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Old 04-27-2010, 11:13 PM   #1
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Default 4T65-E Transmission Swap Out

Hello,

Last Friday I swapped out my 2001 SE tranny with another 4T65-E that I pulled out of another 2001. Here is the deal:

My wifes 2001 SE has had issues in the past with the maximum adapt / long shift code. I replaced the PCS solenoid and flushed it. It lasted awhile, but ended up slamming into gear again within 40,000 miles. Finally lost 1st and 4th because I just didn't get to it quick enough.

So, since I had a tranny that I know was good I decided to swap out the problematic unit. The replacement worked fine in the other car it was pulled from. Unfortunately, it slams into gear and whines just like the other trans due to max pressure being applied. However, this time the long shift code is not being set. It set a 0730 code....incorrect gear ratio. Reset and drove the car around with the scan tool monitoring and it doesn't like 1st and 2nd...3rd and 4th seem to be within spec. Keeps setting 0730. So...I have an extra PCM with identical service #'* and part #'*. Tomorrow I will have the other PCM flashed at the dealership and see if that helps me out. I would appreciate any info if someone here has been down this road before. I have never had to deal with a gear ratio issue in a non-four wheel drive vehicle before and wonder what exactly I should be looking for. I don't like to be the "throw parts at it guy" but it eases the pain when I have the spares. Thanks and good night.....
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Old 04-28-2010, 06:52 AM   #2
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Sounds like the donor trans has a different final drive ratio. If your paying to have the PCM flashed/whatever. Don't bother. Just have it programmed to the proper ratio. The model on the backside of the transmission data tag can tell you exactly what FD it has. Dealer should know this.
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Old 04-28-2010, 07:37 AM   #3
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I'm on the same page as Mike here.

Either swap the differential from the old trans to the new one or have the pcm flashed for the gear ratio in the new trans. Sounds like you had A gearset in the original trans and put B in with the new trans.

The gearing is only on the diff as long as these were both non-hd transmissions.
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Old 04-29-2010, 04:07 PM   #4
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Thanks for the pointer guys. I really appreciate it. I have the car at the dealer and have asked the service manager to check for the tag and program in the correct final drive ratio. I will let you know how I make out with that.

While I had it apart, I gave her a fresh set of ultra premium rotors, ceramic pads, a wheel bearing, and a left half shaft. Should be good to go for quite some time once the tranny issue is resolved.

Thanks again and take care.....
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Old 04-29-2010, 08:15 PM   #5
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Hello again,

I just got off the phone with the dealership mechanic and I am not real happy with the report. He said that he had flashed the PCM with no problem, but I have a transmission with an incorrect drive ratio. The car is all set, but needs another transmission.

???????????

I asked them to do as Mike said....program the PCM to match the final drive ratio from the transaxle ID tag because I swapped trannys and it kept posting the P0730 "incorrect gear ratio" code. That'* right......he reported to me that the car is all set but there is a problem that happens to be the very reason why I brought the car in for service in the first place. Just so you guys know, I was polite and didn't give him a hard time as he is not the senior man and may not have that much knowledge on the topic. I will speak with the lead tech tomorrow.

My question to you my good people is this.....Is it a difficult procedure to locate and input the new data / criteria regarding the FD ration in the PCM? I am sorry, but I have no experience at all with any PCM programming procedure and have never even seen the magical tool required to perform the task. It is frustrating to me that I can rip the damn car into pieces and reassemble it with every fastener back in it'* proper place, but I do not have the ability to gain access to the PCM parameters and make changes via a decent scan tool. Oh well....that'* how it goes. I am unsure of the next step. If these guys tell me that it is a parameter that can not be reprogrammed....what do I do then? Try another dealer? Mike....I live less than two hours from Elmira....want a quick side job?? Worst case is what?? Swap out the differential from the other tranny? Can that be done with the trans in the vehicle? I have rebuilt a few standard trannys, but am a "swapper" when it comes to the automagics.

Again, thank all for your help with this frustrating issue. If you guys can bail me out of this one, I will certainly try my best to return the favor somehow, some way. Take care............
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Old 04-30-2010, 08:28 AM   #6
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I have HP Tuners with the ability to make that change for you. All I'd need is to know the gear ratio and vin number. Then I could write that onto a pcm. I don't have any 01 Bonneville pcm'* around to write onto, otherwise I could do this today.
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Old 05-06-2010, 05:29 PM   #7
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I wanted to follow up on this thread and let the readers know that the problem is no more. Thanks to Billboost37 and Mike1995, and some good old fashioned problem solving, I managed to get the tranny squared away.

Turns out, that there were a couple different transmissions available in 2001. My car originally came with a 4T65-E 1PAB transmission with a 2.86:1 gear ratio. My donor transmission was a 4T65-E 1PBB with a 3.05:1 gear ratio. They are identical in every other way (to the best of my knowledge). That is why the tranny kept tossing the P0730 “incorrect gear ratio” code.

So, one of two things had to happen. I either had to find a way to change the vehicles onboard computer (PCM) to accept the 3.05:1 ratio or swap the differential with the original to physically change the gear ratio back to 2.86:1.

I opted for the PCM programming change because it sounded easy and quick and I had never messed with a front wheel drive differential before. Well, in my case it was not quick nor easy. My buddy has been a GM certified mechanic for many years and has some nice tools. He tried to make the change via his Tech 2 scanner and his Snap On Modis scan tool. No luck. Off the car went to a local dealer. They also could not make that single change. All they could do was download the original program associated with my VIN and program my PCM with that. That was useless to me because now I had a nice fresh updated PCM program with the original 2.86 ratio. They were however kind enough to alleviate me of $130 for not fixing my car and telling me to replace the whole transmission.

OK…since I was spinning my wheels trying to get the PCM reprogrammed, I figured I would tackle the differential swap so I could finally give my wife her car back and she would give me back my 95 Bonnie…..she missed me and I missed her. Yeah….the car.

I took a bunch of pictures along the way and will post them along with some detailed steps that I had taken when I get a chance. But for now, just know that once the differential was swapped out with the original, the PCM was happy and the transmission shifted like new again. It took me a few hours but was well worth the effort.


So…what did we learn when replacing your own transmission?

1- Check the tag on your original tranny and the donor tranny and see if the part number matches BEFORE you install it.
2- If they do match, you would not even be reading this so I will quit right here.
3- If they do not match, you are not completely dead in the water. You either have to reprogram the PCM or swap out the differential to make a match.
4- The differential job can be done with the tranny in the car without any specialty tools if need be, but would be easier to do prior to the swap.
5- Billboost37 said that the tool / application HP Tuners can make the ratio change rather easily to your PCM so you may want to search for someone that can make that change for you.
6- Do not go to my local dealer.
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