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Rear CV shaft lengths

1K views 5 replies 4 participants last post by  nicolas-eric 
#1 ·
So adding a SYE and CV shaft to my rig was part of the long term plans, but add together some slippage in my jerry rigged press and a little bit of my inattentiveness at the wrong moment and I managed to mutilate one of the retaining clip grooves in my stock slip yoke shaft last night trying to change u-joints.

I put the call out on the local parts exchange for a replacement shaft and there don't seem to be any out there yet, but there is a guy near by with a SYE kit and CV shaft that look to be in good shape. My question is, does anyone know/have experience with what length drive shaft I'll need?

It's an '01 Sahara with the 4.0L/NV3550/231 and a D44 in the rear. The stock shaft was 16.5" from centre of the u-joint to the end of the slip yoke.

I've got a 2.5" spring lift in it now with a 1" motor mount lift hoping that I could keep the t-case skid in it's stock position.

Looking at the online stores for specs, it seems as though a 14" collapsed length works with 2" lift, 15" with a 4" lift. This shaft appears to be a 15" from the photos and he claims it's for a 4" lift - which should be a touch too long...but I have the option now to do a low profile skid plate or to use the adjustable arms to push my axle back a little...

So any thoughts from those that have been here before? Do I need a 14" collapsed like the website specs suggest or will I be able to squeeze in something a little longer with or without the extra changes to t-case height and control arm length?
 
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#3 ·
Get a measurement and call a DL shop

Popping my cherry on this one. I'm new to the forum, but not new to Jeeps and 4WD.

You need to install the SYE and then measure for the DL. They (the DL shop) always wants a center to center, matting surface to matting surface, or some combination of the two measurement. Of course you can always talk to them to determine exactly what measurement you'll need. They determine the proper length of the driveline. You could always droop and compress the suspension to determine this yourself ;)

However, in your application (SYE in a 231 and D44), you'll be center of u-joint to center of u-joint. I always position mine flat so the measurement I give is as centered as possible. (i.e. center of u-joint and center line of would be DL). Here's a link to pictures of how it's done: Trig 102

Key to note there is bottoming or over extension of the driveline. Depending on the suspension set up and the amount of travel you get, these can be issues. There's a myriad of solutions that are right, wrong, expensive, and cheap.
 
#4 ·
At the end of the day the seller made me a good enough deal that I've bought the new t-case with the sye already installed and the driveshaft and I'll take the gamble the shaft will work. So I'll bolt everything up as soon as I get some time, pull my springs and shocks to bottom the axle with a jack and hope that the driveshaft doesn't bottom out and report back so maybe I can help someone with a baseline at least.
 
#5 ·
So I finally got back to this project after some serious interference from the need to work to make a living, but have some figures to share in case they will help someone else down the line:

My base setup: '01 TJ Sahara - 4.0L I6, NV3550, NP231J, Dana 44 with Rough Country 2.5" lift springs and 1" motor mount lift

Bolting in the used transfer case I picked up with a standard slip yoke eliminator kit, and bottoming the suspension, I got a very rough but useable guideline measurement of 15-1/4". The drive shaft I picked up had a compressed length of 15-1/2". In theory I could have adjusted my suspension control arms to move the axle back 1/4" and made the shaft work but with zero room for error, or maybe pushed the axle back 1/2". For reference, at full suspension extension the shaft length grew by only 1/8" so installation would have been difficult.

Given that my original setup was based around decreasing the angles on the stock slip yoke output and I was now moving to a double cardan shaft anyways, my next thought was to raise the transmission 1" to match the mml and body lift to be installed. My shaft length measured the same way actually dropped by 1/4" to 15" even. Raising the trans 2" (1" more than the motor) dropped my length further to 14-7/8" at full suspension compression. Raising the transmission was not the solution I initially thought it would be.

In my case, I had picked up the drive shaft and transfer case used - but the shaft had literally been unpackaged, installed, removed and sold to me - the previous owner had ordered the wrong length shaft and sold the whole kit to me for less than the price of the shaft alone. So my solution is to again re-sell the transfer case of unknown history and I'll install a super short slip yoke eliminator in my own t-case (now on order) and use the drive shaft I picked up at a steal of a deal.

So, if you find yourself here because you have a 2-1/2" lift and run into a deal on sye kit and drive shaft, my opinion based on this is that the shaft should be at most 14-1/2" compressed length - if it's more than that seriously consider just buying new at the right sizes to fit your project. To do it again that's what I would have done, but I got in a hurry and made a purchase before getting all the details together, but at least I'm able to make it work and my mistakes may have given someone else a little more information to work from
 
#6 ·
Every Jeep is different..

I would install the SYE and rotate the rear axle that it comes close to the right angle for a CV driveshaft.Then you can measure how long your new driveshaft has to be. Order the new driveshaft.
Until you have the new driveshaft installed, drive with 4Hi and front wheel drive...

Thats the way I did it..
 
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