Anyone ever have to change the coupler from the hydrostat to the gearbox? I have a 1688. I think my input shaft on the pump is shot too. There is only about 50% splines left on the shaft. Am I going to have to have the pump tore down and have a new shaft installed? Yuck. I wonder why they never put a grease zerk in there way back when, the new coupler has one. Thanks for any comments.