Couple 4T65e-HD questions

Hello!

I own a 1999 Grand Prix GTP, mostly stock, this Fall I might build a fairly typical 3.4" Pulley setup. 3 questions:

1. I have "performance shift", as you probably already guessed by the car's trim level. There is a mentality in the GP community that running in performance shift mode will help protect your clutch plates from wear (less slippage). Is this truth or a myth?

2. I've read somewhere that you if you use the 2.86 differential, and 37/33 gears, you can end up with a 2:55:1 final ratio. How feasible is a rebuild using this ratio?

3. I noticed that after doing the typical alternator rewire modification, (simply a larger gauge "jumper" between fuse block and alternator) that my transmission seems to shift firmer and more quickly. Is this likely a result of the modification, or just the fact that the PCM reset while the battery was disconnected and the PCM "learned better" while driving again?

Originally Posted by GTP131

Hello!

I own a 1999 Grand Prix GTP, mostly stock, this Fall I might build a fairly typical 3.4" Pulley setup. 3 questions:

1. I have "performance shift", as you probably already guessed by the car's trim level. There is a mentality in the GP community that running in performance shift mode will help protect your clutch plates from wear (less slippage). Is this truth or a myth?

Pretty Much a myth. The Shift times are slightly quicker, and the pressures are firmer, but really its just Engine RPM that is the Difference

2. I've read somewhere that you if you use the 2.86 differential, and 37/33 gears, you can end up with a 2:55:1 final ratio. How feasible is a rebuild using this ratio?

I wouldnt use this ratio. you will have PCM issues running a not recgoinzed Diff/Gear set. The only main stream ones that GM used in cars is the 2.86, 2.93, 3.05, 3.29, and 3.69

3. I noticed that after doing the typical alternator rewire modification, (simply a larger gauge "jumper" between fuse block and alternator) that my transmission seems to shift firmer and more quickly. Is this likely a result of the modification, or just the fact that the PCM reset while the battery was disconnected and the PCM "learned better" while driving again?

The car has an Adptive Shift function, so that being said the Trans is learning how you drive

Originally Posted by 2003 SSEi

Pretty Much a myth. The Shift times are slightly quicker, and the pressures are firmer, but really its just Engine RPM that is the Difference

I'm almost positive the PCM has only one set of shift points.

Although I appreciate the responses, I was looking for some answers from Trannyman rather than random "internet people". Otherwise I would have posted in the standard transmission category.

Hello,

I appologize for the slow reply but dont look at this section often unless we make a new thread with an update. It is always best to email TechSupport@TripleEdgePerformance.com for technical questions, or send us an email letting us know you posted and have a question.

I will answer you questions below in BOLD


Hello!

I own a 1999 Grand Prix GTP, mostly stock, this Fall I might build a fairly typical 3.4" Pulley setup. 3 questions:

1. I have "performance shift", as you probably already guessed by the car's trim level. There is a mentality in the GP community that running in performance shift mode will help protect your clutch plates from wear (less slippage). Is this truth or a myth?

In terms of a stock pcm tune- Driving in performance shift mode does give you slightly quicker and firmer shifts but is not that much of a difference over the normal driving mode, and as mentioned above the shift points are moved up a bit and is more of a difference in that.

Now if you got a custom tune or ordered an upgraded pcm from one of the 3800 vendors you will definately have firmer shifts in performance shift mode as there are seperate tables for normal and performance shift so you can have a dual profile setup which works well for most people, but a lot of really personal preference.


2. I've read somewhere that you if you use the 2.86 differential, and 37/33 gears, you can end up with a 2:55:1 final ratio. How feasible is a rebuild using this ratio?

This is true, but not sure why you would want this unless you are 90% easy highway driving and hoping to pick up a small increase in mpg. Also-the 2.86 final drive/differential is by far the weakest and has a very poor history of failures and we avoid using these even in stock applications if at all possible. Your rpms will be a few hundred lower cruising down the highway but your load also goes up to work against the lower ratio, so without testing this in depth and proving its worth I wouldnt hassle with it. You could use a 3.05 ratio final drive and split the difference and is a much more durable option but I really dont think it is going to do what your intentions are looking for.


3. I noticed that after doing the typical alternator rewire modification, (simply a larger gauge "jumper" between fuse block and alternator) that my transmission seems to shift firmer and more quickly. Is this likely a result of the modification, or just the fact that the PCM reset while the battery was disconnected and the PCM "learned better" while driving again?

Typically transmission adapts dont reset unless you clear them with a scan tool capable of this or if the pcm is completely reflashed. The only way to know is to scan transmission data and look at the adaptive cells. Changing voltage characteristics can have a small effect on how everything operates and will be more stable. I have not personally experienced this, so back to using a scan tool to verify. Honestly if the transmission adapts are reset it will likely shift worse initially if everything is stock as the pcm will compensate for wear and age by raising adaptive shift pressure over time, and when this is reset and brought back to 0 starting point it will have to relearn to your aged transmission.

Thank you very much Trannyman. Those were the answers I was looking for.