Jump to content

Allision Problems

jd4110

Recommended Posts

jd4110 Enthusiast

jd4110

Posted
Posted

I have a 2001 2500HD 8.1L with the allision, It was working fine last week, drove it home and parked it and did not have any problems. This morning I warmed it up and got in it to go to work and it will not move. I put it in reverse and it is like its in netural, If I put in in D it makes a loud clunk and will move onlly slightly. I don't know if the transmission control mod. can cause this or not, or can a transmission go bad just setting still. Any one had or seen this problem?

Thanks for any help!

 

Just as a note I live in Alabama so it's not real cold and the truck has 89k miles.

By-Tor New Member

By-Tor

Posted
Posted

Same exact thing happened to my 02' HD's Allison last week. I replaced the neutral safety switch and all is fine once again.

 

In addition to what you are experiencing, my gear indicator on the dash was acting up and my doors were not unlocking automatically when I shifted into park.

 

 

It was a 10 minute job and I got the safety switch for $97 from my friend's shop.

 

 

 

Good luck.

By-Tor New Member

By-Tor

Posted
Posted

It's on the drivers side of the tranny. It's located on the gear selector shaft. You'll see where your shift cable goes to the shift arm, the safety switch is about 6" long and the shift shaft slips through it.

 

It might pay for you to take the truck to a shop in your area and see if they can pull the code for you. I can't remember but I think my code was u700 but please don't quote me on that. I do know that the code had to be reset before the truck shifted properly.

Bud Enthusiast

Bud

Posted
Posted
I have a 2001 2500HD 8.1L with the allision, It was working fine last week, drove it home and parked it and did not have any problems.  This morning I warmed it up and got in it to go to work and it will not move. I put it in reverse and it is like its in netural, If I put in in D it makes a loud clunk and will move onlly slightly. I don't know if the transmission control mod. can cause this or not, or can a transmission go bad just setting still. Any one had or seen this problem?

Thanks for any help!

 

Just as a note I live in Alabama so it's not real cold and the truck has 89k miles.

 

 

 

 

Same thing happened to me except mine

sit for about 5 weeks. I had it taken to the

dealer where it worked fine. The story I was told is the

Allison bleeds back trans fluid bad. I was told

that if I had put the truck in park and let it

run for a while it would have been ok. Same

problem as you, I don't know!! Mine has been

fine after that!!

 

Bud :thumbs:

ABQFirefighter Enthusiast

ABQFirefighter

Posted
Posted

jd4110,

My Ally did exactly the same thing. Thought it was the NSBU (neutral safety switch), so I ordered one from GMDieselTech.com. Got the switch overnighted, installed it and all was well, so I thought. I drove it for about 5 miles, parked it, came back out and the tranny was doing it all over again!

I was pretty close to a dealer, so I limped it over there, stuck in 2nd gear. Dealer diagnosed and determined that the TCM (trans computer) was bad. They happened to have one in stock and I needed my truck back. So, $1100 later, the truck was fixed and has been fine ever since. By the way, after I got home, I found the computer at GMPartsDirect.com for around $400 when the dealer got me for $700+. Oh well, had to have it done.

 

Good Luck!

MemphisDoug Enthusiast

MemphisDoug

Posted
Posted

I just had the same problem with my Allison. All kinds of crazy things were happening. The PRNDL was screwed up, I was getting big clunks when shifting between F and R. The truck wouldn't shift past 3rd on the road and I was getting various fault codes. There is a TSB out there about replacing the neutral safety switch with a new one that shields the area where the shaft passes through it. It seems that our trucks throw junk up on the switch when making left turns which eventually shorts it out. The shield is supposed to cure that. The biggest problem I had with changing mine was getting the larger of the two electrical connectors out of it. You would swear it had been super glued into the switch. I had to break the switch away from around the connector to get it out. After replacing the switch and clearing the codes, all was well again.

jd4110 Enthusiast

jd4110

Posted
  • Author
Posted

Thanks to everyone!

