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Old 10-02-2008, 09:34 AM
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4L60E Hard shift mystery driving me crazy

Any Tranny pros out there that may be able to give me a hand with this before I spend a bunch of $$ at a shop would be appreciated.
I have a 2004 5.3 Vortec + 4L60E from a Silverado that I have transplanted into a fiberglass 1980 Jeep CJ7.
All works awsome except for my 4L60E.
Upon shifting from P or N into D or R it slams into gear so hard that it squaks the tires. (the CJ is light so it doesnt take much, but still dont think it should shift that hard).
Shifts from 1 to 2 often are hard as well. Other gear shifts and down shifts seem smooth.
It has always seemed a little hard but it has been getting worse.
I have cleaned the MAF, adjusted the PRND switch (and verified position), my Speedo is getting signal from the computer and works fine (so I am guessing my speed sensor works), RPM display works so i know PCM is getting signal on that. I also went through the engine/trans "learn" procedure for the PCM. I dropped the Tranny pan and replaced the pressure control solenoid with a new one. (didnít help). (fluid looks clean and doesnít smell, and nothing in the bottom of the pan)
I am running out of ideas short of swapping out the Valve Body.
Please HELP
Thanks
Eric

Last edited by ericanderson; 10-02-2008 at 10:00 AM.
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Old 10-02-2008, 10:23 AM
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I'm by no means a tranny pro, but ...
a common 4L60E problem that I've seen several times is the valves in the valve body stick and supply wide open pressure when they shouldn't.

The fix is to either use a new valve body, or bore out the original and put upgraded valves in.
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Old 10-02-2008, 10:23 AM
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I would check the lockup torque converter solenoid. It sounds like the converter is close to stall or lock. As if the RPM were up...
Tim
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Old 10-02-2008, 11:35 AM
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I don't think the lockup solenoid is capable of being enabled in 1st or Reverse. Only 2nd, 3rd & 4th.
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Old 10-02-2008, 01:16 PM
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As vehicle weight goes down.. the converter stall must go up. This may be part of the problem
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Old 10-03-2008, 04:50 PM
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That is true that under normal circumstances the converter is not permitted to do lockup in first or reverse. But if the idle is under a 1000rpm and your getting that hard of an engagement when the forward clutch is engaged then there is something going on in the converter is my first thought. But I guess the line pressure could be the problem as well.
I believe there is a line pressure tap on the outside o f the tranny, so put a gauge on the line pressure tap and see if its high at idle and in Park.
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Old 10-03-2008, 08:33 PM
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Thanks to everyone so far that has commented.
I will see if I can get a pressure gage this weekend and check out the line pressure. On very rare occasion, when everything has run for a while it will go into gear almost like it should.
Any idea what the pressure should be at idle in Park?
Would a high pressure point towards a bad converter, or valve body?
Is the lockup controlled by a solonoid in the valve body or some otherway?
I am thinking I should be able to "Back probe" the wires coming off of the PCM and see if the lockup is energized or not. (i have the wireing diagram for the 2 connector blocks off the PCM) I just dont know if it should be energized or not energized when going from P to D? (I would guess not)

Thanks again everybody.
Eric
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