The Stovebolt Site Forums The Shop Area Engine Shop Help! My new clutch doesn't work.

Last weekend I installed a completely rebuilt 235 engine in my '49 half-ton. The engine has a brand new clutch pressure plate, clutch housing, throwout bearing, and resurfaced flywheel. I had no problems with the engine installation. This weekend, I installed the clutch linkage, clutch pedal and return spring. I adjusted the free-play on the clutch pedal per the Shop Manaual. After 2-1/2 years of rebuilding, I can almost feel myself driving!

Now for the bad news. When I press the clutch pedal, everything looks and feels right, but the transmission does not appear to be disengaging from the engine. With a friend in the driver's seat, and the clutch pedal depressed, I can't push the truck while it is in gear. However, if I shift to nuetral, and I can push the truck.

What could be wrong?? Is it normal for a new clutch to "stick" or did I screw something up? When I crawl under the truck, with my friend operating the clutch, I can watch the clutch fork and throwout bearing move freely and depress the tongs on the clutch housing. Everything looks and feels right. The only thing I can think of is maybe I installed the clutch disk backwards.

I have this sinking feeling I'll need to pull the engine out again. Help!

Are you sure you have the right throw out bearing, there are a couple different ones available and if yours it too short it won't allow the clutch to fully disengage.
Ask me how I know.

No need to remove the engine. The clutch disc being installed backward is a common mistake, and the wrong throw-out bearing is another possibility. The clutch disc should be marked with something like 'Flywheel Side.' Also, one side of the hub stands up from the disc more than the other side- that side goes to the pressure plate. You have to remove the transmission for either the throw-out bearing or the disc issue, but you don't have to remove the engine. Even if you find the throw-out bearing is the wrong one, I would suggest checking that the clutch disc is installed correctly before re-installing the transmission. That is a small additional effort that may save you removing the transmission again.

Harvester

I'm 99% sure it's not a throw-out bearing issue because I compared the new bearing side-by-side with the old bearing before installation. The two bearings were identical.

I carefully checked the clutch disc before installation. There were no words like "flywheel side" stamped on the disc. I do remember that the hub on one side of the disc stands up higher than the hub on the other side. I think I installed the high-side hub toward the flywheel. Is that backward?

if you read the previoue response from harvester, you will find your answer to the c/disc hub
ron

THe to brgs might have matched up but did you match up the pressure plates. There are 2 different styles. Remove the lower cover & have your asistant press down on the clutch & watch what goes on. The disc should turn freely when it is down but we know its not.

One other source of the problem could be that the disc is too big i.e. wrong size. That happened to me on a 54 Fo%$ I-6 once. I had to drive it across town to get the right size disc with no clutch. That takes a good battery and a good ear for gears.

I'm not sure this horse is dead yet, so I'm going to keep beating it....

I crawled under the truck and watched the pressure plate as my assistant pressed the clutch pedal. When the clutch pedal is released, the pressure plate firmly pushes the clutch disc against the flywheel. When the clutch pedal is depressed, the pressure plate moves away from the clutch disc (I would estimate 1/8 to 1/4 inch), and the disc is no longer pinched against the flywheel (I can wriggle it slightly).

I bought the disc, pressure plate, cover, and throwout bearing together as a kit, so I don't think it's the wrong disc/plate combination. I'm guessing I installed the clutch disc backwards because everything else seems to be working as it should. Harvester says the protruding hub on the clutch disc should face the pressure plate (toward the rear of the vehicle). The diagram in my Shop Manual seems to show the opposite (the protruding hub faces forward toward the flywheel).

Is there any way to verify that the disc is installed backward without removing the transmission and/or engine? Do others agree that the protruding hub on the clutch disc should face toward the rear of the truck? Could somebody check their shop manual and tell me if I'm seeing things? If the clutch disc is installed backward, would you expect the clutch to behave like mine?

Thanks! I wish I had asked these questions before assembling the whole darn thing.

Norcal49er

It sounds like you are going to gain additional experience in dropping the tranny.

Doh! I might have figured out the problem. I bought the clutch kit over a year ago, and this morning I looked at the receipt. The kit is for a '47 to '53 3100, which matches the truck. However, the engine is a '58 235. Can one of you experts who has swapped out the original engine for a 235 confirm that I need to use the later model 235 clutch?

Funny thing is, the '47-'53 disc, pressure plate and housing bolted right up to the 235 flywheel and transmission splines. No signs of any problems until I installed the engine.

You must have the correct flywheel or the pressure plate would not have bolted up. Your '58 flywheel and pressure plate has 6 bolts. The earlier '47-'53 had 9 bolts for the pressure plate to the flywheel. I think you got the clutch disc in backwards as Harvester told you.

That would not be the problem. When the swap took place they probably used the early model bell housing & flywheel. If it fit it should work. You either have the dics in backwards or your pilot bushing is hanging up on the trans shaft.

I just took delivery of a complete clutch kit from Jim Carters this weekend. Pressure plate, disk, throw out bearing etc. I have the disk in my hand as I type. It is a 9" disk with 6 bolts on the pressure plate.
One side of the clutch plate is raised considerably, the other side IS stamped "flywheel side".
Hope this helps.
Rick...........

