Transmission knock or ???

FRITZ47

FRITZ47

Senior Member
I have the nicest running '47 Ford Convertible with original flathead V8. It starts in 1/2 a turn and sounds and runs perfectly. Good oil pressure, plenty of power, quiet engine, and the smoothest clutch I have ever had in any pre-war car. Earlier this week, we had it in the shop for some generator work and a tuneup. One of the guys at work picked it up this morning and the car was in our parking lot this afternoon, waiting for me to take it home. (The employee had left for the day and said nothing about any issues).

After work I started the car and put it into low gear and let out the clutch, and as soon as the clutch was released, the car moved smoothly, but there was a loud knock, but it was not an engine knock, as the engine was running as smooth and quiet as ever. I pushed in the clutch and the knock immediately stopped. I gave it some gas in neutral and no engine noise and no knock. I let out the clutch again and there was the knock. I shifted into second and the knock continued. In high gear the noise seemed to subside (not sure of this) and was not noticeable, however I did not take it on the highway, as didn't want to do any damage. Most of the testing was in our large parking lot in first and second gear. In reverse there was the same knock as soon as the clutch was released. The noise sounded as if there was someone under the car hitting the frame or the transmission with a hammer - knock, knock, knock, knock, etc. It is a heavy knock, and definitely not an engine bearing knock, and the only time it can be heard is when the clutch is released. Push the clutch in and the knock stops immediately.

Earlier today, we just changed the engine oil and added about a quart of 85-135 transmission gear oil to the transmission (it was low), so I do not feel that we were low on fluids. The rear end was full and did not need any fluid.
One friend said it could be a throwout bearing, or a transmission bearing. I have had many flathead Fords in my life and have never heard anything like this. I also know the difficulties in pulling the engine to get to the transmission, so am hopes that there might be a simple solution.

Any advice will be greatly appreciated. Thanks,

Fritz
 

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Drain the oil....into a screened container. Look for metal pieces (ie: gear teeth). You could have some missing from the low/reverse sliding gear. If you see gear teeth, remove the side shifter housing and inspect the gears for the proof.

Could also be a broken u-joint but skeptical on that. Let us know what you find.
 
I drove my car with that kind of knock (not the high speed vibration of the U-joint shot as Ross F-1 suggested) for years and it never got worse until my foot slipped off the clutch one day. Then the one tooth that was broken off became a whole mouth full. I still drove it for a few months without 1st or reverse, even over the mountains, before I got around to rebuilding the ****** and replacing those broken gears. BTW, you don't have to remove the engine to remove the ******, just the rear axle and torque tube.

P.S. Your car is absolutely gorgeous. Love it.
 
I would guess the guy didn't know how to drive it and chipped a tooth on 1 st and got could up in main drive gear and cluster.
 
I had a very similar problem, I thought it had to be the throughout bearing. In neautral it sounded bad and once the clutch was depressed it went away. I was preparing to adjust the clutch first and removed the floor board. The rubber boot on the clutch pedal was hitting the edge of the frame causing it to ride up on the pedal arm. This stopped the pedal from completely returning to it's normal position. It was as if I was "riding the clutch" I trimmed the rubber piece to clear the frame and all was good. I would check to make sure your pedal is returning to it's highest position wether it's adjustment or obstruction. keep us informed.
 
Thanks everyone for some great ideas and theories.

Prior to hearing the knock, we put it on our lift and our mechanic (Bob) changed the oil, added brake fluid (it was synthetic) , added air to the tires, checked the rear end (it was OK), greased the car and checked the transmission level (it was almost a quart low), so he added 80-135 weight gear oil to fill level (it overflows out a hole when full). I am going to recheck everything on Monday. I just talked to Bob, and he said he drove it to the gas station and heard the knock for the first time yesterday. When he drove it back from our mechanical shop the day before (1/4 mile away) there was no knock. I have driven the car some during the past year and no such knock. We do not feel that we stripped any gears as Bob and I are very familiar with driving a column shift car. The clutch is perfect and the column shift linkage is like a new car (no slop or looseness - very quiet and as new).

