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Thread: help with tranny upgrade 97 GTP

  1. #1
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    help with tranny upgrade 97 GTP

    gone thru the last GM reman(#5)
    all the others were under extended warranty and GM warranty.
    Im looking at a trans in a junkyard G6. Its a 2006 G6 GTP with 3.9.
    Its supposed to have a 4T65E but i dont think its an HD like the GP has.
    So question is can someone verify by tranny code(Ive looked everywhere to try and decode it) Also can someone give some input on the things I need to change to make this work. I know I need to add my external Pringle switch,and possibly use a RH axle shaft off a GP GT model with a non HD unit.Anything you can add to this will help.
    Also of note is that the complete 3.9 motor is still there,may snag it as it needs to come out anyway.

    What pattern is the bellhousing on the 3.5/3.9?
    Last edited by v6droptop; 09-29-2010 at 08:48 PM.

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  3. #2
    Mud in the hvac box again FlyinGTP's Avatar
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    3.5/3.9 both use the 60 degree also know as the fwd bell housing bolt pattern.

    the only differences between a 4t65e and 4t65 hd is a larger diff and cover and final drive gearing of 2.93. In your case you may want to look for a comp g version of the 4t65e hd, they had 3.29 gears from the factory and also have the paddle shifter valve body. also the 03 and newer wiring of the gp trans will be nearly plug and play in your old car. so any 97-02 4t65e will require a bunch of repining the trans connector. The easiest thing you may want to do is get a g6 gtp trans as a direct bolt in deal, and then get hd upgrade for the differential and diff cover along with the gp gtp pass side axle.

    out of curiosity what keeps happening to your other transaxles. I have seen some pretty heavily modded gtp's run stock trans for a long time with out killing them. and they make way more power then a g6 gtp.
    Peeing in people's cheerios 24/7!
    97 GTP & 00 GP GT



  4. #3
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    May have mis understood
    I have a 97 GTP
    I just bought a junkyard engine trans out of a 2006 G6GTP 3.9
    The G6 is manual shift(i guess just like tap shift only uses a shifter control not a paddle.)
    I got the passenger side axle from the G6 in case I need it too.
    I may switch the diff out of my old GTP trans and also the sprockets to retain the 97 GP GTPs ratio
    the G6 supposedly has a 3.69 ratio
    I may sell those to help offset this.
    I dont know what the failures were as local dealer did them under extended warranty.
    One cracked the case and this may have also. This one wont even lock in park so something bad wrong inside.
    Now that I have a trans I can use for parts Ill dive into it.

    So what sums this up is
    97 GP GTP 4T65e-HD needs replaced
    have 06 G6 GTP 3.9 trans (4T65e) with manual/auto shift and 3.69 ratio

    How hard is it to adapt a manual/auto shift of should I just use the 97s valve body?

  5. #4
    Mud in the hvac box again FlyinGTP's Avatar
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    i did misread it i thought you had a g6 gtp you were trying to put a gp gtp trans in. you do not want a g6 trans for a 97. 97 is what i have and is a major pain in the ass. it has a unique pin out and connector setup for the transaxle. this means that without completely re pinning the connectors a 98-02 trans won't work because the internal trans harness is different. it gets even better in 03 they changed the internal harness and setup again. the newer ones need more repinning to make it work. also anything with a manaul shift option has a different valve body and selector shaft in it. a 97 pcm will have no way to utilize that function. the pcm was changed for 98-02 and then a different style pcm was used starting in 03. only the newest style unit is capable of tap shift or manual shift stuff and i'm doubtful the 03 style pcm could even do it as it was in between stuff similar to like obd1.5 in the fbodies.

    after enough rewiring is done it should be possible for 97 pcm to control the newer trans, but it will not be plug and play and the manual shift selector shaft and valve body are going to be an issue because you will not be able to use manual 1,2,3. because the shifter layout went PRNDM once in M you would use the paddles to select the manual gear. Ultimately i don't think you will be able to make this work with your current setup. I would probably take that transaxle back and get my money back. what you ultimately want is a 97 4t65e HD with a XA valve body. it will also be labeled in a MN7, and you will want one with a 2.93 final gearing. If you can not find a 2.93 final drive unit you can have the gearing changed via hp tuners.

    If you truely want to try and make the manual shift unit work, what you will have to do is get a 04 and newer comp g pcm, a comp g floor shifter, comp g paddle unit which will likely require the clock spring and steering wheel and then splice it all together rewire the engine harness to make it work with the new engine or trans(probably easier to just get a 04 comp g engine/trans harness and chop the electronic throttle stuff out. then use hp tuners to change the comp g standard 3.29 gearing in the pcm to 3.69.
    However you will probably need hybrid flash to make this work as the manual shift cars were all drive by wire throttles which can not control a iac valve your cable throttle needs. and unless you know somebody getting a hybrid hp tune is not an easy task for a v6 pcm if at all. so you may want to swap in electronic throttle too for ease of pcm use. Overall it's probably not worth the hassel for something that doesn't shift fast enough and tends to hit the rev limiter a lot.

    ultimately you need to reflash the pcm with the correct gearing failure to do so will cause internal damage to the transaxle.
    Peeing in people's cheerios 24/7!
    97 GTP & 00 GP GT



  6. #5
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    Again I want to change the diffy and sprockets gears with the 97 so I will have a HD diff and correct 2.93 gear set,no tuning needed.
    The Pringle switch will be used from the 97 so that I dont have to rewire for the selector switch.
    I can handle changing pinouts and or making a custom harness.I have some spare pigtails and can even make adapter harnesses so no wires are cut.
    What Im not sure of is the valve body and if left in auto mode in the 97 car will the 06 trans shift fine ?
    Good 97 GTP trans are impossible to find.Ive given up on GM remans.thanks for helpin,keep the input going

  7. #6
    Mud in the hvac box again FlyinGTP's Avatar
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    well the hd diff doesn't determine the final drive that is determined by the drive chain and it's sprockets. if your going to swap that between transaxles you may as well rebuild the 97 because it's pretty much all apart at that point. the drive chain can't be removed until nearly the end of the disassembly process.

    you could swap the selector switch however the selector shaft will still be different and the valve body still will have issues. It's a lot of work to have a partially functioning transaxle.

    your probably better off to rebuild the 97 and upgrade a few of the weak links and call it a day you will save yourself some major headaches.
    Peeing in people's cheerios 24/7!
    97 GTP & 00 GP GT



  8. #7
    Newbie PRICES GRAGE's Avatar
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    the gm remans arent that good as most think if u read there build specs they only relace worn or damaged parts they do not update them i had many gm remans apart 700r4s 4l60es 4t60 and 65 and 4l80 there not good rebuilds if u were going to buy a reman i use Jasper if the reman route is takn but i usually rebuild trannys in house swaping the newer unit is not going to be a easy task and youll have a lot of time making it work my suggestion is send both to a rebuilder have them use the newer drums and sprags keep your final drive the ecm will need reprogramed if changed have them install a trans go shift kit theres a few other mods to make one work right and stay together

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