Clutch Tech Tips


Clutch Grinding Noise

Farm Jeep underside

Q asked on the Bulletin Board: "I have a 1951 Willys Jeep that is making a grinding sound, sort of like there are little rocks rubbing when I push the clutch in. A neighbor said it might be a throwout bearing. Is this possible? Where can I buy one and is it possible for me, with basic tools and knowledge, to replace it? The manual that I have does not show how to do that. Today I had a hard time putting it in gear, then it worked OK, but grinding sound got louder. Any advice appreciated."

Steve: "Sounds like your throwout bearing is about ready to give up the ghost. That's the bad news. The worse news is that the transmission/transfer case will need to be removed in order to change it out. I wouldn't even consider NOT replacing the clutch plate and pressure plate, and resurfacing the flywheel while it is apart. They're not horribly expensive, and it is a bear of a job dropping the tranny/transfer assembly. Those buggers are HEAVY! The whole job is not all that difficult, just a bit of a challenge getting the tranny in and out. RENT A TRANNY JACK. Much safer that way."

Dave: "You're definitely going to have to tear it down before you have a catastrophic meltdown. I've done this job both ways and I think it is easier to pull the motor. At least this way, you're mostly working from the top. Get a motor hoist to simplify the job. While you have the motor out you can do those 101 things that you always need done under the hood but have always put off."

Tim: "I agree with the previous posts -- actually the trans/transfer case comes out really easily, but use a jack to support it as it slides out, so you do not put any pressure on the transmission input shaft. You do not want to bend this. Don't forget to replace the pilot bushing (the bronze bushing in the center of the flywheel). Probably a good time to reseal the front of the T90 gearbox to get rid of that annoying leak as well."

Jyotin: "You'll probably notice that all the replies to your post are similar. However, you've asked several questions. First, the throwout bearing sounds as if it could be the culprit, however the clutch and/or pressure plate could be failing too. In any case, it has to come apart, so at this point it doesn't really matter what is wrong.

"Now for the second part of your question. With basic tools and basic knowledge you are better off to take it to a shop to have it done. You cannot just replace the bearing -- the clutch and pressure plate and pilot bearing should go too. You may need a new fork or fulcrum and other hardware upstream towards the pedal. When replacing the clutch you'd need to remove the flywheel and have that turned too. Then you'd have to put the flywheel back on and make sure that you have aligned the timing marks, if any. Then you'd need to put it all back together. Getting the transmission back in place makes taking it out look like child's play. I'd take it to a reliable shop to have it done. The only difference in cost would be the labor charge, and it is well worth it to have it done right. One mistake in doing it yourself means you get to do it all over again..."

Tom had another idea: "I did several clutches in my life time on my Jeeps. For me it was always easier to pull the motor than to drop the trans and transfer case.

"You leave the radiator on the grill, disconnect the upper and lower radiator hoses from the engine block. Take the grill off as one assembly after you disconnect the wiring harness on the fenders. Take the battery out for safety reasons. Use a couple of head bolts to rig your chain lift from the motor. Use an offset wrench through the accelerator pedal linkage hole in the firewall to get to the top tranny bolts. Unbolt the motor mounts from the jeep frame, not from the engine block. Swing the little piglet out and change your clutch, front seal and throwout bearing. Oh, and resurface your flywheel while you have it out before you put the new clutch in. Re-rig the motor so the front end hangs about an inch lower than the rear end, swing it in place, bolt it all back up, pour your antifreeze back in, check for leaks and you are good to go. With air tools you can do it in about 3 hours in the freezing cold. I know, I did a few that way.

"I even did the V-8 clutch that way on my 1972 304 V-8. I prefer doing it this way as I am not on the ground, fighting heavy components, driveline re-alignment, and other issues."

Clutch Linkage Upgrades

Clutch linkage kitSeen at left is a clutch linkage kit available for about $60 from suppliers such as The Jeep Guy.com. But instead of just replacing clutch components, is it worth considering any upgrades?

Matt inquired on the Bulletin Board, "What setup are most people using on a stock F-134? Anyone used a roller chain from Advanced Adapters? They state it will not work on a stock bell housing. Any tricks for a more trail-dependable linkage?"

Steve: I used to break the 1/4" rod that went from the pedal pivot to the control tube pivot all the time. Then I took 2 pieces of flat stock and drilled them on each end and sandwiched them around the pivots, and used grade 8 bolts.That lasted for a long time. Right now I have a 1/4" rod with a clevis on each end which is adjustable. I'm still doing my restore so I have not been able to road test, but it is up on blocks and I can start it and go through the gears and it seems to work fine. But in a pinch, a piece of flat stock cut to the proper length with a hole in each end and some good grade bolts could get you out of the woods.

