How if everyone doing today? first let me say I am new to this forum. I own a 2003 Chevy 2500 HD duramax with a 6 inch lift, 20 inch rims, 35 inch mudd grapplers, 5 inch exhuast, PPE hot tune programer, tv/dvd with 2 12s under back seat, train horn and I love it so very much!!! Today I am having some problems and was hoping some of you chevy buffs could help, here is my problem:

well I had a train horn put in earlier today and when I left the shop I stopped by at a store for the wife and when I pulled in I felt the tranny jump out of gear and rev up like in neutral. I slowed down and when I hit the throttle again it was fine, right before parking the check engine light came on. I turned off the truck and when we got done shopping we left. At first it was fine but a couple miles down the road we stoped at a light and it did the same thing. Then a couple miles from the house it would not shift into a higher gear running at 2000-3000 rpms without shifting (it usually shift at the very highest 2500). pulled in the house and parked it because it is absolutely pouring outside.

I do believe this means tranny problems any my question is does anyone else have any suggestions this could be? My big thing is knowing worst case scenerio like how much does a full tranny rebuild usually run? I live in orlando florida. Thanks everyone.

Welcome to the forum! You will find many interesting things here. Be carefull this might become an addiction! HAHA.. but really.:D

I don't know what could be wrong? I have never heard of anything like this before? I know there are many guys on here that own tranny shops that will be able to help you out. Good luck. My best bet. Electrical problems. But could be way off.

update: the rain has slowed so I decided to first check Tranny fluid. Correct me if I am wrong but it is the dipstick against the firewall on passanger side. Well I lost my main owners manual when moving recently but had the owner assistance book. The truck has been off for a couple hours so I did everything the book says to do for the cold check and I triple check my tranny fluid level and its at the tip top of the hot!!!!! It was a nice clearish red color but it is WAY higher than my booklet says. I do not know how to take any fluid out so if someone could help me with that it would be great. I dont know if this is the problem because I have not had a tranny fluid change in a little while but it sure seems like something I should fix anyways, it cant be helping the problem because EVERYWHERE in the book it says DO NOT OVERFILL. Any help appreciated.

it sounds like you need a rebuilt tranny $2000-$5000 depending on what you plan to do. I cant comment much on the fluid level, it cant be that much of a problem though if you have been running it like that for 5 years.

Change your spin on filter and bring the fluid level down to mid-hot on the hot grid on dipstick. Make sure you still have a magnet on your filter. See what happens after that.

where is the magnet on the filter? Do I go get a new filter or am I just taking it off to drain the fluids alittle? Not very knowledgable about diesel sorry. Can I pick up one of those filters at like discount auto or advanced auto?

Leaving out info will lead to wrong help from us. Did you not have a P0875 code along with a CEL?

took out the truck today, drove it around for 45 minutes with no issues. half a mile from home I hit a red light, the light changed and when I hit the throttle it was like it was in neutral, let off the gas it went back down and then it caught and off I went. check engine light came on and it threw me codes: 0700 and 0875, 0700 is a transmission control system (MIL request) says in my manual.

where is the magnet on the filter? Do I go get a new filter or am I just taking it off to drain the fluids alittle? Not very knowledgable about diesel sorry. Can I pick up one of those filters at like discount auto or advanced auto?

Replace the filter as it may be plugged. Magnet sits on top on the filter next to the threads. Use Allison oem filters only.

Not trying to steal this thread, but mine has acting the same way for awhile now. Mike do both the spin on and the internal filters need to be replaced?

I have heard alot about changing the NSBU when having tranny problems, what is this and should I look at changing that? how much do they cost?????

I have heard alot about changing the NSBU when having tranny problems, what is this and should I look at changing that? how much do they cost?????
Search "NSBU". IIRC, the stealer is around $200 and the Allison dealer is $70. Something else was out there telling us the tan colored switch (as opposed to black) was the updated one. Also, I read quite a bit about harness corrosion and rub-through.

And the NSBU is the Neutral Start Back Up switch. It tells the computers what range is selected and, when failed, can cause what you've got, and/or loss of the gear selector indicator in the instrument cluster.

so is this something you would recomend replacing just to see if it fixes it? Is it easy to replace? Also will the upgraded one work if my truck had the regular one in it?

so is this something you would recomend replacing just to see if it fixes it? Is it easy to replace? Also will the upgraded one work if my truck had the regular one in it?

It's not my $70, but I would change it (if you have the black one) and certainly service both filters and the oil.
BUT, hopefully someone else chimes in on here. I wouldn't be opposed to finding a good tech in the area first and making some inquiries. Maybe, even an allison dealer.

The tan is the revised one. Yes it will fit (and it's supposed to be more reliable. Try seeing if there is an allison dealer nearby http://www.allisontransmission.com/locator/mappoint/index.jsp?country=US. I think I'd rather pay them for a diagnosis before dumping too much into guessing.