JLG 12 - 55 powershift

Will not engage cold .Very foamy oil cold

Foamy oil usually means your inducing air into the system. Is the fluid level correct ? Does it go away and start shifting after the unit warms up ? And how cold is cold and do know what fluid is in the machine ? In extreme cold climates you may need to change specs of the fluid itself to get proper operating. Did this just start once the thermometer dipped ?

Fluid is full ,temp here is in the low 50's if the machine warms up 45 minutes it works perfectly. I don't know how air gets in maybe there is a seal in side. Diagram shows the fluid pick up right to pump but the pump is high up

Is the oil foamy after warming up?
I'd be inspecting the pickup tube. Is there a filter on the pickup line? Check the seals there.

Foamy oil in the trans come from the oil being to low. Make sure you are checking running . When added oil pour it in slow. When get it to near full . Let it run for a second then shut it down. Let the oil get the air out for a while. Restart it and check level. I had one in the pass do this .

I even tried over filling same problem.someone told me that there was a common problem with a seal in the pump but I have not found any thing about that

So back to my original question how long have you had this machine and when did the problem start ? Just when the temp dropped ? The pick up is in fact direct to the pump from tank through a suction strainer. Pump location does not matter since its a pump. It creates suction hence the suction line. 50s is not cold enough to really affect viscosity. No one accidentally put diesel in the hydraulic fluid thinking they where fueling up ? Thats about 95% of our hydraulic fluid issues is owners/workers pouring diesel into the wrong hole. Does not take much diesel to degrade hydraulic fluid. So is this your machine ? You fuel it yourself ect

No contamination the machine has 2300 hours If the machine set for 2 or 3 weeks it might not be slow to engage but when it got cold it takes longer.also the machine will move but very high stall speed.and you do not get the positive engagement until it warms up.we have serviced it no change warm it up no problem all day.It does not seam to be slipping but very high stall speed on converter .if you put it in gear and throttle it cold starts moving but very high rpm and 30 seconds it fine.Ido not want to damage the power shift so I let it warm up

I would put a gauge on it and check pump put pressure. See if you can isolate to converter or pressure side