Gerty the Gremlin Posted February 19, 2023 Share Posted February 19, 2023 First post here. I recently purchased a 1940 Pontiac Deluxe 26. The car is in fantastic shape with no rust and she is a great runner. My issue is this, while driving I get a decent vibration in the car, but while cruising if I push in the clutch, let the engine idol down and gently let the clutch back out the vibration goes away. I’m guessing that I need a new clutch disk and pressure plate, but I have been wrong before. What are your thoughts and what clutch disc is in this car? I have scoured the internet but have come up short. Thanks again for your help!! 1 Link to comment Share on other sites More sharing options...
keiser31 Posted February 19, 2023 Share Posted February 19, 2023 41 minutes ago, Gerty the Gremlin said: First post here. I recently purchased a 1940 Pontiac Deluxe 26. The car is in fantastic shape with no rust and she is a great runner. My issue is this, while driving I get a decent vibration in the car, but while cruising if I push in the clutch, let the engine idol down and gently let the clutch back out the vibration goes away. I’m guessing that I need a new clutch disk and pressure plate, but I have been wrong before. What are your thoughts and what clutch disc is in this car? I have scoured the internet but have come up short. Thanks again for your help!! Cool car! Welcome to the group. Definitely sounds like a clutch issue to me, but others here will have other ideas. 2 Link to comment Share on other sites More sharing options...
JACK M Posted February 19, 2023 Share Posted February 19, 2023 While you have the tranny out I would take a good look at the pilot bearing/bushing what ever it has. 4 1 Link to comment Share on other sites More sharing options...
Gerty the Gremlin Posted February 19, 2023 Author Share Posted February 19, 2023 I haven’t dropped the trans yet, I’m trying to do as much research as possible before I start taking things apart. I’ve learned my lesson in the past about taking things apart when parts seem to be difficult to find. 1 Link to comment Share on other sites More sharing options...
straight8pontiac Posted February 19, 2023 Share Posted February 19, 2023 (edited) Welcome aboard Gerty... Several resources which have been invaluable to all Pontiac owners here on the forum. 1. Farther down in these Discussion Forums are 2 Groups..A. Pontiac and Oakland B. Pontiac Flathead Owners... Much discussion takes place here. 2. Early Times Chapter (ETC) of the Pontiac Oakland Club International (POCI). President of ETC Tom Myers- etcpreztom@gmail.com 3. Kurt Kelsey- known here on the forum as KornKurt, parts dealer of early Pontiac's- kelsey@prairieinet.net 4. Another knowledgeable individual here on the forum is Bloo who frequents often and provides much insight. 5. California Pontiac Restoration for Information and parts as well. Hope this helps...Dave Edited February 19, 2023 by straight8pontiac added name (see edit history) 2 Link to comment Share on other sites More sharing options...
Marty Roth Posted February 19, 2023 Share Posted February 19, 2023 45 minutes ago, Gerty the Gremlin said: I haven’t dropped the trans yet, I’m trying to do as much research as possible before I start taking things apart. I’ve learned my lesson in the past about taking things apart when parts seem to be difficult to find. 1. Do you notice any difference in the vibration A. While accelerating with the engine pulling the car B. While maintaining constant speed C. While decelerating with the driveline "pushing" the engine 2. Is there any vibration when the car is stationary and you rev the engine to the approximate speed of the driven vibration? 3. When you cruise to the speed of the vibration take the car out of gear, and release the clutch normally A. with engine idling B. with engine revving Is there any difference in vibration? 4. Repeat #3, but holding clutch pedal down, and in all three options, do you notice any differences? 5. Pay careful attention to Universal Joint(s) A. looking for any slack B. Looking for any scoring on surfaces per rollers within caps 3 Link to comment Share on other sites More sharing options...
1939_Buick Posted February 19, 2023 Share Posted February 19, 2023 Would also check the rubber engine - transmission mounts. 5 1 Link to comment Share on other sites More sharing options...
