45fre or 545rfe
 

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I think if you call the parts department at a Dodge Dealership, they can tell you what Transmission you have using the VIN number.

Well, that is how they determined which Tranny Pan I needed.

Somewhere on here there is a post about Engine and Transmission options by year.

The 45rfe and 545rfe are identical hardware wise, the only difference is in the computer. Early ones were only programmed to use 4 speeds where late 02 and 03s were programmed to use 5 forward speeds. I believe that if the PCM has 4 connectors it's 545rfe and if it has a separate module for the transmission (3 plug pcm) it's the 45rfe, but you can get a Grand Cherokee tcm that gives you the 5th gear making it a 545rfe.

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you are very close on the information you are sharing.

the programming and 2 second gears is all correct. however the 45rfe and 545rfe are physically identical as far as they are built, the will bolt up with the same engines ect.

the 45rfe is also (by your description) a 6 speed, but is programmed to only use 4 forward gears.

my friends here have great ideas. but ill add my ideas. think about running the trans you use throu a good shop and have it freshened up and put a shift kit in. all so i have found an external filter. that i like.
use ONLY steel brake lines. copper WILL break off. the factory uses steel for a reason!!!! mopar most use 3/8 dia tube, but some might be 5/16. i think most have the fluid in at the rear left side. here is an EXTERANL filter, i found. have one on my 01 dak. my idea is when you put a new filter in side this one will help from having to do the inside one as often.*
the old auto zone 2210 magenfine filter is no longer available at auto zone. BUT i did find the same thing as JX-160 brand-- ATP. at a real parts house uses 3/8" tube. a JX-150 for 5/16 tube. ONLY use high pressure hose. If you must. SAE J1019 217 psi working. NOT fuel hose for a carb engine.

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