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Thread: Transmission not working properly

  1. #1
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    Transmission not working properly

    Alright, so I have a very, very strange problem that perhaps some of you can help me with.

    1995 Regal, L67 engine swap, 3.4 pulley, headers, CAI.
    1999 Monte Carlo PCM
    2003 Buick Century 4T65E + HD trans, 3.29FDR, 86k miles

    A friend of mine finished the swap for me recently, and due to problems tuning (partially due to rotten vacuum hoses and also due to insufficient fueling), he left me with his HPTuners interface so we can get the tune working.

    The transmission doesn't catch 1st gear. Its that simple. Plus, it occasionally slips at WOT at higher RPMs in 2nd and 3rd. When colder, it will stutter while accelerating from a stop in 1st gear or simply not catch on until a higher RPM, but after you abuse it for a while, the slipping becomes worse.

    I went to a transmission shop and they pulled a code: P0748 - pressure control solenoid electrical. They tried to convince me that the sprag assembly is broken and that's why it doesn't engage first gear. The clutch pack isn't bad because if it was, the clutches would be burning against each other and my fluid would smell. It does not smell.

    If I manually downshift into 1st gear when slowing down and coming to a stop, at exactly 10mph (as is in the tune), every single time, the car will give a a light jolt engagement into 1st gear, and when I accelerate from that stop, I have perfect gear engagement and can roast my tires all day long. If I know I'm going to come to a complete stop, and I downshift into 1st gear after I've already stopped, I will have 1st gear when I accelerate again. If I do not downshift into 1st, I have no first gear, and upon acceleration the car barely moves.

    I've already tested the PCS. Resistance is 5.3ohms, and there is no wiring fault between the 20-pin trans connector to the PCM on the PCS high and low wires. This transmission was bought with a 6 month warranty from a company that parts out auto insurance auction cars. This particular transmission had 86k miles and the salesperson said that this transmission was road tested before being pulled.

    I have heard that the PCS is different between the years 2002, 2003, and 2004, and that the 2003 transmission has an electrically different PCS. As a temporary solution, we've disabled the P0748 code to prevent the car from going into limp mode, as it is perfectly driveable so long as it doesn't do that. I'm wondering if the 99 Monte Carlo PCM doesn't know what to do with this transmission.

    My guess right now is that there isn't enough line pressure to engage the clutches, and I'm considering altering the Force Motor Current tables in order to increase line pressure. I don't know how this PCS differs from the 98-02 versions.

    Any light anyone can shed on this issue would be very much appreciated. I'd like a more intelligent answer than just "you need a rebuild now" because as I mentioned, if I manually shift the gears (using the shifter linkage), everything works like a charm, and the car goes like a bat out of hell, which leads me to believe that the problem is not mechanical.

    Thank you in advance.

  2. #2
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    Quote Originally Posted by XtremeRevolution View Post
    Alright, so I have a very, very strange problem that perhaps some of you can help me with.

    1995 Regal, L67 engine swap, 3.4 pulley, headers, CAI.
    1999 Monte Carlo PCM
    2003 Buick Century 4T65E + HD trans, 3.29FDR, 86k miles

    A friend of mine finished the swap for me recently, and due to problems tuning (partially due to rotten vacuum hoses and also due to insufficient fueling), he left me with his HPTuners interface so we can get the tune working.

    The transmission doesn't catch 1st gear. Its that simple. Plus, it occasionally slips at WOT at higher RPMs in 2nd and 3rd. When colder, it will stutter while accelerating from a stop in 1st gear or simply not catch on until a higher RPM, but after you abuse it for a while, the slipping becomes worse.

    I went to a transmission shop and they pulled a code: P0748 - pressure control solenoid electrical. They tried to convince me that the sprag assembly is broken and that's why it doesn't engage first gear. The clutch pack isn't bad because if it was, the clutches would be burning against each other and my fluid would smell. It does not smell.

    If I manually downshift into 1st gear when slowing down and coming to a stop, at exactly 10mph (as is in the tune), every single time, the car will give a a light jolt engagement into 1st gear, and when I accelerate from that stop, I have perfect gear engagement and can roast my tires all day long. If I know I'm going to come to a complete stop, and I downshift into 1st gear after I've already stopped, I will have 1st gear when I accelerate again. If I do not downshift into 1st, I have no first gear, and upon acceleration the car barely moves.

    I've already tested the PCS. Resistance is 5.3ohms, and there is no wiring fault between the 20-pin trans connector to the PCM on the PCS high and low wires. This transmission was bought with a 6 month warranty from a company that parts out auto insurance auction cars. This particular transmission had 86k miles and the salesperson said that this transmission was road tested before being pulled.

    I have heard that the PCS is different between the years 2002, 2003, and 2004, and that the 2003 transmission has an electrically different PCS. As a temporary solution, we've disabled the P0748 code to prevent the car from going into limp mode, as it is perfectly driveable so long as it doesn't do that. I'm wondering if the 99 Monte Carlo PCM doesn't know what to do with this transmission.

    My guess right now is that there isn't enough line pressure to engage the clutches, and I'm considering altering the Force Motor Current tables in order to increase line pressure. I don't know how this PCS differs from the 98-02 versions.

    Any light anyone can shed on this issue would be very much appreciated. I'd like a more intelligent answer than just "you need a rebuild now" because as I mentioned, if I manually shift the gears (using the shifter linkage), everything works like a charm, and the car goes like a bat out of hell, which leads me to believe that the problem is not mechanical.

    Thank you in advance.

    Post your tune so we can poor though it. Also just so you know, the 4t65E and 4t60e have a few parts that are known for going bad and causing the problems your talking about. I personally have rebuilt a few of them and replaced broken 4th clutch hubs that for some reason let it work sometimes and not other times.

