Repair of 2spd PTO unit

Repair of 2spd PTO unit

This repair info pertains to the removed PTO unit. Use this info to replace shafts ,brakes or clutches within the unit. Start by removing the 4 3/8" bolts that attach the pump housing to the unit. The pump housing is bell shaped 7 1/2" in diameter. You may need to jar it loose with a soft faced hammer. Set unit aside ,usually no further disassembly is necessary for the pump.The large snap ring holding the clutch PAC can now be removed along with the clutch PAC. If the clutch PAC is to be replaced no further dissassembly is required. To continue dissasembly ,the large spring in the center of the clutch carrier needs to be compressed enough to remove the snap ring. This may be done in a press or by making a simple tool. I will explain how to make the tool in another post. Be careful removing this spring , it should expand to at least 5" in length if it is to be used again. With spring removed ,remove snap ring above clutch piston.This snap ring is a stop for the clutch piston so it cannot over stroke if the clutch PAC becomes too worn.Thread in 2 1/4" X 4"+or_ bolts into the threaded holes in the top of the clutch piston. By use of the 2 bolts as handles pull up with a twisting action to remove the piston. Inspect the outer lip seal and inner Oring seal on the piston for wear, nicks or heat damage.These seals should be replaced and are included in the seal and gasket sets I use and sell.With piston removed the next step is to compress the brake piston springs that are pushing the clutch carrier up against the snap ring inside the carrier. You can either use a press again or the same tool that was made earlier. Basically you need to push the carrier drum down enough to remove the snap ring. With the snap ring removed ,the clutch carrier drum can be pulled up off the splines of the 1000 rpm shaft. The 2 Teflon seal rings on the drum can be replaced at this time. If they look good( no sign of wear ,nicks or cuts) I leave the old ones in place.Installing new ones is a procedure in itself.The new ones need to be warmed up in hot water ,stretched, installed and re compressed. With the drum removed ,the remaining 2 bolts holding the rear cover to the valve housing of the unit can now be removed. The spring pressure of the 3 brake piston springs will push the cover away from the unit valve body as you loosen the 2 remaining bolts. There are 2 dowel pins that may hang up the separation process. Lift off the valve body . Inspect the 3 brake pistons. There should be at least 3/32" of brake pad material remaining on the end of the pistons ,if not they should be replaced. At this point the the idler gear and it`s 2 thrust washers can be removed and set aside. Now removal of either of the 2 shafts ,bearings and seals will be self evident.Any questions or comments? I will go through the assembly procedure in another post. JLS

For IH tractor parts go to http://stores.shop.ebay.com/redrunrite This is my ebay site ,I have many popular and also hard to find IH tractor parts listed there at competitive prices. Also by going through ebay you can check out my feedback rating and if you have a question about a part or a trouble shooting question ,you can ask it there. Ebay has a great messaging system that is very secure.If you don`t see the part you need please ask me as I have access to many more parts. I also have access to parts for other brands than IH. I can`t answer nearly as many questions on other brands though. I also have a great supplier for quality engine rebuild kits for almost any Ag or industrial engine.Check out my ebay site Redrunrite and bookmark it. When your in the ebay site find my site Redrunrite by going to community type in redrunrite and then click on view sellers items or on the ebay search bar type in IH and any tractor model # such as 706,856,1066 and at least one of my parts should be listed there. JLS

Rebuilding the removed Pto unit: With the unit removed and standing as in the picture the pump assembly and sump tube can be removed after removing the four 3/8" cap screws. It may require a blow to the side of the pump housing with a soft face hammer to jar the pump loose.Note the pump will be sealed to the center housing by a small Oring or a ring shaped gasket. With the pump removed a new clutch pac can be installed. The clutch pac is held in place by a large snap ring.Remove the snap ring and remove the clutch pac . The pac will consist of 5 fiber discs in between 12 steel plate.If there is any sign of burning, or warped discs, the pac should be replaced. On high horsepower model tractors a heavy duty pac is available. The heavy duty pac is the same discs and steel plates, only there are 7 fiber discs and 9 steel plates. The heavy duty configuration is 2 steel plates ,1 fiber disc,1 steel plate ,1 fiber disc, 1 steel plate and so on, ending with 1 steel plate. The standard duty configuration is 2 steel plates,1 fiber disc, 2 steel plates and so on. These clutch pacs are available in my web store www.redrunrite.com or on Ebay in Redrunrite store under pto. The burned out clutch pac is the most common problem with these units. To further disassemble the unit a special tool is needed to compress the large spring that is inside the clutch pack. I will get into how you can make this tool in a future post. JLS

