I just purged out 16 quarts of old ATF out of my 2001 Expedition (4R100 transmission). But now I'm getting a new noise I wasn't getting before. A sort of whining/whirling sound when in reverse (and only reverse, other gears seem fine).

I did the flush according to proper procedure, draining the pan, filling with new ATF, emptying through the return line into a clear hose and bucket, running the engine at idle through all gears for several seconds, adding more ATF, etc.

I've got 16 qt all new Motorcraft Mercon V in this thing. Why on earth am I experiencing whining?

Note:
I did notice the new filter was pretty hard to get on and stay up. I basically put the pan in place and forced the filter in that way since it would not stay up on its own. Could I be experiencing fluid cavitation due to air getting past the orange o-ring on the filter? If so, wouldn't that affect ALL gears, not just reverse? And if so, how do I prevent this issue and get it to seal, why would bolting the pan in place not force a tight seal?

Confused.

 

Did you remove the old O-ring when you took out the old filter? It usually sticks up in the bore.

Also, 16 quarts isn't enough to fully flush a 4R100. The system holds 18 quarts and it usually takes another one or two to fully flush it.

Low fluid level can cause this, and will show up first in reverse because the demand on the pump is highest in reverse.

 

ok, I will check levels again. The manual says 16, plus I put in exactly what I took out, so I don't see how I could be any lower than original.

Yes, the original o-ring came out.

 

Regarding the filter, should that o-ring on the tube be pushed all the way into the port it mates to, or just come in contact with it, holding it super snug? I had one heck of a struggle getting it to go in, it was very tight, so I never really made it go in. Instead, I got it to make contact and put the pan up to hold it in place, and the bolting of the pan is the only thing that really forced the filter up to any depth there.

 

The O-ring needs to be inside the bore. If it is just pushed up against it, I think you found your problem.

 

Grrrr. So frustrated. I can't get to the bottom of this. I dropped the pan, made sure the filter was secure (fit nice and snug into the bore, awesome, held itself in place this time). Filled to exactly the middle of the of the hi/low on the stick for "hot" (after driving for a bit).

Still has this new noise! I'm not sure if whining, but kind of a hissing sound. It's not loud, but noticeable.

I notice it in gear 1 too, not just reverse, but I think it is more prominent in reverse. Dang it. I have a long road trip in 2 days, which is why I decided to change ATF in the first place. I just didn't expect to gremlins to come out.

 

I just drove 1500 miles hauling a 2500lb trailer without issue. But reverse still has this freaky sound. I also experienced a bit of slip in reverse if under load (like, I left the brake on).

Clearly reverse is not doing well, so I'm glad I don't have to drive 1500 miles in reverse, but am not too happy or confident about this condition. Ticking time bomb, and I dunno where to go from here aside from a rebuild. I just don't get how a simple fluid change can cause this. Some techs I talked to say "maybe some air got in, it will purge itself out". Right. After 1500 miles, still no!

 

A transmission will purge itself of air within the first few seconds of starting the engine. That's not the problem.

Are you certain the fluid level is correct? Are you reading the level with the trans fully warmed up and the engine idling in park?