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Front "rumble" with hubs locked

Discussion in '6.9L IH & 7.3L IDI Diesels' started by DrCharles, Jan 25, 2020.

  1. DrCharles

    DrCharles Full Access Member

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    We've had some snow, ice, and rain recently, and it's about 2.5 miles on dirt & gravel (now mud) roads to get to pavement, so I locked the front hubs on my '93 IDI but stayed in 2H.

    I got to the highway without using 4WD and didn't bother to get out and unlock them. Transfer case stayed in 2H - I do know not to engage 4WD on dry pavement ;)

    But above 35-40 mph there is a pronounced "rumble" and low-amplitude vibration from the front axle area, which goes away with the hubs unlocked. Is this a sign of bad U-joints? Or am I just not supposed to leave the hubs locked at highway speeds?

    thanks
    Charles
     
  2. Philip1

    Philip1 Full Access Member

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    You can lock the hubs then crawl under the truck with the transfer case in 2wd and spin the front driveline by hand and see where the slack in the system is

    Sent from my SM-G975U using Tapatalk
     
  3. hesutton

    hesutton The Anti-Anderson Supporting Member

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    Yes sir. The front axle/driveshift doesn't like turning that fast. I'd crawl under the truck and look at the front drive shaft for any slop at the joints. If the joints are worn, the vibration/rumble will be worse.

    Heath
     
  4. Black dawg

    Black dawg Registered User

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    Pretty common if you have the driveshaft with no cv at the t case end. Most of the time the trucks with the cv driveshaft will run down the highway with little vibration.

    I don't really like running these down the highway with the hubs in unless necessary. The spindle bearings don't hold grease good enough, and tend to get dry and wear on the stub shaft.
     
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  5. DrCharles

    DrCharles Full Access Member

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    Thanks for the tips. I'll check the joints when I get home at the end of this week - assuming it's not raining or snowing as usual this time of year ;)

    Definitely just a u-joint, not a CV joint on that driveshaft.
     
  6. 1992 idi 73

    1992 idi 73 Registered User

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    Mine does the same thing, I'm pretty sure it's the front driveshaft not being the best balanced thing in the world.
     
  7. nhwrench01

    nhwrench01 Registered User

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    mine does the same thing,, had it on a lift in 4wd. used a stethoscope to listen to everything while it was running and turning... found the transfercase was bad. lots of "grinding" noise . pulled the drain plug and saw lots of semi-metallic oil come out. so, I got a used one,,, still haven't put it in, only time its in 4wd is plowing, but I have to do it soon. .. might want to pull the plug and see what the oil looks like, and go from there.
     
  8. DrCharles

    DrCharles Full Access Member

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    I rebuilt the t-case myself after buying the truck (previous owner had either run the wrong oil or it hadn't been changed since new, and when I drained it, pieces of plastic came out which I learned were shift fork pads). All new bearings and seals, did the oil pump case mod... Although it's certainly possible something else has gone bad.

    Like you, I hardly ever use 4WD and only at low speeds... guess I'll leave the hubs unlocked on the highway ;)
     
  9. franklin2

    franklin2 Full Access Member

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    Noise in the front is not normal. Ford didn't sell these trucks with a vibration in the frontend. You should be able to drive with the hubs locked in at any speed. But, As these things get older things get loose, besides u-joints the biggest culprit is the splined coupler in the shaft gets worn out. And then you have people that lift their trucks and the driveline angles get off, more reason to vibrate. And then there was a TSB from Ford for f250's with some front driveshaft vibration problems. The TSB solution? Put the f350 double cardan joint shaft on the f250 to get rid of it.

    I have a f250 with a 4 inch lift, always had a bad vibration. I did what the TSB said and put the f350 front shaft and yoke in it, no more vibration at any speed.
     
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  10. Black dawg

    Black dawg Registered User

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    I have yet to drive one of these trucks with just the two joint driveshaft that didn't vibrate. I don't think the tsb was addressing some trucks that vibrate.....it was addressing the people that complained about it.
     
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  11. SLC97SR5

    SLC97SR5 Full Access Member

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    Where are the spindle bearings?

    I have a screeching sound for the first few miles from the front end when the hubs are locked. The wheel bearings are good and the u-joints are new. I assume it is the caged needle bearings but I don't recall seeing any when I did ball joints or serviced the wheel bearings.
     
  12. Black dawg

    Black dawg Registered User

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    Spindle bearings are in the back of the spindle, where the stub shaft goes through.
     
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  13. Black dawg

    Black dawg Registered User

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    there used to be a tool (grease fitting)that you could screw on the end of the spindle (with the lockout removed) and use a grease gun to push grease all the way through the spindle to lube that bearing.
     
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  14. notenuftime

    notenuftime Full Access Member

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    I thought I had front end problems at one point, bad noise. Here it turned out to be my carrier bearing. Noises and vibration sometimes seem like there coming from one area, better to check all over.
     

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