4t80e Park Range Switch (hard shift, no reverse lights)
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  • 1 Post By basscatt
Cadillac Seville / Cadillac Eldorado Forum Discussion, 4t80e Park Range Switch (hard shift, no reverse lights) in Past Cadillac Vehicle Discussion; Before i start off let me just say the Valet switch is not the reason why my trunk won't open. ...
  1. #1
    Se\/illian is offline Cadillac Owners Member
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    4t80e Park Range Switch (hard shift, no reverse lights)

    Before i start off let me just say the Valet switch is not the reason why my trunk won't open. I saw those threads, and it's not what i'm dealing with.

    Just want to make this clear. I removed a 4t80e FROM a 98 SLS and installed it in my 00 Seville.

    The car runs and drives now. I made a bulleted list of the symptoms below. All this leads me to believe I don't have a working "Park Range Switch" So i dropped the pan and valvebody on both transmissions the 2000 has an internal range switch, the 98 does not have it internally. And the wiring harness connectors are all different.

    So does anybody know where the 98 has it's park range switch so it can determine which gear it is in?

    -No hashtag indicator on the PRNDL display on the instrument cluster
    -Trunk or Gas door does not open via switch or remote
    -Really Hard shift into reverse
    -Firm shift into all forward gears

    This thread i found talks of a similar issue but the thread ends with somone claiming it to be the Transmission Pressure Switch. I do not believe that would prevent my gas door from opening, or the gear shift indicator from functioning either.
    http://www.cadillacforums.com/forums...ear-after.html

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  3. #2
    basscatt's Avatar
    basscatt is offline Cadillac Owners Master
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    Re: 4t80e Park Range Switch (hard shift, no reverse lights)

    This thread i found talks of a similar issue
    but the thread ends with somone claiming it to be
    the Transmission Pressure Switch.
    I do not believe that would prevent my gas door from opening,
    or the gear shift indicator from functioning either.
    http://www.cadillacforums.com/forums...ear-after.html

    ------------------------------

    I would have to agree with you on that one -
    I can't imagine a trans pressure switch would prevent
    the trunk and gas doors from opening -

    installing the wrong trans COULD have a link -

    the gas door and trunk buttons will NOT work -
    unless the car is in PARK -
    possibly neutral also - but I never checked -

    so - if the trans does not signal it is in PARK -
    the trunk and gas door buttons won't work -

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    Se\/illian is offline Cadillac Owners Member
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    Re: 4t80e Park Range Switch (hard shift, no reverse lights)

    yes so now i have to find where they put the switch on the 98 cars to get this car to behave properly. I cannot believe GM changed so many things on these cars so frequently, hardly cost effective.

    My friend was looking at some exploded views of the 98 shift cable linkage and he says it looks like it mounts on top of the transmission near the throttle body. Any input?

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    basscatt's Avatar
    basscatt is offline Cadillac Owners Master
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    Re: 4t80e Park Range Switch (hard shift, no reverse lights)

    Quote Originally Posted by Se\/illian View Post
    yes so now i have to find where they put the switch on the 98 cars to get this car to behave properly. I cannot believe GM changed so many things on these cars so frequently, hardly cost effective.

    My friend was looking at some exploded views of the 98 shift cable linkage and he says it looks like it mounts on top of the transmission near the throttle body. Any input?
    ---------------------------------------
    rather than trying to mickeymouse the 98 trans to try to get it working -
    just get the correct trans - and be done with it -

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    Se\/illian is offline Cadillac Owners Member
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    Re: 4t80e Park Range Switch (hard shift, no reverse lights)

    Quote Originally Posted by basscatt View Post
    ---------------------------------------
    rather than trying to mickeymouse the 98 trans to try to get it working -
    just get the correct trans - and be done with it -
    putting that trans in was not a walk in the park to do by myself. I'm looking to sell the car anyway. I'm already upside down on what i've got into it. As it sits it doesn't need much to make it a nice driver again. All i really need to make that happen is a blower motor, steering angle sensor, and that gear shift position switch. If it's as easy as ordering the part and installing it on the shifter itself under the center console than i'd rather do that.

