PatHenry

Obviously, the perfect size and thickness that fits perfectly is,... well,.. perfect. However, I have a situation where all seems perfect, but I'm a tad worried that my shaft may be just a bit too long. Yes, I know, I'd rather be a bit too long than a bit too short...

Ok, all kidding and innuendo aside - here's the situation:

95, 4.0l 4wd AX15, C8.25 rear axle, stock height XJ riding on very recent 235/75R15's. I had an issue with vibe, determined to be my rear driveshaft and it's probably not correctable (certainly not obviously correctable). The driveshaft has new spicer u-joints, they seem tight, I can't find any evidence of a thrown weight or new damage, but this shaft has been banged around a bit and has some damage in a couple of the ears. I may look into either taking to a machine shop for inspection/balance, maybe a new rear driveshaft, I haven't researched the options and prices yet.

I am currently using a driveshaft that I was given by a friend of a friend that believed it to be out of a 94 XJ, same configuration. It is NOT the same exact part, but IS the older style (slip yoke forms part of the seal at the transfer case) and bolts to the rear axle cleanly. The biggest difference is that this shaft is roughly .5-1" longer than my original driveshaft.

Based on my research, I've found a direct reference to my configuration (C8.25, AX15, 1995) stating the proper length is exactly 31". I haven't measured my original driveshaft yet, but that sounds correct and I suspect I'll confirm that length when I measure tomorrow.

I believe the shaft I'm running now is out of a manual XJ 1994 4wd but with a D35. This driveshaft is longer, but slightly thinner so they may weigh exactly the same.

It should be noted that I have NO noticeable issue driving with this slightly longer driveshaft. I would expect a driveshaft that is "too long" would bang when the suspension compresses and I would hear or feel at least something "off" in that situation. It should also be noted that I replaced the rear springs (shocks as well, of course) within the last couple of years and so I have good height on the rear end (or in other words, no sag).

What I am hoping someone can tell me with a high degree of confidence is whether I can run with this driveshaft for normal driving or if I need to get the exact proper driveshaft back on ASAP? Certainly there is a bit of wiggle room due to the nature of the suspension flex, so I guess I'm mostly hoping I'm well within that variance even with an extra half to 1 inch of length so I can take my time and make a smart decision on the replacement.

I don't do any hardcore wheeling or routinely haul heavy loads in the trunk of the Jeep. The most action this old beast sees is 12" of snow and the occasional hauling of home improvement supplies and groceries.

Dave51

Are there wear marks on the old shaft that could give a clue as to worse case scenario?

Dave51

Or load the back till you get to 0 degrees driveshaft/pinion angle. That would be as close as it gets.

BwanaBob

If I'm not missing something, this is what I would try:

Mark/note where the slip yoke sits on the transfer case splines. Then,
detach the driveshaft at the rear pinion. Then move the driveshaft forward
and see how much it travels in on the splines. On normal driving you'll
need one inch at the most. If you have two or more inches, no problem.

I had a shop near Indianapolis shorten a front driveshaft for me and it
cost $40. The guy said it didn't need balancing. That would have been
$25 more.

PatHenry

No strange wear... it's just so damn odd... I fully expected to see a shiny spot where it threw a weight or something indicative in the u-joints.

What is "worse case scenario"?

I can only say it's the rear driveshaft since I did all the other things and once I swapped the shaft, vibe was gone... so it's definitely the cause... Jeep drives really nice with the close but a bit longer driveshaft.

I mean, I guess I could see the transfer case output shaft with a bit of play and the longer shaft is hiding it by riding further back in the "logical" sense. I don't know if that is something that could happen or not, just thinking out loud.

PatHenry

This is a great idea Bob!!!... I'm worried the current shaft is too long, but your principle remains the same... see how far it moves in before bottoming out.

Obviously the front shaft structure is very different, but what sort of stuff did you encounter that caused you to shorten the driveshaft?? I suspect that I would feel and/or hear a bang/poppy sort of thing if the shaft was bottoming out by compressing too far. Something akin to the folks with 97+'s that are in need of lube where the shaft sticks....

$40 for a resize and $25 for a balance.... wow... if prices were that cheap around here I'd have that old shaft in the local machine shop tomorrow... lolol They want like $80 for just a balance and they're the only place I've found anywhere near me that deals with driveshafts. There is a Jeep shop nearby that may have some connection/expertise that I might try.

We don't get a lot of folks customizing cars around here and when they do, they're the "rice burner" sort of stuff... small imports or sound systems. Folks around here all drive late model SUV's or "spotlessly clean pickups"... lol. We have 2 private boarding high schools entirely in town and the public high school is shared with the next town over, so it's that sort of place.
I was in Indy once on a work trip and between that and the fact the city is known for racing, I definitely felt like it would be the kind of place where it would be easier to find auto machine service shops....A lot of good people in that area as I recall.

Dave51

The yoke bottoming out, either internally or externally. With the pinion angle at -0- degrees, that's as far as it will advance into the transmission.

And I'm thinking it can't be a lot. The front of the leaf springs are fixed. As the differential comes up from a bump or heavy load, the shackles cause it to move back, negating some of the forward movement of the driveshaft.

So load up the back with weight and see if the yoke moves.