Transmission reprogramming

[randym]

I have asked several times about whether the 55mph shift to 1st senerio worked only for the Allison or if it also reprograms the 4L80E, never to recieve an answer.
For those interested I found this weekend that yes the proceedure does in fact effect changes with the 4L80E 8.1 Suburban (2001) package. Most noteably it now allows the 4-3-2 downshift which is critical in many towing situations. Many times before the fix this weekend I was faced with passing a slower vehical being unable to access 2nd and wondering if I would have enough acceleration to get around before a head-on collision occured, (not really cool in my book and something that could be directly linked to GM's incompetant programmers!).

[odoh]

While you didn't come right out to say it in clear text, we are left to assume you actually executed the procedure yourself? If so, kind of gutsy I'd say. Glad it worked out (safely) for you. Thanks for the feed back. ~ odoh

[randym]

There's nothing gutsy about it, once placed in 1st the trans. immediately takes 3rd slows down and then takes 2nd slows down, hits what seems to be a neutral situation for a split second and goes to first. The whole proceedure is really very smooth actually, and the breaking effect gets you down to 1500-2000 rpm relatively quickly so before engaging 1st gear you should make sure there is no other vehicle within sight behind you and also that there is ample shoulder availible to pull onto so that you can slow to about 5mph as I did in the four times that I did the proceedure in succession.
- -Add, I also actually used 60mph for a starting point rather than 55; also it is well documented that this works for the Allison but I have never seen any comment on the 4L80E or for that matter the 60E either for which I feel the results would be the same.- -

[ 05-30-2002: Message edited by: randym ]</p>

[Wally]

randym,
You're either very brave, very trusting, or just nuts :D
I couldn't bring myself to do it to my Ally when when I had it and sure as heck would have never tried it with a 4l80. Every time I seriously considered doing it with the Allison the vision of 6000 dollars worth of tranny parts laying on the highway put it right outa my mind.

[sonofagun]

This issue gets discussed a lot. The bottom line is that the shifts are made well below red line. The downshifts are aggressive so be prepared for that but they are no more aggressive that if you were pulling a load uphill and the trans downshifted. If a shift from lower to higher rpm won't hurt the engine or trans then it won't hurt it whether you initiate the action or the computer does. This is simple logic guys. You may elect to not do it, ok. It seems to put the trans back in fast learn mode if that is beneficial to your situation.

Bob

[randym]

Surely you folks are not so naive as to think that it would shift directly to first while running at 60mph. GM may have some ignorant programmers but you can be assured that they only err on the side of overprotection and not in providing a function that would cause damage.
Now if you are into the sadistic sort of thing then go right ahead and throw it into reverse at 60 and I think that the converter will not be the only thing that is torqued, I've personnaly see cases with a measureable amount of twist from that maneuver.