Rocket Man's 02 Denali Build Thread AKA "THE BEAST"

[Tonyrodz]

Pretty sure it’s electrical otherwise it wouldn’t shift manually, from my little knowledge this seems to be correct. If I’m wrong about that assumption somebody please correct me. The trans was completely gone through and rebuilt after that issue also, there should be no silicone in there. The fluid looked good and clean.
One thing I can note after today is it doesn’t appear to be heat related because on the first test drive earlier today I drove it until the trans was warmed up and it didn’t fail but later after it cooled down I drove it maybe 1/4 mile- the trans temp was still at the bottom of the gauge- and it failed.
The issue with the battery light, seat belt light, and stereo rebooting might be the ignition switch. I went out a little while ago and was messing around with it running in the driveway, dropping the shifter lever down into first and back to park and one time the engine died. It might be the fob hanging and being knocked by the shift lever. I wiggled the ignition a few times and it seemed iffy, like it was possibly intermittent. One time I barely touched it and the engine stopped and then restarted without missing a beat. I hate throwing parts at it but things like the 6 year old battery and now the ignition switch are maintenance items anyway. I ordered a new Standard switch (with harness) from Rock Auto while I can still get one. Seems there are parts for this year that are becoming hard to find. The 99-02 stuff is different than the 03-06. The OE one is discontinued. I have noticed before that the steering wheel controls can quit if I use the tilt on the steering wheel and that’s part of the ignition switch harness. I doubt that’s the issue with the trans but i can still eliminate it.
I wonder if the trans wiring harness runs near the headers. Possibly wiring that’s heat damaged. There’s still lots if stuff to check unfortunately.
I also have to remember to grab a data log and send it to BB; I just put the Autocal in the console so next time it acts up I can pull over and plug it in.
I just resigned to the fact it may take awhile to figure this out. Intermittent electrical problems are my least favorite thing to troubleshoot. At least at this point it points to an electrical problem.

At least you're sticking with it and not giving up. What exactly is the procedure--what do you press--to do a data log on your Autocal?

 

[Rocket Man]

At least you're sticking with it and not giving up. What exactly is the procedure--what do you press--to do a data log on your Autocal?

You still haven’t sent a datalog to BB? All you have to do is scroll through until it says” record data” .

 

[Tonyrodz]

You still haven’t sent a datalog to BB? All you have to do is scroll through until it says” record data” .

Really?? I scrolled but didn't see that--or, I didn't remember seeing it. UGH!!!!!

 

[89Suburban]

@Rocket Man

 

[adventurenali92]

I just realized that I had the exact same issue as you’re dealing with @Rocket Man .My trans did the exact same thing just shy of a year after my rebuild. Trans wouldn’t shift down on its own unless I manually commanded it to shift down with the handle. Took it back to my trans shop and it ended up being a stuck valve body. He replaced it and it solved the problem.

 

[Rocket Man]

I just realized that I had the exact same issue as you’re dealing with @Rocket Man .My trans did the exact same thing just shy of a year after my rebuild. Trans wouldn’t shift down on its own unless I manually commanded it to shift down with the handle. Took it back to my trans shop and it ended up being a stuck valve body. He replaced it and it solved the problem.

Thanks Chase. You’re the second person to suggest the valve body. I really don’t know squat about transmissions and Performabuilt made it sound like it’s electrical so I was focusing on that but I guess the valve body is electromechanical? Anybody else think it might be that? @pwtr02ss what do you think? I’m not going to pull the pan again until I send a log to BB and hear back unless it’s a real good chance it’s the valve body. @BlackBearPerf do you think Justin will be able to look at a datalog for me fairly quickly or am I looking at weeks? I won’t be needing a tune, just a look at the log to see if the ECM is calling for downshifts and they’re not happening.

 

[Rocket Man]

Reading through Performabuilt’s website it looks like they modify the valve body so I’m waiting to hear back from them if they do or if I could use a rebuilt Sonnax unit if I need it. I might have to get one from Performabuilt if it’s needed.

 

[pwtr02ss]

Thanks Chase. You’re the second person to suggest the valve body. I really don’t know squat about transmissions and Performabuilt made it sound like it’s electrical so I was focusing on that but I guess the valve body is electromechanical? Anybody else think it might be that? @pwtr02ss what do you think? I’m not going to pull the pan again until I send a log to BB and hear back unless it’s a real good chance it’s the valve body. @BlackBearPerf do you think Justin will be able to look at a datalog for me fairly quickly or am I looking at weeks? I won’t be needing a tune, just a look at the log to see if the ECM is calling for downshifts and they’re not happening.

I suppose it could be something in the valve body. I'm really not sure. I hope you figure this out so I can add it to my knowledge for the future. Like I said, I'm still confused on why it'll manually work but not work when the truck commands it. The intermittent part is also confusing. I suppose it could have something sticking in the VB that frees up when in manual mode? I'm only knowledgable to the point of failures I've experienced, none of which have been your problem.

Keep us posted

 

[Rocket Man]

I suppose it could be something in the valve body. I'm really not sure. I hope you figure this out so I can add it to my knowledge for the future. Like I said, I'm still confused on why it'll manually work but not work when the truck commands it. The intermittent part is also confusing. I suppose it could have something sticking in the VB that frees up when in manual mode? I'm only knowledgable to the point of failures I've experienced, none of which have been your problem.

Keep us posted

I just got a return email from Ryan at Performabuilt who said it sounds like it’s in limp mode which is purely a communication issue from the vehicle. He said to unplug the harness from the trans and if it doesn’t change then I need to address the tune or vehicle wiring. The only way I can do that is to get it to fail, and then come home and then get under it and unplug that and go for another drive. Maybe I can fit under there if I drive it on my ramps so I’ll have to see if I can do that. I had my Silverado’s 4l60 go into limp mode once when I mistakenly pulled the TCM battery fuse and it feels the exact same. It just stayed in third unless I manually shifted down, and wouldn’t go into fourth.

 

[Bigkevschopshop]

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