So what causes a transmission to whine on deceleration? It shifts great, quiet on acceleration but once it warms up when I decelerate I get a fairly pronounced whine.

Last summer I noticed this. Took it apart over the winter and replaced first and second syncros and dog teeth. Everything else looked great.

Is this terminal or something I can live with?

Ring and pinion are either set up incorrectly or you have a bearing or something starting to fail. I had that happen to mine. Turn out the big nut on the input shaft that has the peened lock washer came off. Completely off. It was banging into the ring gear and dinging it up. I was moments away from a major failure.

Yikes. Hopefully the nut isn't the problem with mine.

As for the ring and pinion is there a way to visually tell if they are failing? Everything looked great, although, not sure I would know exactly what to look for.

I rebuilt my transmission at one of the tranny clinics, when I got it in the car, it shifted great but whines same as yours.
This is what I've been told, because I had to replace the main bearing, the pinion depth has to be reset, the stacked gaskets. Not sure if I need more thickness or less to set it at the right depth and stop the whine.
Haven't researched how to fix it yet, just put in a different transmission for now, but would like to get the other one fixed....it shifts so much better, but I couldn't handle the noise. I've also been told that it won't damage the transmission to run it this way, but too annoying for me. You said you took yours apart, maybe the pinion depth is off on yours too.
Hope this helps, someone with more experience may have more info, or correct mine


Jeff

It is very possible the pinion depth is off. I did measure the old gasket thickness and got .021. When I put the box back together the gasket set only had .010 gaskets so I used two for .020. Hopefully .001 won't make that much of a difference.

I had a pronounced whine last summer. Thought is was the tranny but I also had a bad hub bearing. Now the hub bearing is quiet but I still have this whine on decel.

There is a set pinion depth that is designated as N, this is the standard. The number on the head of the pinion is gotten at the factory on a special machine that ran the ring and pinion together and adjusted the pinion OUT from center line until the quietest running arrangement could be found. This number is the N number etched on the head of the pinion and is to be added to the standard N when setting pinion depth. You can try to adjust on your own with gaskets, but to do it right you need an expensive tool which I do have.

Loss of initial pinion depth can lead to the noise issues you are having, but are you sure that the intermediate plate bearings are good? These are more common.

There is a range with the pinion, too. You have .18mm of wiggle room (IIRC)

I would be glad to check/set these for anyone who wants to ship to me, stop by, or show up at one of my clinics.

The large intermediate bearing looked fine, and the small one I made sure the cage was not broked, per the video. To me it looked good. However, not having been in a tranny before I honestly can't say for sure. I did take apart 3 to over the winter. One I could tell the small bearing was shot because I could spin it and feel a flat spot every 5 rotation or so. It was very minor but I could feel it.


When spinning the shaft I could hear some bearing noise but it was consistent with the other trannies...

Should I not drive it? Drive and monitor for increased noise? I guess if I blow it up I have 2 more donors that I can assemble. Maybe I'll just start building my backup now.

As I stated, the fine tune that they do to the R/P is strictly for noise abatement. It will not damage the transmission to drive it. If it worsens, it is not likely the diff but rather an intermediate bearing. Other bearings to check include the rollers on the end of the shafts, and their races. Sometimes the races move in their hole in the case because the tolerances are too lax. This causes the races to spin and wear the case and bearing further.

If I get a case with known howl in higher gears I think about the large pinion intermediate plate bearing. A case of howl at higher engine RPM, the smaller input shaft intermediate plate bearing. Howl on decel ONLY does make one think that it is the R/P because the other bearings dont see a difference on accel or decel that is appreciable in how they operate, but the R/P change from push to being pushed.

Did you check the diff bearings?

I did check the diff bearings and they looked ok. No real play. Thinking about it now I probably should have just changed them since they are cheap enough.

If one of the diff bearings developed play, that would allow the diff to move latterally and change the mesh of the ring and pinion, thus creating the howl....is that the thinking?

Thanks for the help so far!

Those two tapered bearings are preloaded to a spec controlled by the bearing spacers/shims, and the pressure applied to the side cover by it's nuts... they have no play. Those specs and the pinion-depth control the lash and wear pattern of your R&P teeth.

Those bearings also wear out, thus changing the spec, which is 0.15mm preload.

Yup, but this is last on my list of suspects. Consider it this way, when the pinion is driving the diff it is pushing the diff away to the left side. When the diff is driving the pinion, it may (this part is my speculating) pull itself closer to the pinion thus changing the preload on the diff bearings.

Changing the bearings can be a bitch. I actual do not have a puller that fits perfectly and end up cutting the cage, removing all the external parts, and then notching the race until it falls off. Sometimes simply heating the race will allow it to fall off, but then you have to let all of it cool and that takes time. Many ways to do it.