Ford 621-62 tractor
 Torque converter
 4 speed forward and one reverse standard transmission combination

Tractor SN#:

 A1001 thru A2307 so you can tell there weren’t a lot of these made
My service manual lists Ford Tractor Division, Birmingham, Michigan

 USAF. Purpose :  Towing planes for military.
SN: Location: LH side of clutch housing on top.
Original color: Ford Industrial Yellow

Transmission: 4 Speed w/torque converter and hydraulic disengagement clutch pack.
Transmission/torque converter oil level check:  Plug right beside the right hand brake pedal.

Main transmission housing has 3 compartments.  First is the clutch housing where the flywheel and torque converter are housed.  Right behind the torque converter is your hydraulic transmission pump.  The second compartment is where the transmission pump is mounted.  Behind the transmission pump is a separate compartment for the transmission clutch assembly.  The third compartment houses your transmission standard 4 speed transmission gears.  Four forward and one reverse just like any other early Ford 4 speed transmission.

Both the second and third compartment of the transmission/clutch housing, hold the transmission/torque converter oil.  There should be NO oil in the clutch housing itself.  If you have the cotter pin hole leaking fluid, then you have a problem with either the pump seal leaking, torque converter has a crack, a leaking fitting or pump gasket.  The main transmission and torque converter use the same oil and should take 5 gallons of Ford M-24C-41 which today is called “Master Trans” oil.  It’s is a light oil for the torque converter and is available at Ford dealers.

Tractor Clutch:  The tractor clutch is not your conventional clutch and pressure plate you see on most Ford tractors.  Because this transmission has a torque converter, Ford put a hydraulic disconnect clutch pack behind the transmission pump in the transmission/clutch housing (second compartment). It disconnects the torque converter from the standard four speed transmission.   It is hydraulically activated and disengages with the clutch pedal on the drivers left side.  The pedal controls a spool valve that takes the oil pressure away from the clutch pack, allowing the transmission to disconnect from the torque converter.  Let the pedal go and the clutch pack activates a piston inside the clutch unit.  It presses with a internal clutch piston. Several small wet clutches together allowing a connection between the transmission and torque converter.  It is not a foot-inch valve like some people say.  Do not ride this clutch pedal.  Either depress it all the way to stop the tractor so you can shift it, or let it go to make the tractor go.  Riding this hydraulic clutch will tear up the clutch plates.   The tractor drives just like a car.  Push the gas pedal down and it goes.  Let go of the gas and hit the brake and it slows right down to a stop.  Depress the clutch pedal to shift the tractor between gears and reverse only. That‘s what it’s for.

If the engine idle speed is too high it will make the tractor try move forward at idle.  Use the brake when stopping and the torque should kick down just like your car.

These tractors are no different from other tractors from the 4 speed transmission back. Except its industrial and doesn’t have a 3 point hydraulic set up or a PTO.   There are three oil compartments in the tractor.  The transmission and torque are together.  What is used on other Ford tractors with hydraulic oil is the center section under the seat and then you have the rear end oil compartment for the differential.  (excludeing Ford 8N, 9N, 2N tractors) Their oil is shared by the transmission, hydraulic system and rear differential.

The Ford 621-62 has a transmission oil temperature sending unit on the right hand lower side of the clutch housing.   It’s taking the temperature of the transmission oil. This unit screws into the hydraulic tractor clutch compartment section behind the torque converter (second section).

This tractor has an external transmission oil filter. In line with the transmission oil cooler.  The oil cooler is in the lower radiator tanks and the lines hook on the front lower radiator tanks.  Transmission oil cools and warms up in the tractors anti-freeze.  Some of these coolers in the lower radiator are a flat brass cooler and others are a round thin walled cooler, similar to a paper towel roller.

Two oil supply lines travel from the right hand side of the clutch housing to the oil cooler, then through the filter and back to the transmission clutch cavity of the clutch housing.

There are no oil lines inside the 4 speed transmission or the clutch housing.  There is a large cavity under the transmission input shaft to the transmission clutch area so the 4 speed transmission and the hydraulic clutch share the same oil. There are oil passages in the clutch housing from the outer steel lines on the right hand side to the transmission pump inside.  No lines at all inside this unit.

This particular tractor was leaking transmission fluid in the clutch housing area of the torque converter a NO-NO.  Upon inspecting, it appears the last seal installer, damaged the seal outer shell on the front of the transmission pump.  You could see dents all the way around the seal.  This happens when you use a hammer to install a seal.  It distorts the seal lip area and actually pulls the lip seal away from its intended contact area.

The torque convert needs to be pressure tested for leaks at its weld or cracks in the shell.  While the torque converter is out you should remove the two drain plugs and completely drain it.  Flush it with clean mineral spirits or solvent.  It’s also good advice to fill the torque converter with fresh oil, before installing the engine.    This assures the torque will be lubricated as soon as the engine starts and helps prime the whole system.

Clutch Pack:  The clutch pack should be disassembled and checked for bad clutch plates and discs.  Also a new piston “O” ring should be installed.   All three steel sealing rings should also be replaced.  Check for grooves where the sealing rings ride.  If you install new steel sealing rings in a groove, it will not seat properly and most likely it will affect the clutch pack by allowing oil to bypass.   The clutch pack is easy to disassemble.  Remove the inner snap ring and the parts will pull out easily.  To remove the piston you will need to put the clutch pack in a press to depress the heavy return spring so you can remove the center heavy snap ring.  Inspect the piston for cracks and scores. Especially in the seal areas (inner and outer).  A control valve is mounted on the side of the clutch housing.  It supplies oil pressure to the tractor clutch pack.  Adjustments can be made to the clutch pedal for the control valve.

I hope this helps any of you who have been trying to get to the bottom of this tractor.   It would appear to me by the looks of the internal four speed transmission gears that the torque converter is kind to it and the torque converter absorbs any major shocks to the driveline.   The clutch pack is sturdy and well built.  Massey Ferguson 205 uses a clutch pack/torque converter in their forward/reverse power shuttle shift but it’s not as heavy duty as this Ford.  The Ford has larger clutch plates, clutch hub and piston.  Massey Ferguson used a 6 speed standard transmission in conjunction with its torque converter/trans system.  If kept well maintained, these units will last a long time.

Thanks again for visiting Bob’s corner.  For questions or comments e-mail: bobscorner@owossotractorparts.com