Bloo Posted February 19, 2023 Share Posted February 19, 2023 Lots of good advice posted above. There's not really much to add. My first thing to check would be the u-joints. You should have an open driveline if it's a standard US market Pontiac. Safely jacked up, one rear wheel on the ground and one off the ground, engine off, car in gear, rock the back wheel back and forth slowly and carefully while "feeling" the outside of a u-joint (don't pinch your fingers!). It probably takes 2 people. You should be able to tell if one yoke of the joint moves more than the other. It shouldn't. That's not a 100% test for all u joint problems but it's close. @john hess had a bad u-joint with symptoms that were very similar to yours on a newer flathead Pontiac. My second guess would be the pilot bearing (for the transmission shaft) in the back of the crank, or the front bearing in the transmission, or both. The pilot bearing might have been a bushing by 1940. There is no way to lubricate it without taking things all apart, and it is possible no one has been in there in decades. That matters more if it is a bearing. Either way, if it is bad it can let the clutch run out of round. Since you have to take the transmission and clutch out to get to the pilot bearing, I would check all the other things suggested above. It would be nice if you didn't have to take out the transmission and clutch. If you do take the clutch out, any problem with the clutch disc should be evident when you can see it. For what it's worth, my 1936 had paint marks on the pressure plate and flywheel. Apparently Pontiac balanced them together. I don't know if this continued in 1940 but I would look for the marks and if there are none I would make some before taking the pressure plate off. Welcome to the forum! 4 1 Link to comment Share on other sites More sharing options...
Gerty the Gremlin Posted February 20, 2023 Author Share Posted February 20, 2023 8 hours ago, Marty Roth said: 1. Do you notice any difference in the vibration A. While accelerating with the engine pulling the car B. While maintaining constant speed C. While decelerating with the driveline "pushing" the engine 2. Is there any vibration when the car is stationary and you rev the engine to the approximate speed of the driven vibration? 3. When you cruise to the speed of the vibration take the car out of gear, and release the clutch normally A. with engine idling B. with engine revving Is there any difference in vibration? 4. Repeat #3, but holding clutch pedal down, and in all three options, do you notice any differences? 5. Pay careful attention to Universal Joint(s) A. looking for any slack B. Looking for any scoring on surfaces per rollers within caps 1: the vibration will increase and decrease depending on speed. 2: sitting stationary with the engine running there is a slight vibration that goes away when the clutch is pushed in. 3: have not tried that, I will on my next drive 4: the vibration is constant until I let the clutch back out. It seems as though the vibration goes away when the clutch is just starting to engage but the vibration will some times come back at full release of the clutch. 5: I have not lifted the car but I did check the UV joints and did not notice any slack. I will lift the car and check again. 2 Link to comment Share on other sites More sharing options...
JACK M Posted February 20, 2023 Share Posted February 20, 2023 (edited) 12 hours ago, Gerty the Gremlin said: 5: I have not lifted the car but I did check the UV joints and did not notice any slack. I will lift the car and check again. There should be no pressure on the driveline when doing this. This why Bloo says to jack up one wheel. I am still leaning towards pilot bushing/bearing. If the car has an open driveline that tranny could be out in less than an hour. I sort of go the other way about parts. One will not know what parts to look for until it is apart and inspected. But yes, do as much troubleshooting as you can first. Edited February 20, 2023 by JACK M (see edit history) 2 Link to comment Share on other sites More sharing options...
R Walling Posted February 21, 2023 Share Posted February 21, 2023 (edited) When checking for vibration, please note that when you step on the clutch WHILE STOPPED, the clutch disk is NOT rotating regardless of the rpm of the engine. (WHILE THE CAR IS IN GEAR) While driving, placing the trans in natural and letting out the clutch, the clutch disk and the pilot shaft are rotating at the speed of the engine RPM. PLEASE NOTE THAT I EDTIED THIS POST Edited February 23, 2023 by R Walling MISTATEMENT (see edit history) Link to comment Share on other sites More sharing options...
John348 Posted February 23, 2023 Share Posted February 23, 2023 Did you try coasting in neutral and moving the clutch in and out? Removing any torqued load coming off of the driveline to see if the vibration changes any? I agree 1939 Buick 80+ year old mounts can cause all kinds of vibration to be felt, and also can cause some severe geometry changes that could stress that front U-joint angle. 1 Link to comment Share on other sites More sharing options...
