Jump to content

GMC 2003 hesitates to shift to 4th speed

Normann

Recommended Posts

Normann New Member

Normann

Posted
Posted

Hi all,

I'm new to my 2003 GMC Yukon XL 2500 and I'm not fully sure if the tranny works as it should. On flat road, I need to exceed approximately 55 Mph before it decides to shift to 4th gear. I have a 496 (8.1Litre), 4L85E and 3:73 diff. I have changed tranny oil and filter, but that didn't change anything.

Is this what I should expect? Or should the tranny be tuned and is it only possible to tune the tranny with a Tech2?

Sven-Erik

Normann New Member

Normann

Posted
  • Author
Posted

Should the SES Light be on if the PCM has codes?

If I read the ODB2 port with a normal scanner, it does not have any codes stored, not even a general code from the PCM.

txab Senior Enthusiast

txab

Posted
Posted

The average scanner you're talking Abnout is unable to read the necessary codes

Normann New Member

Normann

Posted
  • Author
Posted

If there are any error codes in the TCM, shouldnt the ECM get a common code (P0700) from the TCM saying that there are trouble codes in the TCM?

gmtech4 Senior Enthusiast

gmtech4

Posted
Posted

If there are any error codes in the TCM, shouldnt the ECM get a common code (P0700) from the TCM saying that there are trouble codes in the TCM?

If it has a stand alone TCM like the Allison , he has a pos 4l85 , I doubt he has a TCM

Normann New Member

Normann

Posted
  • Author
Posted

Ok, thanks for the information. Then I guess the PCM might have error codes from the transmission and that these are not triggering the SES light. I will take it to the dealer and have it checked.

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Latest Articles

  • Posts

    • 2017Z
      2020 Trailboss 6.2 replacement

      By 2017Z · Posted

      Looking for advice from this group. Took my flawless 2020 6.2 TB to an unnamed shop for routine rear brakes and oil change. Tech forgot to put oil back in after the full service and needles to say, destroyed my engine.  It’s all on their shop video so they are responsible.   I had my Chevy dealer do the analysis and they confirmed its compromised and said engine replacement. The manager said they only get GM reman engines from GM with full 3 yr warranty and the one they would put in is not same as what’s they are swapping out on 21-25 for recall.    I am looking for advice why that would be a different engine because obviously I had the good 6.2 year and replacing it has my concerns with that recall for 21-15   Also what’s the pros and cons of accepting the engine swap vs telling the shop that bricked the truck to pay up so I buy a new truck. I’m concerned about stigma resale eventually if I just decide to get rid of it after the swap or other issues showing up after the swap out.  
    • GN2018
      AFM Disabler Question

      By GN2018 · Posted

      Just looked up my records.  I've never gone over 5000 miles between oil changes.  At 46K miles, I have 10 oil changes.  I hope that will help.  I also installed the disabler last year.  I've still had a few times when it didn't seem to engage (which I can tell because the start stop feature kicks in), but for the most part, I think it's working.  For some reason, GM did not include the number of cylinders running in the information screen like I had on other models.  In my Cadillac, it shows me when it's running on 4 cylinders on the fuel milage screen.  I can't find that on my '21 Denali.
    • davester
      Wiring Help, Please

      By davester · Posted

      you might read through the info on gmupfitter.com for your truck, to find a good power source.
    • Grumpy Bear
      AFM Disabler Question

      By Grumpy Bear · Posted

      Melling I believe is/was the OEM on the lifters who explored this problem some years ago. The white paper they generated on the topic indicated two items of note when I read it. 1.) They only fail on the switch. Prevent the switch, prevent the failure. 2.) The majority fail due to deposits messing up the timing of that switch. Anyway that's what I got from it.    Mine have always been active, 195K+ now, and my oil maintenance is surgically clean.    Of course this assumes good parts. That is no heat treat issue or machining flaws. I get comfortable that these issues are in the rearview mirror by about 30K. IMHO naturally. 
    • Chuck FB
      2 speed transfer case optional now?

      By Chuck FB · Posted

      Yes, the key seems to be with the half tons that if it has the Z71, then it definitely has the two speed. What got me was that the two speed AND the lower geared towing package option could not be chosen together the last few years unless it was mated up to the 6.2. Want the 3.0 duramax and 3.73 tow gears ... nope, can't get the two speed transfer case ( neighbor son realized that after he had bought his used 3.0 half ton .. where the frick is the low range ? ! ).    I am still unsure which truck series, the half ton or the HD truck that the original poster is referring to for sure other than yes his question is in the HD section of this forum but that doesn't guarantee the question got asked in the right section.  

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...