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4th gear and TCC lockup issues

9

99coupegtp

New member
Hey all,

I have a 4T65E-HD with around 25k miles on it and a couple days after a recent road trip with some vigorous mountain carving it has started to do strange things.

At speeds less than 50mph 4th gear and lockup will work most of the time but TCC lockup will disengage and the transmission will downshift to 4th under light throttle conditions despite the PCM commanding 4th and lockup.

At interstate speeds, 60mph+, the issues with 4th and TCC lockup are even worse.

These issues seem to get a bit less noticeable after the transmission fluid has reached 160-170*F but it still doesn't work perfectly.

Anyone have any ideas what the cause of this may be?

Sent from my LGUS997 using Tapatalk
 


99coupegtp said:
At speeds less than 50mph 4th gear and lockup will work most of the time but TCC lockup will disengage and the transmission will downshift to 3rd under light throttle conditions despite the PCM commanding 4th and lockup.
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Oops, meant to say that it will downshift to 3rd, not 4th.
 
Mine does this and not sure why, I did figure that when mine does it, it will have a pending code. Not sure what the code is bc I never have my scanner. It doesn't trip the cel and won't show up in the aeroforce but as soon as I hit clear codes it goes into lockup and shifts normal. If I'm driving in town I always leave it in 3rd bc if I have it in drive it's always down shifting. Not sure if you're having the same issue but you might check pending codes.
 
Yeah I've read that but this is way different than that. Its commanding lockup according to the TCC duty on the aeroforce gauge.

The way it's working now is not the way it's worked for the past 2+ years.
 
selliott said:
Mine does this and not sure why, I did figure that when mine does it, it will have a pending code. Not sure what the code is bc I never have my scanner. It doesn't trip the cel and won't show up in the aeroforce but as soon as I hit clear codes it goes into lockup and shifts normal. If I'm driving in town I always leave it in 3rd bc if I have it in drive it's always down shifting. Not sure if you're having the same issue but you might check pending codes.
Click to expand...

Ah, I was hoping the aeroforce gauge would get trans codes... Well since I now know it doesn't, I'll take it somewhere and have it scanned. Thanks!
 


99coupegtp said:
Ah, I was hoping the aeroforce gauge would get trans codes... Well since I now know it doesn't, I'll take it somewhere and have it scanned. Thanks!
Click to expand...
I'm not sure if the aeroforce reads trans codes or not I just know that pending codes don't show up. If your out driving and it does it again try clearing codes and see if it immediately goes into lockup.
 
selliott said:
I'm not sure if the aeroforce reads trans codes or not I just know that pending codes don't show up. If your out driving and it does it again try clearing codes and see if it immediately goes into lockup.
Click to expand...

Gotcha, either way I had O'Reilly's scan it yesterday and there were no trans codes.
 
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