SLAMMIN ALLISON / No GM support.

[Dave K.]

I have a 2001 Chevy Crew Cab Duramax / Allison auto with 59k miles. The truck is stock and I do a little light towing.

I have recently had the truck in the shop twice to remedy a hard erratic shift problem. It will slam into second gear hard enough to throw a can of coke from the holder, rev-up between gears and as well downshift hard from 3rd through 1st with a bump just before stopping.

The dealership cannot find any codes that show a problem. Apparently they did a recent update / recall to the computer as of 6/06/03 to remedy shift problems. I was told this was an update to help the trans learn driving habits and shift accordingly. Well it worked ok for a couple of weeks but now it is doing the same thing as before. The dealership stated that they are "researching" the problem but without codes there is nothing they can do for now.

I was also in contact with Chev Customer Service along the way. Ya, they were polite and kept in touch with me but todays closing conversation left me with a "Sorry you're not satisfied, but there is nothing we can do." Basically I was told if I find out how to repair their product, keep my bills and maybe there will be a campaign or recall and I will be eligible for reimbursement for the repair. To say the least I am not a happy camper. :mad:

Anyone else have the same or similar problem??

Any ideas??

Dave K.

[dmaxalliTech]

Dave, how do you feel about a trip to Grand Rapids to get it FIXED??

[kbrowns]

Dave K.

My father-in-law is having same problem. He has a '01 2500 Ext. cab long box with 36000 on it. He's never had any of the updates, he's a little leary about those. His truck has been running great until this. They pull a 5er to AZ every winter and he has been very impressed with the truck. But then again he was a F*&d man before, so it migh not take much to impress him :D

dmaxallitech,

I would be interested in the fix. Don't think my father-in-law could make it to MI. Is it an update they download or what?

[oyazi]

Had similar issue w/mine but not as violent as you describe. The valve body was replaced and resolved the problem.

[dmaxalliTech]

kbrown, I would start with the updates for sure, Hard to say what the final fix will end up being with Dave K. truck. I will post results if he brings it down

[kbrowns]

Dave K.

any update on the tranny issue?

[dmaxalliTech]

Yo Dave, How is that truck working for ya? I am confident that its fixed. Let us know bud! Thanks for the business, I enjoyed meeting you.

[kbrowns]

dmaxalliTech,

My father-in-law took his truck in and they told him that they are unaware of any updates for this problem or the Idle Surge which he is now starting to have also. I'm not around dad's truck that much but I can definitely hear it(idle surge), tech said neither problem could be "reproduced". I've searched on this site for the update #, I'm sure it's hear but can't seem to find it. Could you point me in the right direction of a update#,code,TSB anything? Thanx in advance for your patience and time.

[Dave K.]

dmaxallitech,

Hey, problem is solved. So far not so much as a hick-up from the trans. shifting. Thanks so much for your time and effort on this. What took you twenty minutes to discover stumped my old service dealer after two separate visits and three days without my truck. The next time I I need repair work done, I'm heading down to Grand Rapids. Your experience shows and is appreciated.

Since the cost to repair the truck was next to nothing, I ordered the "Hot Juice". Yee ha...

If you haven't already, I'll let you post the repairs done to the wiring problem I had.

Thanks Again

[RVGuy]

Would someone provide details about the "fix?"

There are several others on the forum also experiencing the allison slam. I for one.

[BassinRVer]

Yes,
Please provide the fix. Mine only slams on hard acceleration while towing. But what is the fix???? Is it the tranny software updates???

[Dave K.]

Rvguy & BassinRVer,

Look under "Allison Wiring Problem" by dmaxallitech. You will learn exactly what was done to my truck. Good Luck.

Dave K.

[dmaxalliTech]

you can refer to above mentioned thread for 'allison wiring problems' or if you want an exact fix on just dave's truck, read on....

He had the wiring issue at the p/s hose return line clamp. the wires that were damaged were
1. input speed sensor signal wire
2. turbine shaft speed sensor signal wire
3. 4wd low signal wire

Dave had two problems with his truck,first being the loss of shifting and failsafe, second, the hard shift, I contribute the harsh shift to the 4wd low signal wire being damaged, when 4 low is commanded, a signal is sent to the TCM bumping line pressure. This wire grounded to send the signal, I think the wire would ground inself or short to speed sensor signals and cause the tcm to think it was in low range, thus causing harsh shift. The speed sensor wiring is what caused the loss of shift and drop into nuetral/no reverse. The allison relies on input speed and turbine shaft speed to determine shift timing, loss of signal confuses it and it shuts down.

The above may not be whats wrong with all trucks, its only what was found on Dave's truck. Its a good place to start looking when trying to find phantom troubles with these...

[RVGuy]

Hmmmmm!

Boy, I don't know. It would seem to me that if it were a short in a wire that my tranny shift slamming would not happen as predictable as it does.

It only seems to slam when I'm in tow/haul while towing and while shifting from either second to third or sometimes third to forth.

Mine never slams at any other time.

Thanks for the info.

[dmaxalliTech]

Jim, dont sound like it, usually is less predictable, sounds like you have other issues friend :(

[YZF1R]

Quote from dmaxalliTech "when 4 low is commanded, a signal is sent to the TCM bumping line pressure ."

What color was that wire that, hmm, grounded?

I'm sure there are a few guys on the board here that raised thier eyebrows on that one! ;)

Steve

[dmaxalliTech]

oh great, now I started something ;)

the wire was copper colored, but the insulation was grey :D :D

[YZF1R]

;)

Steve

[dmaxalliTech]

I must correct myself, I have been unable to find anywhere that the tcm does indeed increase line pressure when 4wd low is enabled. I was able to find, however, that shift adapts are useless in low range, they do not exist. I stand corrected though on the line pressure bump.

[YZF1R]

Well, I guess it's good you noted that before the weekend project mods started. :D

Steve

[Bigwheel]

dmaxalliTech:
Nice Job!, Thanks for the info on the fix!.
:cool: :D

[Billy14]

Oh Well,

My TCM harness is routed well below & out of the way of the power steering spring clamp. :rolleyes: The obvious sure would have been quick & easy.

Next!

Billy