Jeff: "I copied the AA setup, bought several parts from them to simplify the mod. I have a stock engine, stock trans, even a PTO shaft running thru the sama area. I was having clutch problems when the frame was flexed up on trails. Stopped my problem on all but the most twisted up trails. I think it cost me around $70 to modify their design to fit my application.

"I bought #50 chain, 1 sprocket and bolt from tractor supply store, misc. parts from AA (chain to cable, chain to pedal parts) to help out. I ended up using a CJ-2A clutch cable instead of CJ-5 part; I think the CJ-5 was 11" long and the CJ-2A part was 9" long. I built my bracket out of 7075 T6 Alum. But 3/8 steel will work."

Oldtime: "This is really a great topic and deserves a hard look! Here is a quote from the Advance Adapters (AA) Catalog:

Jeeps 1941-1971: 'These jeeps use a torque tube that pivots off the stock jeep transfer case. The clutch pedal and bell housing arm use rods that connected to the transmission torque tube. The design was more than adequate for small 4 cylinder jeep vehicles. On V-6 and V-8 conversions that are equipped with heavier clutches, a greater mechanical advantage is required. We offer a new assembly that removes the torque tube and rods and replaces them with a sprocket and chain. This controller utilizes the stock pedal and clutch arm. It can be easily installed and offers a great mechanical advantage on any vehicle whether stock or converted.'

"I say: for starters it is correctly referred to as a 'lever and tube' not a 'torque tube' as is indicated by AA. Furthermore, directly speaking, the engine size has nothing to do with clutch control adequacy. Only the required pressure plate activation force is involved. According to AA their product utilizes a sprocket. A concentric sprocket allows absolutely no mechanical advantage as does a lever or a cam. This is an important consideration due to the various clutch activation forces that are involved for differing clutches. A simple roller bearing sprocket is merely a device to efficiently divert the pull direction of the linkage. So apparently the AA unit does not, as it claims, offer a mechanical advantage unless this utilizes a sprocket cam (a non concentric sprocket) which is not mentioned.

"From my understanding, what the AA product does provide is an efficient bearing face to reduce friction. This standard linkage problem can be solved by better methods in my opinion, and still retain the stock linkage components. Not mentioned is the AA mechanism's advantage of flexibility due to the use of a long chain. A cable going around a pulley wheel would function similarly. Here again stock linkage can be modified to allow for more frame twist. There are excellent and simple modifications that can be made to the existing linkage. But first we must fully understand the standard."

Parts List

Early CJ Clutch Control

"To upgrade without detailed observation and analysis of the standard is only foolishness. Clutch control gives one the ability to effectively operate the clutch; to smoothly engage or to disengage the pressure plate with the driven disc. We will begin at the interface between man and machine, 'the pad.' The earliest MB and GPW pads were made of cast steel. Having multiple raised 'nubs' they provided for a non-slip human to machine contact. Next in pad evolution came the stamped steel pads referred to as 'diamond top pads'. Here the potential for foot slippage did increase somewhat. Lastly from Willys Motors came the pads with grooved rubber covers. Those are the supreme pads for barefooted operation.

"The slight differences of the pad shaft lengths has virtually no effect upon the input leverage because the pedal (long lever) length remains constant for all early CJ's having frame mounted pedals. Since the clutch and all other basic Jeep controls are frame mounted, we can and do have a true driveable chassis. (See the CJ3B Chassis Test video at YouTube.)

"The pedal (long lever) is mounted to and pivots at the pedal shaft. The pedal shaft is secured and rotates in the pedal shaft retainer bracket which is mounted to the frame. A short lever on the pedal shaft weldment extends from the shaft for output. Leg pressure is amplified by the pedal (long lever) and pivots at the pedal shaft thus reversing direction of applied force. The leverage available in this portion of the clutch control is a predetermined ratio that does not change over the early CJ's. A 1/4"-diameter rod of primitive design connects the pedal shaft output lever to the input lever on the control tube. The control tube has two main functions. To again, reverse the direction of the applied force and to fine tune the mechanical advantage. Here several different lever lengths were incorporated for different clutch makes, clutch diameters or transmissions. Therefore appropriate lever length and linkage combinations need to be considered.

"These control lever and tube weldments all pivot on ball studs attached at both the frame and at the transfer case. The ball studs are a primitive bearing surface. Normally the control tube is positioned horizontally and not at odd angles to the direction of pull. If you have a lowered rear engine crossmember or have otherwise affected the stock symmetry, linkage problems may occur. An adjustable clevis yoke attaches the cable control to the output lever of the control tube. At its other end the cable control attaches with a ball swage into the control lever socket. This clutch control lever (fork) applies final mechanical advantage against the ears of the carrier which positions the release bearing. All that aside, we now seek to take look at typical worn parts and provide an adequate solution to upgrade the components for more efficiency more dependability and a longer service life."

