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Old 02-21-2011, 07:21 PM   #1
icecats87
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quick question about a transmission

I have a 2001 grand am gt with a 4t45e tranny it has the 3.29 gear ratio i got a free transmission from a member on here its a 4t45e but a 3.15 gear ratio, will this cause any problems at all besides a little lack of performance, will it hook up perfectly and will the car run? thanks for for help
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Old 02-21-2011, 07:34 PM   #2
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It will hook up to the car fine, and it should run, but your shifting might act funny.
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Old 02-21-2011, 07:45 PM   #3
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It will hook up to the car fine, and it should run, but your shifting might act funny.
How funny do you think? my professor was doing calculations and was saying something like a 3% **** rate difference or something he said it wouldnt really be noticeable just wanted to ask if anyone else had a thought because i almost have it out of the car and didnt want it to not work after all the time it took to drop it
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Old 02-21-2011, 08:18 PM   #4
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I thought you were going to swap out the diff

There are other parameters in the PCM that are different, that might prevent it from running well. I tried a GAGT PCM in my '99 Alero, and after putting about 10 miles on it, the shifting became harder and it just did not act right. The PCMs can be reflashed, possibly a dealership could do that and retain your VIN# and OS for the vehicle.

Now I do have a 2001 GrandAm V6 PCM that you can try if you want. Only way to test it is install it, do the relearn, and see if it works.
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Old 02-21-2011, 08:30 PM   #5
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I thought you were going to swap out the diff

There are other parameters in the PCM that are different, that might prevent it from running well. I tried a GAGT PCM in my '99 Alero, and after putting about 10 miles on it, the shifting became harder and it just did not act right. The PCMs can be reflashed, possibly a dealership could do that and retain your VIN# and OS for the vehicle.

Now I do have a 2001 GrandAm V6 PCM that you can try if you want. Only way to test it is install it, do the relearn, and see if it works.
Was going to do the diff swap but my teacher said it wasn't worth tearing a completely good tranny apart, then said the 3.15 ratio wouldnt make that much of a difference so i guess ill tell my teacher that and ill probably swap the diff out
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Old 02-21-2011, 08:32 PM   #6
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like aaron said, it may shift weird, because the pcm has a set gear ratio its programmed for..and your changing that..may even set a code for incorrect gear ratio..so the worst that happens is you swap it, and get a reprogram for that transmission code.

edit..if you swap diffs. have fun with alllllll them parts x|
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Old 02-21-2011, 08:35 PM   #7
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alright i have the PCM from mpracing so would i be able to just send it back to get re programmed for 3.15 ratio?
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Old 02-21-2011, 08:38 PM   #8
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Quote:
Originally Posted by icecats87 View Post
alright i have the PCM from mpracing so would i be able to just send it back to get re programmed for 3.15 ratio?
i dont see why he couldnt do that
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Old 02-21-2011, 08:43 PM   #9
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i dont see why he couldnt do that
And then it wouldn't "shift funny" with it programmed to 3.15 correct?
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Old 02-21-2011, 08:45 PM   #10
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i wouldnt think so
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Old 02-22-2011, 03:40 PM   #11
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AaronGTR has made plenty of valid pointsAaronGTR has made plenty of valid points
Yeah, your teacher is probably thinking that it won't make a noticeable difference in acceleration... it will, but not a huge difference. The thing is, he probably has NO IDEA how the computers in these cars work. It is a completely electronically controlled transmission. Sometimes it shifts based on MPH and throttle position, sometimes based on engine rpm, depending on how hard you are driving. Messing with the gearing when it is programmed for a 3.29 FDR is why I said it might shift funny. Either use the correct diff, or get the PCM reprogrammed to properly work with the new one.
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