645 payloader

Your 645 you can gut the clutches out of the front. The cover on the front is aluminum remove it and you are in the high gear clutch pack there is a snout that sticks out and has sealing rings on it. That is how high gets its oil and they have been known to break. Then low and reverse. Take the cyl. Off and retract it will give you more room. The back side has the converter and pump drive gears and sprague. The steering pump is on the ladder side and the charge pump is under the lift pump. If you have good pressure and it doesn't shutter when in the gas trying to push
I would bet converter or sprague. The converter has a little snapping inside that the parts book or repair does not
Show if that fails it lets the two halves run into each other and they don't last 5 min. And get real sluggish. How do I know we ran 645 and 745 loaders for years and have had every bolt out of them. The sprague ass. Will get destroyed if you have a pin head in it shifting rev to forward and not bringing the RPM down. To get the tranny out
Remove hood,remove radiator and steel shell together. There are 4 3/4 bolts holding it on,set it down on 2 4x4 blocks where the frame would be that way you don't smash the lower radiator. Next drain oil out of the tank about 40 gal. Take steer pump off and feed and pressure lines off the pumps. Take shift linkage off and the temp gauge. Remove driveshafts. On the ladder side on the bell housing right ahead of the oil filters there is a 1"plug remove. Inside there is 12 3/8 Bolts recessed inside the flywheel. USE A LIGHT NOT YOUR FINGER TO FEEL FOR THE HOLES ,turn engine by hand IT WILL CUT OF THE END OF YOUR FINGER! Yes we had that happen. Take 4 bolts out of rear engine to frame remove throttle rod,battery cables,charge system. Hook chain and lift gently ,remove 12 bel housing bolts and engine slides forward take GREAT care on the flex plate on the converter as they bend easily.
At this to get the tranny out you need to jack the tranny up just lightly,remove the two oil cooler lines and the tranny mounts.THE MOUNTS are all what is left holding 1100 pounds up. If you are still alive carefully let it down to ground take great care of the valve body on the right hand side of the tranny don't hit it! Dent it and 800$ gone. Once on the ground put a come along on the top of the tranny,there is a lift point up there that you can screw a eyebolt in. Next you must raise the rear of the loader off the ground 28" block it good. Let the tranny down while rolling it towards the rear of the machine next drag it out and you have earned a days worth of work. If you take the tranny apart call me I will help as there is 4 different valve body gaskets. Do not interchange as when you go to high it will put it in two gears at the same time and stop in record time with you against the windshield. Also sprague goes in one way backward and you start all over(yes I've done that) they are a real simple tranny and work great just have to take your Time on repair.

Yep there is no way to get them out the top without a fire wrench