Two Cylinder Magazine

The John Deere Two-Cylinder Clutch
Part II
by Mike Williams

In Part I of this series, overhaul and repair procedures for the clutch pulley, clutch operating sleeve, toggles, and dogs were covered. With those parts in like-new condition, it’s time to move on to things that need to be examined, and perhaps repaired, before installing the clutch pulley on the crankshaft.

The area of the crankshaft where the inner bearing (a bushing, actually) of the clutch pulley rotates needs to be measured to make sure that it is within specification, as does the bronze bushing in the clutch pulley. If the crankshaft measures within tolerance, a new bushing can be purchased and installed in the clutch pulley. If the surface on the crankshaft is worn undersize or is out-of-round, the crankshaft must be ground and a new bushing machined for the clutch pulley to fit the crankshaft. The running clearance on the bronze bushing is 0.0015" per inch of diameter.

The race for the outer clutch bearing is on the outer end of the crankshaft and is replaceable. I recommend replacing this race as a matter of course. However, there is one exception: On the “50”, “520”, and “530” Tractors, instead of fitting a bearing race for the outer clutch pulley bearing, Deere opted to specially harden this area and the bearing runs directly on the crankshaft. If you have a crankshaft from one of these tractors that is worn in this area, it can be repaired; but, it will be expensive. The hardened area can be machined away with carbide tooling, then welded, machined to specification, and then heat-treated once again to provide a hardened surface.

The surfaces of the clutch pulley, sliding disk(s), clutch driving disk and pressure plate (adjusting disk) that contact the clutch facings should at the minimum be bead-blasted to remove rust and other crud (scale, etc.). These surfaces need to be as smooth as possible. If they are rough, they need to be ground with just enough of a cut to make them smooth. A tool post grinder is the best way to do this, as doing them in a lathe is just short of impossible. Once the parts are clean, inspect them for heat cracks and checking. According to a John Deere Service Bulletin, as long as cracks or heat checks do not extend into the hub, the parts are serviceable and need not be replaced.

New clutch facings and disks are still available from Deere but, in most cases, the clutch adjusting disks are not. If you have a good one, be careful with it, as good used ones are becoming increasingly more difficult to find.

The roller bearing in the clutch needs to be cleaned and re-packed with synthetic grease. If there’s any question of whether the bearing is serviceable, replace it, as a bad or worn bearing can cause troubles you don’t even want to think about. These bearings are available from John Deere or almost any bearing supply house.

With the bearings in good shape, one other thing must be checked before installing the clutch, and that’s the end play of the crankshaft. Crankshaft end play should be no less than 0.005" and no more than 0.010". Excessive crankshaft end play needs to be adjusted to back to specification before installing the clutch pulley, as side-to-side movement of the crankshaft will adversely affect the operation and adjustment of the clutch.

One last item remains to make the clutch assembly like new; new rivets and spring clips for the clutch cover. These are available new from John Deere at a very reasonable price. I use a back-up tool made from a piece of 1-inch round bar stock and a piece of 1/2" threaded rod to install these rivets. Cut the piece of bar stock so that it is about one-inch smaller in diameter than the inside of the clutch pulley, and then cut it into two equal-length pieces. Drill and tap one end of each piece about 1-1/2" deep for 1/2-13 threads. Mill or drill a “pocket” in one end of one of the pieces of bar stock, just deep enough to locate the head of the rivet. Grind the blank end of the other piece of bar stock to approximately conform with the shape of the inside of the clutch pulley.

Assemble the back-up tool, slide the rivet through the spring and pulley casting. Place the “pocket” end of the back-up tool against the head of the rivet, and then screw the two halves of the tool apart until the rivet and spring are held tightly against the pulley, with the opposite end of the tool firmly in place on the other side of the pulley. Once the rivet and spring clip are firmly in place in the clutch pulley, I use a No. 2 welding tip on the torch and heat the protruding end of the rivet cherry red, and then gently peen the rivet with a small hammer. The rivet may have to be re-heated two or three times. Once the counterbore is filled, excess material can be filed smooth, making a nice, neat job.

Now, the clutch pulley can be installed on the tractor. Install the inner clutch facing, and then install the drive disk. The proper installation of the drive disk is a very critical area, and care must be taken to ensure that it’s done correctly. Installation procedures for the clutch drive disks were discussed in an article on pages 40 and 41 of the July-August 2005 issue of Two-Cylinder. Some wear on the outside splines, where the sliding drive disks run, can be tolerated, as can some wear in the splines of the sliding disks. A common clutch complaint is that the clutch is noisy or “rattles” when released. This is because of the wear between the splines of the clutch drive disk and the sliding disks. The only solution to this complaint is to replace everything, which can be quite expensive and is only necessary if the tractor is being used regularly in the field. A good way to avoid the noise is to release the clutch, take the tractor out of gear, set the brakes, and re-engage the clutch, which will eliminate the noise and reduce further wear.

Model “A” clutch lever and link welded shut prior to re-drilling to correct wear in the holes.

