1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Automatic Transmission

Discussion in 'Front-Engine Rear Drive Fiats' started by vircar, May 14, 2018.

  1. vircar

    vircar original owner

    brooklyn new york
    i recently purchased a 80 spider 2000 with an automatics trans. the car has been sitting in a garage for 15 years, has over 100k on the transmission the car was a daily driver until the day it was put in the garage it had over heated and blew the head gasket i got the car running, now the question the trans has reverse, first and second but doesn't shift into third could this be, because it was sitting idle for so long (the fluids were change by previous owner 200 miles before it overheated on him 15 years ago and i just change it now).
  2. Rod Midkiff

    Rod Midkiff True Classic

    Eugene, OR
    not knowing this specific trans I am only guessing. But might be something along the lines of a stuck governor. Drive it a little see if warm/cold makes a difference. (I am guessing you already checked the fluid level) running in Neutral Trans warm, car level.??
  3. vircar

    vircar original owner

    brooklyn new york
    its an opel GM trans have ran the car for a while and drove it for a while
  4. kmead

    kmead True Classic

    Grand Rapids, MI
    It’s the same transmission used in the Chevy Chevette as well so it can be serviced in the US with domestic parts.
  5. Peter Cecil

    Peter Cecil True Classic

    St. Joseph, MO
    It is the same auto transmission that was on many postal service vehicles so it is pretty tough. I believe that Rock Auto sells a complete overhaul kit for under $100. The fluid and filter are easy to change.
  6. Dr.Jeff

    Dr.Jeff True Classic

    Sin City
    BMW even used that trans in some 3 series US built models.
  7. vircar

    vircar original owner

    brooklyn new york
    filter and fluid were changed
  8. Paul Valente

    Paul Valente Automotive Engineer

    Motor City USA
    GM THM-200. Check the cable that goes from the trans to the throttle. If it sat a long time, perhaps it is frozen.
    Smell the fluid and compare it to the smell of new ATF. It is smells burnt, that is bad. The trans shop guys say it smells like money :)
    Generally, the clutches fry as a result of a seal going bad. The clamp force isn't maintained, the clutch slips under load. Things get hot. People walk home. I'd reach out to Steve H. He owned an Aamco Transmission shop and has probably seen hundreds of TH200s.
  9. vircar

    vircar original owner

    brooklyn new york
    thanks the fluid was change 200 miles before the previous owner overheated the car and it was red and i just changed it and the filter when i had redid the head
  10. I don't have a lot of experience with the TH200 but in principle, is very similar to other GM units. If the transmission was working fine then and isn't now, and you changed the fluid, there are a number of things that could be causing the problem. Understanding how it works is key to troubleshooting.

    The 200 has a TV (Throttle Valve) moved by the cable attached to the throttle linkage. The TV cable controls the transmission's internal "line pressure". It also has a "governor" which is a device spun by the output shaft and regulates "governor pressure" to output shaft speed. The shift valves are moved by the differential between line pressure and governor pressure. If line pressure is above governor pressure it moves the shift valve to the lower gear position. When the line pressure is below governor pressure moves the shift valve to the higher gear position.

    So when taking off from a stop; you open the throttle which raises line pressure. As the car accelerates governor pressure rises. When governor pressure exceeds line pressure, the transmission upshifts. And obviously the more throttle the higher the line pressure and the more speed it takes to raise governor pressure enough to force the upshift.

    Given that, if the shifts are late and hard, the TV cable is likely stuck, or miss adjusted to its wide open throttle position. This creates a situation where it will shift to 2nd at fairly high rpm regardless of throttle position and therefore you would have to turn a LOT of rpm in 2nd gear to force the shift to 3rd. So a test drive should demonstrate the 1-2 shift point. If the upshift is normal (not delayed) then its not likely the cable or a stick throttle vavle. If the problem is the cable or its adjustment, this is an easy fix. Disconnect the TV cable from the throttle linkage and check for smooth and free operation. If not, you found the problem. If so adjust it all the way in both directions and see if that effects the 1-2 shift timing.

    It could be a stuck cable or TV valve in the valve body.

    If its been sitting for years then it could also be that the internal seals, in this case the lip seal in the direct clutch drum, have gotten hard from age and are no longer sealing. So the TV cable/valve could be working normally and when the shift valve moves the line pressure bypasses the lip seal in the drum and doesn't apply the clutches. So it doesn't shift.

    If the TV cable and valve seem to be working normally, you could try adding a bottle to Lucas transmission additive, drive it some and see if the 2-3 shift begins to work. If not, it will likely need to be gone through.
    Peter Cecil likes this.

Share This Page