kdaddy Posted June 25, 2007 Report Share Posted June 25, 2007 84 DeVille 200-4R Transmission. Ok here is my issue. The transmission downshifts from 2nd to 1st hard and late. Also if I stomp on it at cruising speed it will engage hard when it downshifts. I have heard that the common problem with these is the TCC solenoid. Are there other things to look for that are common in these transmissions? FYI- trans filter and fluid changed correctly. No leaks. Pan clean as a wistle. Link to comment Share on other sites More sharing options...
Caddynut Posted June 25, 2007 Report Share Posted June 25, 2007 I don't know about that type of transmission, but on my older vehicles when the same thing happened I had a vacuum modulator valve on the transmission go bad. They were a cakewalk to change because they were located on the outside of the transmission with a vacuum tube going to it from the carburetory. I could tell it was bad because it would pump transmission fluid through the vacuum tube up to the carburetor. Like I said, I don't know if it is the same set up, but that sounds like the same symptoms I had. 2008 BMW 328xi 2007 Chrysler Aspen 2001 Cadillac Seville STS 2000 Ford Ranger XLT1998 Mitsubishi Spyder Convertible 1996 Saturn SC-11991 Ford F-1501979 Chevrolet Caprice1968 Ford LTD1965 VW Beetle "Herbie The Love Bug Replica** 1961 VW Beetle Link to comment Share on other sites More sharing options...
kdaddy Posted June 26, 2007 Author Report Share Posted June 26, 2007 caddynut, What was the purpose for the vacuum modulator valve? What did it do? Kyle Link to comment Share on other sites More sharing options...
Cadillac Jim Posted June 26, 2007 Report Share Posted June 26, 2007 The vacuum modulator is a diaphragm vacuum servo that moves a piston in the transmission. The position of the piston determines when and how hard the transmission shifts. The effect of the vacuum modulator is that the transmission shifts later and harder at lower vacuum -- more throttle, and sooner and softer at very light throttle which gives higher vacuum. It's always mounted low because it must be in the plane of the shift plates, just above the oil pan but below the gears. The vacuum modulator is a throwaway part. The reason is that it's often bent by jacks or road debris and then sticks (probably your problem) and it can wear out, not being fully lubricated by automatic transmission fluid. If it gets a really good whang with a jack, it can puncture the diaphragm, and then the vacuum sucks up ATF; then the car shifts late and hard and smokes. I changed one on a THM 400 a couple of times in a few seconds each. It was held on the transmission with a snap ring, and the vacuum hose clamp was spring-loaded. All it took was a pair of pliers. This doesn't speak for the 200-4R, though. In cars with electronically controlled transmissions, its function is taken by the MAP sensor, TPS, the engine speed sensor, the output speed sensor, and the vehicle speed sensor, along with the PCM/ECM. -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
kdaddy Posted June 26, 2007 Author Report Share Posted June 26, 2007 Jim, I did the diagnostic on it and no codes came up. If I am not mistaken early OBD systems like on my 84 DeVille did not diagnose tranny problems. That being said my tranny is clean, filter was not plugged, no leaks, no copper partilcles in the pan, and little to no particles at all. In other words it it was super clean. If I'm not mistaken I believe that there are two sensors within the tranny. The TCC solenoid and a 4th gear pressure switch. I hope someone else had this issue come up so I can get an idea. Kyle Link to comment Share on other sites More sharing options...
