Transaxle trouble Options

[Hank914]

I earlier added to the "what you did today thread" but I thought I would start a new thread with some more details on my transaxle troubles.

So I recently installed by rebuilt tranny after the PNW tranny clinic. I also converted from tail to side shift, and all the bushings. The previous owner (40 yrs) rebuilt the engine after 97k miles in 2007, but afaik did nothing on the tranny. The bushings were shot. Last weekend, after logging 120 test miles around Central Oregon, I thought I'd take her down to the Bay Area. About 130 miles into the trip, I hear a loud bang and spin a 360 into the ditch. During the fun, I figured I had a blowout. But not tire problems just a locked up rear differential.

I pulled the tranny and this is what I saw. (Please excuse the large photos, but it adds detail)




So I opened up the tranny case and found some interesting stuff.

Pictures to follow...

[Dr Evil]

Well, I have received and have have had time to go through the guts of the tranz. Interesting things found. Lets start with the main culprit that caused the casualty. The roller bearing in 1sy gear failed and welded the pinion shaft to the gear. Thus, the tranz was always in 1st. You can see where this would be a problem when you select 5th.

Above of the gear is what the roller bearing should look like.


The race of the int plate bearing was welded to the washer that goes between first and the bearing. You can see the discoloration on the washer from the heat.


So, why the hell did this bearing fail? Great question, and a great time for some teaching on a very fine point in rebuilding that I have only come across about 2 times.

The bearing and the inner race should be able to pass through the gear with very little friction (basically none if kept parallel to the gear face). I salvaged the dog teeth off of the old, welded 1st as they were in perfect shape. I installed them on the new 1st and then checked everything for fit. That is when I noticed that when the roller bearing and inner race were pushed through to the side of the gear with the dog teeth, it started to bind and eventually stuck. This was odd. I took the dog teeth off and everything pushed through without effort. So, the teeth likely shrank the ID of the gear by such a slight amount that every thing bound up and failed. I put a different set of teeth on the gear and tried everything again and noted that the roller and inner race moved through the gear with no issues.

So, likely scenario is that the dog teeth were manufactured to poor tolerance, closed the ID of the dog teeth side of the gear by a small amount when installed, caused the roller bearing to bind, which welded everything together, and caused the stack to seize.

The easy lesson; if stuff is sticking, look for a cause.

The only other casualties from this; 5th gear had one tooth with a mark on it so 5th was swapped, and the large pinon roller bearing had wear on the race.

Hopefully folks can learn from this. Always good to share things like this.