Clutch Control Upgrade

"Typical clutch control component wear or failure indicates the weak links to be addressed. Attempting to remain near standard in design, here are my preferred solutions.

"The first area of notable wear is the pad itself. The MB cast steel nubs are easily built up. The diamond top pads are not so easily repaired. The rubber covered pads generally are in found in fair condition.

"The next area of concern is the pedal shaft pivot wear that manifests as pedal slop. Beginning with model M38 the military pedal shaft bracket is superior to the CJ pedal shaft bracket. A complete upgrade to the military pedal shaft and frame mounted bracket is one consideration, or a good upgrade repair of the stock system can be used. Rather than simply replace worn components, here I suggest one reuse the stock parts. Surface weld the interior diameter of the pedal shaft bracket with hard facing rod, and regrind to the standard 1" bore with a die grinder. (You won't be able to drill into the hard face.) Similarly the worn outer area of the pedal shaft should be built up withhard facing metal and ground back to specs. The 1/4" diameter holes of all lever ends should be noted for exact location, then plug welded with mild steel and re drilled. It would be ideal to drill the lever holes oversize and install with a press 1/4" I.D. diameter bronze bushings by 5/16" width. Or increase the steel lever widths to 5/16" for greater surface contact area.

"Discard the primitive rod as they frequently break at the right angle bends. Replace with a rod of 1/4" diameter having a clevis at both ends. This rod need not be adjustable, so welded clevis ends will suffice. Install stainless clevis pins. Or even rebuild your original pins with a hard face. The idea is to decrease friction by use of dissimilar and/or hardened metals.

"On to the control lever. Don't forget to hard face the control lever bore. Also build up the mating control lever ball studs, making sure the internal parts (spring and seals) are operational. Lastly the hollow worn pockets found on the ears of the bearing carrier should be hard faced and ground smooth. Now if that's not an improved clutch control I will eat my clutch!"

Cable Lubrication

The standard 3B has lever and rod clutch linkage, but Jeeps with optional engine transplants may have a clutch cable. There are also comments here about lubricating the speedometer cable.

Oz posted this: "I will be replacing the clutch cable on my 54 3B and wonder if there are recomendations as to lubricating the new one. (I have the cable system because the engine, trans and transfer case are transplanted from a 69 CJ-5.) Should the cable be left dry? Or should it be lubricated? Seems like it should be lubricated with something although it also seems that the lubricant may attract and hold dirt,sand,etc. I am also replacing the speedometer cable and have the same question and concerns for it."

Jyotin suggested, "Generally a lithium-based lubricant does not 'travel' or absorb too much dirt, as opposed to oil-based lubricants."

Oldtime mentioned, "I've been told that cable-actuated clutches have some tendency to short out. The cable can act as an engine ground. But that issue aside, I like to lube my parking brake and speedometer cables with fine dry powdered graphite. This is carried in a thin evaporating oil for ease of application. I don't know what the cyclists are using these days."

Oz responded, "The graphite seems to be the way to go for the speedometer cable. I have been told that most lubricants that are thin enough (viscosity) to be effective for the speedo cable will eventually run out to the bottom of the cable as the cable is run somewhat vertically to get from the transfer case to the speedometer assembly. I'll call around to the auto parts stores and see if anyone has a special speedo cable lubricant. Tthe last time I checked into 'mechanical' speedo parts the young man at auto-zone didn't know that they were any such things. As for the clutch cable, I could see how that could become an electrical path to ground; after all the path of least resistance is all that it takes.The clutch cable is positioned horizontally therefore I believe that whatever lubricant may be used, it should stay there for a reasonable period of time. I'll check at the cycle shop to see what's available there."

Oldtime added, "Here's one that somehow came to mind last night. I had this thought about how soapstone feels really smooth. So I looked it up in the dictionary. It seems that soapstone is the mineral steatite, sometimes called talc. Talc is in fact used as a lubricant. On the plus side the soapstone is also used as an electrical insulator. Unlike graphite which could conduct current, soapstone may prove to be the ultimate clutch cable lube for those who don't keep their engine ground cable in good order. Just a thought. I think I'll try it myself."

Thanks to Ken Bushdiecker and all the contributors. -- Derek Redmond

The illustration of the underside of a Jeep is from a Willys Farm Jeep brochure, Form No. KW1706, and the clutch linkage diagram is from the 1956 Parts List.

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Last updated 18 January 2009 by Derek Redmond redmond@cj3b.info
All content not credited and previously copyright, is copyright Derek Redmond