Knocking

[Dan Mock]

Hi Out There Need Exxperince Guys In The Drive Train It Seems That Every Time The Car Makes A Complete Reveloution Its Makes A Knock In Third Gear I Just Installed A Rebuilt Motor And Tranmission. Its Not A Motor Knock Its Just The Only Way To Describe It. Need Help. The Car Is A 1929 Tudor With A 1928 motor In It.

[H. L. Chauvin]

Question 1? No knocks in 1st & 2nd

Question 2? Knocks more or less on acceleration or decelleration?

Question 3? With inexpensive mechanic's stethescope, or with 1" x 1" x 24" piece of wood or broomstick placed on parts of metal drive train or engine, (opposite end of stick on your ear), what "specific" area(s) is knocking noise coming from?

Question 4? Any more specific details of what happens when?

[midgetracer]

It could be a broken tooth on the cluster gear in the transmission. Remove the top and check the gears.

[bogdonj]

Distributor sitting lose or worn? H.L is on the right path with trying to narrow down the exact place of the noise!

[Fred K-OR]

"Complete Revolution" Question revolution of what? Is this a revolution of the wheels? Or ???? Guess I am thick headed.

[CarlG]

Sponsored Links (Register now to hide all advertisements)

Back when I was a young pup, and my Dad was riding with me in my 31 Fordor, it developed a knock. When I was accelerating as in pulling away from a stop sign, the knocking would get more rapid. When I stopped, it would stop.

Turns out that Dad had a screwdriver in his hand and was banging on the outside of the door, in exact tune with the engine rpm.



Thanks Dad!

[Dan Mock]

It Only knocks In Third gear Stops When You Push In The Clutch One Revolution Is To Me One Cycle Of The Tire. Knock Is Consitent Weather You Speed Up Or Slow Down. The Transmission Was Rebuilt But A Used main Shaft Was Installed. As Far As The Distrubtor Goes I Have The New FS Ditrubtor And Its Perfectly Timmed With A Timming Light.

[H. L. Chauvin]

Remove inspection plate on top of clutch housing & with a flashlight try to observe & listen to what happens when the depressed clutch appears to cause the noise. Then report back your visual & audible findings.

[JoeWay]

Originally Posted by Dan Mock

It Only knocks In Third gear Stops When You Push In The Clutch One Revolution Is To Me One Cycle Of The Tire. Knock Is Consitent Weather You Speed Up Or Slow Down....

It the knock is repeating with each turn of the tires, it almost has to be in the rear end--probably the ring gear. But then it should be present in all gears. If it is repeating with each turn of the engine/driveshaft but only in third, it is probably in ther transmission.

BTW, your use of caps for every word is rather disconcerting--makes your posts hard to read and must take a lot of extra work.

Joe

[Dan Mock]

sorry guys i mixed up the part about the clutch. when you push the clutch in third gear the knocking goes away.

[H. L. Chauvin]

Originally Posted by Dan Mock

sorry guys i mixed up the part about the clutch. when you push the clutch in third gear the knocking goes away.

Hi Dan,

1. Appears with the above quote, coupled with your first question & your response #7, i.e., that "the main shaft is used", it is sugested that prior to total disassembly & transmission removal, it would be a good idea to first remove the transmission tower assembly to try verify how "used" this main shaft really is -- especially when it is in 3rd gear, whereby the transmission is in direct drive, such that the engine is turning the main shaft, & the main shaft is turning the drive shaft, all in one (1)straight line.

2. Next, in your 1st question, it appears you have "verified" that this knock is "not" an engine knock.

3. Assuming you are able to correctly determine where a knock is "not" coming from, are you sure the knock in 3rd is coming "from" the transmission, & if it is, try jacking up one rear wheel, place transmission in third when engine is running to try to verify if the knock is sounding louder on the front or on rear of the transmission while verifying same with a mechanic's stethescope or similar device.

4. When you depress the clutch you report that there is no knock. I am sure you realize that depressing the clutch causes the transmission to stop turning; hence, it appears that the knock is happening "behind" the clutch.

5. Not at all trying to guess what you will find, but from the above comments you have enough information to suspect "what" is causing this knocking, especially in trying to shake the "used" main shaft when the transmission is in 3rd gear.

Hope this helps -- please let us know what you find.

[d.j. moordigian]

4. When you depress the clutch you report that there is no knock. I am sure you realize that depressing the clutch causes the transmission to stop turning; hence, it appears that the knock is happening "behind" the clutch

If the car is moving and out of gear, the main shaft is turning.
If the car is moving and in gear, the main shaft and cluster are moving.

[H. L. Chauvin]

The above two (2) added paragraphs are correct, e.g., when the car is moving, & out of gear, the main shaft is being turned by a force from the "rear" of the transmission, i.e., the drive shaft.

And when the car is moving in gear, the main shaft is being turned by a force from the "front" of the transmission, i.e., the engine.

In either case it may be more difficult to sound test the front & rear of a transmission while the car is moving in 3rd gear.

To better explain the above paragraph 3., to try to pin point the cause of the knock, a sound test can be conducted on both the front & rear of the transmission with the rear wheel jacked up. This allows testing while running in 3rd gear; & also allows testing after the clutch is depressed, after the rear wheel to stop turning, & then allows one to hear what happens when the main shaft "stops" turning while the engine is still turning.

Hope this helps to better locate the exact source of the knocking.

[Kevin - Illinois]

Hi Dan... I have the exact same problem with a newly rebuilt engine and tranny. My rebuilder asked me to pull the tranny and bring it to him which I did yesterday. Everything in the tranny looks perfect but we did find end play (you could hold the tranny and pull both shafts in & out) in both the main shaft and main drive gear to the tune of over .050 each. He fixed both on the bench while I was there. Unfortunately I won't be able to get things back together until Monday due to other commitments. I'll let you know what happens then...

[Dan Mock]

Hi guys Sorry It took so long to reply but i just finished putting a used rearend in the car on tues. that solved the knocking problem in third gear.