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Swapping a 99 GT trans into 97 GTP

logan809

logan809

New member
I have a friend with a 99 gt parts car and is willing to give me the trans in exchange for some help working on it. My tranny is pretty well destroyed in my car so I figured why not get 3.29s for free? Hes a close friend and i personally know it shifts firm, no play or slip etc. My question is: what all will need to be done for the swap? I have read something about the torque converter and flex plate being different, and something about tranny fluid lines being different. Also, is there any electrical differences between the 99 non hd and the 97 HD? Any help would be greatly appreciated.
 


will also need to get it tuned as well. Shifts are set up for the 2.93. I put a regal n/a trans in mine with the 3.05. Luckily there wasn't a huge difference and the car drives fine. You will also have to either do a diff swap or buy an na cv shaft for the passenger side. Electrical is the same.
 
Also flex plate and torque converter should not be any different but if your doing the work yourself and plan to keep the car awhile it might not hurt to get a new converter. Lines could very well be different you will just need to get new fittings which I got from Napa.
 
Electrical - Same

Diff:
As mentioned, take the passenger axle or if your HD diff is still good. Swap that in with your diff cover. That would take up the extra space. The non Hd diff is smaller.

PCM:
Sometimes pcm's accept the new ratio, however you should have it put into the tune.

Trans lines:
97 is definately a threaded fitting, 99 should be a click style. When you take the trans, take the lines as well. Then connect at the radiator of your car. Poof, magic.

Flex: NA has a 245mm pattern, SC has a 258mm pattern. If you want to use the converter that comes with the new trans, either switch the flex, redill the holes or hog out the holes. I've done all and they all work well. I'm not saying hogging out the holes is the proper way, I'm saying it seems to work fine.
 
I didn't have to do anything to my flex plate? Mine came from on 01 na regal. Difference in vehicle maybe? I used the converter from the regal.
 
Which converter did you use, that would have something to do with it.

Flex holes are different based on the trans and converter.
 


Well the pump shaft broke on the original and wasn't sure if the converter was damaged so I used the one that came from the regal.
 
Odd.

Although the last trans swap I did was on a 99, he had been through 8 transmissions and his flex was dual drilled. I was pretty sure that wasn't stock.
 
Yeah all in all it was pretty painless. Wasn't nearly as difficult as I always thought it was be. Although the trans was bad still one heck of a learning experience.
 
Your transmission came from a '98 Riviera.

If it is still the same transmission and you haven't broke it again.

Doofy McDooferson.
 


If I would have known what I know now. I would have fixed the first one because that trans was still good.
 
Yeah well when its the first time iv.done it and you tear into things you havent touched before. That's when it helps. Anywho I will need to get a toon with the 3.05 doesn't like to shift at wot after rebuild.
 


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