i have had a vibration in my drive shat for a while now.. i thought that it was the tires. i had the BFG mudders and they wore funny and some of the vibration went away when i got the A/T tires on there...

but the vibration has gotten worse over the past few months.... it used to only vibrate at 75 but now the vibration is really bad at 45 and it doesnt get better the faster i go... if i speed up then it goes away but when i cruz or coast then it comes back and shakes the $h!t out of my truck...

not really sure if it's the shaft or if my u-joints are going out but i need to figure it out before it destroys my truck and leaves it in a pile of bolts...

I would look at your Steering components before Driveline. do a search for Death wobble. you will find a bunch of info on how to diagnose your problem. Hope this helps..

yea check the steering as well but D-shafts/u-joints are easy to check. Grab the shaft and try to push/pull back and forth on it. If it moves you need new u-joints.

True that, however, you need to jack up the rear tires so that spin free and then rock the shaft back and forth to see if there is free play. Otherwise the torque applied of being in park/gear and combined weight will make it very difficult to see if your u joints are faultly.

Type of rig and what has been done to it may help in the diag.





and yes I got the bronco part

You could also set the brake, chock the tires, and set the truck in neutral.
that will release the stress, and free the u-joints to be tested for play as described above.

did you lift it? how much? according to the experts at the driveshaft shops that write the articles in the 4wd magazines, the 2 u-joints have to be within 2-3 degrees of each other's operating angle. also, to run that driveshaft at 5000rpm's no u-joint can operate at greater than about 2-3 degrees. my buddy's blazer's top u-joint by the t-case was at 17 degrees, and the lower one at 12 degrees, no wonder he spit the driveshaft out.
so we (I), put a cv joint at the top, and we rotated the rear axlehousing so that the lower u-joint was at a downward 2 degrees. this is so that when you're on the gas the housing rotates upwards slightly to about zero degrees - +2-3 degrees. the cv joint has 2 u-joints that are connected in the middle by some magic that keeps them at precisely the same angle cancelling out any vibration there. so the single u-joint at the bottom must not be more than 2-3 degrees upwards or downwards so it doesn't make vibrations by itself.
you can get shims to rotate the axle slightly, or you'll have to cut off the spring perches and shock mounts and reweld them if you need more.

Do you wheel this?

Could your shaft be bent?

Do you carry spare when wheeling?

If no, what will you do if you break a joint on the trail?
Pick up some new joints at your local auto parts store & swap them in.
You'll then have spares for emergencies.

Is the rear rear pumpkin offset or inline of the Tcase output?

ujoints will vib badly when they are done, you are probably way overdue for replacement anyway so just pony up and pull the trigger.

broncograveyard sells new shafts with all the ujoints you need for under $300 (for my 78I think I was around $400 with new yokes for TC and dif, I upgraded to the 79 stuff), so check your pricing to see if the complete assembly is a better deal

the truck is a 92' f-150 4x4..
i use it for hunting.. the is a leveling kit on it with 31's.. nothing extreme...

so i was on my way home the day that i orig posted this question.. getting gas.. i start the pump walk in side the store... i come out with my bag of chips and a pepsi and notive a puddle of trans fluid under my truck.. i crawl under there and look up...
the T-case was resting on the skid plate!!!
the tail end of the trans case had snapped off (but i could still move the truck enough to get it on a trailer)
that case is not supposed to just snap.. but what are the odds of the same thing happening twice.. i just had the tarns replaced for almost the same thing.. it crached in a different place....

i think that it is related to the vibration.. it only happens when the truck is in gear and moving... i now think that it may be in the rear axel....