Soon after I got my 05 Envoy XL Denali running after a painful DoD delete process and driving it back to my home 4.5 hours away (graduated and moved out of my college apartment) my transmission started slipping in 3rd gear, sometimes grabbing 4th gear. A little bit after that, I completely lost 3rd gear (almost completely felt like neutral, have to rev it past 5k to even feel like I'm getting any semblance of power). From some brief research, this seems very much like a mechanical failure, as I didn't get any shift solenoid codes or anything like it, but I did get a torque converter clutch circuit code among other transmission slipping codes:
The strangest thing is that when I tried driving the car just to see how it's doing the next day, 3rd gear seemed to grab again. I didn't dare go fast enough to require 4th. What's up with that?
Feel free to correct me if I'm wrong, but no matter what, the fix seems very invasive and given that my full time job is starting soon, I will not have the time or energy to do this job myself. I will take this to a local transmission shop for an inspection and to decide whether it's worth saving this thing, but if I were to go for a rebuild, I was wondering what you guys recommend to upgrade for increased durability. I'm not trying to blow a ton of money into parts (want to stay under ~$1000 total), but I want something that will be better than before especially in terms of 3-4 gear reliability. I'm not going to race this thing, but I may tow a lot, with loads up to 4500-5000lbs. Technically the transmission should have been able to handle this stock but we saw how this ended up for me.
These are the parts that seem to come up all the time, therefore I'm looking to see if I should include these. Feel free to let me know if I should redirect my funds to different parts:
Sonnax 77733-06KA input housing kit. Really uncomfortably pricey but it claims to help with 3-4 clutch pack failure.
Sonnax 74602-01K reaction shaft kit. Don't fully understand what this does but it seems to come up in every rebuild post.
BEAST sunshell. OEM sunshells are common failures, but it may not be an issue on 2005 onwards transmissions so please let me know if I don't really need to go for this. I've heard people mention a heat treated OEM sunshell but I can't find it.
Sonnax HP-4L60E-01 performance pack. Seems to replace a lot of wearable parts, but I was happy with how the car shifted (until the transmission blew up) so if it just affects shift feel I won't bother.
Am I missing anything, or should I get rid of anything? I also stumbled across this rebuild kit: https://cyclonetransmission.com/pro...s-zpak-1993-2004?_pos=12&_sid=86e03ee43&_ss=r
If this has all the necessary upgrades I will stick with this, and my wallet will be happy too.
The strangest thing is that when I tried driving the car just to see how it's doing the next day, 3rd gear seemed to grab again. I didn't dare go fast enough to require 4th. What's up with that?
Feel free to correct me if I'm wrong, but no matter what, the fix seems very invasive and given that my full time job is starting soon, I will not have the time or energy to do this job myself. I will take this to a local transmission shop for an inspection and to decide whether it's worth saving this thing, but if I were to go for a rebuild, I was wondering what you guys recommend to upgrade for increased durability. I'm not trying to blow a ton of money into parts (want to stay under ~$1000 total), but I want something that will be better than before especially in terms of 3-4 gear reliability. I'm not going to race this thing, but I may tow a lot, with loads up to 4500-5000lbs. Technically the transmission should have been able to handle this stock but we saw how this ended up for me.
These are the parts that seem to come up all the time, therefore I'm looking to see if I should include these. Feel free to let me know if I should redirect my funds to different parts:
Sonnax 77733-06KA input housing kit. Really uncomfortably pricey but it claims to help with 3-4 clutch pack failure.
Sonnax 74602-01K reaction shaft kit. Don't fully understand what this does but it seems to come up in every rebuild post.
BEAST sunshell. OEM sunshells are common failures, but it may not be an issue on 2005 onwards transmissions so please let me know if I don't really need to go for this. I've heard people mention a heat treated OEM sunshell but I can't find it.
Sonnax HP-4L60E-01 performance pack. Seems to replace a lot of wearable parts, but I was happy with how the car shifted (until the transmission blew up) so if it just affects shift feel I won't bother.
Am I missing anything, or should I get rid of anything? I also stumbled across this rebuild kit: https://cyclonetransmission.com/pro...s-zpak-1993-2004?_pos=12&_sid=86e03ee43&_ss=r
If this has all the necessary upgrades I will stick with this, and my wallet will be happy too.
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