I put this adapter on a 4490 case tractor with approximately 180 pto horsepower to run a 350 bushel John deere 1210a auger cart. Worked as intended. I ran several thousand bushel through over the fall and winter of 2022. I used low rpm usually idle so as not to overspeed and cause damage. I then had to use a much bigger tractor (case 2870 : 280 horsepower) that had a large 1000 to small 1000 adapter hooked to this small 1000 to 540 adapter for several loads and had no problems. Again minimal tractor rpm/idle. Please keep in mind unloading auger cart into semi trailer or wagon involves minimal forward or reverse travel and no turning at all, pretty much just stationery pto work. I was most impressed that this spring (2023) after the adapter sat out connected to the tractor outside all winter in snow ice and rain (north central Ohio) that it slid right off effortlessly even though I didn't grease or oil the splines before installing. I'm very surprised I didn't have to beat it off with a hammer! Good buy in my opinion, much cheaper than changing the shaft on the auger cart, as I may need to run on a tractor with only a 540 shaft sometime anyway. Thanks for reading, hope this helps. I will try to add pictures and or video later if possible.

This item broke on the first use while haying. The coupling that locks onto the 21-spline shaft broke and the PTO shaft came off the tractor. Thank goodness it didn't do any damage to the mower. I am now looking for other options.

After much searching, I found the 21 spline to 6 spline adapter at Tractor Supply. Online ordering was easy, shipping was very fast, item fit just fine, outstanding transaction!