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so my 72 Cutlass decided to play games with me again ! After completing an Indoor Car show and competition, coming home with a top 50 out standing car s and also a top5 displays. The Cutty didn't seem to be happy with the results, and got back at me for some reason. A few weeks ago ( actually Thanksgiving ) I had posted how I had lost a shifting capability in my TH 350 Auto Transmission. Well it happened again but with an added bonus ! Bluish white smoke from the exhaust. To the point my friend was lost behind me in a fog of exhaust ! The car wouldn't shift out of low even when the trans was hitting higher then usual RPMs to cause the downshifts. This was for about 2 miles from home. About 100 yards from the house was when the foggy exhaust started to occur. Now there are two considerations, First after speaking to my engine builder who completely rebuilt the engine now bored 0,60 over back in the Summer of 2019. He said it could be the Transmission shift transducer ( Modulator ) is sucking trans coolant into the the top of the engine. so first I will check the Vacuum line for any fluid. If it is dry the second possibility would be the Head gaskets. I was not able to get the car back to the engine builder to re torque the heads in 2020. I pulled plugs 3/5 on the passenger side and the were oily and smelled strongly of fuel. I also pulled plugs 4/6 on the passenger side and they were dry and no fuel smell. Is it possible that the PVC valve in the valve cover on drivers side is bad? Ore possibly just the drivers side head gasket could be bad. Shouldn't all 8 spark plugs bee the same condition wise? The other final question since this seemed to be long winded, is when the engine was rebuilt the second time. The engine builder said the valley pan gasket is not need in that engine model. The car was built 8-71 so I assume the engine is considered a 71 350 5,7 L 4BBL. Can any one confirm that valley pans were not used in this 1971 engine? Fusick's Automotive said they were not used in the model year engine. Any input would be appreciated. Passenger side plug #4 Drivers side plug #3
I'm fairly sure all 70s era engines used valley pans. But that does not mean a valley pan is required - my engine does not have one as I used composition style gaskets with no valley pan. The lack of a valley pan is not gonna result in the issues you are experiencing.
If the vacuum modulator failed and is sucking in transmission fluid, I would expect ginormous clouds of smoke out the exhaust and no transmission upshift until very high engine RPM.
So does this match your symptoms?
Last edited by Fun71; April 5th, 2022 at 02:05 PM.
Hi Fun 71,
I did pull the vacuum line at the transducer this afternoon and stuck a Q tip up in the hose and the was trace amounts of trans fliud on it. but to to the point of saturation ! But yes same symptoms as before. During the first time a changed out the shift modulator, shift cable and detent( kick down ) cable. And the trans mission shop also replaced the shift transducer module. Then the re occurrence was exactly the same as when it was repaired the first time. Car wouldn't go over 10-15 MPHs and the engine seemed to have hi RPMs and no torque.
If the vacuum modulator failed and is sucking in transmission fluid, I would expect ginormous clouds of smoke out the exhaust and no transmission upshift until very high engine RPM.
Beat me to it. This is the most likely cause that fits both symptoms (smoke and no upshift).
One easy test is to temporarily disconnect and plug the vacuum line to the modulator. The trans still won't upshift except at 5,000 RPM or so, but the smoke should stop. That would be a very strong indicator that the modulator is leaking.
X2 on the culprit being the vacuum modulator. They are fairly inexpensive and very easy to change. As far as your intake gasket, I would not worry about it, and it would not cause your shifting issue.
Thank you everyone ! I will order a new shift transducer and let my Transmission guy know that it could be faulty ! Does anyone have a go to Trans module that they prefer to use with good success?
You're really throwing me off by using the terms "shift transducer" and "Trans module". I can't tell if you are using different terms for the same part, or you're referring to two different parts, but both of those sound like parts from a new vehicle with an electronically controlled transmission, which your car does not have.
The transmission vacuum modulator is the part that we suspect is causing your issue.
Last edited by Fun71; April 5th, 2022 at 03:21 PM.
