Truck Wont Shift

Flashy2003 · September 17, 2010

Hi, I have a NBS 07 Silverado 1500 LTZ. Over the last six months Im having trouble every now and again with the truck not shifting. When this happens the speedo doesn't work the truck wont shift out of first and if i bring the speed up the abs light comes on. If I put their truck in neutral and bring it to a stop it will be fine. This happens once a week now. It only seems to happen from a very slow rolling start. Like coming of a stop light or sign. I do have a BB Motor/Tranny tune. But it was in for a while before this started happening. What do you guys think????

Stex · September 17, 2010

Dealer time, trans or elect/computers/sensors...

Flashy2003 · September 17, 2010

I gave up on my Dealer. They are just parts changers not mechanics. Every time I bring the truck in for something they say "Well there's no code so we cant fix it".

So I'm my own warranty this time

Dealer time, trans or elect/computers/sensors...

Se77vN · September 17, 2010

I gave up on my Dealer. They are just parts changers not mechanics. Every time I bring the truck in for something they say "Well there's no code so we cant fix it".
So I'm my own warranty this time

Dealer time, trans or elect/computers/sensors...

You may want to take it in to someone who specializes in tranny's then... I hear ya on the dealer thing, but the tranny is something that should be taken to an expert. As long as they are not out to rape you, you should get an honest answer if you took it in and let then open it up. Sorry I'm not more help, but the tranny is not something to be fooled with if you don't know what your doing.

Flashy2003 · September 17, 2010

I was thinking along the lines of changing the VSS. But I never had an issue with one or delt with this before. Would a bad VSS cause this?

I gave up on my Dealer. They are just parts changers not mechanics. Every time I bring the truck in for something they say "Well there's no code so we cant fix it".
So I'm my own warranty this time

Dealer time, trans or elect/computers/sensors...

You may want to take it in to someone who specializes in tranny's then... I hear ya on the dealer thing, but the tranny is something that should be taken to an expert. As long as they are not out to rape you, you should get an honest answer if you took it in and let then open it up. Sorry I'm not more help, but the tranny is not something to be fooled with if you don't know what your doing.

minibike132 · September 17, 2010

I was thinking along the lines of changing the VSS. But I never had an issue with one or delt with this before. Would a bad VSS cause this?

Yes a bad VSS, circuits to and from or PCM would cause this. If was an older vintage I would look at the PCM because this was pretty common in the 2000 model year range because of water intrusion. It isn't something I've seen in an 07 though.

I gave up on my Dealer. They are just parts changers not mechanics. Every time I bring the truck in for something they say "Well there's no code so we cant fix it".
You are not going to get a diagnosis on something that isn't acting up at the time, we don't have crystal balls. A code leads down a path for diagnosis, it isn't something that says "replace this". You can only look at so many things that can cause the issue before you just replace a part and see if it works. I can find what is causing any issue that happens all the time, but if it is something that only happens sometimes it's going to be a best educated guess.

So I'm my own warranty this time

Dealer time, trans or elect/computers/sensors...

You may want to take it in to someone who specializes in tranny's then... I hear ya on the dealer thing, but the tranny is something that should be taken to an expert. As long as they are not out to rape you, you should get an honest answer if you took it in and let then open it up. Sorry I'm not more help, but the tranny is not something to be fooled with if you don't know what your doing.

This isn't an internal trans issue, it is an electronic issue.

You are right on with the VSS. The VSS sends the speed signal to theTCM, TCM sends it to the PCM and the IPC over the data line. If the PCM doesn't get the VSS signal or it is corrupted the trans will default to a particular gear to protect itself. I am sure that it isn't first gear, you probably just percieve that it is because there is no shifting. Usually the defaulted gear is 2nd or 3rd.

The abs light is secondary because the wheel speed is something other then what is being reported by the VSS. The ABS sets a code and disables itself because it knows there is a disconnect and cannot make proper adjustments without the correct data.

There is a bulliten that may apply it is PIT3521G (google it). If that doesn't work, this won't be popular but I would remove the tune and see what happens and go from there.

jblakeney · September 17, 2010

AAMCO................ They know transmissions.

Jbo

minibike132 · September 17, 2010

AAMCO................ They know transmissions.

Jbo

Good luck with that, they don't know electronics.

Flashy2003 · September 26, 2010

I changed the VSS. It wasn't that. Now I guess Ill change the TCM.

Flashy2003 · October 16, 2010

OK, I changed my TCM and still not fixed. I checked the tranny fluid and when it was hot the line was in the cold area. Why would it be low. Does it get burned up? And could this maybe cause my problems?

minibike132 · October 17, 2010

OK, I changed my TCM and still not fixed. I checked the tranny fluid and when it was hot the line was in the cold area. Why would it be low. Does it get burned up? And could this maybe cause my problems?

There is a bulliten that may apply it is PIT3521G (google it).

Didn't do this yet huh.

Flashy2003 · November 26, 2010

Well just in case anyone cares. The truck was fixed. A clip in the transfer case broke and allowed the shaft that has a magnet on it that feeds the VSS. To shift away from the VSS.