I'm getting a short growling noise in 12th and 13 in my 13 speed. Started out as only when coasting downhill, i.e. not on the throttle. As soon as I would get on the throttle, noise would disappear. Growl for 5 seconds, sometimes longer, then stop. Noise comes and goes, but is getting worse. Friday it was noisy under throttle. Transmission was a brand new reman a few years ago, just before I bought it. I don't put many miles on it. Possible driveline angle// rear ends? Its not the typical overdrive howl, it seems like a bearing rattling, but its just in the top gear, doesn't matter whether overdrive or direct.
Are you getting any fore and aft movement in the shifter when letting off and on the throttle? My guess and it's a good one-the rear main shaft support bearing in the front section. Any metal on the magnetic fill and drain plugs? Normally when the rear support bearing starts to go you will only hear it in the higher gear ratios. And those bearings can run 1.2 million or 100,000 and sometimes less. If the shifter has a very slight amount of movement it's the main shaft moving fore and aft pushing on the shift fork. If I'm only doing a back section I always replace that bearing also in the front section. What model is it and what year? Truck Shop
I was kind of hoping it would hold together until I can get a couple cranes delivered monday/tuesday, and then dive into it. I haven't dropped the oil to check for debris on the plug yet. The shifter had a worn out isolator bushing that we just replaced. I can't say that I noticed a lot of movement, but with the condition of the isolator bushing, I'm not sure I would have noticed. Transmission is a RTLO 16713A in a 1998 western star. Was a brand new reman when I purchased the truck around two and a half years ago, installed by the previous owner, but purchased from a reman place. Probably doesn't have 40,000 miles on it since the reman. We just use it delivering crane, within a hour of the shop. It really sounds like a bearing being loose for a little bit, then "locking" itself back in place like it should be ,until it comes loose again.
Doesn't do it at all in 10-11, but that would have the stress on the other side of that shaft wouldn't it? I will also say that I don't hear it at all when in the low side of 12-13, which made me think that it was speed related, hence the driveline or possible rear end.
By the way- thanks for the advice truck shop, I know you've been into a few of these......
To keep things simple you have low range and high range. On the high range side it's 5th direct/over, 6th direct/over, 7th direct/over, 8th direct/over. The noise is in 8th direct/over. 3rd and 7th direct/over is the main drive gear on the input shaft the next gear back is 4th and 8th direct/over. When it's in either 4th or 8th that puts thrust back and forth on the main shaft and the rear main shaft support bearing is taking the load. Look at the gear sets below in a photo of a high torque 13spd I rebuilt. Truck Shop
Thought I'd update, I crawled underneath early this week, it was the carrier bearing. Glad I'm not dropping transmission, and thanks for the advice truck shop. Evidently the torque would make it twist over and it would only rattle when going fast enough ground speed, while "coasting". Glad we got it caught when we did, broken u-joints are no fun. Now I just have to find the boost leak in my air to air. It started on my drive to a job today, I can hear it on a hard pull. Checked clamps with a wrench before heading back, and it wasn't as bad on the way home (still heard it twice), but I was kind of babying it home. Its always something.
Good for you, normally you smell a carrier bearing before you feel it. Had one last year that melted the rubber, shaft was only supported by the hoop. Anyway you got an easy fix. Truck shop