Hi guys, first of all, Happy New Year to everyone.

One of my biggest concerns has always been the transmission, and for the past few weeks I’ve been hearing a noise. At first I didn’t know where it was coming from, but thanks to some friends I was able to locate it, and it seems to be coming from the TH400 transmission installed in my car.

I’ll try to explain the situation with as much detail as possible so you can help me identify the problem.

The transmission fluid was changed about 4,000 km ago. The fluid level is correct and the color is red/clear, as it should be. Gear changes are completely smooth; I don’t feel any slipping in any gear, and I haven’t noticed any vibration at all. The noise can be heard in all three gears. In third gear (D), it is much quieter, almost unnoticeable, but it is still there.

I have recorded a video so you can listen to the noise yourselves. I’m sure that with your experience you’ll be able to help me determine where the problem is coming from. Honestly, I’m not sure if the issue could be the output shaft bushing and rear seal, or possibly internal bearings, planetary gears, etc.

On the other hand, I have the feeling that the car might be lacking some power, but please take that with a grain of salt because I’m not completely sure.

Here is the link to the video:
Thanks in advance.

Regards

 

I have heard similar noises when using a filter with cloth filtering media and cold ATF. The noise goes away once the fluid warms up. I’m not sure what has changed with filter manufacturers, this wasn’t a problem until a few years ago. If you go to Napa, request a “Allison” filter. I think the part number is 4954. It’s the same filter used in heavy duty th400 applications.

If the noise is constant regardless of temp, then the filter isn’t the issue.

Remove the oil pan and inspect for shrapnel. If it’s clean, next thing I’d suggest is removing the driveshaft and flat towing the car at the same speed you heard the noise before. If the noise is gone, you just confirmed either driveshaft or transmission making the noise. If it’s transmission, you’re going to need to do a thorough autopsy to figure out where the noise is coming from.