6620 combine drive belt ?

[chamernik93363]

I have a 6620 JD combine.  We have noticed that the drive belts slip when under a load.(going up a hill, etc.) We repalced the lower set of drive belts, tighten them and still have the same issue.  The belts seem to be slipping on the lower pulling on the transmission.  Is the pulley getting to the point of needing to be replaced or rebuilt or is there an issue with the transmission?  Any help would be greatly appreicated.  Thanks

[tractor12]

several things to look at , is the combine a hydro transmission or has clutch? if it is the hydro and you do not smell belts burning then u may have the relief valves leaking on hydro trans. you can switch them to find out if you have a weak one,, check with dealer  to find out  how to do this , he  should be able to tell you how to do it no charge.   If you have a variable speed clutch system then the variable speed pulley could be hanging up and making belts slip, or your clutch is possibly slipping. does it slip in low gears or notl. if it is in the pulleys they would need to be rebuilt and installed and adjusted. good luck

[chamernik93363]

Thanks for the info. It is a hydro.  We did burn up belts while traveling on the road  in 4th gear going up a hill. The belts do not slip in lower gears but we did notice that they did seem to slip in 3 rd gear now as well when going up a hill. In otherwords seemd to be getting worse.  I will check out the relief valves you talked about.  Thanks again.