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Delayed 1-2 shift, 4L60E

This is a discussion on Delayed 1-2 shift, 4L60E within the Technical / Maintenance forums, part of the General Discussion category; I have a 94 Suburban that I picked up for a song. It had sat for 3 years, and the ...

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    Registered User wedunit's Avatar
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    Delayed 1-2 shift, 4L60E


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    I have a 94 Suburban that I picked up for a song. It had sat for 3 years, and the only issue I find is that it won't up-shift from 1-2 with any throttle pressure at all. If I back off of the throttle at any speed after reaching 20+ mph, it'll up-shift, and work fine through the rest of the gears, including lock-up in 4th. However, it is extremely touchy about throttle pressure. Outside of the TPS, what other component tells the ECM that there is throttle pressure that would translate to info sent to the transmission? I realize that this trans is 90+% the same as the 700R4 of the early 80's, with just a few electronic mods. Since there is no TV cable on the 4L60E, is the MAP sensor part of the info management componentry for the trans? Could either of these sensors failure result in the symptoms I described for tranny? Any input would be appreciated, and thank you in advance.

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    Registered User wedunit's Avatar
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    Re: Delayed 1-2 shift, 4L60E

    No one has any ideas? I thought this would be a place that there would be lots of interaction, but I guess I was wrong. Maybe if I posted what MY thoughts are concerning this problem, and then see if it elicits any response:

    What do you think about replacing the 1-2 accumulator piston with a Sonnax pinless at the same time I put in an updated Corvette-style 2nd apply piston? Should do the trick, don't you think? I know they make heavier stuff than OEM-style, but I really don't expect to be pulling a trailer, or doing any off-roading, as it's Mama's car.
    Thanks for your response.

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    Do a burnout deadtrep's Avatar
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    Re: Delayed 1-2 shift, 4L60E

    does that truck have a TV cable?
    2000 Silverado 2500 NV4500 5 Speed 14 Bolt FF. Farm Truck.
    1972 Chevelle 383 Stroker. Money Pit
    1999 Dodge Intrepid 2.7L. Best Car Ever
    1984 Pontiac Parisienne 454. Burnout Machine
    1987 GMC V2500 Sierra Classic. Old Faithful

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    Registered User wedunit's Avatar
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    Re: Delayed 1-2 shift, 4L60E

    The 4L60E is electronic. The "E" is what that stands for, I've been told, so, no, there's no TV cable. Since I've replaced the TPS, the other shifts are a bit crisper, but still no 2nd. If I put the selector in manual 2nd there is only first gear, it will not upshift to 2nd when releasing the throttle. If the selector is in 3 or OD, it up-shifts to 3rd when I take my foot off the throttle at speeds over 20 mph. Since there is a solid 3-4 shift, and then TC lock-up, I'm thinking that the 2nd apply servo is stuck or leaking for some reason, because if the 2-4 band was toast, there would be no 4th. Can you tell me if the 1-2 accumulator piston would affect this shift, and how? Basically, there is no 2nd gear, any how, any way. In manual 2nd there is no engine braking, but there is engine braking in manual 3rd, and engine braking in manual 1st.
    I'm definitely going to install the Corvette-style 2nd gear band apply servo, but I guess my main question is: Would it be necessary to replace the 1-2 accumulator piston? Would that have an effect on the 1-2 shift? It sounds like it would, but I'm not well-versed enough in auto transmissions to know for sure. I'm an old gear man, worked on Spicers, Fullers, and Rockwells for years in the heavy equip industry, but have little experience with automatics.
    Thanks for any help.
    Last edited by wedunit; 12-07-2010 at 05:03 PM.

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    Registered User wedunit's Avatar
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    Re: Delayed 1-2 shift, 4L60E

    bumping for a reply...

 

 

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