[TheDodgeGuy]

I got this off of www.wjjeeps.com from their model year differences page. It was listed as a "New for 2001" feature.

Automatic transmission, new 545RFE five-speed with 4.7-liter engine provides a second overdrive ratio for increased highway fuel economy and reduced engine noise at highway speeds (Note: A Flash upgrade was introduced on September 15, 2000 which when performed on 1999 and 2000 models adds the new second overdrive ratio to upgrade those transmissions to 5-speeds)

They had the 545RFE back in '01 and we never got it till the Gen 2 redesign??!? What gives?

Here's an exact link to the page, which is about 2/3 of the way down. www.wjjeeps.com/newoptions.htm

Since the Grand Cherokee WJ is very similar in drivetrain to the 4.7L Durango, I wonder if this flash would work on our TCMs? Only thing to consider is that the WJ uses a 3.73 axle ratio compared to our standard 3.55. If this flash adds a second overdrive ratio, there's the minute possibility that highway RPMs might be too low and the tranny might "hunt" back and forth between gears. I haven't done the math to determine exactly how much difference in cruising RPM there would be between a D with 3.55s and 265/70R16 tires and a WJ with 3.73s and 235/70R16 tires at a given road speed to see if this might present a problem or not.

Regardless, it's quite interesting.

 

[Silver Ghost]

I thought the 545RFE transmission was available in D's sometime during the 2002 model year, but I can't find the reference.
Anyway, I put together a little spreadsheet to calculate RPM's at speed based on Rear-end/OD gearing/tire diameter.
I set it up for a basic D with 3.92 gears and 31X10.5R15 wheels, but it's easy to replace values.
I've attached it for anyone who wants to play with it.

Joe.

 

[tomk]

My '03 certainly has a 545RFE.

 

[DurangoPaul]

Just out of curiosity, how does a software upgrade change gear ratios that are determined by hard parts?

 

[MuddyMike]

Probably added torque converter lockup to another gear rather than just top gear. Also, IIRC, the OD gear set is separate from the main gear set, so it'd be possible to engage the OD gears while the tranny was in 2nd, thus giving you another ratio. Both could be done with software.

 

[tomk]

The (5)45RFE has three gearsets and six clutches, so there are a lot of gear ratio possibilities.

 

[TheDodgeGuy]

My '03 certainly has a 545RFE.

Are you 100% certain? I finally got a straight answer from a knowledgeable dealer tech regarding this and he told me it was a Jeep only flash. That the Durango TCM won't accept the reflash? something to do with emissions at highway speeds.

We concluded that all '00-'03 Durangos/Dakotas only had a 45RFE not a 545RFE.

 

[tomk]

Straight from the '03 FSM and my '03 moroney sticker so, I'm pretty certain.

 

[TheDodgeGuy]

Well? Whiskey Tango Foxtrot! If the '03 has it, I can't see what the big deal is regarding emissions. Do you have the 3.55 or 3.92 axle ratio?

Also, somewhat unrelated (I think), your tires are smaller! Mine came with 265/70R16 tires and, according to the label, yours are only 245 in width, making them a smaller overall diameter too. I didn't see anywhere in the optional equipment where a P265 tire was added in place of it either.

I'm going to dig further into this. I have all the literature from '00-'03, so I'll see if there was a running change somewhere. Heck, maybe I'll just buy a used '03 TCM, install it and see what happens.

 

[FSTDANGO3]

The 03 also has one computer under the hood that controls everything where the others have two, one for the tranny and one for engine management. My friend's 03 has a 4 plug PCM.
As for the flash it can't be done to the 00, 01 ,02 because of the separate tranny computer. The 03 obviously has it.
I'm going to ask my friend at the dealer if there's a way of installing an 03 PCM/tranny computer set up in my 01 just to see what he says. Then mine could be flashed accordingly.
Steve
DOC Pres

 

[TheDodgeGuy]

Because of the difference in crankshafts from '01-'03, a PCM swap isn't possible. I forget the exact details, but I think it was something like the later models had twice as many "teeth" on the crank for the crank sensor as the older ones did.

Back to the drawing board, I guess. Maybe a TCM out of a '01 WJ Grand Cherokee??