I've searched for numerous subjects, and only found one real good posting, which provided a URL to a website with excellent information on Universal Joints, Single Cardan, Double Cardan, etc.

However, my question still remains...Where is the driveshaft slip yoke positioned when measuring for changing the length?

I have purchased a used 75 GM front CV shaft (1/2ton) that is too long for the rear of my CJ7 (just finished rebuilding it last night). Ok, so, it needs to be shortened, np right? I've determined that (fully loaded on level ground), I need a driveshaft length of 23" (rear pinion is aimed directly at tcase, measurement taken centerline of cup to centerline of cup). Do I want the driveshaft compressed, 1/2 compressed/extended, or extended or some other combination when determing the amount to remove from the used on. I think the d-shaft has about 7 or 8inches of travel in it today. Do I need to extend/compress the rear suspension and take more measurements? Should I install the CV end on the t-case, the slip end on the axle, and using an angle finder make them parallel and mark/measure that way? I'd like to do it the right way, and only once.

FAQs about my rig and its setup...It's a 79 CJ7 w/ 350TBI, SM465, NP205. I have widetrac axles installed (D30/M20) in an SOA configuration, using YJ packs w/AAL's. It also has a 2" bod lift. No brake lines or shocks installed yet. No idea how much travel/compression I have. It currently rides on 33's (most likely will run 35's or 37's once road worthy). Maybe this would be a good TOTW (I searched that as well)..


Thanks,

Chris

When I had my shaft shortened:laughing: I just took a static measurement and told my driveshaft guy when I took it in. Are you doing the work yourself? A standard leaf sprung rear doesn't require a lot of travel. I bet I have less than 2" of travel in mine when the suspension is extended/compressed. With that much travel you need to make sure it's not too long or you'll cream your t-case. With that much travel it won't hurt to be a little shorter than 23". Haven't really answered you question though. In my case I assume my driveshaft guy shortened my shaft so that the static measurement I gave him is the length of the shaft when 1/2 way between fully extended and fully compressed.

I'd give it about 2" for compression, maybe a little more if you have a lot of up-travel @ the axle. Mine only compresses about 1" from static position.

I checked the shaft tonight, after I finished rebuilding the CV section. I can get the slip joint to open up 3 inches before the splines start to show. Anyone know how much further it can be opened before "you've gone too far"?

Recurve, I was thinking of doing the samething. Have the shaft made to length with the slip part in the middle of its travel. I haven't talked to my d-shaft guy either though, so I really don't know. Just wonderin how everyone else has done it and so far, 2 for 2 have just given their d-shaft guy a static measurement.

Thanks,
Chris

PS. Here's (http://mail.nicorenergy.com/ctatar/images/P8160201.JPG) what my CJ looks like today.

Just give the shop a static measurement and they will cut it to that length with the slip in the center of its movement.Some driveshaft have a longer spline than others,I have seen a few separate,and they have all been on the front.The problem is twisting the end of the splines if you are under power when it separates.