Once the drive disk has been installed, the clutch disks and sliding drive disks can be installed. It’s a good idea (especially on tractors with multiple sliding disks) to check these parts for burrs and notches, and smooth them if found. Then, lightly lubricate the splines with a coat of synthetic grease and install. Assemble the rest of the clutch, but for now don’t try to adjust anything, because a number of other parts need to be checked and perhaps repaired so that your newly rebuilt clutch will work as its designers intended.

Now is a good time to check out the clutch linkage and operating shaft. Many of the joints will likely be worn, and will need to be repaired for smooth operation of the clutch. Let’s start with the clutch lever itself. Remove the lever and check for wear in the pivot bore, and the holes for the operating rod and pin. If these areas are worn, they need to be bored and a bushing created to bring them back into specification. The clutch lever end of the operating rod can be welded up and redrilled. Check the pivot pin for wear, as well. If the pivot pin needs to be replaced, use a clutch pivot pin puller! Trying to beat out a pivot pin with a hammer will usually result in breaking the ear off of the first reduction cover.

The yoke on the other end of the clutch operating rod is made of malleable iron. If there is excessive wear in the yoke, braze the holes shut and re-drill them. Do not attempt to weld them shut with a heli-arc or a stick welder, as the yoke will break.

A broken clutch operating shaft, showing the results of tightening the clutch too tight, which can cause fatigue cracks and breaks at the top of the splines.

Now to the operating shaft: If there is wear in the pivot pin hole, weld the hole shut and re-drill it (7/16" for early “B” tractors, 1/2" for all other models). The operating shaft should be inspected closely for vertical cracks, especially just above the splined area, because if the shaft breaks, the clutch cannot be released. If there is wear in the area where the shaft runs in the bearing housing, it can be built up with bronze and machined to specification, but usually the wear will be in the top bore of the bearing housing. The housing can be bored for a flanged bushing. There should be 0.005" clearance between the shaft and the bushing. The lower bore of the bearing housing seldom wears, and in most cases can be used as is.

Model “A” clutch bearing housing showing
flanged bushing to correct wear.

The splines on the operating shaft should be inspected for wear, as should the the splines in the clutch fork. Minor wear can be tolerated, but excessive wear in either part means replacement is necessary. Also inspect the snap ring groove on the operating shaft. Lately, if there is wear in this area, I’ve been machining the groove 0.030" deeper, and using an “E” clip which is available from McMaster-Carr Company of Chicago, Illinois. It’s easier to install than the original snap ring, and I’ve had good luck with this setup.

The other area where excessive wear is often found is in the bronze clutch collar. The original working area of the collar is 5/16" thick from the factory. If there is more than 1/32" wear on one or both sides, the collar should be rebuilt with silver solder and machined back to a thickness of 5/16". I do not recommend rebuilding a collar with more than 1/16" of wear on one or both sides, as the silver solder alloys are very expensive. Availability of new collars is spotty, so, if you can’t find a new one, try to find one with the least amount of wear.

With all parts renewed, it’s time to assemble the clutch operating parts. When assembling the clutch operating shaft and clutch yoke, the arm of the operating shaft needs be 90 degrees from the yoke, or as close as is possible. On some tractors, the angle may be very slightly more or less, but the operating shaft and yoke must be positioned correctly or the clutch will not work.


View of clutch operating shaft showing built-up and re-machined area, plus snap-ring groove machined for type “E” retaining ring.	Rebuilt bronze clutch yoke after being rebuilt and re-machined.

Install the clutch operating assembly into the tractor and hook up the clutch linkage. Now it’s time to adjust the clutch. My method of adjusting the clutch is this: Tighten all three of the adjusting nuts evenly to “snug”, take out all play, and then back them out until it takes pull of 90 pounds at the end of the clutch lever (70 pounds on an early “B”) to lock the clutch into the engaged position. More force than this is just overkill; multiplied through the pivot points, there is a tremendous amount of pressure on the clutch parts, and making the lever hard to snap in and out will just stress the clutch and won’t make it hold any better.

Model “B” pulley brake arm rebuilt with a
flanged bushing and a new riveted-on brake pad.

Now that you’ve rebuilt your clutch from end to end, it’s time to set the pulley brake, which is essential for proper clutch operation. On the “Lettered Series” Tractors, if there is wear in the bore where the operating shaft passes, it can be bored and then bushed back to size. Many times, the pulley brake pad has worn completely away, and the casting itself is somewhat worn. The casting can be built back up with bronze, and then sanded to shape. Rivet on a new brake pad. It’s nicer and neater than the clip-on brake pad.

Adjust the screw on the pulley brake so that it just clears, and does not drag on the clutch pulley when the clutch is engaged. If there is too much clearance, when the clutch lever is pulled back too far it can actually move the operating sleeve enough to re-engage the clutch.

On the “Numbered Series” Tractors, the pulley brake is operated by a pin in contact with the clutch yoke. Setting the pulley brake correctly on these tractors is also very important, and must be done using the proper method. However, there were a number of changes made in the way that the adjustment was done over the years, and the procedure differs between models. Lack of space prohibits going into all of the different procedures here. Instead, my best advice for setting the pulley brake on the Numbered Series Tractors is to obtain a Service Manual and take the time to study it carefully, as the adjustment procedure on the later First Numbered Series Tractors, and the “20” and “30” Series Tractors, though not difficult, is time-consuming and absolutely must be performed “by the book” for best results.