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    Re: 4t80e Park Range Switch (hard shift, no reverse lights)

    Quote Originally Posted by Se\/illian View Post
    putting that trans in was not a walk in the park to do by myself. I'm looking to sell the car anyway. I'm already upside down on what i've got into it. As it sits it doesn't need much to make it a nice driver again. All i really need to make that happen is a blower motor, steering angle sensor, and that gear shift position switch. If it's as easy as ordering the part and installing it on the shifter itself under the center console than i'd rather do that.
    -------------------------
    and PITY THE FOOL WHO BUYS IT - right?
    maeng9981 likes this.

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    Re: 4t80e Park Range Switch (hard shift, no reverse lights)

    The range switch change came with the 00 Northstar update. The 00+ cars will not be equipped with the extra wiring 93-99's had. The 93-99 ones are mounted on top of the trans and reads directly off the shift rod, with two separate wiring harness for neutral safety switch and shift range indicator. The 00+s are internal to the transmission and utilizes the trans wiring harness. I don't think there is any alternative to this or a way to make a 98 trans work with a 00 car. Either major wiring modification is required (which is not recommended at all), or it's just not possible.

    The harsh shift might have been caused by the shift adapt. Your PCM has learned the behavior of your old trans, and still has line pressure settings for your old trans. The service manual suggests that you reset the shift adapt function whenever you replace the transmission using Tech-II. But I believe the PCM will re-learn itself over time, it just takes longer than starting out fresh.

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    Se\/illian is offline Cadillac Owners Member
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    Re: 4t80e Park Range Switch (hard shift, no reverse lights)

    Quote Originally Posted by maeng9981 View Post
    The range switch change came with the 00 Northstar update. The 00+ cars will not be equipped with the extra wiring 93-99's had. The 93-99 ones are mounted on top of the trans and reads directly off the shift rod, with two separate wiring harness for neutral safety switch and shift range indicator.
    Thank you maeng9981!!! You are on point. This is what i was unsure of. My friend, who is very Cadillac minded, was looking at the exploded parts view and said the the sensor was on the shift rod. I've disassembled two 98' 4t80e's. I didn't remember seeing anything that resembled a range switch. I just noticed the linkage was much different, and had a oddly shaped cast aluminum arm bolted to the casing.

    Quote Originally Posted by maeng9981 View Post
    The 00+s are internal to the transmission and utilizes the trans wiring harness. I don't think there is any alternative to this or a way to make a 98 trans work with a 00 car. Either major wiring modification is required (which is not recommended at all), or it's just not possible.
    I'm almost certain it is possible. When you compare the wiring schematics of the two respective shift range indicators, the wires still retain all the exact same pin out designations. It's just a matter of depinning the transmission harness and routing those wires to the 98' configuration and crimping a new connector.

    Quote Originally Posted by maeng9981 View Post
    The harsh shift might have been caused by the shift adapt. Your PCM has learned the behavior of your old trans, and still has line pressure settings for your old trans. The service manual suggests that you reset the shift adapt function whenever you replace the transmission using Tech-II. But I believe the PCM will re-learn itself over time, it just takes longer than starting out fresh.
    Correct. It did adapt after driving the car. The shifts in all forward gears have become less harsh, but as a failsafe the PCM has kept the line pressure higher since it has no signal from the range switch.

    Quote Originally Posted by basscatt View Post
    -------------------------
    and PITY THE FOOL WHO BUYS IT - right?
    Yes and No I do plan to be honest and disclose 100% what has been done with the receipts I've saved. I may go as far too mark the trans pan and side case in big writing "98 SLS". I do pity the next poor soul that has to work in such cramped confines to replace that bastard tcc solenoid. What is about to be done to the trans is reversible, at the expense of repinning or just replacing the harness.

    We all know that these transmission have an extremely low failure rate. I cracked the aluminum casing on mine and the fluid leaked out while i was commuting home from work one day. I can't fault the transmission for not knowing how to rev match it's downshift. The car was at 40mph and decided to reach down into 1st gear and thrash the motor mount i had been limping around on for the last 3 weeks.
    I suspect Northstar motor mounts are made out of defective breast implants.

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    Quote Originally Posted by Se\/illian
    I suspect Northstar motor mounts are made out of defective breast implants.

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    Re: 4t80e Park Range Switch (hard shift, no reverse lights)

    This thread should have been called, "Is a '98 & '00 4T80E trans interchangeable?".

    But since it's already done, it does look like the rewire is possible.

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