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03-19-2013
I have a 99 Pontiac Grand Prix GT n/a that is starting to have slight transmission issues. I talked to my local transmission mechanic (who is the only transmission mechanic I will have work on my car) about the issues and a possible rebuild but with a change in the final drive ratio from the 3.29 to the 3.05. He wasn't sure if it was possible and what, if any, computer issues that might cause. I guess what I am wondering is if it can be done and what all it involves. Anyone with any idea?
Last edited by rbob900; 03-19-2013 at 06:16 PM.
03-19-2013
Final drive? You mean changing your differential and you only have 3.29 gears if you have a comp G or GXP
03-19-2013
I thought the 97-03 GP GT's had 3.29 gears, while the GTP has 2.93?
If you change the gear ratio you would have to tune for it I would think or it would confuse the PCM and cause strange shift points and whatnot.
03-19-2013
You'd definitely need a tune but no only the comp G and GXP came with 3.29 gears all other cars came with 2.93 and trim level (SE, GT, GTP)
03-19-2013
you sure about that fella? lolall other cars came with 2.93 and trim level (SE, GT, GTP)
03-19-2013
Se and gt had 3.29
03-19-2013
And you have to tune for the swap
03-19-2013
Yup you would need a tune.
03-19-2013
A 99 Grand Prix SE (with a 3.1) had 2.93 gears I know this for a fact
03-20-2013
Then someone swapped the trans because from the factory they had 3.29's. My grandma had one.
03-20-2013
GM 4T60-E transmission - Wikipedia, the free encyclopedia
Although I don't see why you would want to go to a lower gear other then fuel mileage you can do it. But it would require a tune.
03-20-2013
The link is to 4T60, 98+ all had a 4T65. Gear ratio's were close, not exact.
asite: I dunno what goofy thing or factory ordered car your Grammy had, 2.93 was only used in SC cars, on any GM 3800 platform from 97 up.
GT would be 3.29
Regal could be found as a 3.05
Bonneville, Park Ave, Riviera, LeSabre etc could be found as 3.05 in an NA version. Most of them could also be found as a 2.86 (or was is 2.85).
I've seen swaps where it didn't confuse the pcm. If you found issues/TCC lockup acting funny then you could reprogram. Or reprogram from the start. IMO you need to reprogram because your shifts will happen too soon based on the 3.29 points. So the 3.05 is likely to be boggy.
03-20-2013
You have to click on the 4t65e once you get into the link. 4t60 isn't a whole lot different then the 4t65 which is why they are combined into one page.
03-20-2013
Can't click from current location. Thanks for the info though, I didn't realize it was in there as well.
03-20-2013
No problem. Only thing about that page is its showing the gxp with the 2.93 and everyone else is saying it is a 3.29. The comp g is listed with the 3.29 though.
03-20-2013
I thnk the GXP had taller gears. Hang on..lets get confirmation
03-20-2013
yup its truth, i was reading an article over on ls1 tech about the monte getting 3.29 and gxp getting 2.93.
03-20-2013
I would love to know why they chose to put a 2.93 in these cars. Maybe a reliability thing.
03-20-2013
Better top end better gas mileage slower acceleration
03-20-2013
Only true reason would be better fuel mileage. From the factory they had a limiter on top speed.
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