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Old 04-26-2003, 05:46 AM
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Post GM 4L80 Questions

Hey guys. I am just wondering if any of you have messed with tuning the 4L80 in the new GM trucks. I would like to modify the shift points a touch and also firm them up. I have been told this can be done with a plug in console and I have access to one. If any of you have done this or know anything about it, please let me know.

Thanks,

Chris

[ April 26, 2003: Message edited by: TurboS10 ]</p>

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Old 04-26-2003, 12:05 PM
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I am not sure what you are calling a "plug in console"

The trucks use "flash" memory in the PCM . You will need an aftermarket programmer to alter the program in there. And then it is limited on what can be done to the shift timing.

Are you looking for higher WOT shift points, or different light throttle shift points?

Most of these controllers raise the operating line pressure to acheive firmer shifts. This puts more wear on the pump of the tranny. A minor increase of pressure does not really harm the pump of the tranny.

There are some tranny only plug in devices that may provide what you are looking for. Many have three settings, "OEM , towing" Heavy duty" as an example.

I would recommend a TransGo shift kit for the 4L80E if you want firmer shifts. This kit alters the shift firmness with the accumilators and different spring, and hole sizes.

The TransGo kit also offers protection from run-away line pressures that blow up drums in the 4L80E.
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Old 04-26-2003, 08:27 PM
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I am talking about an aftermarket plug in programmer. I believe it is JET brand. I dont want to do anything mechanically due to warranty. I am actually wanting to lower the 1-2 shift point. It is at almost 6000 rpm and the engine begins to fall off just short of that. 5500 would be perfect. I would also like to firm it up just a bit through out the range.

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Chris
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Old 04-27-2003, 06:00 AM
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You need to take the truck in for service work since the factory WOT shift points are not near 6k RPM. Depending on your power train the max RPM shift should be near 5400 RPM

I believe the V8 factory rev limiter is at 5600 and fuel pump shut down is 5800 for the small blocks. I would to check since my memory is fuzzy on this.

I guess there is the possiblity that the tach is incorrect too.
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Old 04-27-2003, 08:05 AM
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I drive 2002 1500 hd with 4l80e what are you going to do with it? Mine shuts off at 95 mph now that sucks, trans shifts ok but could be harder but did that to my 96 Z-28 banging shifts are fun for awhile but everyday driveing pain in the butt.

[ April 27, 2003: Message edited by: airworld2 ]

[ April 27, 2003: Message edited by: airworld2 ]</p>
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Old 04-28-2003, 02:09 AM
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The 1-2 shift point is about 5700-5800. The 2-3 is more like the 5400 stated above. There is no fuel or rev limiting at that point.

As for the use, it is a daily driver and soon to be tow vehicle. I just wanted to firm up the shifts a little bit, not make a neck snapper out of it. I know what you mean airworld about it getting old. One of my th350's will about break your neck. I dont want anything like that. I just dont like the "sloppy" shifts at WOT the factory setup seems to have.

Maybe I need to have it checked out as stated above. Does anyone know for sure what the shift point is suppose to be? It is used, and has 50k on the odometer.

Chris
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Old 04-28-2003, 03:19 AM
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Once you use it as a tow truck(may not be what you meant) warranty goes out the window I'll bet. 4l80e is one good transmission,100,000 miles before you have to worry. Good thing GM didnt put those in everything I wouldn't have a job.Shift point's are ok tweak epc solenoid a bit you'll be happy with results ,sounds like you need a bit more pressure to make your tranny firm but not rock hard.

[ April 28, 2003: Message edited by: airworld2 ]</p>
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