2nd gear start in 4l60e
Thread Starter
Teching In
Joined: Aug 2015
Posts: 11
Likes: 0
2nd gear start in 4l60e I have the 2003 Denali with 4l65e and noticed something odd. When I start out in manual 2nd gear if I push the throttle to about 75% it will downshit to 1st for a second and it isnt supposed to do that. It shifts back to 2nd right after that. It shifts hard and runs throught the gears fine in d3 d4. It does have a Transo shift kit but the only other issue since rebuild is slipping of TCC clutch once hot under moderate throttle. I am trying to see if the two issues are somwehow related.
I dont remember it ever doing this before the rebuild but it did do this before I bought HP tuners and tuned it. I noticed on HPtuners scanner it throws a 1860 code (pending) when this happens but never any other time, Its like the shift to 1st makes it think it is slipping for a second, and it almost feels like it. I dont think this is good for it, so I have only done it a couple times to try and figure out what condition causes it.
I dont remember it ever doing this before the rebuild but it did do this before I bought HP tuners and tuned it. I noticed on HPtuners scanner it throws a 1860 code (pending) when this happens but never any other time, Its like the shift to 1st makes it think it is slipping for a second, and it almost feels like it. I dont think this is good for it, so I have only done it a couple times to try and figure out what condition causes it.
TECH Junkie
Joined: Dec 2012
Posts: 3,614
Likes: 1,326
From: Iowa
So you have hp tuners...do the following and report back.
-LOG the issue. See if 1st gear is being computer commanded...or is it commanding 2nd and hitting 1st gear anyway
-Check shifter adjustment
-do a line pressure test
-check band clearance. Should not be more than .125
2nd gear has the forward clutches and the 2/4 band applied...
first gear has just the forward clutches applied
slip the band and guess what it will feel like...you guessed it...1st gear.
Do the recommended above and report back. If you aren't sure how to do any of those...do a quick search on this forum and you'll find how-to's
-LOG the issue. See if 1st gear is being computer commanded...or is it commanding 2nd and hitting 1st gear anyway
-Check shifter adjustment
-do a line pressure test
-check band clearance. Should not be more than .125
2nd gear has the forward clutches and the 2/4 band applied...
first gear has just the forward clutches applied
slip the band and guess what it will feel like...you guessed it...1st gear.
Do the recommended above and report back. If you aren't sure how to do any of those...do a quick search on this forum and you'll find how-to's
TECH Enthusiast
Joined: Jan 2019
Posts: 677
Likes: 490
From: Roxana, IL
No reply in 8 days, so I thought I might post this from my GM 4L60E technician guide.
Manual Second (2) gear range is available to the driver when vehicle operating conditions make it desirable to use only two gear
ratios. These conditions include descending a steep grade when engine compression braking is needed, or to retain second gear
when ascending a steep grade for additional engine performance. In Manual Second, the transmission can upshift and downshift
between First and Second gear but is prevented from shifting into Third or Fourth gear. If the transmission is in Third or
Fourth gear when Manual Second is selected, the transmission will shift immediately into Second gear.
Note: First gear in the Manual Second gear selector position is only available on some models at low speeds and under heavy throttle.
Manual Second (2) gear range is available to the driver when vehicle operating conditions make it desirable to use only two gear
ratios. These conditions include descending a steep grade when engine compression braking is needed, or to retain second gear
when ascending a steep grade for additional engine performance. In Manual Second, the transmission can upshift and downshift
between First and Second gear but is prevented from shifting into Third or Fourth gear. If the transmission is in Third or
Fourth gear when Manual Second is selected, the transmission will shift immediately into Second gear.
Note: First gear in the Manual Second gear selector position is only available on some models at low speeds and under heavy throttle.
