Tranny or electrical problem?

[lmholmes11]

I started my truck and it idled fine for about 5 mins. I shifted into gear and the 'D' was blinking on the shift indicator. If I remember correctly the battery message light was redbut I'm not positive bc I was too busy trying to figure out what the heck was wrong. So I shifted into park, shifted back into drive...and nothing. It would rev up but not engage. I shut the truck off, turned the key to start and nothing. I eventually got it started, put it in park and off I went.....I know I need new batteries, what does everyone think?

[lmholmes11]

Another note, no SES codes were thrown.

[ricksofla]

I just bought an 02 w/ 314,000 on the duramax / allison. I was doing about 55 (cruise on) hit a dip and the tranny disengaged (the motor revved real high like it was in nut.) and the check engine light came on. I let off the gas and it engaged back so I kept going. now, I don't have reverse and it seemed to raise the trans. temp gauge a little, not to the red but close. this all happened 125 miles after I bought the truck! Help! (Its my first diesel truck.) Thanks, Rick

[lmholmes11]

Anyone have any ideas?

[DmaxMaverick]

If you need new batteries, start there before anything else. Low/inconsistent system voltage can/will cause a bunch of electronic issues, including TCM faults, with or without SES illumination. If your batteries are in poor condition, most problems will occur immediately after a cold start. They system is taxed as much as it will ever be, and takes time to recover. Bad batteries can sap all the alternator is able to put out, leaving little for other systems, leading to electronic issues. Your restart and driving off indicates only that a sufficient charge had been completed, allowing system voltage to stabilize enough to not cause problems with the TCM. Continuing in this condition will eventually cause other issues, including permanent system damage, and premature alternator failure.

Replace both batteries and clean up the terminals. It's also not a bad idea to clean up other essential connections, such as power and ground points. A quick stroke with a wire brush and application of fresh dielectric grease goes a long way.

[lmholmes11]

Thank you very much for the reply Dmax. I'm also thinking part of the problem could be a faulty NSBU. At $40 why not. I don't think constantly driving into a lake to launch a jetski is good for it.

[DmaxMaverick]

Could be. But, maybe not. I do not suggest doing anything electrical/electronic until your most basic components of the electrical system are healthy. Low voltage, regardless of the root cause, have shown time and again to cause several issues throughout several systems, including tranny behavior. You're not the only one launching a boat. I do, several times a year. I know of several who do it with their GM truck, similar to ours, with no problems. One of them in salt water (not that I would ever to that). His truck has issues due to it, but not the NSBU, for some reason, which is counterintuitive.

Replacing the NSBU may or may not solve a problem. In any case, it will not cure your bad battery issue.

[lmholmes11]

What is the reccomended cold cranking amps for duramax batteries? I baught 750 cca. Also, would it be worth it to take my truck to the dealer and get the TCM software updated?

[DmaxMaverick]

750 CCA batteries are fine, as long as they are the right series (correct application for your truck).

If you've never had the TCM updated calibration installed, I recommend you do. There were several improvements over the years, and a worthwhile update. If it's been done since about 2003-4, there isn't much, if anything, to gain by doing it now.

[Kennedy]

Thank you very much for the reply Dmax. I'm also thinking part of the problem could be a faulty NSBU. At $40 why not. I don't think constantly driving into a lake to launch a jetski is good for it.

I'd be more inclined to think it was simply a drainback issue although 5 minutes of running should have solved that.

[lmholmes11]

I'd be more inclined to think it was simply a drainback issue although 5 minutes of running should have solved that.


Yeah I drove to class, then to dinner after (3 hours or so) and then when I left from the restaurant thats when my truck began to act up. So I definately had more than 5 minutes of drive time before it happened. Hmm...

On another note, I dropped the pan, replaced both filters and there were barely any metal shavings

[Kennedy]

I would still check with the dealer to see if any of the drainback updates were ever performed.

[lmholmes11]

Ok I will check. What exactly is a drainback? Should they be able to tell me by my vin number?

[DmaxMaverick]

I don't think your problem is related to drainback. This is a condition when the ATF in the torque converter drains back to the pan after sitting for a period, usually several days to weeks. The issue is not serious or damaging, only an inconvenience. When this happens, a short idle time then a restart almost always cures it. The worst that will ever happen is you may get a little fluid leaking from the upper vent (a few drops of ATF), or be a few minutes delay before you are able to drive away. The "fix" requires disassembly of the lower tranny (in-truck). An expensive repair with no warranty. I've experienced this condition once, after mine sat for several weeks. The severity of the condition seems to vary from truck to truck, with most never experiencing it under any conditions.

If yours did this, the SES should be on, and TCM codes (P0700, P07xx) should be present (control-main pressure low, or something to that effect). Once it seems to return to normal, the SES should remain on for a while.

Are you still having issues with the display and no-go? Battery indicator still on?

[lmholmes11]

Since my last post I have replaced both batteries and I. Replaced the nsbu switch. All seems fine so far. I will keep this thread updated. I appreciate everyones help. On one of the nsbu electtrical connection I found that it had a substence that resembles glue around it. I'm assuming for sealing off the connection to the weather elements. Does anyone know what that could be and if I need to re apply? Or will dialectric grease work fine?

[kaylabryn]

I think that goo is a sticky dielectric grease. I usually just put a little on all the connections that external to the vehicle.

Mike