This question is intended for those who have rebuilt more than a few.

It's a buzzing sound (like quickly spinning a 1/2" drive ratchet while holding on to a deep socket mounted to it) in park (but only sometimes) then abruptly goes away when put into drive and also is not there while accelerating or under a load, but (sometimes) comes back while coasting but much quieter.



I've never experienced this one before.

I did fail to test the OD cancel button to see if activating it did anything either in park or coasting.

Anyone have any thoughts on this one?

 

Not an expert but it sounds like a valve chatterring Probably Main pressure regulator check suction tube for sucking air. Hopefully a pro will answer you.
DD

 

What "suction tube"?

 

In the oil pan may be connected to filter on one end and the other end should have a seal going into the case of the trans housing. Make sure its tight in the housing. Once again I'm no expert on these trans but Trans in general have to have similar components and there fore similar problems. I built Allison trans in another life.
DD

 

Filter is in right and tight.

I built these for about 4 years at a Ford truck dealership and thought everything was perfect, and double checked everything as far as I can remember.

The new input shaft (to match the new steel planitary) was tight going into the new torque converter though.

The old shaft fit both converters easily with some wiggle play, but the new shaft only fit the used converter with play, but I doubt that is the problem.

I just have to get it home to pull it again and check things out further.

 

Try checking your transfer case. I had the same type of noise at the times you are describing and chased it down in the transfer case. I was told that the case was trying to shift into 4 wheel drive when not under a load. I have a hand shifted transfer case. I had to replace the transfer case with a rebuilt one.

 

My truck seems to be doing exactly the same thing and the transmission was just rebuilt. I never heard the noise previously, it only started after getting the truck back from a trans-rebuild and I'm presently trying to figure it out. I've got several posts on the IDI diesel forum. My truck is a 1994 F250 IDI turbo-7.3 diesel, 4WD with E40D. I don't have any noise while in PARK. My noise comes on suddenly while coasting on a flat road - seems to be most noticeable when driving maybe 25- 30 MPH, tach at 1500 RPM. The second I even slightly push down on the gas (diesel) pedal, the noise goes away. I've been checking computer error codes and keep getting #93 - coast clutch solenoid circuit failure.
I DID try hitting the OD button and it makes no difference - it does not stop the noise.
Somebody asked me to describe the noise - and I wasn't very good at it. But, after reading your description of it sounding like a rachet turning - that does kind of sound like my problem. I was comparing it to sounding like a small Jake Brake.
I've been trying to work with the shop that just did the rebuild since it's under warranty. But, I'm finding out they are either liars, or incompetent, or both.