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hi, i see you covered this before but here goes,have 710k,1973 x swiss army,42000kms on the clock?,well heres the problem,a vibration that starts at 40/42 mph,and gets worse the faster you go,55 mph,have fitted two new propshaft ujs,tried shaft yokes in line and at 46 degrees as the shop manual,tyre size is 265 70 16 and have been standing a long time as the section of tyre that was in contact with the ground has perished and cracked about 12inches on each tyre,have balanced ok but still possible tyre case damaged?engine/g/box mounts ok,all t/tube nuts/bolts tight,still has vibe on overrun,not quite so bad in 4x4 but still there,any thoughts,veiws,ideas,cure would be welcome..

Welcome to the forum
Sorry your 1st post is a problem post vs a fun photo post
I would say your just going to get a lot of guesses as that is a tricky thing to try and diagnose over the internet.
My bet is on your bad tires (if at all possible try to replace them even with some 2nds or used ones). Going that fast with old, hardened and cracked tires is very risky esp in a Pinz if you have a blow out!
Many Pinz get some vibration esp at speed and some of those cases are caused by an unbalanced drive shaft.
Cheers - post some photos of your truck and put your location in your profile
Dan

First, there are alignment arrows on the short (exposed)shaft, make sure they are in correct position.
After fitting good tires test the front enclosed driveline by engaging 4x4 and drive up to the speed the vibration was occouring.
If the vibration is greatly diminished you have found the source.
Please add your location to your profile...................................................
Search archives for front driveline upgrades or repairs

Third vote for an unbalanced, enclosed, internal driveshaft. Sorry.

Ditto Jim's comments on aligning the u-joints in the propeller shaft. I own a snowcat that has a replacement transfer case, because when the p.o. replaced the u-joints in the drive shafts they didn't line it up right and misdiagnosed it as a bad transfer case. (Upside is I own a spare t-case now.)

I figure it's a slam dunk on the front drive shaft. Mine does the same thing, vibration at speed. When I throw on the 4x4, she goes away. Someday I'll wish I balanced it......

I get a little of this vibration as well, it's very slight and oscillates. Starts around 50mph, it's barely noticeable really. I'll try putting her in 4wd next time I'm out.

hi thanks for all the replies,fitted new tyres,vibe still there,in 4x4 goes slightly but still noticeable,beginning to lean to rear diff problem,carrier bearings!when rear raised and wheels spun sounds like a graunching/bearing related noise,drained diff oil,small amount of foreign/metal parts on magnet on drain plug,anyone had the same problem?,well i guess i am going to remove the rear axle and strip it to check,should be interesting, :?:

Given the "noise", I'd be inclined to drain the rear wheel units before I pulled the full axle. Lots less work. Plus, you just might find some debris that's floating around. ??

Weird, I expected the front (internal) driveshaft.

hello again,yes its me same old prob, vibration but with a twist,any one had problems with the four wheel drive hydraulic cylinder?well used the pinzs a lot last w/end,and the vibration came and went to point where there was no vibration at all not a single noise/vibe, has anyone had the same problem?yes i know by engaging the awd it changes but this was entirely different. perhaps the sleeve that engages sticks! and does not release fully even though the hydraulic pressure is released,maybe clutching at straws anyway lok forward to a reply..

If you're inquiring whether it's possible a locker is not unlocking, yes that happens. If it's leftmost locker handle (the one that engages the front axle), it would prevent that vibration at speed. But it would also provide some resistance turning on road, as the axles are binding against each other.

Often flushing the hydraulic line to the locker slave will cure the issue, although mechanical failure/s can also cause it.

I have noticed a vibration at speed that randomly disappears after stopping then resuming full speed. I chocked it up to balancing beads not doing their job part of the time.

But you probably don't have balance beads since you just replaced tires.