Violent shaking

So I have been having this issue over the past couple days. It started off minor with minor vibration when accelerating from a dead stop. Now it’s violently shaking the whole truck when I accelerate from a dead stop. I don’t know what it could be but its very worrying to me. Does anyone have any idea what it could be?

P.s. it only does it from stopped. It doesn’t do it after a couple seconds and doesn’t do it when I speed up from slowing down.

Have you checked the U-joints on your drive shaft?

William

I have not but I will take a look real quick

I joints seem fine. Any other places I should look?

Pinion bearing wear/rear-end yoke movement? The early (short pinion) Sterlings have issues with this…



Another thing to look at (if the driveline is tight) are the front caliper pins. One of mine became loose and caused “death wobble”. Does applying the break smooth it out at all?

I was thinking the same thing on brakes.  If it's sticking enough it could cause an issue (if on the front).  

That pinion gear is pretty gnarly.

The rear diff is something that’s on my agenda to get taken care of next. There is no wobble on the drive shaft what do ever. I will have to look at the front brakes in the morning. It might make sense if it is the front calipers. I was just hoping it wouldn’t be anything major that I would have to deal with right now.

I had a vibe that was u joints. Looked at them twice. Thought they were ok.

Finally jacked up the truck and could see they were bad when I rotated the driveshaft.

Something to consider if you don’t find anything else.

This. Bad U joints are hard to diagnose when the driveshaft is under load. With parking brakes on and shifted to neutral, try it then. Any play is no bueno. Even so, jacked with the wheels free to turn is the best way to check.

Well I looked at the brakes and they look completely fine. I guess U-joints are next to replace. Luckily they are not too expensive.

Sometimes you can feel a u-joint at speed too if you can completely unload the driveshaft.  I learned about bad u-joints on a couple different vehicles that way, you can feel it vibrate.  You would notice it if you are cruising and you let off the gas partially and the vehicle is maintaining speed without drive from the engine (i.e. going downhill) but you're giving it just enough gas to not drag the driveshaft either, thus having no load on it in acceleration or deceleration.  

Yeah I’m starting to feel some vibration while driving. Hopefully I can get it fixed soon. The main reason my truck is constantly under maintenance is because I scrap part time and constantly have a trailer hooked up to it because I live in an apartment and have no one close enough to me to park it at. But luckily the u-joints are something I can work on at work because I’ll be getting a bench vise soon enough and I’ll have all the tools I need to replace them.

Can anyone recommend some good U-joints for a c-6 auto to a full float rear with 4:10 gears? I don’t do a lot of heavy towing but I do haul loads of atleast 2000lbs or more quite frequently. The rear differential has two snap rings and two sides that bolt up and the transmission yoke has 4 snap rings.

I like Moog and Dana u-joints.  And the Rock Auto catalog is pretty good for figuring out which ones fit.  Go here, which should take you to the u-joint selections for your 1986 F250 w/a diesel and see the part numbers and sizes.  But you'll have to measure what you have to ensure you get the right ones.

Then, armed with the part numbers, you can order from RA or even Amazon.

Whatever the brand, I always make sure to get greaseable ones. That’s my preference and a lot of them are not (greaseable) these days…

Would it be possible that fluid is leaking from the rear differential and causing the vibration? My rear differential is covered with grease and oil, and after putting the transmission in neutral I felt no movement from the drive shaft or U-joints. I will still replace them to be on the safe side but could the rear end cause these problems. If so how bad is it to repair it. I’ve never done differentials before.