Possible Transmission Noise?

[the1970s]

Hi all,

My dad is getting to the age that he has stopped driving and as a result I have been tasked with cleaning up his 2010 Expedition and putting it up for sale. For as long as I can remember, anytime I drove it I would occasionally get a weird, intermittent, grinding noise/vibration between 35-60 mph. I vaguely remember my dad telling me he had the transmission rebuilt by a transmission shop at about 135k miles and it has done this ever since. I believe the shop changed the torque converter after that with no difference. The truck now has about 190k miles and I'm now trying to figure out what this noise is and if it is easily fixable.

I went on a test drive and was able to determine it does not make this noise in 1st or 2nd gear. It will make the noise in 3rd gear, and with the shifter in drive, it seems to happen much less frequently in tow/haul mode. This seems to rule out a problem with the torque converter lockup? It seems to happen worst at low throttle settings when transitioning from a period of coasting back to cruise throttle. There is some vibration when this happens and a small loss in power but the noise is the most obvious symptom. Sometimes it makes the noise for half a second and sometimes the grinding lasts up to 5-6 seconds. I have driven the truck and checked mode 6 data for misfires, since I have heard a misfire often appears as a transmission problem with these trucks, but I only had one misfire count after driving 10 miles.

Any suggestions for things to check and next steps to take? I am also looking for a factory service manual for this truck if anyone knows where I can get one

Edit: This is a 2wd model

 

[max78]

Check your pinion on the rear differential.

Chock the wheels!!!!!

First check to see if its tight with zero up, down, left and right play. After that you can remove the drive shaft with the tires off the ground and feel it by hand. Check the rotation for smoothness.

 

[the1970s]

As a follow up:

based on some of the many threads I searched through on the forum, I choose to add 2oz of lubeguard's "Instant shudder fix" friction modifier to the transmission fluid. The noise instantly got better and its possible that it is gone entirely. So clearly the noise is caused by the transmission. The existing fluid did look a little dark so I think I will go ahead and change the filter/fluid and refill with another 2oz of the additive

 

[jrny4rbys]

We had the transmission shudder on ours as well. Did a fluid change (first one ever and we're at 225K miles!!!) and added the LubeGuard. So far, so good!