KHE Posted June 26, 2007 Report Share Posted June 26, 2007 Locate the vacuum line that connects to the modulator and disconnect it. If you see trans. fluid in the line or the nipple on the modulator, replace the modulator. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
KevinW Posted June 26, 2007 Report Share Posted June 26, 2007 The THM200-4R does not have a vacuum modulator; T.V. pressure is controlled via a cable at the throttle body. At higher mileage, the TCC solenoid may stick at higher temperature (less clearance for the plunger) due to accumulation of normal wear debris. If the TCC remains engaged beyond normally commanded periods, harsh shifting may be observed, and possibly a stall on approaching a stop (although TCC application is hydraulically disabled in 1st, it is possible for a stall to occur while coasting-down in 2nd depending on the circumstance, since the closed-throttle 2-1 shift occurs at a very low speed). To confirm this possibility, disconnect the electrical connector at the transmission; this will prevent the ECM from applying the TCC. Replacing the TCC solenoid is straight-forward, requiring removal of the pan and possibly the filter. Remove some fluid via the dipstick tube to avoid the usual mess associated with dropping the pan; remember to clean the magnet (unless a 'mechanic' has stolen it at some point). ___________________________________________________ Link to comment Share on other sites More sharing options...
kdaddy Posted June 27, 2007 Author Report Share Posted June 27, 2007 Kevin, I disconnected the plug into the transmission and the problem went away. That being said it IS therefore the TCC. I do have a question for you. Why would the transmission still function normally without the TCC hooked up? Is the tranny now functioning like a pre-electronic tranny? What could be the consequences? And if there are consequences explain why/how the consequence occurs. Hope to hear from you soon! Kyle Link to comment Share on other sites More sharing options...
PAUL T Posted June 27, 2007 Report Share Posted June 27, 2007 Have you checked the T.V. Cable? It comes off the carburator and goes to the tranny. I had some experience with it on my 88 cutlass supreme classic. It is easy to adjust. Just reset it and push the accelerator (engine off) to the floor and it adjusts itself. My problem was a bad vacuum hose though. There should be a vacuum diagram under the hood, check to see if the vacuum hoses are not leaking or that they are in the right place. Link to comment Share on other sites More sharing options...
jschunke Posted June 27, 2007 Report Share Posted June 27, 2007 I've had the torque lock disabled on my '84 Olds for over a decade now. It has the 200-C (3-speed) tranny. The torque lock was not disengaging. Never fixed it because it appeared to be a difficult job. Link to comment Share on other sites More sharing options...
KevinW Posted June 28, 2007 Report Share Posted June 28, 2007 Kevin, I disconnected the plug into the transmission and the problem went away. That being said it IS therefore the TCC. I do have a question for you. Why would the transmission still function normally without the TCC hooked up? Is the tranny now functioning like a pre-electronic tranny? What could be the consequences? And if there are consequences explain why/how the consequence occurs. Hope to hear from you soon! Kyle TCC application is the only electrically controlled function of the THM200-4R. All gear changes are handled mechanically via the valve body (using inputs from the governor and T.V. cable). The TCC reduces slippage in the torque converter (somewhat of a fluid coupling) under conditions where torque multiplication is not necessary; this reduces the conversion of mechanical energy to heat, improving driveline efficiency. TCC application benefits from electronic control because of the required complexity for sufficient refinement. The control algorithm assesses variables such as vehicle speed (different thresholds depending on the status of the 3rd gear switch input), rate of throttle movement, coolant temperature, fuel control status, etc... ___________________________________________________ Link to comment Share on other sites More sharing options...
kdaddy Posted June 28, 2007 Author Report Share Posted June 28, 2007 Kev, So what your saying is that by disconnecting it I basically have an "old school" transmission now. In other words it is operating like a tranny prior to electronics. Give me a Yes or No if I'm correct. Hope to hear from you soon! Kyle Link to comment Share on other sites More sharing options...
kdaddy Posted July 18, 2007 Author Report Share Posted July 18, 2007 So is it a Yes or No regarding disconnecting the TCC. Just in case you missed the similar post. Link to comment Share on other sites More sharing options...
KevinW Posted July 18, 2007 Report Share Posted July 18, 2007 No, I am not aware of any "Old School" transmissions with an overdrive top gear (0.67:1) and no TCC. ___________________________________________________ Link to comment Share on other sites More sharing options...
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