Technical 53 Chevy - Beeping Noise when Stopping

So I drove it for about 20 min yesterday until I heard the beeping noise then came back home and quickly put it up on four jackstands. I put it in drive and ran it up to 20 mph after I felt it go to second gear and the let it slow down but no beeping/whistling noise.

Then I put it in drive and didn't touch the gas pedal and shifted it into neutral and the noise came in every single time I tried that. Then I got my friend to carefully do that while I listened and it was definitely from the transmission.

Then I shut the engine off and disconnected the vac modulator line and tried that and the noise wouldn't happen. I tried plugging it back in and then disconnecting a few times and the noise was only there with the vac line on.

Funny thing is that I suspected the vac modulator long ago and one time i drove it until it it was warm and making the beeping noise then disconnected the vac line at the intake and plugged it and the noise was still there when slowing down but only when I was in at least second gear or if I slipped it from drive to neutral. Maybe the no load condition on jackstands makes the noise go away when i disconnect it. Weird!

In any case I'm going to go to Napa and buy the modulator.

 

good luck!

 

Thanks but luck was not on my side.
I replaced the modulator and drove it and it made the noise after driving for about 15 min.

How weird that when I put it on jackstands and shift from drive to neutral it makes the noise but not when I try it and the vac line is disconnected. Must be load related. I remember when I drove it a long time ago and disconnected the vac line to the modulator it still made the noise.

So frustrating...

 

Still have that beeping noise,huh?? I guess it's time to throw in the towel and buy some ear plugs.

 

Yea I know!!

 

Have you tried replacing the vacuum line all the way to the engine? Could be a restriction in line causing the noise.

 

Thank you for your help. Yes I replaced the rubber and steel line completely. The only thing I can think of is the rubber hose connection on to the nipple. It's pretty tight though but might not be the exact size and like I said a long time ago I drove it until the noise appeared and disconnected the vac line and plugged it at the intake and it made the noise.

I wonder if the fluid is just not a good kind. The noise only appears after 20
min of driving when the trans warms up.

Last June I replaced the shifter shaft, the rooster comb (the old one was slightly bent), new filter (it's pointing the right way), new valvoline dex/merc fluid, a new gasket and pan (the old one was dented from the previous owner), fixed the fill tube because it had a hole, new modulator vac line and rubber ends, a new flywheel cover, and a new modulator (yesterday).

I wonder if the trans fluid is running too hot... There are lines going to an intercooler though. Maybe the valvoline stuff isn't that good hmm.