• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

C5500 duramax 6.6L guru mechanics needed

RI Chevy Silveradoman said:
Your right Ferman, but it is still worth a check, as a few of the newer switches have failed. We need some more info here to zero in on the possible causes. I would also clear the codes and see if they come right back, or if they take time to reappear.
Click to expand...
A failed NSBU cannot cause what he is describing. They can fail, bu it will cause a range shift inhibited message, or a flashing gear display. Also it will leave you with nothing, or 3rd and reverse(and you can do quite a bit more than 10 in 3rd). Also the P0500 is an ECM code set when it doesn't receive a replicated speed sensor signal from the TCM.
 
How much have you spent on parts with no cure specifically the mentioned speed sensor replacements? Wiring is zero fun and most people don't "get it" when looking for shorts, breaks, wiggle tests, etc. After spending $100.00's on parts on the other end of a bad wire it's cheaper to have a auto electric shop look at it. Further the sensor could be electrically fine, but, coated with metal shavings from a bad bearing etc and quit working. It could be cracked that lets water in to the sensor and yet resistance test fine. New parts don't mean good parts and may introduce further problems. A tooth off the sensor wheel could be broken off. Other related broken items on the circuit could be causing this sensor to throw a code.

Just saying there is a point where you don't have the tools and experience to solve a major problem and throwing parts at it may not solve it and just get expensive. There is no shame is using a shop and learning what was wrong for future repairs. Sometimes It's the best and cheapest course of action. Shop may even be the GM dealer who knows about the ultra hard to find problem because they did 10,000 warranty claims on that model for that problem.

THEFERMANATOR said:
I just checked ALLDATA for info on the circuit for an 01(thats what I have), and you need to check it for ANY other codes. Most scanners(including those at the parts stores) CANNOT read TCM codes, you need a high end scanner to read TCM codes. Without checking for TCM codes, this is going to get REALLY expensive to try and fix. You need to particularly look for a P0721 or P0722.
Click to expand...

This tool alone is expensive.
 
It maybe to soon to say for sure, but we're pretty sure the problem is fixed!! Thank you so much for your help!

When I told him about the NSBU, he was fairly sure that it could be the culprit. He ended up taking a blow dryer to it and taking it for test drives afterwards. Initially he only had first gear, after the first drying, now he had second, then third, then OD. So he took it off and at 2 am, smashed it open hoping to see some corrosion LOL but there really wasn't any noticeable damage. So now that he needed a new NSBU he decided to get new output sensor since he was going for parts anyways. The Allison dealer here said that the three sensors on the transmission were all the same, and cheap $30 each, so he changed them all, put the new NSBU on, and it's driving like a dream now.

I told him he should go drive through some water to see if it's really fixed LOL He mentioned something about putting some sealer or something on the sensors at think to keep out the moisture.

You guys are great! Many thanks again!
 
He has taken the truck to the local GM dealer, unfortunately there is only one that works on this size truck and he has not had good experiences to say the least. That's kind of his absolute last last resort. But thanks for the concern WarWagon. No one likes to pay big money for someone to fix something and have to end up having to do it themselves anyways.
 
Well the good news is you got it fixed. I didn't think the NSBU switch was a common problem on the MD trucks like the early Allison in pickups
 
I don't have the manual in front of me, but make sure the speed sensors were put in the same as the old ones were. Theres a certain way each sensor has to go in so that the sensor portion picks up the teeth on the wheel correctly. This is done by how the sensor is clocked in them ounting bracket. On a new sensor it isn't a big deal, but as they age it can cause issues if they are not clocked correctly.
 
I hear you on that: finding a good shop is always "fun". Dealers are dead last on my list for sure, but, once and awhile they have a gem of knowledge that helps after local shops are stumped.
 
btfarm said:
Well the good news is you got it fixed. I didn't think the NSBU switch was a common problem on the MD trucks like the early Allison in pickups
Click to expand...
The 01-early 03 pickups used the same switch as the 4L60E/4L80E did. The switch worked fine for them because it was spaced out from the trans some, and it's only functions was start in gear protection, and to provide a gear postion to the cluster(they use an internal pressure switch to tell the PCM what gear is selected). On the ALLISON the switch was tucked in tight to the trans which allows dirt and debris to get wedged up and caked around it, and the ALLISON used the switch to tell the TCM what gear was selected(it used the internal pressure switch to tell the TCM what gear it is actually in). Since the switch is now a safety feature in the ALLISON, it is a bit more sensitive, hence the problems with them. Pretty sure the KODIAKS all used the newer single plug switches which were built better from the get go as ALLISON QUICKLY realized there was a problem with the old black 2 plug switches.
 
You must log in or register to reply here.
Back
Top