Stupid question time...driveshaft tech?

[Critter]

I needed a new front driveshaft for my Blazer and I ended up finding a set of front and rear online. I have a 6inch lift and I knew that the front would probably have to be lengthened. As expected the front shaft will extend all the way and just barely reach. My question is can I take the short end off of the rear shaft and put it onto the front? I’m not sure what the proper name for the short slip-on end of the shafts are called, but the rear looks to be at least an inch longer than the front. Keep in mind I rarely take my K5 off of the pavement at the moment, there are still too many things I need to fix. Eventually I would have a shaft made that was the proper length, but for now is there any reason why this swap wouldn’t physically work? I realize that I run a risk of over extending the shaft, but I really want to put something in there for now so I can make sure all my 4x4 parts are working properly.

[Burt4x4]

Hmmm, never done that but the first thing that came to mind was balancing issue & making sure you slide on the short slip end in the same location the other one was in when you slid it off...assuming to that the Ujoints are the same & the splines too...give it a try, like yousaid it is a temp fix until you get it done right...

[Wreckless_71]

yeah I think Burt is right... pull 'em apart and check out the splines on the shaft and compare the two. Then make your decision, I think it would work just fine.

[LONGHAIR]

First you have to determine that the splines will match. If they do, the next factor is "phase". That is the relationship of the joints to each other. They must be "clocked" so that they are in the same rotation. Example, If you place the driveshaft on the floor so that the yoke is flat (standing on the yoke) the other end must be exactly the same way.
If that is the case and you have some travel in the yoke when installed, this could be done as a temporary fix. My only real concern is that there is really no need to have the shaft even installed if you don't intend to use the front axle (4x4).

Just so you know, that piece is called a "slip yoke" and the spline end that is goes on is called the "stub"

[shilo]

This is really interesting. Go for it. I dont see a balance issue as the front barely spins if at all while in 2wd. And This will get you testing stuff such as transfer case engagement and hubs and basicly see if your 4x4 functions.

[Critter]

Originally Posted by LONGHAIR

First you have to determine that the splines will match. If they do, the next factor is "phase". That is the relationship of the joints to each other. They must be "clocked" so that they are in the same rotation. Example, If you place the driveshaft on the floor so that the yoke is flat (standing on the yoke) the other end must be exactly the same way.
If that is the case and you have some travel in the yoke when installed, this could be done as a temporary fix. My only real concern is that there is really no need to have the shaft even installed if you don't intend to use the front axle (4x4).

Just so you know, that piece is called a "slip yoke" and the spline end that is goes on is called the "stub"

Thanks guys. Yeah I am up on the whole phase and clocking thing. I just didn't know if there was anything else that I might be forgetting. Slip yoke, I thought it might be that but up to now I had only used that term for a yoke that slides into a trans tailshaft, but it makes sence to use it here also. I appreciate the help.

Originally Posted by shilo

And This will get you testing stuff such as transfer case engagement and hubs and basicly see if your 4x4 functions.

This was my reasoning for giving this a try. It wouldn't stay that way forever, but would be nice to "test" my other components. Plus I haven't found a local shop yet that I would trust build me a longer one.

Next question...how do these slip yokes come off of the drive shafts? It looks like the collar at the end unscrews and maybe there is a keeper of some kind inside that keeps the yoke from coming all the way off the shaft. I tried pretty hard to get either of these to unscrew but with no luck. I didn't want to get too rough and ruin something. Should I break out the 18 inch pipe wrenches?

[Wreckless_71]

Yeah Unscrew the "collar" then the slip yoke should pop right off with a little bit of finesse... all that old grease bui;d-up and what not. There isn't any keeper.

[FormerMember]

Originally Posted by Critter

Thanks guys. Yeah I am up on the whole phase and clocking thing. I just didn't know if there was anything else that I might be forgetting. Slip yoke, I thought it might be that but up to now I had only used that term for a yoke that slides into a trans tailshaft, but it makes sence to use it here also. I appreciate the help.



This was my reasoning for giving this a try. It wouldn't stay that way forever, but would be nice to "test" my other components. Plus I haven't found a local shop yet that I would trust build me a longer one.

Next question...how do these slip yokes come off of the drive shafts? It looks like the collar at the end unscrews and maybe there is a keeper of some kind inside that keeps the yoke from coming all the way off the shaft. I tried pretty hard to get either of these to unscrew but with no luck. I didn't want to get too rough and ruin something. Should I break out the 18 inch pipe wrenches?

Usually, there's a grease seal that keeps all the gook out. Might have to twist the cap off, I have seen older shafts that the seal threads on. I've used a pipe wrench (gently) to good effect.

Also, I agree with the others... if it's the right size, run it. I've had square front drive shafts made of simple 2x2" ID box tube in 2x2" OD box tube. This rig had seen 55mph in 4wd....

Most people I know don't even bother balancing a front shaft.

[Blazer1970]

Phasing does not matter on a front shaft with a double cardan joint. Put it together any old way.

[Critter]

Well I had a little time today so I went and tried the swap. It worked perfectly. I pulled them apart, cleaned the splines and put a little new grease on and then back together. The front shaft now has about 1 3/8inches of “extra” spline before it reaches its maximum length. I wasn’t able to drive it yet being as I need to get some new u-bolts for the u-joints. I see no reason why it shouldn’t work fine though. I will update after I get it bolted up and go for a test drive.