First diesel rig, vibration question

[SparkandFire]

Hello all. I'm new to the site (well, new to diesel rigs in general) and I had a quick couple questions about a '86 F250 4X4 w/ the 6.9 IDI engine. The guy I am buying from had the engine rebuilt about 30K ago, and ever since it has had a vibration at highway cruising speed (60-65 mph)

I have read somewhere (I think on oilburners.net, come to think of it) that if the engine is rebuilt, and the flywheel (C6 Trans.) is not reinstalled in the same position it was removed, that could cause significant vibration. Is that possibly what happened to this truck?

What kind of damange could happen by running the truck like this?

Thanks!!!

 

[motox tech]

could be driveline out of balance?

 

[SparkandFire]

It would be great if that is the problem, perhaps it was damaged when the engine was rebuilt. The previous owner said the vibration started when he picked up the truck from the rebuilder. Apparently he argued with the guy who rebuilt the engine for a while, but he (the mechanic) died suddenly, and so the argument was dropped.

I want to restore the truck and make it a daily driver, but I need to figure out this vibration problem first.

 

[Pearl_Diesel]

Sounds like a U-Joint to me. If it was engine, it would happen at all speeds at the same RPM, not just a certain speed.

 

[SparkandFire]

I'm going to check for sure this weekend, I just spoke with the guy and he said Ford did a vibration test and said it was the engine (heavy piston/bad crank/etc...) But, who knows... I will check the driveline/ujoints first...

Again, thanks for the input!

 

[Agnem]

You have a 4X4. So put the transfer case in neutral and put the C6 in drive, and run it up to the RPM you usually see your vibration at. If no vibration, then you have rulled out the engine and transmission. Shut the engine down before you try and put the transfer case back in gear, or before taking the C6 out of drive, or your going to be making some very ugly sounds with your truck.

 

[SparkandFire]

You have a 4X4. So put the transfer case in neutral and put the C6 in drive, and run it up to the RPM you usually see your vibration at. If no vibration, then you have rulled out the engine and transmission. Shut the engine down before you try and put the transfer case back in gear, or before taking the C6 out of drive, or your going to be making some very ugly sounds with your truck.

Terrific diagnostic advice, thanks!!!

 

[Goofyexponent]

Shut the engine down before you try and put the transfer case back in gear, or before taking the C6 out of drive, or your going to be making some very ugly sounds with your truck.

He isn't kidding!!!! Brings a new meaning to the BIG BANG threory.....after the grinding stops

 

[Cincinnati Guy]

He isn't kidding!!!! Brings a new meaning to the BIG BANG threory.....after the grinding stops

Been there done that!

 

[fury9]

X2, X2

 

[sootman73]

yea same applies when you are adjusting rear brakes and the rear tires are off the ground. but i wasn't moving! clink clink clank clank as the park lever tries to engage....