MF 35 (and up) Tractor Assembly Notes|
by Jack Wetmore
Massey Ferguson 35 Tractor Parts
These assembly notes are for Massey Ferguson tractors with a two stage clutch and 6 speed, 8 speed and mutli-power transmissions. I see a lot of discussion forum messages regarding damaged clutches from improper assembly.
The objective is to have the engine and transmission slide together safely and easily until the gap between the two halves is less than 1/4", BEFORE tightening any of the bolts holding the two together.
Using bolts to draw the two halves together will damage the PTO clutch, sometimes the main clutch, and probably the input shaft retainer housing - the casting which carries the throwout bearing. The outer (PTO) shaft can be driven back, forcing the 4" d (+/-) snap ring in the back to break off the retaining groove in the casting. If you're lucky, the snap ring and casting pieces don't chew up any of the transmission gear teeth when you start up.
If you have a punched-out PTO disk center, pull this casting to check it. If it's broken, be sure to clean the bits out of the transmission. Some have a gasket or o-ring to seal them, and these may be destroyed in the process. We reassemble with a light butter of silicone.
It's a really good idea to replace the seals now while you have it apart. Transmission leakage is a common problem, and the seals are cheap. Seals for the six speed unit are 195 501M1 and 195 503 M1, aftermarket numbers 50151S and 450400. There are a number of different seal combinations for the larger shafts in the other transmissions. The only aftermarket sizes I've found are a National 451100 for the small shaft on the 8 speed, and Nat 1037 for the small shaft on the multi-power.
On the multi-power units, the sealing rings will likely require replacement. The larger ones (186 198 M1) are available aftermarket for under $5 each. Haven't found anyone but Massey Ferguson who carries the smaller ones (186 581 M1).
If the casting is damaged, it can be reworked at a machine shop, or replaced for $250 or so US (aftermarket 2000 prices). If the present casting has a sleeve bearing rather than a roller bearing at the engine end, a new throwout bearing carrier ($25+/-) will also be required.
Checks Before Clutch Assembly:
Clutch assembly and alignment is covered well in the shop manuals. Before reassembling, however, some preliminary checks will help assure a successful repair job and eliminate the need for tearing the tractor apart again because of a dragging clutch.
Check the pilot bearing in the flywheel; replace if it is at all rough. It's cheap - a standard 6203 ball bearing.
You should check both clutch disks for runout or wobble. 1/16" or more will cause dragging and gear grinding when shifting. We recently received a newly rebuilt disk with about 3/16" runout. We've also had the situation where the center on the larger disk had been pushed forward by a previous incorrect assembly and rubbed on the pilot bearing housing, causing dragging. This one took me three splits, and a bible-sized volume of profanity, to find.
Runout can be measures by placing the clutch disks on the input shafts in the front of the transmission, and spinning the disk. The disks should slide on smoothly. If they don't, there are burrs or dirt on the disk or shaft splines that could cause later stiff movement and a dragging clutch. Clean them up.
You check the hub-to-flywheel clearance by pressing the large disk against the flywheel. Less than 1/32" will allow the hub to contact and drag when the lining wears down; if it touches now the clutch will drag immediately.
It's nearly impossible to correct either of these problems satisfactorily in the shop; a replacement disk is the best solution.
At this point, before clutch reassembly, it is a good idea to remove the three pressure plate free play adjusting screws and lock nuts (located between the springs around the perimeter of the pressure plate). Make sure the wrench flats on both the cap screws and the lock nuts are sharp (not rounded off). Clean the casting holes so the bolts go in easily. Lubricate the bolt and lock nut threads with an anti-seize compound.
These can be adjusted from below the tractor without splitting it. It's cramped quarters in there, and the threads usually set up quite firmly over time. Making sure the heads are good, and the cap screws turn freely now makes the job a lot simpler when needed 5 or 10 years down the road because the PTO won't stop.
When assembling, double-check the alignment of the clutch disks on the clutch pilot tool. This tool should fit snugly in each of the clutch disks. A few thousandths off here will cause hours of grief trying to get the splines engaged. If the pilot tool can be inserted full depth and removed easily with everything tourqued up, it's ok.
After the clutch is installed on the flywheel and the release lever bolt heights set, the primary pressure plate free play is set with the three cap screws you just cleaned up. This adjustment determines when the PTO clutch starts to release - when you feel the extra pedal pressure about half way down.
Various books call for .080 - .090". This setting is often too large - the PTO does not stop completely when the pedal reaches the floor, and you cannot engage the PTO lever without grinding. A setting of .055 - .065" has proven satisfactory.
Safety and Lifting:
Once the clutch is installed, the engine can be mated to the transmission.
