I am trying to repair a JD 750, has a beautiful salt undercarriage but the pumps and motors are very weak, best price I have found for reman transmissions is Hydrostatic Transmission service LLC, does anyone have any experience with these folks? Who would you recommend dealing with? Also the main issue with the transmissions is the pistons and barrels are very worn, where can I send the barrel to have it resleeved and put new pistons in? Any advice is greatly appreciated. Thanks JW
I can't give you any specific help on suppliers or workshops. I can tell you though that even though it sounds like a good idea, resleeving is out of the question (until some one proves me wrong). When you are talking the extremely high pressures typical in hydrostatic transmissions, the clearance between piston and bore has to be so small that after a sleeve was fitted (assuming you could make one hard enough) it and the piston would have to be precision ground to suit each other. The barrel would be weakened by the machining and would probably crack under pressure. You wouldn't be able to buy new pistons by themselves; only a rotating group which is the barrel assembly, pistons and port plate and probably piston feet and swashplate. The failure of one piston will contaminate and bring down your whole transmission so it's not worth the risk. Good luck!
i worked in the rebuild room at a JD dealer a few years ago. we had a local outfit attempting to resleeve, and crimp on new slippers to pistons. over 1/2 the pistons we sent out came back with more end play than we started with. after the 1st sleeve pulled out, and destroyed the trans we had just rebuilt and reinstalled. you might say we were lucky, the machine made it 50ft outside the shop before the trans lost all it's charge pressure. :badidea that was the last time we used them, they were outta business in 6 months. :drinkup
Thanks for the back-up crewchief. Did anyone have bets on how long it would last? One thing we did have success with was using rotating groups out of Czech made copies of Sunstrand pumps and motors. We could buy the complete unit, strip it and modify the shaft and throw the rest away for less than the genuine item. They were using Sunstrand drawings. Not that Sunstrand was that expensive. It would be good if someone could pick the JD components as a propriety brand (Bosch-Rexroth, Linde) and buy the parts direct but JD probably make their own stuff anyway.
we were confident in what they were doing, and they guaranteed the repairs, actual savings on the pistons wasnt that much, we lapped plates and slippers if they werent in bad shape. that one cost them 2 new rotating groups for the motors, plus R&R shop labor and our time in the rebuild room to teardown both transmissions, inspect and reassemble. i've seen a lot of OEM sleeved blocks pull the sleeves out of them over the years. :drinkup
Hey, thanks for the replies I could only build about 2000 psi. out of the L.H. transmission and charge pressure was at 150 psi. under load, upon dissassembly I found that the pistons were very worn in the barrels (stuck a dial indicator on the side of a piston with it inserted in the barrel and could move it .010") new cylinder block groups through sundstrand are about $2k the company I found with the cheapest reman price is also offering a reman cylinder block (which I assume is resleeved) for a cheap price also, as usual cheap is scary. JW