Chasing driveline vibrations

[orange150]

I’ve been getting some driveline vibrations around 45mph. A couple things I’m thinking not may be is either my u-joints are out of phase or I need to tighten up the end play on the D300.

These pictures are hard to see, but my driveline angles are 83.5 on the transfer case and 82.5 on the rear axle.

Here are the endplay readings on the rear output with the yoke torqued down:

The only thing that worries me is the end play, I’m assuming one degree of difference isn’t enough to make a difference on the driveline angles.

Thoughts?

 

[jeepinmatt]

@marty79 this is how its done.

 

[jeepinmatt]

That endplay seems pretty excessive and is where I would start.

 

[NickMaul]

Ef the end play stuff. I toyed with that for way too long when I had mine. Honestly bad end play would probably equal noise. Inspect that driveshaft first since you have to do a bunch of BS to get to those end play shims...

 

[orange150]

That endplay seems pretty excessive and is where I would start.

That’s kind of where my head is at right now.

Ef the end play stuff. I toyed with that for way too long when I had mine. Honestly bad end play would probably equal noise. Inspect that driveshaft first since you have to do a bunch of BS to get to those end play shims...

Not really. Just need to remove the remaining bolts, remove the breather, and pull it off. It’s about ready to go but I needed to grab another beer and check NC4X4

I mean I guess I could check to see if my driveshaft is out of balance? It’s a Tom Woods that I bought when I did the AX15 swap.

 

[Croatan_Kid]

Is the 1 degree difference in the downward or upward direction on the pinion? If it's down, that'd be better. It'll obviously want to rotate upward under power.

 

[orange150]

Is the 1 degree difference in the downward or upward direction on the pinion? If it's down, that'd be better. It'll obviously want to rotate upward under power.

If my beer laden, too lazy to go actually look at it, math is correct. The tcase is down by 1°

 

[willness33]

Is the 1 degree difference in the downward or upward direction on the pinion? If it's down, that'd be better. It'll obviously want to rotate upward under power.

Under acceleration at low speeds for sure but at 45mph things should be about neutral. Loose pinion in the rear?

 

[marty79]

@marty79 this is how its done.

haha. on a serious note though, I'm by no means an expert but 1* difference? from my understanding of my research and videos lately there's a lot more than 1* allowed in variance so it doesn't seem the OPs issue is with the driveshaft angle but joints or t-case bearing/endplay as he mentioned. I might be totally wrong too lol, I'm still learning, but 1* off seems so minute to cause issues. Don't mind me though, I'm here for learning purposes as well...carry on

 

[Croatan_Kid]

Under acceleration at low speeds for sure but at 45mph things should be about neutral. Loose pinion in the rear?

That would depend on what gear he's in. 5th gear at 45 would obviously put more strain on it than 3rd or 4th gear at 45.

That being said...does it matter what gear you're in at 45 when the vibes happen?

You could always slide a washer or two under the transmission mount and see if adjusting the angle changes anything for better or worse.

Are the splines of the slip joint in the driveshaft free moving and greased up?

 

[willness33]

That would depend on what gear he's in. 5th gear at 45 would obviously put more strain on it than 3rd or 4th gear at 45.

That being said...does it matter what gear you're in at 45 when the vibes happen?

You could always slide a washer or two under the transmission mount and see if adjusting the angle changes anything for better or worse.

Are the splines of the slip joint in the driveshaft free moving and greased up?

Maybe I've never had enough HP to twist the axle in higher gears. OP has a 258 (I think) so I was considering he's probably in 4th at 45 and about running out of grunt.

Recently I had a 45mph vibe that went from hey that's a driveline vibe to holy shit I might not make it home from work within 2 days. Bought new ujoints, climbed under to drop the shaft and to my surprise, my ujoint strap bolts had backed out 2 turns. Theres my cool story brah.

 

[Croatan_Kid]

Lots of variables up in here

 

[braxton357]

Just for the record, driveshaft speed and load has no relation to transmission gear or engine rpm. I also don't see your output shaft endplay causing intermittent vibrations. After being sure it wasn't tire related or a loose suspension/driveline part, id be taking the driveshaft to get balanced. If your joints are out of phase the shop would fix that too.

 

[Croatan_Kid]

I agree that it's probably driveshaft related, but how would driveshaft speed not be directly related to engine RPM? Or output torque related to a given gear selection?

 

[orange150]

Well I removed one shim and it feels much better. Unfortunately I had to order the rear output seal so I have to wait until tomorrow to wrap it up.

If I’m still getting the vibration after that I’ll throw some washers under the transmission mount and see if that makes a difference, then move on to check the driveshaft for balance.

 

[braxton357]

I agree that it's probably driveshaft related, but how would driveshaft speed not be directly related to engine RPM? Or output torque related to a given gear selection?

Upstream of the transmission output shaft it does matter, but it only takes x amount of force to push a cj down the highway at 45 whether you lugging it in 5th or screaming in 3rd, driveshaft seeing the same load and rpm either way.

 

[orange150]

Got it all back together and lubed up. First test drive felt surprisingly good. Took it up to 50mph and felt no vibes.
If that was it I will be amazed. That is not how my luck typically works.

 

[jeepinmatt]

If there was a little play in the output shaft, the vibes could have been the forward and back motion as the ujoints rotate in and out of their happy 90 degree quadrants.

 

[willness33]

If there was a little play in the output shaft, the vibes could have been the forward and back motion as the ujoints rotate in and out of their happy elipses

I think most of us take for granted the simple path of the ujoint per revolution. There's really a lot of direction changing, speeding up and slowing down just for one spin. Like helicopter rotors but safer.

 

[jeepinmatt]

I think most of us take for granted the simple path of the ujoint per revolution. There's really a lot of direction changing, speeding up and slowing down just for one spin. Like helicopter rotors but safer.

I dunno, helicopter rotors might be inherently safer, just higher risk upon failure

 

[willness33]

I dunno, helicopter rotors might be inherently safer, just higher risk upon failure

It does all boil down to the penalty for failure.