra charge.

 

And yes, the goal is to allow for full compression without the stub bottoming out inside the slip yoke. For off-road purposes, it sure wouldn't hurt to allow for even more compression with the longer setup.

 

Yes, I was talking with springs fully compressed, like dropping unexpectedly off a ledge or something.

 

Then yes, measuring this way, accompanied with installing a longer slip and stub is to account for full compression. Thanks man!

Justin