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Hard shift from 1st to 2nd

This is a discussion on Hard shift from 1st to 2nd within the Technical / Maintenance forums, part of the General Discussion category; 99 NBS 5.3 192k miles Sometimes....not always when changing from 1st to 2nd gear, I get a bone jarring shift. ...

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    Hard shift from 1st to 2nd


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    99 NBS 5.3 192k miles

    Sometimes....not always when changing from 1st to 2nd gear, I get a bone jarring shift. I drive about 12-15 miles home from work. Around mile 10 it shifts super hard from 1st to 2nd, and a much milder but still not normal shift 2nd to 3rd.

    Any ideas on this? I appreciate any thoughts.

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    Re: Hard shift from 1st to 2nd

    CEL on or any codes stored? a code can be stored without a CEL, but will show up when scanned.

    Any particular variable that may be present when the trans shifts?

    Hot, cold, wet or dry weather is usually a factor in intermittent problems.

    Does it do it while accelerating hard or casually?

    If the trans is failing most of the time the shifts are smooth or lazy, so a hard shift is usually not a problem for the clutch packs (better and quicker contact means less wear) but it could be a problem for other parts if it's too harsh.

    I'm not too well versed on common 4L60E failure areas and diagnosing individual tranny parts is hard too (that sounds very wrong ) It could be your servos or accumulator pistons causing the hard shifts. Might also be the valve body or a worn out seperator plate.

    It could also be worn out mounts (too much movement during 1-2 shifts could cause crazy results) or it could be u-joints as well.

    Best thing to do is get the ECU scanned or hooked up to a proper scan tool and have it taken on a test drive. The tech can watch a variety of variables to narrow down what could be causing the problem such as incorrect line pressure, TC lockup issues, etc.

    Then i'd crawl underneath and start looking for worn out mounts and u-joints.


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    Re: Hard shift from 1st to 2nd

    There is no CEL. I'll go get it scanned to see if any codes are stored.

    There doesn't seem to be any other symptoms. It doesn't matter if it's hot, cold, wet, or dry. It doesn't do it everytime though. I never get on it very hard, so its always casual driving.

    Is there anything special/specific I should look for on a worn trans mount or u-joint?

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    Re: Hard shift from 1st to 2nd

    possible causes:

    http://www.fullsizechevy.com/forums/...ack-stock.html

    2. 1-2 shift does not happen at WOT until you let off the gas: Best case: try replacing the TPS. Middle case: leak in the 2nd gear apply circuit (servo assembly or 1-2 accumulator).
    Doublecheck by using the pressure gauge and watch for a big drop when the PCM commands 2nd gear. Worst case: poor line pressure rise (see below).
    3. 1-2 Shift shudder at WOT; delayed or abnormal 1-2 shift; There's a problem ONLY on the 1-2 shift: 1-2 accumulator piston cracked or stuck ****ed in the bore.
    Check the yellow spring inside the accum housing for breakage. Also, if the accumulator housing walls are scored, the housing must be replaced. Easy fix in the pan.
    4. 1-2 shift is delayed and harsh, may not shift into OD: Check TPS for smooth and linear electrical response over the entire range of motion. If not, replace.


    It possibly could just be worn out.
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    Re: Hard shift from 1st to 2nd

    Just to add to neumanzz's post:

    a working TPS should read 0.5V closed and 4.5V at WOT. give or take a few tenths. If it's more than 0.2 to 0.3V off then it will need replacing. The TPS sensor is auto-calibrated (if you try to adjust the TPS yourself) so if it's not within spec than it's in need of replacement.

    There are alot of articles on adjust TPS sensors on the net, but it won't help you with the more computer controlled vehicles. I could do it on my Honda but it was basically the same TPS that was used back in the late 80's. Calibrating it doesn't save it from being worn out, it's basically the way people would prolong the life of an expensive part. To replace the TPS on my civic required me to replace the entire TB itself. Luckily i had 3 spare used TB's, cuz i'm a spare parts whore.
    Last edited by Koots; 08-13-2009 at 03:36 PM.


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    Supporting Member 94383Z71's Avatar
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    Re: Hard shift from 1st to 2nd

    Quote Originally Posted by AMC99Z71 View Post
    Around mile 10 it shifts super hard from 1st to 2nd,
    you drive 10 miles in first?

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    Re: Hard shift from 1st to 2nd

    Quote Originally Posted by 94383Z71 View Post
    you drive 10 miles in first?
    I never even caught that at first

    BTW, if that's you in your avatar, you look almost exactly like some guy that i went to high school with. It's kinda creepy to me


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    Re: Hard shift from 1st to 2nd

    my 2004 sorta bumps if you get on it from 1st to 2nd...
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    Re: Hard shift from 1st to 2nd

    Quote Originally Posted by Koots View Post
    I never even caught that at first

    BTW, if that's you in your avatar, you look almost exactly like some guy that i went to high school with. It's kinda creepy to me
    I almost didnt bring it up, I though it was me mis reading

    and yeah thats me

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    Re: Hard shift from 1st to 2nd

    Quote Originally Posted by 94383Z71 View Post
    I almost didnt bring it up, I though it was me mis reading

    and yeah thats me
    Haha yeah, you don't look exactly like him, close enough for me to threadjack and comment on it ...Unless you are him...


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    Re: Hard shift from 1st to 2nd

    Quote Originally Posted by 94383Z71 View Post
    you drive 10 miles in first?
    Ha, not quite. Stop signs and traffic lights along the way. The point was that it doesn't occur at the mile 1 or 2 signs/lights.

 

 

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