710M vibration.

Diffs, axles, lockers, transmissions, portals, that kind of thing.
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Jbird
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710M vibration.

Post by Jbird » Wed Aug 29, 2018 10:15 pm

Image[/img]Hi. I just purchased a 710M and am experiencing a vibration issue at highway speeds . I realize it's a military vehicle and not a new Lexus but around 80 kmph the whole truck has a buzz that will loosen fillings in your mouth. It's fine at 70,75 and then it starts right at 80. It has aggressive tread tires that appear to have a single weight on each wheel. Not sure if I should try to engage the 4wd ? Would this narrow it down or try balance beads or just ditch the tires? Thanks for accepting me here and thanks for any help.

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rmel
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Re: 710M vibration.

Post by rmel » Thu Aug 30, 2018 1:17 am

Does it get progressively worse above 80kpm? Once the
vibration sets in, does a gradual deceleration result in
a gradual reduction of vibration or does it stop suddenly.

Any idea where it's coming from; front, rear, left or right?

What is the tire make and size, some brands are notoriously
difficult to balance out with rim weights. Oh, any indication
a wheel got a serious whack on the trail and perhaps
eccentric in the axial direction. If you have access to a
wheel balance just spinning the wheel up by hand would be
a good test for that.
Puller: 71' 710K 2.7L EFI aka Mozo
Follower: Sankey MK 3, 3/4 Tonne
Rescue Pinz: 73' 712M

Driver: Ron // KO0Q

undysworld
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Location: Blue Mounds, WI

Re: 710M vibration.

Post by undysworld » Thu Aug 30, 2018 6:36 am

Jbird,

Sounds like the internal front driveshaft may be the reason. Do a search here for "balanced drive shaft".

It's a somewhat over-complicated piece, and somebody re-engineered a fix. I don't recall the specifics, my truck does not have the problem, and it's more common in 710s than 712s due to the longer front shaft on 710s. It requires removal for the repair.

To check if this is the issue, drive the truck on a straight section of road at speeds that cause the vibration, then engage the far-left locker lever (the one that engages the front axle) and see if the problem disappears. If it reappears when you lift that locker lever, then that's your problem.

Good luck.

Paul
It is better to go skiing and think of God, than go to church and think of sport. Fridjof Nansen
I hope to die in my ski boots... ...just not today. Me

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rmel
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Location: Woodside, CA
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Re: 710M vibration.

Post by rmel » Thu Aug 30, 2018 10:00 am

Here's a link on the forward driveshaft modification -- no details though.
viewtopic.php?f=13&t=11403&p=85508&hili ... aft#p85508
Puller: 71' 710K 2.7L EFI aka Mozo
Follower: Sankey MK 3, 3/4 Tonne
Rescue Pinz: 73' 712M

Driver: Ron // KO0Q

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4x4Pinz
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Re: 710M vibration.

Post by 4x4Pinz » Thu Aug 30, 2018 12:52 pm

It's a somewhat over-complicated piece, and somebody re-engineered a fix. I don't recall the specifics, my truck does not have the problem, and it's more common in 710s than 712s due to the longer front shaft on 710s. It requires removal for the repair

Not quite true. The torque tube is the same in both 710 and 712. Distance from front differential to transfer case is the same in both trucks. There central tube has an extension piece in the 710 to make up for the rear wheels being farther back then the 712.
Generally the balance issue is much more noticeable in the 710's as they drive them more and faster. A lot of the issue comes from the seventies balancing practices and that maintaining highway speeds was not that big of a concern.
Read up on the drive line balance issue and check the items that have already been discussed. There is a lightened/balance driveshaft option but it comes with a price.

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