Gerty the Gremlin Posted March 9, 2023 Author Share Posted March 9, 2023 Gentlemen, well I’ve pulled the transmission and have a question. The throw out is a bushing not a bearing. Should the carbon disk rotate in the cast housing? It has a grease fitting which to me implies that it should. Mine does not move at all, and will barely take grease. Link to comment Share on other sites More sharing options...
avgwarhawk Posted March 9, 2023 Share Posted March 9, 2023 I would say this is a bearing. I see no other reason for a grease fitting but to fill the bearing housing with grease. Link to comment Share on other sites More sharing options...
F&J Posted March 9, 2023 Share Posted March 9, 2023 2 hours ago, Gerty the Gremlin said: Should the carbon disk rotate in the cast housing? No, the carbon is fixed, meaning it does not spin in the housing. The grease fitting should only lubricate where the housing slides on the guide tube on the transmission. Link to comment Share on other sites More sharing options...
Bloo Posted March 9, 2023 Share Posted March 9, 2023 The fitting is probably for oil. On the 1936 model, it is a flip top oil cup. The oil is supposed to soak through the porous carbon. I have noticed zerks on slightly newer models, and can't imagine how grease could work at all. Oil guns existed at that time. What does the shop manual say about it? When mine was out of the car during a transmission overhaul, I soaked it in clean hot heavy motor oil for a few hours, and also filled the oiler cup. The carbon does not rotate, it just stays oily and runs against a smooth steel surface on the pressure plate. The grooves are a wear indicator. When they're gone, it's worn out. That one is kind of chipped up. I don't know how much it matters, but I wouldn't want it falling apart, because it would probably damage the surface on the pressure plate. I would consider replacing it. 2 Link to comment Share on other sites More sharing options...
Grimy Posted March 9, 2023 Share Posted March 9, 2023 1 hour ago, Bloo said: The fitting is probably for oil. On the 1936 model, it is a flip top oil cup. The oil is supposed to soak through the porous carbon. I have noticed zerks on slightly newer models, and can't imagine how grease could work at all. Oil guns existed at that time. What does the shop manual say about it? On pre-war cars, the presence of a zerk does NOT automatically mean chassis grease should be applied with a lever-operated grease gun! As @Bloo says, check the shop manual! For pre-war cars, often motor oil or gear oil or water pump grease were dispensed via zerks to various components. For some water pumps (I'm talking to you, 1937-48 Cadillacs), the car came with a small, very low pressure cylinder with a turn knob to dispense water pump grease; if you use a lever-operated grease gun you will blow the seals instantly as a very much younger me found out the hard way. Likewise, the definition of "grease" was very loose--everything from 90 or 140 gear oil to 600W to 00 water pump grease to chassis grease. RTFM for your car to see what kind of lubricant was specified for each component and with which piece of equipment it should be applied. 2 Link to comment Share on other sites More sharing options...
Gerty the Gremlin Posted March 13, 2023 Author Share Posted March 13, 2023 I think I have found the cause of the vibration in the driveline. While I had the transmission out I decided to do some preventative maintenance on things. The first thing I did was pull the U joints to inspect and grease…..boy am I glad I did!! Both U joints were beyond shot. I’ve ordered new ones and am waiting on them to arrive. 4 Link to comment Share on other sites More sharing options...
63RedBrier Posted March 13, 2023 Share Posted March 13, 2023 Glad you found the source of your vibration! And, thank you for sharing your experiences and photos… 3 Link to comment Share on other sites More sharing options...
Gerty the Gremlin Posted March 15, 2023 Author Share Posted March 15, 2023 Finally got it all assembled and took her for a test drive. WOW is all I can say! I never knew how smooth these cars can ride when everything is working as it should. Thank you to everybody that threw out ideas and advice to figure out my problem. It’s a great feeling knowing there are still good people out there that just want to help. walter 3 Link to comment Share on other sites More sharing options...
john hess Posted March 16, 2023 Share Posted March 16, 2023 glad you got it figured out.. lots of help here on forum.... Link to comment Share on other sites More sharing options...
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