I've seen this mistake made sevral times over the past 40 years or so. When the clutch disc is installed backwards, the dampening springs in the clutch hub drag on the flywheel attaching bolts even with the pressure plate fully retracted. The part of the clutch disc hub with the springs in it should be installed with the thicker side away from the surface of the flywheel.
Jerry

Well, unfortunately, I'm no closer to solving this mystery than when I started. I pulled the engine out of the truck last night and removed the clutch. The clutch disc is installed correctly! The raised face and springs are toward the pressure plate side. I misunderstood what was originally being said about the raised hub, because the flywheel side of the disc also has a small raised hub where the splines mate with the drive shaft. Anyway, I'm sure it's right. The pilot bearing also looks normal and the clutch disc slides freely onto the splines of the transmission shaft.

So, I'm not sure where this leaves me. I guess I will reattach the disc and pressure plate to the flywheel and try to bench test the clutch with the engine out of the truck. Obviously, the clutch disc needs to spin freely under these conditions. If it does, then the clutch is okay and the transmission shaft must be binding on the pilot bearing.

It's a good thing I enjoy this hobby and I don't do it for a living.

I had the same problem when I put a 235 in my 1949 GMC 3/4 ton. The kit that I ordered had pressure plate, throw out bearing and clutch for 1949. The clutch would not release when all was installed. Finally ordered just the clutch disc for a 1962 chevy which is where the the 235 started. The hub for the clutch disc on the 1962 was shorter front to back than the 1949 clutch disc and apparently was causing the problem. The hub on the 1949 clutch disc was too long and put all in a bind when I bolted the pressure plate to the flywheel. I put the later model clutch disc in and everything works fine now. The truck is not on the street, but all seems to work well and I can run through the gears, start and stop with no problems. You may want to check with more experienced mechanics, but that seems to have cured my problems. If you still have the old clutch and pressure plate from your original, check it against a clutch for the model year of your engine.

Chapter 16: I reattached the clutch disc and pressure plate to the flywheel, and the fork and throw-out bearing to the bell housing. Then I tested the clutch by attaching and moving a long lever arm on the end of the fork. The clutch disc spins easily when I simulate pressing the clutch pedal! From this I can only conclude there is nothing wrong with the clutch.

The only explanation I can think of is binding between the pilot bearing and the transmission shaft. I will replace the pilot bearing and re-install the engine to see what happens. I guess I shouldn't be surprised. Under a different post on this site (search under "pilot bearing"), I explained that I had to beat the tar out of a new pilot bearing to force it into the engine. Maybe I damaged the bearing even though it visually looks fine. Stay tuned.

Sounds like it - was it hard to get the shaft into/out of the new bushing?

May want to put new pilot bushing into freezer for a while before installing. Heard that this works pretty good to slightly shrink the bushing, but did not have any problems when I replaced mine.

You shouldn't have to pound very hard to install the pilot bushing, but the freezer suggestion is a good idea. There is a bushing driver for installing the bushing, but nearly any bushing driver of the proper outside diameter will work better than a hammer and punch.

Another possibility for your trouble is misalignment between the transmission case and the bell housing. Before you install the engine, make sure the clutch releases properly, then attach the transmission and see if the clutch releases with the transmission installed. If it doesn't, there is a misalignment with the case. There is a procedure in the shop manuals to align the case with shims, but you have to disassemble the transmission and use a dial indicator to take measuements. I have the procedure, I think, and can get it for you if it comes to that.

Harvester

you may have also been given the wrong pilot bushing as you shouldn't really have to pound the snot out of it to install it.
recently while installing a pilot bushing in a 283 I ordered a pilot bushing and it was about .023 over size and that is the difference between a b656 and a b656p p/bushing( can't remember the exact measure but that is close). if you don't know the difference you will pound it in and possibly get it a litle off kilter in there
ron

Some crankshafts for automatic transmission engines had a slightly oversize hole where the pilot bushing should go. That big bushing is for using those cranks in stick shift engines. Pounding the big bushing into the smaller hole will misalign it, or shrink the inside hole and make it grab the pilot shaft.
Jerry

I removed the old pilot bushing tonight and installed a new one. The old one was jammed in so tight nothing would budge it. Pushing it out from behind with play-dough and grease failed miserably. I finally cut it out with a hack saw.

I took your advice and froze the new bearing. Then I put a light coat of grease on the outside. It still took considerable force to get the bearing into the engine, but nothing like the first time. I tried driving it in with a wood dowel and a hammer but that wouldn't work. I finally placed the ball end of a ball and peen hammer into the bearing and tapped on the other end with a two-pound sledge. Presto.

I have my fingers crossed that this will solve the problem, but I'll let you know in a day or two. If you don't hear from me again, it means the clutch still doesn't work and I sold the whole dang garage and bought a boat.

A boat is just a hole in the water you fill with money!! Good luck with all.

I comment regularly that my life would be far simpler if my hobby were model railroading!!!

Problem solved and case closed! The lesson learned here is don't beat yer bearings. You might not see the damage, but it's there. Thanks for the help!

