Rebuilt 4L60E- second gear start
Rebuilt 4L60E- second gear start Freshly rebuilt stock 4L60E with stock converter. Everything works as it should except for it starts off in second gear. Sometimes it will go into first if you shift into D1 and run it up to around 30MPH and let off the gas. When it does go into first, it holds fine, doesn't slip and will shift out normally when the lever is moved to D2. The next time you stop and take off, it starts in second again. The GM manual says for second gear starts, the forward sprag in assembled backwards. If this is the case, would it work sometimes like I've described above? All the clutches, seals, pistons, solenoids, etc inside are new. Everything including the valve body was disassembled and cleaned, and the cooler flushed. There are no codes in the PCM, and it is showing the proper commanded gear at the right times according to the Tech 2. Anyone have an idea on what to look at first?
If the sprag were assembled backwards you would have more problems than that,
I would check over the 1-2 shift valve assembly just behind the 1-2 solenoid perhaps the spring that returns the valve is missing, wrong one or broken since valve body was disassembled , Note the 2-3 does not have a spring while the 1-2 does and a rather stiff one at that.
And check that the 1-2 shift valve assembly is in there properly . and you might consider changing the 1-2 solenoid if you dont find and issue there.
I would check over the 1-2 shift valve assembly just behind the 1-2 solenoid perhaps the spring that returns the valve is missing, wrong one or broken since valve body was disassembled , Note the 2-3 does not have a spring while the 1-2 does and a rather stiff one at that.
And check that the 1-2 shift valve assembly is in there properly . and you might consider changing the 1-2 solenoid if you dont find and issue there.
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I'm fairly confident the 1-2 and 2-3 valvetrain are assembled correctly. Obviously I'll be checking them again though. 
Both solenoids are new AC-Delco units. The line pressure is around 110psi at idle, and rises with the throttle as it should. Drove it again and noticed another symptom. With the lever in any forward gear, the vehicle will not roll backwards, even on a sharp incline. Obviously, this is with the vehicle stopped, and still in second gear. Moving the lever from D4 to D3, 2, or 1 makes no difference. In reverse it will roll forward if on an incline, as expected. I'm wondering about that sprag now.
Both solenoids are new AC-Delco units. The line pressure is around 110psi at idle, and rises with the throttle as it should. Drove it again and noticed another symptom. With the lever in any forward gear, the vehicle will not roll backwards, even on a sharp incline. Obviously, this is with the vehicle stopped, and still in second gear. Moving the lever from D4 to D3, 2, or 1 makes no difference. In reverse it will roll forward if on an incline, as expected. I'm wondering about that sprag now. Yep, I was very careful to get the right VB bolts in the right spots. Didn't want to stab one through into the shell! The line pressure is about 10% high across the board according to the service manual. Since it was consistent before and after the rebuild, I didn't really think it was a concern. I thought maybe someone had installed a larger boost valve to bump the pressure.
On The Tree
Joined: Jun 2007
Posts: 165
Likes: 0
From: haltom city/DFW, Texas
Clutch pack and band clearances can be a problem if they are too tight . Like Frank said , if the 1-2 valve train is not correct it can give you a wrong gear start . Spring goes in first then the valve !!
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I did find the cause of this. Turns out I had the 3-4 shift valve and spring installed in the valve body backwards. This caused a leak in the Signal A circuit that prevented the 1-2 valve from compressing it's spring, which in turn passed D4 fluid into the 2nd clutch circuit, applying the band. I corrected the 3-4 valve and spring, and all was good.
I did find the cause of this. Turns out I had the 3-4 shift valve and spring installed in the valve body backwards. This caused a leak in the Signal A circuit that prevented the 1-2 valve from compressing it's spring, which in turn passed D4 fluid into the 2nd clutch circuit, applying the band. I corrected the 3-4 valve and spring, and all was good.
Teching In
Joined: Jun 2023
Posts: 3
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GMC safari 2005 transmission rebuilt, not starts in 2nd gear with no codes I just rebuilt my transmission and it starts in 2nd gear and eventually switches into 3rd after reving high. Not picking up any codes or check engine light.
Maybe the same problem, will go drop the valve body.
Maybe the same problem, will go drop the valve body.
Zombie thread revival!
I did find the cause of this. Turns out I had the 3-4 shift valve and spring installed in the valve body backwards. This caused a leak in the Signal A circuit that prevented the 1-2 valve from compressing it's spring, which in turn passed D4 fluid into the 2nd clutch circuit, applying the band. I corrected the 3-4 valve and spring, and all was good.
I did find the cause of this. Turns out I had the 3-4 shift valve and spring installed in the valve body backwards. This caused a leak in the Signal A circuit that prevented the 1-2 valve from compressing it's spring, which in turn passed D4 fluid into the 2nd clutch circuit, applying the band. I corrected the 3-4 valve and spring, and all was good.
