BMW1 42 #1 Posted July 11, 2016 I recently acquired a 1973 18 automatic and it has been running great and the forward/reverse had been working great. I recently started to use the tractor to pull my new 1300lb around and it's been doing fine. I just use the tractor to pull the trailer to the street and to return the trailer to it's parking spot under the deck. There is a slight incline but nothing major and its about 100 feet each way. Have done this about 5 times in the last two weeks without any issues. Today when I tried to back the trailer under the deck it goes very slow in reverse for a few feet and then stops. There is a slight incline to get under the deck. If I get off and push the tractor it will continue to move. I check the transmission fluid and it was almost a quart low. I added a quart - it had type F ATF in it - but it still did not work any better. It works fine in forward even with the trailer attached. Reverse will work, as long as the tractor does not have to go backwards up an incline. Anyone know what might be wrong? Share this post Link to post Share on other sites
953 nut 59,785 #2 Posted July 11, 2016 The first step with any Hydro performance problem is to replace the fluid and filter. Since you have Type F ATF continue using it, the NAPA filter number is 1410. This will probably fix the problem. It could be one of the "Acceleration Valve" springs on the Reverse valve needs replacement. They modulate the fluid flow to keep the operation from being jerky. If the fluid and filter change does not clear the problem let us know and we will continue on. Share this post Link to post Share on other sites
BMW1 42 #3 Posted July 12, 2016 Thank You for the response. I won't get to it until this weekend. I will try that and let you know what happens. Thanks again. Share this post Link to post Share on other sites
BMW1 42 #4 Posted July 18, 2016 Replaced the filter and filled the transmission with new type F ATF. To test, I backed up a small ditch in my back yard, tractor only, no trailer. I barely made. Had the engine wide open. and it went very slow. Still don't understand what is wrong. Share this post Link to post Share on other sites
pfrederi 18,638 #5 Posted July 18, 2016 The sunstrand manual you can download here is the place to start. http://www.wheelhorseforum.com/files/file/24-transmission-hydro-sundstrand-sm-492-4206pdf/ The linkage adjust would be the tart. That is not hard to do. If that doesn't resolve it then the Charge pump check valve or acceleration valve issues require significant work. Not a afternoon project in the driveway. There are several threads here about repairing sundstrands. 2 Share this post Link to post Share on other sites
BMW1 42 #6 Posted July 20, 2016 Thank You. I will start there. Just need some time. Appreciate the help. Share this post Link to post Share on other sites
