Gear Lash and Driveline Vibrations - It wasn't the drivelines

[Awesomlmtv]

Had drivelines rebuilt: new slip joints, new u joints, removed the cardboard deadener, high precision balance ($2077.75) and driveline vibrations persist.

Does this appear to be the correct gear lash and free play in an LMTV alxe?



I have climbed under other tucks to check third member free play, and none of them budged. Does your LMTV sit this loose?

 

[Awesomlmtv]

Below 44 MPH, or up to 50 MPH under load, there are no vibrations present. Big improvement, but not the 55mph I was looking for.

 

[Kemper]

Just got my high speed gears in a few weeks ago. I had my driveshafts rebuilt as well.

Here is a video is with my new rear section. Still had the paint on the gear teeth.

IMG_7944.MOV

drive.google.com

Hope that helps


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[simp5782]

That is normal play for the pinion.

Is the vibration felt in the seat or the steering wheel? In the gas pedal? Or brake pedal?

 

[Awesomlmtv]

Steering wheel and a little in the gas pedal. When the front axle is unloaded a phasing in and out of vibrations, almost like a carrier bearing or something were completely shot. I did not notice any free play.

If I did tighten up the gear lash, would it reduce that play? My rear axle has considerably less.




rrrrrrrrrrrrrrrvrrrroowwwwwwrrrrrrrrrrvrroowwwrrrrrrrrrrrrrrrrrvrowrrrrrrrrrrrrrrrrrrrvrowww with increasing frequency the faster I am going.

 

[coachgeo]

Steering wheel and a little in the gas pedal. When the front axle is unloaded a phasing in and out of vibrations, almost like a carrier bearing or something were completely shot. I did not notice any free play.

If I did tighten up the gear lash, would it reduce that play? My rear axle has considerably less.




rrrrrrrrrrrrrrrvrrrroowwwwwwrrrrrrrrrrvrroowwwrrrrrrrrrrrrrrrrrvrowrrrrrrrrrrrrrrrrrrrvrowww with increasing frequency the faster I am going.

dont recall the content of the whole thread on this...... have you rotated the tires? If not do so and see if the vibration changes / follows the tires.

 

[NDT]

How are your wheel end spider gears? These make a growling noise when not set up right and contribute to all your lash.

 

[Awesomlmtv]

Previous owner was knowledgeable about the gear hubs, and had extra shims for them. I am thinking that he had set the lash when he did the rebuild. I can hear the gear hubs make a pitched whirring sound. I will look into checking them for good measure.

@Kemper That is quite helpful. It appears your rear driveshaft and mine have similar play. Thank you.

 

[Kemper]

Something to consider. I had my truck on jack stands and took it up to speed without tires just brake drums installed. I know this was super sketchy. I still felt some vibration at high speed even with freshly rebuilt and balanced drive shafts and “new” gears. I’m not sure how this will play out on road since my tires still needs to be balanced.


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[Floridianson]

Question. If any one remembers my front drive shaft was out of phase buy three splines. Yea moron who took it apart did not mark it some how. I could have rotated one way or the other to get it back into phase. If a drive shaft is balanced when assembled and in phase if you then remove slip joint end and rotated it 180* back to a correct looking phase would it now be out of balance? Mine now runs no problem with vibration in the front end.
As for gear play to much you could chip a tooth to little bet it would run hot. Had a 915 that had about that much play but never had a problem with vibration.
If the drive shaft is correct then as someone said look into the hubs. When I did all of mine someone left out a hub thrust washer on one axle. If I remember it was member NDT nice enough to send me a thrust washer no charge.

 

[NY Tom]

On my old deuce all of the shafts I have found have one wide tooth so you can't screw up the phasing. At least I don't think so.

I wanted to ask it sounds like these newer trucks don't have that? Seems like a simple fail-safe solution to me.

 

[Suprman]

If the front end alignment is off you get vibration.

 

[Ronmar]

Do you have an IOS device(iphone, ipad)? There is an app called sonic tools. It uses the accelerometers in the device and can display the sensor information from all 3 sensor axis, in a Frequency spectrum like a spectrum analyzer. If you can measure the frequency and Know at what speed and gear you are moving, you might be able to identify the source more specifically...

The hardest part is converting things into Like terms and into hertz or cycles per second. for example, a 46.6” tire covers 146.4“ per revolution. At 55 MPH you are traveling about 968”/sec so the wheels are rotating at about 6.6 revolutions per second.

A measured vibration of 6.6HZ at 55MPH would clearly be from a tire/wheel. @ the 2:1 hub reduction a 13HZ Vibe would be axle related. At around a 3:1 differential ratio, a 39HZ vibe would be a driveshaft. If you have a tach or way to sample the RPM sensor, you can also work the other direction. 2600 engine RPM would be 43HZ And anything in between that and the 39HZ driveshaft would be transmission...

 

[Floridianson]

On my old deuce all of the shafts I have found have one wide tooth so you can't screw up the phasing. At least I don't think so.

I wanted to ask it sounds like these newer trucks don't have that? Seems like a simple fail-safe solution to me.

Yea my MTV does not have the wide spline or key. Now my M37 does and yes simple fail safe.