To start this off, I purchased a 1970 Dodge Dart a while back and have been using it as my DD for about 4 months and have put roughly 3,500 miles on it. This car was grandmother owned for nearly the entirety of its existence and has only 113,000 documented miles, and the transmission, as far as I know, is original and likely never rebuilt. However, I have noticed in the past couple of weeks that the transmission sometimes whines just a little at idle. This occurs only after I have drove a while and it is warmed up, and it occurs whether the car is idling in any of the forward gear ranges, neutral, reverse, and park. This has led me to believe that the noise is probably coming from either the pump or the torque converter. Should I be worried about this and start saving my money for a tranny rebuild or am I just being paranoid?

FSM lists for buzzing noise:

Low fluid level.
Pump Sucking air.
Valve body malfunction.
Overrunning clutch race damage.

Probably low fluid is your problem. Check level when transmission is fully warmed up in neutral on level ground, add fluid as needed to bring level back to mid-way between low & full on dip stick.

If this cures buzzing problem, it may be a good time to change fluid & filter, adjust bands, and refill with fresh fluid. I suspect it has been a long time since servicing of this transmission has been performed.

If correcting fluid level does not fix the problem, than it is valve body problem, or a pump problem. Valve body can be removed with trans in car, pump repair requires trans to be removed.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Thanks for the advice! I did as you said and warmed up the engine/trans and then put it in neutral to check the fluid level. It was making the buzzing noise as I opened the hood, and it really didn't seem to be coming from the transmission; it seemed more like it was coming from the top of the engine somewhere. I brought out my piece of heater hose that I use as my makeshift stethoscope and prodded around the engine until I found the source. It turned out to be a vacuum leak on the vacuum flapper switch on the snorkel of the thermostatic air cleaner. As soon as I disconnected the vacuum line from the switch, the noise immediately went away. I went ahead and plugged the line because I discovered that the switch was not working correctly, as the flapper was halfway up and the air cleaner was still drawing in hot air even though it is 90 degrees out today and the engine was fully warmed. It seems to run a lot better now and the noise has gone away. Thank you again for your response and advice.

I have to wonder- did you have the vacuum routed directly from the carb to the flapper valve or did the vacuum route through the temp sensor in the air cleaner first?

nope. it was routed correctly from the carb, through the temp sensor, and then into the flapper. My guess is that the temp sensor must be bad because it is still allowing some vacuum to get to the flapper even when the engine is hot.

I have new air cleaner vacuum thermostats when you're ready to fix the problem correctly—that thermostatic air cleaner makes a significant improvement in fuel economy and driveability, and it's worth keeping in working condition.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

That sounds good. PM me with the price if you want to.

Glad you didn't have to mess with the transmission. Amazing how checking transmission fluid level lead to the problem... ;~)

Dan is right, having that warm air flapper operational will make for better drivability and economy once the planet cools this fall.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

I think you "Once the northern hemisphere of the planet cools this fall." Like the rotation of hurricanes and water down the drain, seasons are reversed in the southern hemisphere.

Back on topic, yes, the heat flapper is a VERY good thing to have functioning properly on your vehicle.