Safe and damage free assembly requires positive control of both engine height and angle, and about 4" of front to back travel for either the engine or the back half of the tractor.
A concrete floor is by far the best work surface. We use a chain hoist and a $40 engine lifting equalizer for the front, and a 2-ton wheeled floor jack under the transmission with the handle out under the PTO.
The engine equalizer is a must; other combinations will work for the rest.
Safety blocking is placed under the engine (8 x 8, 2 ft long, blocked securely up to about an inch below the pan). A piece of 3" or 4" channel 3 ft long on jack stands or blocks about an inch below the very front of the transmission bell housing will provide safety for this part. The clearance spacing is not critical, but the closer the better. How far do you want it to drop if something lets go?
The hydraulic jack plate is set under the transmission about 6" back of the channel, to allow the jack and transmission to move forward the 4" or so without hitting the safety channel. The jack stands or blocking under the channel are spaced out to the sides so the jack wheels can move forward without interference, and should have clearance in front of the tractor wheels as well.
Two locating studs 7/16", coarse thread, 4" long (bolts with the heads cut off, or redi-rod) should be screwed into either side of the transmission in holes about half way up to guide the two halves together. Carefully clean the splines on both transmission shafts, and oil lightly.
Just before you lift the engine clear of the floor or bench, recheck the engine equalizer chains, clevises and mounting brackets for security. We had a chain jump off the locating slots once, because it wasn't seated correctly. Check to see that the engine is aligned vertically - you may have to reset one of the lifting chains if one side is high.
Moving the Two Halves Together:
The following discussion assumes moving the rear section forward. If you're using a moveable crane to hold the engine, reverse the movement instruction.
Raise the engine to the proper height and adjust the equalizer until the spacing between the transmission and engine mounting plate are about the same top and bottom - about 4". Move the rear unit forward about an inch, engaging the locating studs. (We use a bar on a 6 x 6 behind one rear tire, prying to lever the wheel forward while holding the jack handle to keep it from swinging. Gives really positive control.) Block the wheel from rolling back. You may have to lift one side or the other of the engine. If the engine is slanted too much you may have to reset the lifting chains.
Recheck the alignment - this is the key to the whole operation.
The clearance between the transmission and engine should be about equal at the top and bottom and side to side; adjust as necessary with the equalizer and hoist. Be careful not to lift the transmission if raising the hoist.
Engaging the First (Traction Clutch) Splines:
Move the rear unit forward another inch. It will probably stop about 2 1/2" from the engine adapter plate as the traction (larger) clutch disk splines contact the transmission shaft splines. Block both rear wheels and set the brakes. Put the transmission into high gear and high range. (This prevents the transmission shaft from turning.)
Turn the engine in one direction with a pry bar or screwdriver on the ring gear until the clutch splines engage and the units slip together a bit. Keep turning in one direction - reversing direction will require a lot of travel to overcome the backlash in the gear train. Should not take more than a dozen teeth if the two units are properly aligned.
Out of gear, brakes off, blocks out, move the unit forward another inch or so until there is a bit of forward pressure on the engine. Block the wheels against rolling back. Clearance should be down to an inch and a half or so if the splines have meshed properly. Check engine/transmission alignment; readjust if necessary.
Recheck the safety blocking under the engine and transmission to ensure they are secure and lined up properly.
Engaging PTO Clutch Splines:
Place the PTO shift lever in the engine drive position. Insert a rod or screwdriver in the hole in the PTO shaft at the rear of the transmission, and rotate the shaft a bit. If it turns freely, the engine/transmission gap is too wide and the PTO splines have not contacted the disk.
Close the gap by pushing back on the engine, rocking a bit, or carefully tightening a bolt on either side of the mounting plate. Use no more than 5 foot-lbs of tourque - a bit more than finger-tight. If more force is needed, something is not lined up, and you will damage the clutch.
If the PTO is locked, there is too much pressure on the clutch - pry the engine forward a whisker until you can just rock the shaft. Rotate the PTO - you will feel the splines "clunking" as they move past one another. You will feel the spot where they seem to be free, and the engine should slip closer together. The gap should close to 1/4" or so, with a bit of help.
Recheck blocking security under both the engine and transmission so they won't fall on you during the next in-close operation.
It is now safe to bolt the two units up, tightening evenly from both sides until the gap disappears. Remove the locating studs; remember that there are two or three different bolt lengths joining the two halves. If your bolt goes nearly to the bottom, or has more that 5/8" of the bolt shank showing before you start turning, it's probably in the wrong hole.
After you get her all snugged up, sit down for a few moments and reflect on a job well done!
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