I am experiencing transmission slippage under load and it feels like it's riding on marbles when i step on it and or travel on the highway at speeds above 55 MPH.

12 months ago i experienced the same issues and what I did to alleviate the problem was to drain the old fluid, add 6 quarts ATF4, and replace the filters with new OEM. All was fine after that until last month. Last month the weather dropped below zero during the early morning hours and the transmission would not go into gear at first. I had to wait a few minutes in park and allow it to warm up before it did.

At random times, I experience my transmission hunting for gears, slipping while under load, and feels like there's marbles under the tires at 55 MPH.

Not sure what I need to do to decipher what the problem is. I read on here that some have replaced their problematic transmission with a used 545rfe from a Ram 1500 hemi without issues.

Is this the way to go? Is a used 545rfe transmission from a Ram 1500 hemi the right way to go?

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2006 Liberty Limited CRD, Deep Beryl Green, Yeti tune, Arp studs, new cams, rockers, lifters, TB. "Green Monster"
2005 Liberty Sport CRD, Deep Beryl Green, GDE Hot Tune, ARP studs. "Rocket"
1982 Fiat 124 Spider Convertible. "Fiona"

The Ram 1500 hemi and the Liberty CRD use tha same transmission, the 545rfe.

The Ram as a different torque converter and it's managed by a different TCM.