New Clutch Noise when decelerate

[mjmoog68]

I appreciate the knowledge and experience on this site. Here is my problem.

I have a 68 Ford F100 2wd SWB 360 FE with a 3 Speed Ford Light Duty 3.03 Manual Transmission. Previous owner converted to 3 on the floor. I have done a complete rebuild of the engine and installed a new clutch as well.

I did my first test drive today and everything was going well while accelerating. However when in any gear and I take my foot off the gas and it starts to decelerate, I get these very loud high pitch squeal / grinding sound. When I press the clutch in it goes away and when I'm shifting it is smooth and sounds normal.

Does anyone have specific tests I should try to correctly identify the issue and does anyone have any ideas what the issue might be?

Thanks

mjmoog68

[BobbyFord]

That's going to be a driveline noise, not a clutch noise. With the clutch depressed you are stopping the input shaft of the trans from driving the rear wheels. What about rolling in neutral, noise gone?
I assume the gear oil level in the trans is correct?

[mjmoog68]

Yes the gear oil in the trans if filled up to the fill port. When in neutral and rolling there is no noise.

[BobbyFord]

Is the rear differential full?
Whatever it is, you're looking for something under load on deceleration. I would check u-joints, axle bearings, mid-ship bearing (if applicable,) rear end gear oil level. Trans front bearings usually make noise in neutral and in gear. Rear trans bearing would usually make noise in 4th gear, under load.

[mjmoog68]

I put it on jacks and can see it now. I think you are right about the rear diff. When I let up on the gas, the drive shaft and the rear diff lurch up and make that noise. I will double check fluids and try again. Thanks for the advice.

[BobbyFord]

I put it on jacks and can see it now. I think you are right about the rear diff. When I let up on the gas, the drive shaft and the rear diff lurch up and make that noise. I will double check fluids and try again. Thanks for the advice.

Definitely check the u-joints. Not just for slop, but for grease. Grease the u-joints if they have grease fittings and take it out for a drive.

[tnlprt]

Sounds like a back lash problem in the rear end

[radioactivelarry]

While your at it take the drive line to a drive line service place and have it balanced and the U-Joints replaced. Should cost around 100 bucks or a little more with the joints, it is well worth the money.

[mjmoog68]

Update ****

Found a local shop and had the transmission rebuilt. Looks brand new and drives great. I also put a new rear differential in and replaced the u-joints on the drive shaft. Runs great, shifts smooth, and nice and tight.

Thanks for all the advice.

[Ranchero50]

Did they find anything wrong?