621 older scraper transmission slips fresh rebuild

[Wipfmister]

I've got an older 621 cat scraper
Transmission is a 5s7777 I believe
It's been freshly rebuilt top to bottom got bout 20 hours on it and 3 and 4th gears r gripping nice then seems like once engine gets more rpm and power they lost grip internally and machine starts slowing down and u can tell engine is no longer laboringuntill I Rev engine back dow then they grip again kinda Same problem with 7 and 8 too maybe 5 and 6 too sometimes
Wat need to be done to correct this
Test pressures??? Internal adjustments???
Wats normal operating temperatures on this transmission and yes I'm running 30 wade cat transmission oil
Any help would be greatly appreciated I can talk personally with whoever would know something just ask for my number thanks much mates!!!

 

[BluewaterLa]

Been years since I've rebuilt an old 621 frame up so my memory may be a bit clouded.
There is adjustment settings that need to be done to the transmission after install, the exact procedures would have to come from CAT dealer or SIS if you have access. If memory serves me correct the adjustments are done with long allen wrenches for the gears. After putting the machine back together I had several testing, adjustments to make and twice had to do the transmission once initially and then after traveling the machine and shifting through the gears once up to operational temperature.
I would get hold of the information through SIS / CAT