2-l shift quality !

[sooty]

I have had a problem with 2 to 1 shift at slow speed. This happens when usually going uphill and slowing to about 5mph with a slight amount of throttle. When you start to accelerate from that point ,sometimes it downshifts and shakes the whole truck. Not good for things in the drive train. I went to the dealer and they said there is a program upgrade that addresses the "2-1 shift quality". It also says that it address's the "overdrive defeat switch". The upgrade # is:15175857. The dealer said that they do not know what the overdrive defeat swith upgrade does.Do any of you guys know what this might change? You get both items and cannot select just the 2-1 shift quality item. As all of you know once the program is installed you cannot change it back. Has anyone else had this upgrade and what does the overdrive defeat switch program change do? Any help is much appreciated. Jim

[Buckman]

sooty,

By all means, you want to have the new calibration loaded. Everyone I've know who have had the calibration updated to address the 2-1 downshift problem has been extremely happy with the results. The overdrive defeat switch (quite simple put), is just that. With the switch, the driver has the ability to lock-out 5th gear to prevent cycling between 4th and 5th gear which might occur depending upon factors such as load, grade and throttle position.

If and when you have the calibration updated, please keep us informed of the results. :D

[Joe Dawson]

When did the overdrive defeat switch become available?

[sooty]

Buckman, I assume that you have to add a switch somewhere to utilize the overdrive defeat function. Is that correct? Do have this function and where did you mount the switch if that is the case. Are there any instructions on how to wire this switch, such as what terminal to hook to. I was sure that the 2-1 shift change would be good, but wondered about the o.d. defeat. Thanks for that timely response. Jim

[Turbo Al]

I just had mine reflashed with update:
15097103 - new calibration to address excessive shifting with cruise on and idle surge.
The annoying 2 to 1 shift when almost stopped has gone completely.
I think this is the one that corrected the problem BUT I also had 15097112, 15097105, 15063380, 15063401 and some of them address drivability problems as well.

Good luck

[mark45678]

I had my buddy call tac about the 2-1 down shift they said my truck had the latest update and could not cure the problem at this time.... at any throtle input with out a compleat stop it bangs into 1st and then move..... I think he said 12% throtle was all that was needed to get this problem to happen! so of your on a steep hill and dont stop with the breaks and let your foot of the go peddle its going to BANG into 1st! :rolleyes:

[sooty]

Does anyone have any information on the "overdirve defeat Switch function"? Jim

[Kennedy]

According to SteveO, it involves a pin at the TCM (much like the fast idle) and a MOMENTARY 12v+ pulse. Now dont hold me to this.

Personally, Id like an OD lock IN that would hold to a tougher set of parameters.

[Turbo Al]

Mark45678: Check to see if you have the same #'s as what I posted, these were the latest updates as of last week, mine went from:
15082517 upgrade to 15097103
15082519 upgrade to 15097105 (dtc p0236)
15063380 upgrade to 15063380
15082526 upgrade to 15097112 4x4 only
15063401 upgrade to 15063401
I would VERY much like to narrow down the upgrade Program that fixed this problem (on my truck) so please let us know if you have the problem and have the second set of Program numbers (or the first).
Thankyou
P.S. what is dtc p0236 calibration?

[Billy14]

sooty

Had the same problem with my 2002. The TCM update below completely took care of the problem on my truck and a friends. Don't recall anything mentioned about this update addressing the overdrive defeat switch but then I don't know if this update would apply to a 2001 truck as well.


posted 03-26-2002 11:28 PM
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Late shift into 1st

If you don't remember, this was a problem I encountered while easing the truck to a complete stop on grade holding only with the throttle, no brake applied. It wouldn't shift into 1st until about 1500 RPM was achieved, slamming down finally breaking both tires loose with a wrenching jolt.

The dealer & bulletin I have sited in the past from GM blamed it on the oversize tires (BFG 295's). When I tried the same senario with a friends' new, completely stock HD identical to mine, it did the exact same thing with my dealer's Service Manager in the passenger seat. He pulled two trucks off the lot & found the same results prompting him to get some info from GM direct.

GUESS WHAT? It worked.

When they replaced my driveshaft they also reprogrammed the TCM. Now, I can approach a steep grade in 2nd, let the truck come to a complete stop using only the throttle, (NO BRAKE) & between 2 - 4 mph that big ole Allison drops into 1st like a transmission should.
With the new driveshaft and this mod, the truck runs soooo smooth through all the gears, I really can't describe the difference.

Here's what my service invoice states:
Cust states trans jerks into 1st on enclines when accelorating
TCM Misprogrammed
Reprogrammed TCM with updaded program
K5364 0.7

This should help a bunch of you guys & thanks for your input to me,

Billy

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[ 04-27-2002: Message edited by: Billy14 ]</p>

[Wont Goof Again]

Turbo Al wrote:

P.S. what is dtc p0236 calibration?

P0236 is a turbo underboost condition. After working the truck hard in hot weather and letting it idle several minutes, I would get this code when re-accelerating onto the highway. There was no noticable impact on performance and after about 30 seconds the SES would turn off. Something about the PCM "expecting" more boost than what it was seeing...

Paul

[Turbo Al]

Thanks Paul

[mark45678]

Turbo Al I will check into this asap my buddy is changeing to a new dealer 20 miles a way still a GMC dealer so it maybe a few days. on the pu side of things I know the service dept MGR there so theres no problem getting the strait story without all the BS they try to feed us! I havnt been by this dealer yet for service I will let you guys know if they have a good Dmax tec!

[Buckman]

sooty:

I would imagine that sometime soon, the dealers would receive a bulletin regarding availability of the O.D. disable switch. As mentioned by others in this thread as well as others regarding towing issues, it's likely that not everyone will desire the feature and I would think that installation of it wouldn't neccesarily be mandatory. As to the location of the switch, I can only guess that the plan is to install it on the instrument panel.

smile.gif

[hardwood]

Does anyone know the GM bulletin number for the PCM calibration applying to this 2-1 downshift problem for 2002's? I am taking my truck in to the dealer tomorrow, so they can check the PCM and TCM for the latest programming.

[Billy14]

Hardwood,

I'll post it again. Read my post on this thread. It's also under 3 or 4 other topics.

This patch was only released from GM a month ago.

Here's what my service invoice states:
Cust states trans jerks into 1st on enclines when accelorating
TCM Misprogrammed
Reprogrammed TCM with updaded program
K5364 0.7

Billy

[ 04-29-2002: Message edited by: Billy14 ]</p>

[hardwood]

Billy14,
Thanks for responding. I have been following your other posts. StevoO mentioned for the TSB update "The Part # for this on a 2001 is 15175857 ". I, along with you have a 2002 model, which probably has a different Part number. I faxed this post to my dealer's shop foreman. He responded that unless he has a GM TSB or P/N, he can only update the PCM if the Tech 2 tells him it doesn't have the latest version programmed. I am trying to help him and improve my chances of getting this update at this dealership.

[Billy14]

hardwood & others,

Please excuse my ignorance here. Are you telling me the K5364 0.7 I keep posting us NOT a useable number? If so, I'll run by my dealer & attempt to get the correct one so all can benefit.

Like I said, this patch really works great! Not only does it improve general street driving, it also tells the tranny to shift down when in 4wd low lumbering up steep rocky grades when you are supposed to use throttle. Prior to this, mine would slam back & fourth between 1st & 2nd.

Billy

[77TransAm]

K5364 is the labor code the dealer charges the work against, and 0.7 is how much time GM allows them to charge for doing the work.