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500, 472, 425, 368 Discussion, Transmission in Cadillac Engine Technical Discussion; Hello, having a hopefully small problem with my transmission. Engine revs and won't seem to shift up to 2nd gear ...
  1. #1
    cady75 is offline Cadillac Owners Member
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    Transmission

    Hello, having a hopefully small problem with my transmission. Engine revs and won't seem to shift up to 2nd gear (max speed 25 mph). The only thing that has changed since last time I drove it was the new headers and exhaust. Car ran fine after rebuilt carb. (one vacuum hose tough to stay on at back) The muffler guy knocked out my trans dip tube and leaked Alot of fluid onto his floor. He replaced fluid and I checked it warm. OK. Any ideas. I was going to put in some of that transmission fluid that promises to improve shifting but this was almost an overnight change. I also notice that on when I shift into drive the pointer is at R. Any ideas? Thanks

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  3. #2
    74eldog is offline Cadillac Owners Fanatic
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    Re: Transmission

    I've got an idea ... but first, what yr, motor, trans etc are we talking about,,, I presume it's a 500 with th-400 or 425....

    If you've got fluid, i would focus on the vacuum hose that is tough to keep on, that line more than likely goes to your vacuum modulator, without that particular line hooked up you won't go past 25 mph.....Not sure where your modulator is located on your tranny, trace the line and look for open ports on the tranny...

    Exhaust guy might knocked it a loose.....

    Good Luck

  4. #3
    cady75 is offline Cadillac Owners Member
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    Re: Transmission

    Thanks, First thing AM will go for vacuum line. I wiggled the one I thought but I didn't trace it out to the other end.

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    cady75 is offline Cadillac Owners Member
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    Re: Transmission

    Yup, that vacuum line was the problem. Drove on highway 80mph no problems. Thanks. Can feel difference from 50 - 80 with my new exhaust manifolds. Just have to smooth out throttle linkage. It feels like there's just two levels, city speed and very fast.

  6. #5
    74eldog is offline Cadillac Owners Fanatic
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    Re: Transmission

    Great News., Glad U Got It Goin!!!!

  7. #6
    cady75 is offline Cadillac Owners Member
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    Re: Transmission

    Having the transmission running good again got me thinking that after all this time I've decided to look at the transmission on my 75 Eldo. Until recently I assumed I had the TH400 in here. As a FWD is it really the TH425 and if it is, any ideas on torque converters to get more out of what this engine is capable of. This is a street car, I don't want to have car revving like crazy coasting to a light!

  8. #7
    terrible one's Avatar
    terrible one is offline Banned
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    Re: Transmission

    Quote Originally Posted by cady75
    Having the transmission running good again got me thinking that after all this time I've decided to look at the transmission on my 75 Eldo. Until recently I assumed I had the TH400 in here. As a FWD is it really the TH425 and if it is, any ideas on torque converters to get more out of what this engine is capable of. This is a street car, I don't want to have car revving like crazy coasting to a light!
    Yes, you do have a TH-425. About torque converters, TH-400 converters will fit your TH-425. I think that the factory converter in your Eldo has a really low stall. 1200 if I'm not mistaken. However, I kind of lack in the torque converter/transmission section. I don't know how high you would want to go since you aren't doing anything to the engine. If I'm correct, you want your converter stall speed to be lower than your cruise RPM, or else it will slip during normal cruising/driving, which will lead to some hardcore wear and tear on the transmission. Maybe an 1800 stall or so?

  9. #8
    cady75 is offline Cadillac Owners Member
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    Re: Transmission

    The engine will have either the MTS #10 or more likely #15 grind with new rockers, 3 angle valve job with longer pushrods. It's this engine that I want to get more power to the wheels not what I have in there right now. I have a pretty much stock 75 Eldorado. This 3 speed auto seems like it would be lagging way behind on its shift points?!

  10. #9
    terrible one's Avatar
    terrible one is offline Banned
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    Re: Transmission

    Oh okay. Then an 1800-2000 stall should be about right, I would think.

    You're right about the stock shift points. They are very early. From what I can gather, there are three solutions to getting it to shift higher.

    The first is grinding on the mechanical governor. Grinding about 1/16" from the inner weights raises the shift point apx 500 rpm.

    Second, I have found that Transgo makes a "reprogramming kit" that, from what I can tell, somehow allows you to set the shift points. Here: http://www.transmissionpartsusa.com/...-000469741.htm

    Last, I heard that B&M makes, or once made, a kit to change shift points, I think through the governor. Don't know much about this one.

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