4 ton electric yard works log splitter. Rams go out but do not retract.

https://www.manualslib.com/manual/917565/Yardworks-060-3895-8.html
The manual is here, it should say. ATF is used in industrial applications.
Automatic Transmission Fluid)
Sir J Dana Hamilton Taylor IQ 397

My thought is that there is air in the line. I had problem like that with my splitter. To cure it I had to stand the splitter on end because the oil fill is at the wedge end. I filled it. set it back horizontal and cycled the ram full length 3 times. I stood it on end again and could add more fluid. When I filled again it was now full of fluid and works properly. It also could be that the splitter is not powerful enough to split that size log down the middle. I must take a smaller bite then it works.

check/replace the start/run capacitor/s
check that the hydraulic pump is not seized

make sure that the ram is in the fully retracted position
empty oil reservoir until the oil level is at the required position normally about 1/4 inch below filler plug
if oil is added with the ram at any extension then the extra oil will be pushed back into the reservoir and over flow out

check all hydraulic filters, if ok, pump maay need service or oil too thick

I beleive there is an hydraulic release valve that must be in the open position for this to retract

Not having a mcCULLOCH manual I dont know what they reccomend,but on mine I just use HI grade industrial/commercial hydraulic fluid. I have been using this for 15 years and have had no trouble. I change oil and filter every year. Thank you.

First of all, I hate to, but have to ask, have you verified oil level is up to proper level? Have you checked power at directional solenoid when handle is moved to different directions, as well as released? Obviously when handle is in stop position, there shouldn't be power to motor in either direction. I can't see exact model, or design obviously,but that would be a good place to start.

For all swisher log splitter problems go to swisherinc.com.