I recently noticed some drive line noise, sort of a high pitched metal whine when on throttle. It will go away completely as soon as I let off the gas. have also had a noticeable clunk going into reverse and occasionally on up shifts.

Yesterday I checked the u-joints for play. I took a quick video and just wondered what you guys thought.

 

Tough to tell but I don't see play there. If you grab it so your hand is around both yokes, and wiggle it again, you should be able to feel if they're moving independently. High pitched metal whine when you're on the gas sounds more like a rear end issue to me.

 

 

Had a similar issue with the driveline banging (but no whining). I replaced the transfer case yolk to try to regain better tolerances on the splines. Made it a little better.

Check the flange on the rear axle to make sure the nut hasn't worked loose.

 

Nope, definitely in the "maybe not" category. The rear end gears are in a completely different mesh, or load attitude when driving vs coasting. So yeah, it's possible to get funky noises that come and go as you work the throttle. Either with a driveshaft, a rear end, and even a wheel bearing or transfer case output, under certain circumstances.

Luckily the shaft is easy to check and/or replace parts on, and the rear end is easy to at least check for fluid levels and condition.
What year and model is your truck? What model and gear ratio rear end? How many miles on the truck? When was the last time the gear lube was changed, if ever?

And in my experience, in 10 different worn out u-joint scenarios you can have 10 different symptoms. Some will make a noise, some won't. Some will be one noise, while some are another. Some will only vibrate and never make a sound. But almost all of them will change tone between acceleration, trailing throttle and heavy deceleration. Axle wrap/spring wrap changes the angles and attitudes of things enough, and there are different failure modes of joints anyway. So it's worth checking out further.
And it's almost cheap insurance just to change them out to new. Especially if you don't know the mileage or condition of them.

Good luck.

Paul

 

 

Thanks for the comments guys! It's a 1995 F-150 2WD w/117,000 miles, 4.9L, E4OD with 3.08 gears. I believe the engine, trans, and rear end are original to the truck. It came with very few records, and none that showed when/if the rear end fluid was changed. Sounds like it's time to put that fluid change on the to do list.

 

And maybe too, since you don't know all the history of the truck, just putting new joints in the shaft will be cheap insurance against a full failure that stops you from driving it.
I'm not usually for just throwing parts at a problem, but until you can actually determine where the noise is exactly, it's hard to pin-point the individual part. Or combination of parts...
At 117k, any originals are well and due for a replacement.

Your initial test of pushing around checking for play is ok for a starter, but to really check the joints you should remove the shaft(s) from the truck to inspect and manipulate each joint and bearing. Looking and feeling for a fault.
I mean, it'd be real nice to know it's a joint and not a ring-and-pinion set wearing out. Even replacing all the joints is a LOT less expensive than the diff gears!

Let us know if anything changes with the fluid change. Even if it is the gear, and the new fluid doesn't help (and it wouldn't if they're truly worn out), it was at least worth it as an inexpensive experiment. And besides, just pulling the cover off to drain the lube will let you put eyes on the gears to see if you can find any obvious signs of distress. Not sure how to inspect for bearing wear in a diff, other than to jack it up and listen to things as you turn the axles. Short of removal I'm not sure there is any other way than free-play or sound? But by the time you have old ones out, you're going to put new ones in anyway, so that would be the last resort I would think.

Here's hoping for a quick and tidy u-joint service!

Good luck.

Paul

 

Paul, I'm thinking the same way. Do the fluid change, inspect and see if there are any changes once complete. And from there, do the U-joints as insurance. There is certainly more movement at the front of the driveshaft than the rear, but makes the most sense to do them both while it's off and then at least I guess you have a baseline of knowing when both were done. I plan on keeping the truck a while, so it seems like the right thing to do. More than once I have replaced a weak part, just to have the next weak part in the system fail in short order. I think I have (finally) learned it's better to spend a little more time and money and save some frustration in the future. Fingers crossed nothing is wrong with the diff.