This information pertains to the PTO unit of IH tractor models 706-1586. The PTO unit on these tractors is a self contained assembly bolted to the rear frame of the tractor. The power is transferred to the unit by a constant running shaft driven by the clutch pressure plate. The constant running shaft powers a hydraulic pump driven by the input shaft of the PTO unit. ( this pump is self contained in the unit and only supplies pressure to the pto unit)The hydraulic pump supplies oil pressure to a control valve inside the PTO unit housing. When this valve is activated , it directs oil pressure from the pump to a hydraulic piston that when pressurized engages a clutch pac which drives the out put shaft.This unit can be removed from the rear frame of the tractor for repair. The complete unit needs to be removed,it cannot be disassembled on the tractor. Removal requires draining the transmission/rear housing oil. Removing the 3PT hitch upper link bracket/cover allows access to aid in shaft alignment.The unit can be pulled back enough to disengage the drive shaft ,care should be taken to not damage the oil sump tube which angles down towards the bottom of the rear frame housing. The complete unit can be removed from the tractor for repair. Using 2 of the long bolts that held the unit in the tractor ,screw them into the 2 top rear threaded bolt holes( they will be sticking out the back while unit is still in the tractor) . They will act as legs to stand the removed unit on them and the 540 output shaft. The input shaft will be pointed straight up. Now it will be easier to repair the unit. JLS

I look forward to hearing from anyone looking for repair or troubleshooting information. My specialty is Farmalls 706 through 1466 but I have quite a bit of experience on older and newer models. Sorry I don`t know very much about the "F" series ,they were way before my time. I really enjoy diagnosing problems and the older I get the better I get at telling people how to do the work rather than doing it. In conjunction with my repair shop I started a IH tractor parts webstore www.redrunrite.com this site is linked to my store on ebay also. I have access to many great aftermarket suppliers of tractor parts that I use in my shop. I picked out some of the most commonly replaced items from the best of my suppliers. I have access to many more parts for IH and other makes, but in my stores I only feature IH parts. JLS

Great IH parts web site

For web site specializing in IH tractor parts check out http://www.redrunrite.com

I have had many people contact me for repair information of IH Farmall tractors. The most asked service questions are on the Hydraulic systems of 706 through 1586 series tractors. The systems are basically the same for all the models in between ( 756 766 786 806 826 856 886 966 986 1066 1086 1206 1256 1456 1466 1486 1468 1486 1566 1568 1586).
The hydraulic system on all these models use the rear frame housing and clutch housing as a common oil reservoir. The oil level should be maintained at the full mark on the dipstick located in the front right corner of the operators platform.CaseIH Hy-Tran fluid is the preferred fluid to be used in this system. Other fluids will work but none are a exact match of Hy-Tran.
There are 3 pumps that supply oil flow and pressure, 1) MCV (multiple control valve) pump/ power steering pump. 2) Hitch pump/main hydraulic pump. 3) PTO pump. I will start with the MCV/ power steering pump .
This pump delivers 9 gallon/minute and approximately 2300 psi at rated engine speed for all model up to 86 series which use a 12 gpm pump. The flow and pressure is regulated and directed in the MCV. The pump is mounted to the inside of the MCV and is gear driven by the PTO driven gear located in the left side of the clutch housing. Pressure and flow from this pump through the mcv 1st) supplies power steering then 2nd) supplies power brakes . 3rd) supplies pressure to shift the TA. 4th) Lubricates the transmission ,differential and final drives.
The 2nd pump is located on the left side of the tractor and just ahead of the rear axle housing. There you will see a mostly square plate bolted to the rear frame. The pump is bolted on the inside of this plate. The pump is gear driven similar to the mcv pump also by the PTO drive train. This pump is a 12, 15 or 17 gpm pump depending on how the tractor was ordered or whether the pump was changed before. All 3 sizes will are interchangeable. This pump if working properly should deliver up to 2500 psi to the system relief valve where the pressure is regulated to the maximum pressure allowed by the relief valve and then powers the 2pt./3pt. hitch and then the remote valves. ( hitch has priority over remote valves).
The 3rd pump is located on the input shaft of the PTO unit inside the rear frame. This pump supplies pressure to the clutch packs of the PTO. Pressure is controlled by the control valve on the left top of the PTO unit. This is just a Brief outline of the workings of the 3 hydraulic systems. JLS