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SmilinSam

Sundstrand gremlins at work

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SmilinSam
One of my work tractors is having mysterious hydro problems with its sundstrand. It will speed up and slow down off and on and even come to a complete stop in reverse every so often before taking off and going again. When It is moving it appears not to be lacking in pulling power either. Does not appear to be a slipping problem, but almost like a intermittent pressure problem. Belt tensions is not the problem, and hydro fluid seem to be OK. Previous owner has used some John Deere brown hydrostatic fluid in it like used on the industrial equipment. I never did drain it as I ran it all year last year every week without any sign of problems. Filter only has about 40 hours on it. Any ideas?

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Ronald Hribar
Can not say this will cure it. But I would drain oil and put new in along with a new filter. That would take that part out of the equation

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SmilinSam
Can you use red automatic transmission fluid? I ask because some of my units have red and some have brown. Heck, some on the Wheel horsed I used to have called for 10W30 motor oil.

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IronPony
I don't know a thing about your transmission but I do know that you can never assume a part is good just because it should be. In this case the filter is within a normal life span but it may not be good. Change it and the fluid as suggested by Ron. Dan

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RayS
The operator manuals state you can use either type F or Dexron. The simplicity says type F and the 700 series Allis manuals state Dexron.

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Simpleton7016
I had similar problems and it ended up being that red bushing on the speed adjust plate thingy ma bob. My bushing was cracked so it would move around with every bump or incline that I hit even when the hydro lever was in a constant position. "Gremlins" is a good description of the problem I had.

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Al
Sam, Don't take the belt for granted. Look at the from drive pulley. If it is U'd out instead of V, the belt will slip even with good tension on the belt. We have had to replace quite a few for the slipping problem. A vee belt gets its great pull by expansion. When the belt enters the pulley the sides are straight. As it starts around the pulley and it conforms to the pulley it squishes out on the sides, wedging against the sides of the pulley. As the belt comes off the pulley and straightens out the squish goes back to flat and it releases from the pulley. Over time and a lot of running the sides of the pulley wear out where the belt squishes out and the wedging action is gone. If you look at the pulley V and the sides are belly'd out, looking more like a U it is bad. With this wear the belt pulls no more than a flat belt. Have someone watch the hydro pulley. Put the tractor against something solid and push the hydro full forward. It should spin the wheels and the pump should not slow down more than the engine speed does. Another place this happens is on the starter-gen pulley. The billet, pulley (machined out of a piece of solid steel) is much worse for this than the stamped steel pulley is. The stamped pulley is so much harder than the machined steel. As these pulley (s) wear the belt has to be much tighter and still slip. This is harder on SG bearings. A new SG belt still slipe because there is no side to wedge to. Al Eden

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johnmonkey
Great read as usual Al. On the starter generator pulley, can that be re-machined to a flat sheave or does it need replacing? Is it an easy swap? Thanks, jh

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Al
Hi, The V could b3 recut into the pulley. The pulley would be in reality smaller in diameter. This would give the starter a little more power cranking, but would require a little more power at WOT (wide open throttle) I can't remember, but about 20 years ago I got into this and I believe the angles of general V belts and outdoor power V belts is 58 dgrees and automotive belts are 63 degrees. This is why automotive belts and outdoor power don't get along. Will someone with the opportunity to access the SAE specs, please correct me or verify my memory. The old machinist that used to do all the stuff for me on my race engines has passed away and I can't just call him and say: John, what were the angles on these belts. He was so wonderful to have for a friend and source of info. Al Eden

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SmilinSam
Al wins half a cookie:D Pulley was fine, but the old belt was stretched just enough that it had little tension on it, allowing it to slip under a load. Thanks Al for pointing me in the right directiondOd

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