Rear Driveshaft Length?

[DanHfmn]

Swapped the 8.25 into the back of my '01 XJ in place of the old 35. Getting some driveline vibes. So what's the proper driveshaft length for an automatic with the 8.25?

Thanks guys!

[stumpXJ]

Should be the same length on drive shafts between the two rear axles you mentioned. Is the pinion bearing bad on the newly swapped rear end?

~James

[DanHfmn]

I don't think so, this is the 2nd 8.25 I installed in the last 2 weeks and they both had the same vibe. New ujoint on the driveshaft too.

It's not a bad vibe, but you get over 75mph and it starts humming pretty good.

In another post someone mentioned having to have their driveshaft shortened...

[DanHfmn]

Found this on another forum....

Measured from the center of each u-joint on the tube part of the driveshaft for 4.0L with AW4 and NP231.


29 spline 8.25 .... 27 7/8"
97 + D35 ........... 28 7/8"
1987 D44 .......... 29 5/8"

I've got a 27 spline 8.25, but I'm guessing the housing is probably the same.

[DanHfmn]

Well I called a local shop and he didn't think the length could be a source of vibes..., unless it was just obnoxiously long/short which I don't think it is.

[stumpXJ]

Good info to know....

I do know on my old Tacoma after removing the driveshaft to do something else, and re-installing it, I picked up a vibration. I had to take it back off and rotate it 180 degrees in the yoke on the axle and it went away. Same driveshaft, and same rear end, but apparently I upset the "zen" of it being mounted one way for its entire life. When I move it 180 out the first time, it didnt like it. Hard to understand why it did that, but it did. Just a thought.

It also seems if the shaft is a little (key word little) longer, it would be better as it is shoved farther into the transfer case and is now supperted even better by having more spline contact. (assuming you dont have a SYE here....) Did you pull the shaft all the way out of the transfer case? If so, maybe the splines are not back in the exact same spot and have a different wear/twist and causing the vibe? (really stretching here though....)

Good luck with it.

~James

[DanHfmn]

Ooh, good thoughts!

I never removed the shaft from the case, but I suppose I could rotate it on the pinion and see what happens.

I think the boot on the slip yoke is loose too, possibly causing a wobble if it starts spinning on one side of the shaft?

[xjman96]

Originally Posted by DanHfmn

Swapped the 8.25 into the back of my '01 XJ in place of the old 35. Getting some driveline vibes. So what's the proper driveshaft length for an automatic with the 8.25?

Thanks guys!

The 8.25 shaft is 1" shorter, you can pick a D35 shaft from the bone yard for a few bucks. I recently paid $20 for an 8.25 shaft.

[DanHfmn]

I can push the driveshaft about 1" towards the tcase before it bottoms out, so that's probably not my issue.

I measured the angles on the tcase spline and rear pinion, they're nearly identical. I could shim the pinion down a little to see if that clears it up. If you let off the gas the vibes go away.

Could also be pinion bearing, but this is the 2nd 8.25 with this same vibe at the same speeds.

Possibility something is worn out in the t-case? The front d-shaft has also had vibe issues in the past, in fact I pulled it out a while back. I attributed it to a bad double cardan joint that I haven't had rebuilt yet. Maybe my t-case is giving me all these issues?