1970 ford 9 inch rear end

[HATMPITA]

I'm having trouble with my old truck. It a 1970 F-100 with a ford 9 inch rear end. The trouble I'm having is a vibration at about 40 mph and up. Its a pulsating vibration and when I put the truck in neutral in goes away. I have checked the carrier bearing and it's tight. I have also checked the universal joints and they all seem to be tight. No popping noise! I took it to my local Ford dealer and they said it could be the pinion gears, the tail shaft of the transmission, or the U-joints (said the pins could have migrated to one side). I have an appointment with them Tuesday to trouble shoot the problem so that I can fix it. Any ideas from my fellow Ford truck owners?

Harry

[mcarlson11]

well, my D60 does the same thing on my 65 f250, I also checked everything, and I think my rearend just needs to be rebuilt. It leaks a lot, and usually loses all of its fluid every 2 weeks. When I put more oil in the noise goes away, so I think it just needs a rebuild. To me, it sounds like you might have the same problem, only without the leaking.

[FORDification]

Has your truck always done this? Has there been any service work done to your truck in the recent past? Have you inspected the driveshafts for missing balancing weights or damage?

The other thing to make sure of is that the driveshafts are phased correctly. That is, the two U-joints must have their bearing caps in the same plane as each other. If you look down the the driveshaft centerline, one U-joint can't be (for example) 45-degrees off from the other. Read the following threads where we were talking about this:

http://fordification.com/forum/viewtopic.php?t=2113
http://fordification.com/forum/viewtopic.php?t=3467