Hard 1-2 shift on 2000 Grand Am 4 cylinder.

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Niece's car has developed a hard 1-2 shift on about every 1 in 3 shifts. Car has 95k, maintenance history prior to 78k is unknown. This is one of those sealed units with no way to check the fluid. I was underneath it last night (changing the engine oil and filter), and the transmission is dry, so it hasn't lost any significant amount of fluid. Thoughts?
 
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Last time the fuel filter was changed? Take it somewhere it can be scanned for fault codes.
 

mrsilv04

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 Originally Posted By: MrCritical
Last time the fuel filter was changed? Take it somewhere it can be scanned for fault codes.
OK. I have to ask about the connection between a fuel filter and a transmission that occasionally shifts hard... Please enlighten me.
 
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Had this happen to me. If the fuel filter is clogged or getting clogged the computer tries to adjust or has the wrong fuel flow. Then the transmisson computer tries to adjust or has bad info. This puts the whole system out of spec and you can get strange problems like this.
 
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 Originally Posted By: millerbl00
Find someone that can change the fluid and use two bottles of Lubeguard red. That fixed mine.
I used one bottle of red lubegard. you used 2 bottles? how long has it been?
 
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Our Malibu (2.4L) has a 'harder than normal' 1-2 shift at times. Could very well be the same transmission as the Grand Am's. It is possible to check the fluid, but you do so by getting the transmission warm and then popping out the check plug on the side of the transmission. It's full when the fluid reaches the bottom of the plug hole. There is a fill tube for adding fluid...but to check it is a small pain. I did change the fluid and filter - it did help some but I'm sure it's days are numbered (but isn't that true for any automatic tranny?)
 
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Helped same issue somewhat in a '99 Sunfire once with a fluid change whith half a pint of Seafoam trans tune added in. To really fix it completely, it may need the Pressure Control Solenoid changed out also while the pan is down.
 
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 Originally Posted By: mrsilv04
This is one of those sealed units with no way to check the fluid.
No, it's not. It's a 4T40E and how to check the fluid on this has been covered extensively in the transmission fluid forum.
 
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