Here is our game plan for Monday:

a) Drain the transmission fluid through a screen cup to see if any chunks of metal are in the case.
b) Either way, remove the side inspection plate for a better look at the gears while transmission is not full of gear oil. Try to determine what is wrong, if anything.
c) Put the plug back in and add new 90 weight gear oil (Ford calls for 80 wt winter and 90 wt summer). Is there any special type of this transmission gear oil recommended?
d) Check the universal joint and lubricate again as maybe this was missed.
e) Short test drive in parking lot to see if any difference in the sound/knock.
f) If still knocking, put the car on our lift and jack up the rear end with rear wheels off the ground, using very solid jack stands.
g) Start the car and run through the gears to see if we can isolate the knock.
h) Once we isolate the knock, go from there.
i) I will post our findings next week.

In the meantime, if any other ideas, please post - I am hoping to drive this car this summer (NE Ohio). Thank you!

Fritz
 
I bought a 47 last fall and seems like 1st gear is straight gears, just have to come to a complete stop .Angled gears seem to go into gear much easier on roll. Check the slider gear close 1st and rev.
 
George/Maine said:
I bought a 47 last fall and seems like 1st gear is straight gears, just have to come to a complete stop .Angled gears seem to go into gear much easier on roll. Check the slider gear close 1st and rev.
Click to expand...

Angled gears "mesh" better because of the syncro-mesh mechanism, if it's working right.
 
You might struggle to inspect the UJ. It's all enclosed in the torque tube.

You ought to be able to judge whether the noise goes in time with the engine or the speed of the car (driveshaft).

In other words is the noise the same pitch at a certain road speed in first and second? If the pitch goes higher in first it is engine speed related. That rules out the UJ and you can focus on the front end of the trans.

If the pitch stays the same regardless of engine revs and gear, then the problem is at the back end of the gearbox, and could be UJ related.

Good luck with it and if you have any questions at all just ask, Barners are always willing to help.

Mart.
 
Doesn't sound like you did any clutch adjustments but I had mine adjusted so the PP opened a little too much and I could hear the counter weight side of the thrust fingers bumping the ****** housing. Closed the gap a little so the pedal wasn't opening so much and it stopped. I run a 10" clutch.

Very nice ride by the way, Good Luck!
 
The guy who picked up your car and put it in the parking lot decided to "try-her-out". He jumped out on the clutch with the engine revved up and did some damage to the main drive gear set.
 
JWL said:
The guy who picked up your car and put it in the parking lot decided to "try-her-out". He jumped out on the clutch with the engine revved up and did some damage to the main drive gear set.
Click to expand...

Exactly my thoughts too.
 
What about this?

Another possibility is that someone who is not familiar with a 3-speed column shift transmission might shift from low into reverse instead of into second. Would something like this cause such a knock? In 1949, my first car was a 1937 Ford (bought it from a used car dealer for $50 with a full tank of gas). I test drove the car (with my father) and it shifted perfectly. The next day, I picked up the car (without my father) and only 3 blocks from the dealer, I "speed-shifted" the car from low to second, but hit reverse by mistake, ruining the transmission. At the time we picked up a used transmission for about $10 or so and got the car back on the road. As I recall it was fairly common for an inexperienced driver to shift from low into reverse! A similar mistake is even easier with a column shift.

Or the transmission gears may have just suffered from metal fatigue ?? Car has original miles of around 30K and always shifted very nicely and has a good clutch. The column shift mechanism is nice and tight and like new.

It may take awhile to figure this out, but when I do, I will post the results. Thanks to everyone for so much help.

Fritz
 
Fritz, I let my son try out my truck (column shift) and he touched Rev enough on the shift to 2nd to make some very ugly noise, "Grind me a pound, please". It happens often with inexperienced drivers.
 
Back in the day it was cool to get 2nd gear rubber "POP THE CLUTCH IN 2ND", The trans are very weak and knocked the teeth in second gear.
As I remember those days that's why I went with a C4 in my 39
 
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