The transmission in our U1300l slowly became more noisy and harder to shift over the years. Not horrid, but noticeable. As part of routine maintenance, I removed the driveshaft from between the bell housing and transmission to grease it. I had noticed in the manual it appears that the input shaft of the transmission should have .04 to .05 mm of slop front to back. I grabbed the flange to feel it, and found I didn't need a dial indicator to check it. The slop was over .5 mm. Thinking of a few solutions, I settled on a shim between the rear cover and the ring that is behind the bearing. Mine has tapered bearings. I have no idea if this will work if yours has the earlier straight roller bearings. Since I had put the driveshaft back, I didn't bother measuring, just have tried different thickness shims. Someday I'll remove the driveshaft from the transmission and measure the slop with a dial indicator to shim it properly. Before I ordered proper shim material, I made one out of .040 inch thick Amsoil gear oil bottle material. It became quieter and shifted better. With the proper shim material (which doesn't squash like the gear oil bottle material did) I tried .030 inch, .025 inch and now have .020 thick in it. It is now shifting easier than ever and is quieter than ever before. See the pictures below for how I did it. If you want your transmission to run as cool as possible, quiet as possible with the greatest chance of longevity, use Amsoil gear oil. I have used it in everything I've owned sine 1977 including my 1966 404 radio van and my 1977 U1300L https://www.amsoil.com/c/gear-oil/25/?zo=23310
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My first crude attempt at making a shim from an Amsoil gear oil bottle.
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The circle cutter I bought on Amazon. This is the best one I've used so far.
The shim stock I bought on Amazon.
Amsoil Synthetic Polymeric Heavy Duty Synthetic Grease is particularly sticky, great for holding shims in place during assembly.
