Clutch Chatter Trouble Shooting on Older Fords

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A frequent complaint among owners of older manual transmission cars and trucks is the issue of clutch chatter. This annoying condition rears its ugly head when the driver attempts to engage the clutch from a full stop, in either first gear or reverse gear. It can be more obvious in one versus the other. Once the vehicle is moving, the issue is generally not noticed during higher speeds and shifting into the higher gears. This list of conditions may help you pinpoint the problem area in your vehicle. Sometimes the repair is fairly simple and inexpensive, and other symptoms are more difficult to make the necessary corrections. If it's a subtle condition in your car, you may decide to adjust your driving (clutch engagement) technique to minimize the chatter and let things go. If the chatter is shaking the entire car badly, you should try to fix the problem as the heavy vibrations can cause other damage to the vehicle over time. 

First, always be sure that you have the clutch properly adjusted. Your clutch linkage has an adjustable clevis that allows you to adjust the free play in the clutch pedal. This means that when adjusted properly, you have approximately 1” to 1˝” of pedal travel at the upper range (pedal up) before the clutch begins to press on the pressure plate fingers (pedal moving down). By disconnecting the clevis to the clutch release shaft, you can rotate it to lengthen or shorten the linkage, then reconnect the clevis. This procedure is usually done from below the car, but the adjustments might be done from inside the Ford 1932 through 1948 cars with the floor boards removed.

The following is a list of possible conditions that might affect the smooth action of the clutch. These are not listed in any particular order of importance.

 

1)    Worn out clutch pressure plate (loose or broken springs, warped friction plate, broken – bent – or out of adjustment fingers. REMEDY: replace pressure plate with a new or rebuilt . If the pressure plate is known to be recently new or replaced, and is the old style with small adjustable contact bolts on the three fingers, they must be adjusted to provide the same contact point with the clutch release bearing. This is usually done by the clutch manufacturer. Some pressure plate fingers have small adjusting bolts/screws at the finger ends. These are not for primary clutch adjustment, but are to assure that the fingers come into contact with the release bearing at the same moment.

2)    Loose pressure plate bolts.The six bolts that hold the pressure plate to the flywheel should be tight (with lock washers) and torqued properly (17-20 ft/lbs). REMEDY: Tighten to spec.

3)    Worn out clutch disc. Particularly the possibility of a broken/cracked marcel plate, or loose/broken springs. The marcel is the thin steel plate that is sandwiched in the two layers of friction material. These thin plate have a slight curve to absorb sudden clutch engagement. Many clutch discs also have several (4-5-6) tightly coiled springs captured around the center hub.  REMEDY: Replace with a new or rebuilt clutch disc.

4)    Worn or warped flywheel. If the surface that mates with the clutch disc is scored, or the flywheel is warped, the clutch disc will not mate evenly with the flywheel. REMEDY: replace the flywheel with a new one, or have your flywheel (or another available used one) resurfaced at a machine shop. This will true up the friction surface again. Check the used flywheel for fine cracks in the friction surface before spending money  to have it resurfaced as they may become a problem again after a short time of use. Also, check the runout of the flywheel with a dial indicator. You should not see more than 0.005” of runout (measured near the outer diameter of the flywheel).

5)    Worn, saggy, oil-impregnated motor mounts. After time, the rubber mounts become too soft and allow too much lateral movement .This would include both the front motor mounts, and the rear mount which is bolted  to the rear of your transmission. REMEDY:  If you have the 1932-36 type rear support, you have the large round rubber ring which was vulcanized to the metal support on the  trans. This type requires disconnecting the torque tube cap, and unbolting the rear support & bearing retainer from the back of the transmission in order  to replac the rubber component. If you have the 1937-41 style support, your trans is supported by the same “donut” style mounts as the front of the engine. They are easily replaced by jacking up the trans slightly, and unbolting the donut mounts to install new ones. The 1942-48 rear support uses a single saddle-shaped mount (rubber bonded to steel)  t hat again is easily removed when the trans is lifted slightly with a jack. The 1949-53 type rear supports are easily accessed under the trans tail housing under the support cross member.

6)    Any loose bolts that attach the transmission to the motor, or the flywheel to the crankshaft, or the trans to a bell housing if so equipped, or to the torque tube. REMEDY: Tighten all bolts. Replace lock washers with new ones if needed.

7)    Anti-chatter rods. Ford installed these two steel rods on most V8 cars and trucks from 1933 through 1941. Called radius rods, they carried Ford’s basic part number 6044, and they were produced in three different versions (lengths). They were not used with 1942 or newer vehicles. The rods can help control engine front-to-rear movement, and are fitted into “ears” on the back of the engine block, and bolted to the frame’s X rails. The forward ends were threaded with fine thread and used a castellated nut at the end. REMEDY: Check the rods for tightness. Adjust the nut against the engine block to put some tension on the rod. I do not have any specifications for this, so you will have  to use common sense on what you do. Over-tightening the nuts will put some strain on the casting of the engine block at the ears, and would pull the motor backwards against the front motor mounts.

8)    Loose radius rod connection for the rear end, or loose rear spring mounting, or loose rear shock absorbers. Consider that if the rear end/axles were allowed to shift about, you could aggravate the smooth operation of the clutch from the natural tendencies of the rear end to twist and move when under load.  REMEDY: Check all mounting points for the rear radius rods, the spring U-bolts, the spring shackle bushings, and shock absorbers for loose hardware or worn bushings, and tighten as needed.

9)    Worn engine main bearings. If  he mains (particularly the rear main with its thrust surfaces) are worn, the engine’s crankshaft will have too much front -to-rear movement, which will contribute to clutch chatter. REMEDY: This can be an expensive repair obviously. The engine must be disassembled and the main bearings checked and replaced.

10) Looseness or damage in the driveshaft/torque tube (32-48 closed drive). This is difficult to spot from any external inspection. Obviously, check all bolted connect ions. A complete disassembly would provide a more complete picture of problems here. This is more of a last resort in  the process of checking for clutch problems.

11)  Improper mounting between  the transmission case and the bell housing. REMEDY: Check mounting surface for burrs or dirt that may prevent both surfaces from continuous contact at all points. A cracked gearbox front housing could also contribute to misalignment.

12) Poor contact surface where the clutch release bearing hub rides on the transmission front bearing retainer. REMEDY: Check bearing hub for excessive wear inside the bore. Check the retainer for wear on its outside diameter (front to rear). Replace either part if you find that the hub can wobble as it moves back and forth on the retainer.

13) Bent clutch release fork  tips. REMEDY: If the fork  tips are not aligned in the same plane, replace the fork with a new one, or a good used one if available.

14) Worn pilot bearing in the flywheel. REMEDY: The bearing helps keep the input shaft (which  the clutch disc rides on) aligned. If you have the bushing type bearing (oilite) it may be badly worn inside. Replace with a new bushing bearing or the sealed ball bearing type. 

15) Worn pilot end on the front of the transmission input shaft (main drive gear). REMEDY: Replacement of this gear requires pulling the transmission and tearing it down to replace this gear. Normally, the pilot end may suffer a slight amount of wear that a new pilot bearing in the flywheel can compensate for, but occasionally the pilot is too worn and will allow the input shaft to move excessively during clutch engagement.

 

Don’ t forget that the chattering problem can be a sum of several problems, each of which is slightly off the original factory installation. Replacing/repairing one single component may reduce the chattering, but not eliminate it if there is a problem elsewhere. Try to address all the possibilities.

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