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Ask Gm Tech (Cam) Your Own Question
Gm Tech (Cam)
Gm Tech (Cam), GMC Mechanic
Category: GMC
Satisfied Customers: 29428
Experience:  GM Grand Master Technician 2007. 14 year experience.
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4l80e in my 2001 Yukon 2500 with 6.0L engine. shifts hard

Customer Question

4l80e in my 2001 Yukon 2500 with 6.0L engine. shifts hard all the time even at startup in the cold mornings no codes ever.
Also in the morning when I start it the engine clatters pretty loud oil pressure at zero for like 20 seconds. then it pops up to 40 pounds as the engine/ oil warms up. run s good when warm.
Submitted: 1 year ago.
Category: GMC
Expert:  Gm Tech (Cam) replied 1 year ago.

Hi there, I am Cam. Can I get your first name please?

With your transmission, what is the exact colour and condition of the transmission fluid? You say it needs to be changed, but if its really brown then a change may not be enough.

I have a suspicion it’s the torque converter clutch causing it, but we can explore that.

Customer: replied 1 year ago.
The color is more of a weak red and does smell. It is not brown at all. In driving last night I noticed it shifts real firm in all gears manually or in automatic. Also if you manually downshift it it shifts down firm as well. Overdrive works great no strange issues. Transmission temp never goes up. I am no feeling any slipping. Still no codes at all. Changed the TPS. Yesterday and Un did the battery terminals for about a half hour cleaned them well and used dielectric grease on them. No difference at all
Customer: replied 1 year ago.
My name is Max.
Expert:  Gm Tech (Cam) replied 1 year ago.

OK Max, that does lead me to think that either you torque converter clutch is slipping or you have just general wear in the transmission. A hard shift is simply the increase of line pressure inside the transmission. With your transmission fluid showing it not Brown, I believe the next best course of action to replace the filter and replace all the fluid. If that doesn't change the shifting, then perhaps we have a feeling pressure control solenoid inside the transmission. It might be cheap enough to consider replacing while you have the pen off. The gasket is reusable provided it's not damaged.