JD 8300 transmission

[806 Curt]

Hey guys, I have a very technical question on an early JD 8300 (below 20000 serial number). I know there are some newer JD techs on here so I need to pick your brains once. From what you know is there a special startup procedure after a complete rebuild of the powershift transmission? The reason I ask this is because I had some bad luck after rebuilding one where the scavenge pump in the transmission seized up after first startup before the oil got to it. More specifically it was the smaller idler gear that seized. What I can tell you is that this pump was indeed oiled during assembly. But what I can also tell you is that I put a couple dabs of lithium grease on the gears to help it prime faster (this was before I truly understood how the system worked). I can also tell you that this very gear was new when I assembled it (old one had a chipped tooth). From some different guys that I talked to, one seemed to think that the grease that I put in there caused it to seize up easier. Another guy thought it shouldnt matter. I measured the gear that seized as best as I could for it being scored up and it appears to be the same thickness as the old gear. I understand that this pump is the last to recieve oil and that it can take up to 2 minutes to get oil. I know the oil has to travel from rear end, into charge pump, fill the filter, fill clean oil reservoir (6 gallons), go to primary pump, and then to transmission, then 5 gallons to fill transmission until the scavenge pump sends oil back to the PTO clutch in the rearend. So I do have an understanding of the system now. Just seems like a really long time that pump has to wait for oil. Unfortuneatly I have to deal with the consequences of a scored pump housing and manifold cover. Next time I am going to figure out how to pre-fill the transmission sump with 5 gallons of oil even though there is no fill plug for the trans. I appreciate any input you guys might have. Thank you.

 

[JDTECH]

I always pack the gear pumps with lithium for better priming. There is no special start up other than what you've done. Fill the hydraulic system and start engine, let idle for 2-5 minutes to let the trans fill to proper level, which is not as much as you think. The scavenger pump is what maintains the proper oil level in the trans. Not sure why the gear seized unless there was some foreign material floating in the system that lodged where it shouldn't have or there was improper tolerance there. Good luck.

 

[806 Curt]

Thanks for the reply JDTECH. I'm with you on putting grease in pumps for faster prime on initial startup. I didn't see any foreign material when I took it back apart. Although obviously I saw bits of metal from the gear seizing. This may be one of those unsolved mysteries. I know for a fact the pump wasn't dry. Tolerance is the only question in my mind. Next time I will pre-install dry with plastigauge just to see clearance.