Not sure if this should be in the tranny section but my LMM gave me some grief towing home last night. 35K miles on it and no problems before. Truck is stock with DPF in place and no tuner. The trip started out fine but after a stop when I'd accelerate the engine would rev up to 3500PRM with now power..... felt like it was slipping. Let off the gas and it would go again but got jerky and I could just feel like the power wasn't completly there. Made it home but then couldn't get reverse. It said shift inhibited. I've seen this message before from other posters but couldn't find a clear reason as to why it does this. Needless to say my trailer is still hooked up but this morning I checked it after thinking maybe I should have restarted the truck last nite and now I have reverse again? any ideas? its going into the shop ASAP but this was quite discouraging. Good think I only had to drive about 60miles to get home!

Not sure if this should be in the tranny section but my LMM gave me some grief towing home last night. 35K miles on it and no problems before. Truck is stock with DPF in place and no tuner. The trip started out fine but after a stop when I'd accelerate the engine would rev up to 3500PRM with now power..... felt like it was slipping. Let off the gas and it would go again but got jerky and I could just feel like the power wasn't completly there. Made it home but then couldn't get reverse. It said shift inhibited. I've seen this message before from other posters but couldn't find a clear reason as to why it does this. Needless to say my trailer is still hooked up but this morning I checked it after thinking maybe I should have restarted the truck last nite and now I have reverse again? any ideas? its going into the shop ASAP but this was quite discouraging. Good think I only had to drive about 60miles to get home!

Does is have a service engine soon light on? Call onstar and have it picked up and taken to a dealer. I dont think they can read codes on duramax equipped trucks...maybe I'm wrong...sounds like a trip to the dealer is in order though.

Ya sorry forgot to mention there are no codes. I have a code reader but didn't plug it in as the CEL isn't on. I just drove it again and reverse is back but it's still revving in gear... it's off to the dealer! Bummer...

Did you check fluid level?

I would change the fuel filter first. That is one thing say after 10,000 miles usually if I get on it and tops out rpms and I let off a little it shift and I keep going. I do that first. Of course check fluid levels and maybe change Allison spin on filter as well. Possible bad fuel maybe at some point.

Brian

Hey guys, yes fluid level was fine and the fuel filter was just changed about 500 miles ago. Sitting at 96% and I use the same fuel station (truck stop) so I don't think it's bad fuel but it's always possible. Don't know enough about the truck to understand if that could lock out reverse though? It's at the dealer now so we'll see. The thing that has me cheesed is it's intermittant and with my luck I wouldn't be surprised if they cannot replicate the problem. Although 3 outta 5 starts today reseulted in the issue.

NSBU-neutral safety back up switch. Mine did that, took it to a friend of mine that owns a tranny shop and an LMM and he changed that and it hasnt happened since. It happened around 50000 miles, now I have 100000

MOD's feel free to move this to trans forum if more fitting...

So I mentioned NSBU to the dealer as a possibility from what i've read here. They say no. Is there a way to test the switch or do you just replace it? But check this out.... it actually scares me what they are doing. There were 2 questions. Dealer: do you have it chipped? I say no. My Question: What do you guys think is wrong? Dealer: We honestly don't know. The tech says he found what looked like clutch pieces and burnt fluid. Instead of replacing random parts to troubleshoot the General approved a new transmission. OK great but the truck only has 30K miles on it and I'm not a fan of a major drivetrain repair this early in life. Don't get me wrong a new tranny is outstanding but I'm more afraid of what will come out of them ripping my truck apart... sorry just don't have much faith in the dealership tech's these days. I'm not sure why but I just don't have a good feeling about this?? Especially if a $80 NSBU switch could have fixed the problem.

What I just can't understand is how the tranny could be cooked? She's towed max 10K lb trailers, had transynd in it with spin on replacements every oil change. I do not trash on this truck at all and drive it pretty easy. I'm wondering if the first recall for elevated idle/tranny fluid flow restriction (FEB 08) may have had something to do with this as the truck went through 4 cold months of winter before this recall was performed.

Interesting to learn and read more everyday that the mighty Allison may not be so mighty. Damn I get grenading a stock one with a hot tune but a stock truck eating one up? Luckily I still have a warranty! Sorry for the rant :o:

Was the fluid level on the Allison spot on, it doesn't like to be overfilled at all, as it will cause issues if overfilled. Hopefully it will get fixed! Chris

Ya I always check my fluids every fill and the tranny has always been in the middle of the hot marker. So i guess all is well that ends well... under 2 days in the shop and I have a new tranny. Seems to run good and the notes say clutch test showed 3rd & 5th clutches are slipping and burnt as well as valve body 1 seems to stick. Crazy man cuz like i said I've babied this thing so I hope it was just a freak thing. The service tech says this is the 2nd one he's seen in 5 years. I'm going to put a post in the tranny section as I don't recall if there is a break in procedure for a new tranny.

thats some bad luck, to low of miles to be into the trans already.

Did they rebuild trans or completely replace it?

Ya I agree and was shocked at first when I had the problem and then when they told me it was cooked. Yes they choose to replace the transmission vs. rebuilding it. Good thing it's still under warranty and I'm just happy I didn't have a tuner which would have probably left me SOL! I'm a bit tenative driving it right now but I'm sure that will pass.

It was a manufacturing defect i would bet. your new one will last 100x longer.