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4T65E-HD code questions

Charlie

Charlie

New member
O.k so i have a 1998 GP GTP with 4T65E-HD trans but is has problems so i went and bought a transmission off a 1999 GP GT wich i beliebe is a 4T65E (Non HD)
Now both transmissions look alike but the HD has 905 S written on it and the other one has 917, Any idea what the difference is?
And i'm going to switch the differentials on both transmission to make the NON-HD an HD does anybody here done this and any luck?
 


You should be able to swap differentials with no problems & it shouldn't give you any issues. It also a plus to have a 4t65e trans w/ a HD differental because it has 3.29 gears (same gear type in a GTP CompG). Search the forums & how-to's to find out more about the diff swap.
 
I do diff swaps. what questions do you have...???
You shoud be good. you have all the parts nec. The only thing that you will have to do is have the pcm reflashed for the trans id number change and the gear change...other than that it is just as straight forward as you stated. While reflashing pcm do line pres. increase and down shift skip, etc... Let me know...
 
I have a Performance reprogrammed PCM (changes shift point) that came with the car when i bought it would that work?
Thanks
 
yep. exactly...sorry fell asleep early...a little on the sick side. should work out perfect. Is it a cookie cutter pcm from intense or zzp?
 
I don't know exactly what PCM it is all the previus owner of the car said it changes shift points while on Performance Shift for faster acceleration other than that i don't know,
But he also gave me the original PCM that came with the car
 


the pcm needs to talk to the trans and the engine...to do this it needs to have a correct "name" to call the trans and engine, ie. the id number on the trans and the vin number of the car need to be in the pcm for everything to work smoothly.
It is just like having a conversation over email...you have to have enter the address to get the info to the other party...if you put the wrong address it won't make it and the other party will not be any the wiser, but they still know you have an internet connection, just like the pcm knows it is connected to a trans and an engine, but the details will not get to the right places if the address is missing or invalid.
 
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