Bad vibrations...WTH NOW??? HELP!

michaelbrainard · Post by **michaelbrainard** » Mon Sep 05, 2005 11:29 am

1977 F250 Camper special ext cab 2x4
460/c6 3.73

I just noticed something and I am not sure how to describe it. I thought it was the differential starting to go bad and howl. It is intermitent....here is the whole story.

Two days ago I was heading into town to get some lumber ( silly me...there isn't any left...thanks Katrina. )....the trip to town (15 miles ) was fine.

Heading back I start having some fuel issues, which I do have from time to time ( I think the float needle is sticking or I have a bad fuel pump - also intermitent.....not the issue at hand )....so as the truck is starving for fuel I notice a hummmmmm starting at the rear of the truck. Strange, as it has never done that. I slowed down and sped up a few times...it was quite faint. A few more miles down the road the fuel issue repairs it self, the hum goes away and home I go with no problems.

I forgot about the hum this morning...heading back to town to see if I can get any lumber yet. Truck is running fine for 5 miles or so then I notice the front end starting to dance just a tad....the steering wheel had just a bit of wobble in it, like a tire out of balance or a tire with a small egg on it. I pull over and check the tires...couldn't feel anything...checked to see if any bearings were obviously loose...nothing. Started up again and drove another 3-4 miles and the hum came back. So now I am thinking the rear alxe is about to explode....and maybe resistance in the diff was causing the truck to bob about a bit...? Anyway, i turned around and headed home. The front end wasn't shaking at this point but the hum was still there....then it stopped and all seemed well again...then it started huming again.

I got home, jacked up the rear end ( and put on stands.... ) and started turning things to look for obvious slack or play. I didn't seen anything extreme.

I did notice, the diff housing was warmer than I expected it to be. How hot should this get? I could put my hand on it but it was quite warm.

I pulled the diff cover and drained the oil...it looked very clean. I was expecting to see metal shavings but it was very clean. The diff itself looks to be tight....?

What do you think???
HELP!

Post by **FORDification** » Mon Sep 05, 2005 12:38 pm

I'm assuming we're talking about a Dana 60, right?

Any differential does get fairly warm with normal driving. Unless it really gets hot, I wouldn't worry about some heat coming from it.

I think maybe at this point I'd be wondering about the tires....like a broken belt on one of them causing the erratic handling? Try doing a tire rotation and then taking it back out on the road, to see if anything has changed. I might also check the rear axle bearings. How long has it been since they were packed, or are they the sealed type?

michaelbrainard · Post by **michaelbrainard** » Mon Sep 05, 2005 12:51 pm

Yes..Dana 60.

The rear bearings were replaced 3 months ago. The Dana 60 is a full floater - and correct me if I am wrong, but the bearings are lubricated by the gear oil...correct? When you pull the axle from the hub you dump quite a lot of gear oil. I did pack them when they were installed......

michaelbrainard · Post by **michaelbrainard** » Mon Sep 05, 2005 12:51 pm

Also, it is a limited slip ( trac loc ) dif....hotter still, right? When I went through the rear end, I also added friction modifier to the lube....

hardtailjohn · Post by **hardtailjohn** » Mon Sep 05, 2005 12:58 pm

I'd be suspect of the u-joints or carrier bearing. Get under there and shake them side to side... you might find a bit of play..
John H.

michaelbrainard · Post by **michaelbrainard** » Mon Sep 05, 2005 1:03 pm

Just found something odd. With the rear in the air and the trac lock diff, turn one wheel, the other should turn the same direction. It doesn't. Well, it doesn't turn the opposite direction like a open diff, but there is "slip" between the wheels...where there wasn't before....what is up with that??

michaelbrainard · Post by **michaelbrainard** » Mon Sep 05, 2005 1:03 pm

Carrier bearing should move quite a bit, shouldn't it?

michaelbrainard · Post by **michaelbrainard** » Mon Sep 05, 2005 3:33 pm

I got desperate and pulled the drive shaft. Removed the carrier bearing from the shaft. The bearing itself seems tight...grease within was clean. the rubber was rotten.

How much play should be in the tale shaft of a C6 Transmission>?????

fordman · Post by **fordman** » Mon Sep 05, 2005 10:05 pm

when my carrier bearing went out it would stop the truck . this only happened when i was going slow though it never messed up on the highway. i thought the rear end was going out. but it wasn't i don't think there should be ant side to side play i dont think their should be any front to back either

hardtailjohn · Post by **hardtailjohn** » Mon Sep 05, 2005 10:20 pm

Sounds to me like you might have found your problem...but there could be more. When I got my '70, it had a vibration like that... and the carrier bearing was new looking, but when I crawled under there and shook it, there was play between the rubber and the brackett.... so I put another one on and it's nice and smooth now.
John H.

michaelbrainard · Post by **michaelbrainard** » Tue Sep 06, 2005 5:20 am

NOPE! Changed it out..and it still does it

68f-250 · Post by **68f-250** » Sat Sep 10, 2005 12:47 am

Did you ever check the pinion nut. I have had mine come loose. I have also had a pinion bearing go out with little warning and intermitent vibration.

fordman · Post by **fordman** » Sat Sep 10, 2005 5:09 pm

that could be it i had a cheebie do that when i bought it. it made a clunk like the ujoint would make but it was just a loose pinon nut

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Bad vibrations...WTH NOW??? HELP!

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