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Discussion Starter #1
Ok this is a strange one. Have a 1975 4 speed all stock. When the temperature drops to 40 and below first start there is a rattle noise coming from the transmission. The colder it is The louder The noise is. The noise stops when you step on the clutch pedal. When the car warms up the noise goes away. Shifting is perfect and crisp. This does not happen at all in the summer. Was told it's the gear oil in the transmission, if it's cold out gear oil is very thick and it needs to warm up to lubricate correctly. Does anyone know what this is? Driving me crazy.
 

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Im thinken shifter linkage since its a rattle & its mounted to the cross member,as the motor warms up & levels out it goes away.
I converted to old 68 & 78 to Hurst's.I like a little free play in my clutch pedal, if you do too just push the clutch in some & see if the rattle goes away,I would look at the z bar & rod to fork for the rattle also.You could check the fork for exclusive play on the throw out bearing too.
 

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Sounds like the throw out bearing, you load the bearing when you press on the clutch. Could be the grease is affected by the cold temp. Possibly the shifter rods but the shifter would be sloppy typically, those stock shifts are long throw and were not as good as a Hurst.
 

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The Counter gear and Input clutch gear may have a bit of wear present.

The Input clutch gear ball bearing may be worn out.
They usually make a strange popping noise when they are failing.
 

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Sounds like the throw out bearing, you load the bearing when you press on the clutch....
this, right here. i feel 100% sure for the reason stated-
stepping on pedal loads bearing. it *might* drive fine
like this for YEARS, my mom's kis sorento 4x4 has been
this way since 60K miles, it just turned 110+K and
is still making noise till you step on the clutch pedal--
and its still driving perfect.
 

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Discussion Starter #6
But this is the old thing it's only when the temperature outside is cold. When the temperature was 20 degrees it was so loud you heard it a good distance away. After a 10 minute drive the noise is gone. Yesterday the temp was 49 and practically nothing at all with no warm-up time. If the temperature gets to 59 degrees nothing at all all is perfect.
 

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But this is the old thing it's only when the temperature outside is cold. When the temperature was 20 degrees it was so loud you heard it a good distance away. After a 10 minute drive the noise is gone. Yesterday the temp was 49 and practically nothing at all with no warm-up time. If the temperature gets to 59 degrees nothing at all all is perfect.
Thats why I was thinking it may be the Front Intput - Clutch Gear Ball bearing.
I had one go bad in a Muncie M21 4-speed in the past.
Shifted perfect.
High RPM Shifts no problem.
Once in a while it made funny popping noises and a light rattle.
The Cage holding the bearings in place disintegrated in that Muncie.
The Ball Bearings never flew out into the Gearset.
Had no Major damage when I took the M21 apart.
Just needed a straight forward rebuild.
I rebuilt it.
Ended up selling it to a guy with a 66 GTO.
 

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Discussion Starter #8
Ok, your not going to believe this, the problem was the gear oil. I couldn't take it anymore and brought 2 quarts of gear oil. There was maybe half a cup of gear oil in the transmission. No mental on the drain plug. Filled it up and quiet as a mouse at cold start. Shifting is smoother and quiet. I think the little oil that was in there had to get warm to completely lubricate. Wow simple oil was the issue. Thank you all, I learned a lot from your experiences!!!!
 

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Glad ya found the problem.

episode of the Andy Griffith Show where Barney thought he got a “great” deal on a used car, until it started acting up and they discovered sawdust in the transmission.
 
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