I talked to a GM guy yesterday and he said that there was a tech bulletin on the fluid draining down after setting for a while and to put it in Netural for a while then shift gears, so I thought I would try that when I got home, but when I cranked it last night it was already working fine, I drove it to work this morning and so far no problems. We'll see.

Thanks again

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Latest Articles

  • Posts

    • Grumpy Bear
      OCI, not when but why?

      By Grumpy Bear · Posted

      I just spent the last 45K miles doing samples every oil change over more than a full year to get the data for seasons and break-in to broke in.    I found the same thing to be true. Something was always teetering on done or had stepped off the cliff long before the OLM was DOA. In fact, I found about a thousand mile difference between summer and winter. That is during the winter half the OLM was STILL too long. Even the severe schedule was to long in the winter.   Now having done the work I can say I was NOT DISAPOINTED. I saw nothing I didn't already know. Nothing my father hadn't already demonstrated in his 2K OCI's pushing dated iron on dated oils and weak filters to mileages well beyond 300K.   Building on his work through use of Lab testing it wasn't hard to find the correlation between 'sight/feel/odor, the things dad relied on, and test results. Use of current viscosity stable chemistries & filters has pushed that marker for my motors out to 3K summer, 4K winter.    So the early lies were 3K on conventional oil and the lie upon the lie was 7K+. turns out to be off by a factor of two.    So... it is true that modern chemistry has doubled the useful oil life. But the base milage that came from was off by double. It's how good lies work. Partly true, sometimes mostly true so that your meter isn't set off. It also means that non-shear-stable shelf oils are only now as good as the old oils were in their best case scenario.    So the question now is how do we improve on that? Thus the question into cleanliness among the other items listed in the post quoted below.    If this bores you, feel free not to participate.       
    • newdude
      2027 Chevrolet Silverado: Official Discussion

      By newdude · Posted

      Is it though?  Like LTZ, not a high take rate.  Current Sierra has AT4, Denali and Elevation as its main bread winners.  Each trim accounting for 25-35% of sales for Sierra.  SLT makes up about 10-15% at best.        Like others have predicted here for GMC, it will be:   - Pro (equal to WT Chevy)   - Elevation (replaces SLE and SLT)   - AT4 (and X)   - Denali (and Ultimate).  
    • Atlas
      OCI, not when but why?

      By Atlas · Posted

      Coming back to this question, *my* answer is no, it's not something about which I'm knowledgeable. I'd need to read up on it and understand how it applies to we the consumer and our oil change regimens.   One of your bolded points is that fresh oil in a container contains particulate matter. I don't think I'm surprised, maybe a little bit that it seems to be a major factor, but there's manufacturing process involved in oil and it doesn't exactly come in sterile packaging.    How much is filtered out on the first start by an acceptable quality filter (AC Delco, as a baseline) filter?   On the GM OLM discussion, just saying that the "number of engine revolutions" appears to be a factor in oil life... cough... maybe driving style *does* matter.    
    • GMTruckGuy74
      2027 Chevrolet Silverado: Official Discussion

      By GMTruckGuy74 · Posted

      GMC has been revising their trim level names over the past several years. Sierra Pro has taken over the Work Truck/SL trim name; Elevation has replaced the SLE (and with the Premium upgrade, SLT) in the SUV lineup of late; AT4/AT4 Ultimate and Denali/Denali Ultimate have been the top of the line in off road luxury and on-road luxury respectively for the full-size pickups and SUVs.    SL, SLE, SLT nomenclatures are gone in the Sierra truck line. Mark my words.
    • GMTruckGuy74
      2027 Chevrolet Silverado: Official Discussion

      By GMTruckGuy74 · Posted

      GMC has been revising their trim level names over the past several years. Sierra Pro has taken over the Work Truck/SL trim name; Elevation has replaced the SLE (and with the Premium upgrade, SLT) in the SUV lineup of late; AT4/AT4 Ultimate and Denali/Denali Ultimate have been the top of the line in off road luxury and on-road luxury respectively for the full-size pickups and SUVs.    SL, SLE, SLT nomenclatures are gone in the Sierra truck line. Mark my words.

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...