    On any note post your tune and it will be easy to see if it is in the pcm.

  3. #3
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    One more note to add, double check your powers and grounds on an engine swap.

  4. #4
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    From what I remember, 2003 transmissions have a hardened 4th, which is why I bought this specific transmisison, thinking that it would be more reliable. Now I'm wishing I had bought an 01 or 02.

    With Cam's tune, I run harsh shifts in the morning with everything working perfectly. First gear engages fine. If I get to my car go to to lunch later in the day, I'm slipping first gear off the line unless I downshift but it otherwise acts predictably. If I drive the car hard as hell, shifts become extremely harsh and TCC locks up after 2-3 WOT runs.

    With Cam's tune P0748 Delete, this morning the TCC locked up on me after 5 miles of driving and would not unlock, accompanied by extremely harsh shifts of course. Basically felt like a manual transmission that you shifted like an automatic without using a clutch. Not fun trying to keep the engine from stalling while you're accelerating at 1500 at 20mph in 2nd, maybe 3rd, I don't remember. I let the car sit, then took it back out after 2 hours and it started slipping off the line again. I drove it hard, 4-5 WOT runs, and TCC didn't lock up this time. Strange behavior.

    Anyways, let me know what you guys see in the tune, if anything. Not sure if a datalog would help, but I can get one of those as well. Under most conditions in the datalog, I was downshifting manually in order to get anywhere. I know my fuel trims are way off, and I'm working on that with Bob. I have a few more tunes to test out, and I need to install my walbro 255lph pump.

  5. #5
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    Anyone have the amperage tables for the shift pressures on a 2003 transmission?

  6. #6
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    I did some more research and found this:

    3. The Pressure Control Solenoid, PCS is different and will NOT interchange, though it may physically fit in either valve body. The solenoid is designed different and does not function the same as the earlier units. If used it can destroy a good trans because pressures will not be correct as the valve body is calibrated different to be used with the new style solenoid as well as different pcm calibrations were made.

    http://www.tripleedgeperformance.com...bout_using.php

    This is why I asked for the amperage tables.

    I called Dave there and spoke to him, and he said that the 03 transmission has only one pressure control amperage table, while the 99 PCM I have uses two (a high and a low). I'm trying to figure out:

    1. if these can be made to work together somehow, and
    2. what the differences are between the calibration settings in the PCMs for the two PCSs.

  7. #7
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    sounds like you need to change valve bodys or pcms. I don't know you might be able to ask support if they can do a segment swap and change the transmission calibration out for you.. I don't know if they can, just a thought. I would change the os to a 03 if it uses the same pcm.

  8. #8
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    The problem is I know of someone who has made this work, I just haven't been able to get ahold of him.

    http://www.nepontiac.org/forum/viewtopic.php?t=4318

    I just need to figure out how he did it and he hasn't responded to my PM yet.
    Last edited by XtremeRevolution; 10-07-2010 at 04:33 PM.

  9. #9
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    Have you tried turning the dtc off so it's not used?

  10. #10
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    Quote Originally Posted by Google View Post
    Have you tried turning the dtc off so it's not used?
    Sorry, I'm a bit new to this stuff. What is the DTC, and how do you turn it off?

  11. #11
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    Quote Originally Posted by XtremeRevolution View Post
    Sorry, I'm a bit new to this stuff. What is the DTC, and how do you turn it off?


    Here's ur sign.


    ..

  12. #12
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    Quote Originally Posted by Google View Post
    Have you tried turning the dtc off so it's not used?
    I did turn off P0748, which kept the PCM from locking up TCC on me when the engine is hot. Don't know why it locked up on me on the way to work this morning though.

  13. #13
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    To be honest with you, I am guessing. I have not done this swap before so without knowing the in's and out's of your pcm and transmission wiring of the three setups it's hard to say. I wuld need to see wiring schematics for all three to figure out what to do/change to make it work. Sorry I am unable to help you more. Someone might know around here though.

  14. #14
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    My 99 GP does the same thing sometimes. Hit it hard from a stop and it just shudders and goes no where. 4th went out of the previous trans but the used one I got doesn't seem much better.

  15. #15
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    Quote Originally Posted by flame View Post
    My 99 GP does the same thing sometimes. Hit it hard from a stop and it just shudders and goes no where. 4th went out of the previous trans but the used one I got doesn't seem much better.

    sounds like a mechanical problem, like the 1-2 band or wear on the 1-2 servo bore in the valve body.

  16. #16
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    I fixed the slipping issue earlier. I adjusted the FMC values to lower them, and every time I lowered them, the car slipped less. Hasn't slipped now in 500 miles.

    However, someone on another forum told me they had the exact same problem due to the trans tune being different. Does anyone here have a 2003 transmission tune (Century, Regal, Grand Prix, etc.) that they could send me so I could compare values?

  17. #17
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    also clean your MAF, with sensor safe CRC throttle body or actual MAF cleaner, especially if you have K &N filters, if the are the hot wire type you may need to use a q-tip.


    I could of had a V8

  18. #18
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    Here is my stock 03 GrandPrix GT it should have the same gearing as your trans but check first.

    02 VW Golf

    98 Bonneville SSE
    03 Grandprix GT
    EcoModder

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    Quote Originally Posted by Google View Post
    To be honest with you, I am guessing. I have not done this swap before so without knowing the in's and out's of your pcm and transmission wiring of the three setups it's hard to say. I wuld need to see wiring schematics for all three to figure out what to do/change to make it work. Sorry I am unable to help you more. Someone might know around here though.
    if u want to look those up shoot me a pm and i can send you wiring schematics i have access to alldata and GM SI

  20. #20
    What gears do you have in the tranny?