Has anyone dealt with an older CAT 621 scraper transmission slipping after a fresh rebuild?

[Elizabeth Williams]

Mine grabs fine at first, but once the RPMs come up in higher gears, it starts slipping and the machine slows down. Could it just need pressure checks or adjustments, or does it sound like something internal?

 

[Elixer G]

On those older Caterpillar 621 machines, low clutch pressure, modulation issues, or linkage adjustments can sometimes act a lot like a bad rebuild.

 

[Robert M.]

Sometimes a weak pump, low clutch pressure, modulation issue, or even linkage adjustment can make it act like the transmission is slipping internally.