Good job! I like reading story's like this. Gives me more confidence when I go out and work on my truck. I know alot obout these trucks from reading everything on this site, but going out and doing it for myself is another thing. Glad you got the problem fixed, norcal49er!

Hi. I have read through many pages and think I know what my problem is but would your help. My 1949 1 ton truck... it worked fine... then I tore it all down and put it back together. It has a SM420 4 speed. I put the all the existing parts (that work fine and looked good)back in and now my clutch will not disengage. I pulled the rear inspection cover off and can see everything moving as it should. I adjusted my linkage to the max... with engine running i cannot get it into gear... they grind. I did notice that when the engine is running and the transmission is in neutural the back wheels spin. If I have the back wheels off the ground I can shift through the all the gears. I loosened and even put spacer washers between the transmission and bell housing hope it would fix my issue. I did not. I do not believe the clutch is stuck to the flywheel and my throw out bearing is installed correctly. I am assuming something must be binding ... causing the clutch to not disengage enought to shift. any thoughts other than what is posted? Thanks.

Are you positive that you put your clutch disc facing the right way? (flywheel side to the flywheel)

To me... it sounds EXACTLY like what was going on with my clutch after winter. Disc stuck to the flywheel. In my inspection, I could see that clutch pedal move the TO, and press into the Pressure plate springs, and then I could see one layer of the clutch disc move (furthest from the flywheel), but the layer that was against the flywheel would not visibly disengage.

Here's something to try...
Put the rear up on jackstands, put it in highest gear... get the wheels spinnin fairly fast, push in the clutch and slam on the brakes. That broke the clutch disc free with no harm done and now I can shift freely wheels on the ground or in the air. It might take a time or two to break free.


Also... make sure you aren't in a barn facing a wall... just to be on the safe side

I pulled the transmission tonight and can see the center of the clutch disk... should the protruding side that goes on the shaft face the front of the truck or the rear? Mine appears to face the rear... my helper is sleeping and I could not push in the clutch to see if the clutch disk would spin. Before when I was under the truck I could see the pressure plate move... but it did not seem to be enough room to see if the clutch disk was moving. I tried the jack it up in the air method and slam on the brakes but it did not work (perhaps I was too easy on it) will work on it more tomorrow night.

I pulled the transmission tonight and can see my clutch disk... could not push the clutch and look so I will get a help tomorrow. Which way is the protruding side of the clutch disk supposed to face? Flywheel side or rear side? My is facing the rear (i think) Also when the clutch pedal is pushed in should the clutch disk move freely?

If you push the clutch in with the transmission out the disc will fall down, the disc is supported by the input shaft from the transmission. As long as you are this far take the pressure plate off and see whats going on.

Just got home and going to pull the pressure plate. I do that when I push in the clutch ... the disk does not move.

ok... Just pulled the pressure plate and clutch disk... I can see where the springs in the clutch disk where hitting the 6 bolts on the crank... this tells me i put it in backwards. I held the just the clutch disk up as it was and could not get it to spin without hitting on the bolt heads... flipped it around and it appears it will work fine. I had the center protruding part of the clutch with the splines facing away from the flywheel. I have done a lot of VW aircooled engines and the clutch disk goes this way... it must be different for the truck. I will put it back together and see what I get. I will be sure to update ... success or another opportunity to try for sucess again. Thanks!

I just put it all back together and it works like a dream! Feel a little stupid about putting the disk in backwards... but I will get over it. I was hoping all along I had put it in backwards. Thanks to everyone that either posted or had posted in the past on this topic. Rob

I doubt you'll find anyone here that hasn't made a mistake and learned a mechanical lesson the hardway

Kudo's on finding and fixing the mistake. I know some folks that would have wore the tranny & clutch assembly's out w/a BFH and ended up w/a much worse problem
Dave

Good catch and a more common mistake than you would imagine

Most guys would have just disappeared after finding out what you did. Good on you for sharing with us! Now when I do it the very next time I have to change a clutch, I will know right away what to look for.
Carl

The Master Mechanic in my shop did exactly this on a rebuild recently, later 235 going into a '39 firetruck.

He is a retired bus and heavy equipment repairman, 60+ years as a mechanic. He put it in the way "they ALL go". Well, when it wouldn't release, it came back out. Took a day to re-drop the tranny, turn it around, and get it all buttoned up again.

No big deal in the grand scheme of things. He said he felt bad about it and offered to not take pay for the day of turning it around, but I said no way - he's batting close to .950 at least, given all the stupid stuff I've tried, only to have him come along and fix it!

Besides, it felt sorta nice for a change when I could point to the clutch where it had "this side toward engine" printed on the disc. Ha!

-Michael

As a teen I replaced a clutch disc in a 54 Ford while parked in the garage. It wouldn't have been a problem except the parts guy gave me a disc too large. Luckily when I started the car I had it in reverse or it would have blasted through the back of the garage. As it was, it just shot back out the garage and petrified my young, know-it-all, behind. Then I had to drive it across town without a clutch, a major piece of hair-raising experience. Experience is the best teacher, if you can live through it.