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  #1  
Old 04-01-2017, 01:42 PM
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4 Speed tapping when in gear and in motion

Howdy-

I recently purchased a 1979 European market 300D with the 4-speed and 56,000 on the clock, and am working on getting it back on the road. Recently, I began hearing a tapping noise coming from under the car while in gear and in motion.

The noise is definitely speed related, and stops if I take the car out of gear or put the clutch in while coasting. The noise never arises if the car is stopped, so it must be drivetrain... somewhere. I can't feel any vibration, it's just noise so far.

My initial thoughts are the driveshaft bearing and support bushing, or maybe one of the rear axles.

Parts are showing up over the next few days to do all the fluid changes. Is there anything else I should be considering? The transmission feels and shifts flawless, and I find it hard to believe there would be an issue with it in light of the low miles. Of course, everything rubber is suspect.

Thanks for your time.

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Old 04-01-2017, 04:32 PM
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If the noise stops when you put it in neutral or put the clutch in, it isn't the driveline. If it were the driveshaft or the CV's, you'd still be getting the same noise at the same speed, regardless of gear or clutch position.
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Old 04-01-2017, 09:09 PM
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I had similar symptoms just this week with my 300TDT with a 4 speed out of a 240D (460K miles). I thought of all the same things as you did with the driveline ect. Turns out the transmission gave out completely. I think the ticking was broken parts in the gear box. When I drained trany oil, there were some pretty big chunks. Now I am on the market for a used 4 speed. It is a first for me, seeing a manual fail like this. kinda strange. I wish you the best.
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Old 04-02-2017, 06:40 AM
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What is meant by gave out completely Gordo? ...could you give more info please?
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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.
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  #5  
Old 04-02-2017, 08:17 AM
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hopefully its a cracked clutch fork,or throw out bearing.I have had trouble with input and output shaft bearings in manual trans do to lube places using ATF in a trans designed for 80 90 w.
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Old 04-02-2017, 10:30 AM
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4Sp

I've got a 4 Speed sitting in my garage, make me an offer.
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  #7  
Old 04-02-2017, 03:33 PM
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Quote:
Originally Posted by t walgamuth View Post
What is meant by gave out completely Gordo? ...could you give more info please?
Lets see...
It started with a faint ticking from the transmission area when the car was moving. I noticed that the frequency of the ticking corresponded to the speed of the input shaft. (faster in lower gears)

less then 50 miles later the problem suddenly got much worse.

Lots of binding with cracking and grinding noise when the car is moving at all in either direction and in any gear. The car could hardly move at all under its own power. (just a few feet)

When I drained the fluid from the transmission there were some chunks of metal almost too big to fit through the drain plug hole that came out with the oil.

When I pulled the transmission out of the car, there was 1/4 inch horizontal and end play in the input shaft.

I wrote more about this failure in another post "300D Clutch issues"
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  #8  
Old 04-02-2017, 04:19 PM
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Location: Phoenix Arizona. Ex Durban R.S.A.
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Possibly the axle shaft

Quote:
Originally Posted by Montgomery View Post
Howdy-

My initial thoughts are the driveshaft bearing and support bushing, or maybe one of the rear axles.
Is it intermittent? I have a speed related tapping, more like a loud banging actually that comes from somewhere under the car which I suspect is an axle shaft. One was replaced some time in the past, the other is original. My noise also vanishes when I put the clutch in or coast in neutral. However the reason I asked about it being intermittent is that sometimes mine will vanish completely for part of or for a whole day or two.

- Peter.

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1981 240D 4spd stick. 347000 miles. Deceased Feb 14 2021
2002 Kia Rio. Worst crap on four wheels
1981 240D 4spd stick. 389000 miles.
1984 123 200
1979 116 280S
1972 Cadillac Sedan DeVille
1971 108 280S
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