nicolas-eric

Hello.

A friend has a 2000 WJ with a broken 45RFE tranny. Now he could get a 545RFE from a newer WJ for a very good price.

IMO the 545RFE is a 5 speed tranny and the 45 RFE is a 4 speed tranny.

Does the 545RFE tranny fit without other modifications?
If not what other parts does he need?

Thanks in advance.
nicolas-eric

huntingman2706217

may help

The 45RFE and 545RFE automatic transmission in the WJ was notable. It included three planetary gear sets rather than the two normally used in a four-speed automatic. This gave it six theoretical speeds, and it would have been the first six-speed transmission ever produced in volume, but it was programmed to only use five of these ratios. Four were used for upshifts, with a different second gear for downshifts. Although five of the six ratios were used, Chrysler decided to call it a "4-speed automatic". In 2001, the programming was changed to make use of all six ratios. Rather than have six forward gears, the transmission was programmed to act as a five-speed with the alternate second gear for downshifts. The RPM at 70 miles per hour (110 km/h) on a 545RFE is 2000 rpm, 200 rpm less than the 45RFE programming. 1999 and 2000 model year WJ owners can have their 45RFE transmission's programming flashed to enable the extra gear as both transmissions are physically the same. The 42RE 4-speed automatic remained the transmission for the Inline 6 engine. It was not changed from the previous model Grand Cherokee's.

nicolas-eric

Thanks !

kent727

I talked to one of the local Jeep dealers here. They are not aware of the reprogramming option to convert the 45RFE into the 545RFE. Does anyone have more information on this? Where can I get the programming done?

Thanks

atommota

Hopefully this isnt too late to help you. I had this done on my 2000 WJ and it worked great. The TSB they will need is 18-025-01.

I placed a copy of the TSB on google docs here:
https://docs.google.com/fileview?id=...YWI4YjE2&hl=en


Tim

5-90

Check the external dimensions - adding a gear range to an established box can make it larger/longer.

You'll need the proper controller for the 5-45RFE, or that fifth gear is just going to be idle. Also, it may not shift into reverse without the proper controller (electronically-controlled slushboxen are shifted by engaging pressure solenoids in various combinations. The "truth table" for the 45RFE and 5-45RFE are probably different.)

45RFE = "Four forward speeds, Relative strength 5 (0/1/2/5/7/8,) RWD mount, Fully Electronic Controls"
5-45RFE = "Five forward speeds, modified version of 45RFE, relative strength 5 (0/1/2/5/7/8,) RWD mount, Fully Electronic Controls"


I don't know what that "relative strength rating" works out to - but you see that it's on an interrupted scale of 0-8. However, I have no idea what that works out to in absolute numbers. Yet. (It's on my list of things to find out when I can finally get hold of a ChryCo engineer.) However, a rating of 5 should be fairly strong - the A727 was renamed to the 37RH (three forward speeds, relative strength 7, RWD, hydraulically controlled,) and the A727 was, for the longest time, the strongest slushbox that Chrysler made. Same league as the GM THM350/THM400 and Ford C6.

If the 5-45RFE were a new design unto itself, it would be the "55RFE." So, it's probably mechanically similar to the 45RFE, but there are key electronic differences - and, as mentioned, probably different dimensions. Check before undertaking the swap. I'd consider the bellhousing to be probably the same (and you're dealing with a V8-287 in both cases, right?) so you want to check the case dims proper and make sure the mount pad is in the same place.

Differences in OAL can result in needing new driveshafts - I think the max you can really expect to be different - and still use the same shafts - is only about 1/2". Differences in "cube dims" (external volume dimensions - LxWxH) could result in floorpan/tunnel mods being needed.

kent727

Thanks! I haven't pursued it any further after hitting the dead end at the dealer. I'll take this with me when I visit them again.

Thanks again.

Kent