Transmission Bangs Into Reverse

Max Technician Glendora, California Posted   Latest   Edited  
Question
Drivetrain
2005 Mercury Grand Marquis Limited Edition 4.6L (W) 4-spd (4R70W)

TRANSMISSION shift really hard into reverse from park or neutral . The transmission was rebuild a few months ago. The line pressure is about 130 psi when its cold and it shifts the worst. When the engine is warmed up the line pressure goes down to 80 psi and the transmission shifts into reverse a lot smoother. the adaptives have been reset and the only ohter thing i have is if i coman the idle down to 600 rpms the transmission with shifts smooth.

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Richard Owner/Technician
Warrensburg, Missouri
Richard Default
 

Everything I can think of that would cause a harsh reverse engagement would affect all of the shifts. Were the pressure readings taken in reverse or drive? They would be a little low for reverse but pretty high for drive. Are there any codes? OD OFF light flashing? A dirty or defective MAF can throw pressures off. Any more info you can provide might be helpful.

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Max Technician
Glendora, California
Max Default
 

yes the pressure readings are for reverse. i found the spec for reverse at idle is 58 to 70. 48 to 100 for all other gears. 190 to 210 for wot stall. it seems to me the idle is high when you first start it and throw it in gear about 1200 rpms which i considered cold start high idle and from there it tapers down to 750 or so. 650 for idle in gear. I cleaned throttle body and maf, disconnected the…

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Randy Diagnostician
Glendora, California
Randy Default
 

Time to call Leo

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Richard Owner/Technician
Warrensburg, Missouri
Richard Default
 

I looked on Alldata and got the same specs you did which I don’t think are correct, this link will give you more realistic numbers, ford-trucks​.​com/how-tos/a/ford…, I would also check for excessive play in the drivetrain.

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Max Technician
Glendora, California
Max Default
 

I think my problem is more of the engine cold idle speed, when she first starts it and jams it in reverse 10 seconds from starting it hits hard once the engine is fully warmed up the transition between park and reverse or neutral to reverse is very smooth. This is a drive by wire the throttle is clean and as far as idle reset all i found was clean throttle body the drive to 60 miles and decel to…

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Richard Owner/Technician
Warrensburg, Missouri
Richard Default
 

Sounds like maybe the vehicle is functioning as designed and the operator needs a little adjustment.

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Jonathan Technician
Tempe, Arizona
Jonathan Default
 

Compare your stall speed to spec. You can get torque converters for those in several different stall speeds. If your fast idle is high with the lower stall speed converter they will bang into gear, however, it usually affects both drive and reverse but it's an easy thing to check and rule out.

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