What type of noise does it make? Mine started making a whining noise last year and still does although it is not too terribly bad. An auto tech told me it was the pump. Going to wait to see if it does finally bite the dust, then will need a rebuild.
It sounds like a buzzing sound, but it is the pump being starved of fluid, and it'll do it upon start-up for about a minute, then it goes away. It'll also do it if I start off in 1 and manually shift it to 2 after the revs get high enough. It began whining after I did the first fluid/filter change this year, which was shortly after the transmission started shuddering in reverse and neutral. Since I have an account with a local parts store I went with the filter kit they had in stock which an ATP filter kit. It has the dacron filter media, whereas the P220 is the brass filter. When I bought the truck in 2012 I did a fluid change and replaced the filter with a Purolator P220 and the pump never did whine with that filter in there. Well, good luck finding the P220 anymore. I contacted Purolator and actually had an email conversation with an actual person, it was refreshing, but they are not producing as many transmission filters anymore. Luckily the local transmission parts vendor I found can get the filter with the brass. The filter in there now is the second dacron one in a couple months. It was about one month after replacing the filter with the ATP dacron filter that I noticed the pump whining. Thinking it may be the o-ring on the pickup tube, I dropped the pan again to replace the original o-ring with two new o-rings, and installed another new filter while I was in there. Upon starting it up after the second filter change, there was no whine from the pump and it was two quarts low because I didn't pay attention to how much fluid it needed a couple months ago. 8 quarts for a fluid drain and fill on this unit. I haven't been driving the truck because the whine came back when I start the truck. Now I can do another drain & fill and install this brass filter, and hope that stops the pump whine. The whine is only bad upon startup, or when I rev it up in 1 before shifting into 2. But again, it didn't whine at all until I installed the dacron filters. I'll report back in the TH400 Acting Oddly thread when I do the next drain and fill. I tried not to jump all around on the subject, but I also wanted to cover all that was done thus far.