You have better guys than me giving you advice but I will tell you that is a beautiful car and a very nice display. Wow.
x2
Also noticed you’re from Malvern, I grew up in Chester county - were you around in the 70s and early 80s? General Sales Cadillac Oldsmobile was a great place back then, the elaborate palaces on 202 S. are a far cry from the old school downtown dealerships. Great looking display and car!
Thank you Sir ! It was one heck of a show 96 hours with 16 hours sleep between setting up the display and final detailing of the car. she is my pride and joy. I did a 7 year restoration 2005-2012 in memory of my Dad the previous owner. I was happy receiving a top 50 Outstanding car but was not expecting a top 5 Displays ! There was serious competition of company sponsored cars and displays that were in excess of 100 G's. But my lighted stanchions did tip the scales in my opinion ! Here is a better picture of the stanchions and the car at the end of the show before it started having its temper tantrum ! LOL
Erik, I was also thinking of going adjustable also. Possibly a B&M adjustable Transducer module, Manufacturer's Part Number:
20234.Since the engine is bored 0.60 over now, with 70 Pistons and a stepped up Cam. Also the Rochester 4BBL is slightly modified too.
Fun71, Sorry Ken, I've heard it called both but we will stick with shift Transducer ! LOL
It doesn't matter if you've heard it called Fred, the people who designed and built the transmission (Hydramatic Division) call it a vacuum modulator.
A transducer is a sensor that monitors a data point and transmits it to somewhere else. The vacuum modulator is an actuator that causes the modulator valve in the trans to move based on engine manifold vacuum (which serves as an indication of engine load).
Burning oil, including ATF is usually blueish, where coolant is white and steamy. Unburned gas is black. How long have the spark plugs been in? The plugs ideally should look the same, I am wondering about why those two are oily, unless you hosed them down with atf coming up the modulator line and that's how the smoke got out.
I don't have anything to offer regarding your trans problems, but X3 on your Most Excellent Staging! I assume you built your stanchions. Where did you get the glass, or did you make those also?
BackInTheGame,
Thank you ! I custom made them. They are made of Azeck PVC boards. I had a sign company route out the panel for the logo insert. And had the logos done on plexiglass in vinyl by a friend of mine. The lighting is set up in the base 12V landscape bulbs and the wiring was all done with quick disconnect RC car connectors. That were able to be run through the electrical conduit I used and painted to match the car as the cross bars. It all can be run either off an inverter or charger pack when electricity isn't available !
Hi Koda,
Yes it was a bluish smoke from the exhaust, And also there was oily residue in the exhaust tips. And for ALL !......... I am now calling it " The Transmission Vacuum Modulator " !!!! LOL. I am planning on ordering the B&M adjustable #2034 Vacuum Modulator tomorrow after I get through to a tech to confirm the part number and speak to them regarding the engine modifications and if the one I'm looking at is correct. Regarding the spark plugs I only pulled two plugs from each side since the car isn't garaged and weather has not bee cooperating these past few days. But yes I will be replacing them all. They have only around 1000 miles on them since the engine was rebuilt in the Summer of 2019.
Interesting Joe that you referred to calling it Fred. That was my Brother's name and he passed away on Feb 9th ! But as I said to Koda and BackInTheGame. I am now calling it " The Transmission Vacuum Modulator " That will really confuse the kid behind the counter at the parts store !!!!!
[QUOTE=ragtopblue;1418606]Interesting Joe that you referred to calling it Fred. That was my Brother's name and he passed away on Feb 9th ! But as I said to Koda and BackInTheGame. I am now calling it " The Transmission Vacuum Modulator " That will really confuse the kid behind the counter at the parts store !!!!![/QUOTE]
Ask for an adult to help you.
BackInTheGame,
Thank you ! I custom made them. They are made of Azeck PVC boards. I had a sign company route out the panel for the logo insert. And had the logos done on plexiglass in vinyl by a friend of mine. The lighting is set up in the base 12V landscape bulbs and the wiring was all done with quick disconnect RC car connectors. That were able to be run through the electrical conduit I used and painted to match the car as the cross bars. It all can be run either off an inverter or charger pack when electricity isn't available !
April 5th, 2022, 01:49 PM
Here we go again !!!!
