45RFE -> 545RFE flash?

KY Liberty · **Joined:** Sat Jul 09, 2005 1:46 pm **Posts:** 1195

jg45 wrote:

It's about 200 RPM.

Cool, I was calculating 200-250 RPM depending on speed. I think that would get me back in the sweet spot.

sleeve84028 · **Posted:** Wed Dec 24, 2008 3:44 pm

This would be a very cool mod for those that spend a lot of time driving down the interstate. I think it's time to do some reading up on this.

Guest · **Posted:** Wed Dec 24, 2008 4:01 pm

is 200 rpm really gonna make that much difference?

Diggerfreek · **Posted:** Wed Dec 24, 2008 4:03 pm

it could

tommudd · **Posted:** Wed Dec 24, 2008 4:03 pm

ThunderbirdJunkie wrote:

is 200 rpm really gonna make that much difference?

I really don't want mine 200 lower, after I get the 4.10s in it should be back to almost what it was stock so I think I will stay where it is. :wink:

also dropping 200 RPMs at say 65 may take it enough out of the sweet spot that it would get worse mileage instead of better, would be like going up 2 sizes in tires ?

tjkoen01 · **Posted:** Thu Dec 25, 2008 12:05 pm

jg45 wrote:

I get the shift to 5th just below 50 mph and it holds down to about 43.

When does the torque coverter lock up? If it locks up below 60 that might help save some gas too.

Merry Christmas everybody!

jg45 · **Posted:** Thu Dec 25, 2008 12:56 pm

Full converter lock is at almost exactly the same time as the shift to fifth. So right about 48 mph by my speedometer. Watching the tachometer very closely, I can see the 200 rpm drop to fifth and then the converter lockup.

ChiroKJ · **Posted:** Wed Feb 04, 2009 9:43 am

just found this....

http://hotrodlane.cc/New%20HEMI%20Tech/ ... 0trans.pdf

It could be helpful. page 21-353 shows that both 45 and 545 have all the same clutches the only difference is the fifth gear where the OD and the 2C are both engaged to give the "5th gear". Also pressures are the same for both as long as the engine is 3.7/4.7

is there a difference between having the TCM flashed to 545 specs and getting a used 545TCM from lets say a durango?

XR · **Posted:** Wed Feb 04, 2009 12:58 pm

I was thinking about asking for an update on how it was working out for JG45.Well howzit going after driving with that set up for a while?

Jeepjeepster · **Posted:** Thu Feb 05, 2009 4:00 pm

I wouldnt mind if mine was 200rpms HIGHER. Would help a lot on all the hills around here but I can see where it being 200rpms lower would help on flat interstates. The 42rle runs around 1800rpms at 60mph.

What kinda mpg do you get around here in lex kylibby? I usually get around 12mpg. :lol:

jg45 · **Posted:** Sat Feb 07, 2009 7:15 pm

I like the revised shift and lockup patterns with the Grand Cherokee TCM. I get full converter lock at 48 instead of 60 and it hold lock pretty well until about 43. There is however, one problem. I thought I was getting a shift to 5th, but I was mistaking the converter lock up for a shift to fifth. I calculated RPM at a given speed to derive gear ratio, and I am only getting a .75OD and not the .67 gear ratio. I have not had time to investigate this yet. I am not getting a CEL so I think ti may be an issue with the TCM I am using. I am suspecting that it is not a 5-45RFE TCM. I may try to get another one that I am sure is for a 5-45RFE.

KY Liberty · **Joined:** Sat Jul 09, 2005 1:46 pm **Posts:** 1195

jg45 wrote:

I like the revised shift and lockup patterns with the Grand Cherokee TCM. I get full converter lock at 48 instead of 60 and it hold lock pretty well until about 43. There is however, one problem. I thought I was getting a shift to 5th, but I was mistaking the converter lock up for a shift to fifth. I calculated RPM at a given speed to derive gear ratio, and I am only getting a .75OD and not the .67 gear ratio. I have not had time to investigate this yet. I am not getting a CEL so I think ti may be an issue with the TCM I am using. I am suspecting that it is not a 5-45RFE TCM. I may try to get another one that I am sure is for a 5-45RFE.

Either that, or everyone else I spoke about this to (APS, B&G, KRC, and my transmission mechanic) was right and it won't actually work because there really are differences between the 45RFE and 5-45RFE. From what I've been told is it only works on a few vehicles that have the 5-45RFE and a flash that doesn't turn on the 2nd overdrive. I hope that's not the case, but I have my suspicions.

tjkj2002 · **Posted:** Sat Feb 07, 2009 9:06 pm

KY Liberty wrote:

jg45 wrote:

I like the revised shift and lockup patterns with the Grand Cherokee TCM. I get full converter lock at 48 instead of 60 and it hold lock pretty well until about 43. There is however, one problem. I thought I was getting a shift to 5th, but I was mistaking the converter lock up for a shift to fifth. I calculated RPM at a given speed to derive gear ratio, and I am only getting a .75OD and not the .67 gear ratio. I have not had time to investigate this yet. I am not getting a CEL so I think ti may be an issue with the TCM I am using. I am suspecting that it is not a 5-45RFE TCM. I may try to get another one that I am sure is for a 5-45RFE.

Either that, or everyone else I spoke about this to (APS, B&G, KRC, and my transmission mechanic) was right and it won't actually work because there really are differences between the 45RFE and 5-45RFE. From what I've been told is it only works on a few vehicles that have the 5-45RFE and a flash that doesn't turn on the 2nd overdrive. I hope that's not the case, but I have my suspicions.

T get the 2nd OD you need to change the 45RFE internals to the 545RFE internals.Using a 545RFE TCM all you do is unlock the second 2nd gear ratio that is only accessible in the 45RFE in WOT passing a certain speeds at highway speeds.

jg45 · **Posted:** Sun Feb 08, 2009 5:55 pm

All I can say is that according to every diagram and schematic of the two I have found, they are the same hardware wise with the only difference being the software. As for the kickdown second gear. That is already turned on on our 45RFE's. It is spec'd for both the 45RFE and the 5-45RFE. You all really should look at this manual. I suspect one of two things, either the TCM I have does not engage 5th, or Jeep added some code to the later TCMs to keep them from engaging fifth on non OEM vehicles. I am probably going to purchase a different spec TCM and try it again, unless someone esle would like to spend the $50 and give it a shot. Even if I don't get fifth, the revised converter lockup is worth it to me. For my driving style and local terrain, the earlier TC lockup is a benefit.

tjkj2002 · **Posted:** Sun Feb 08, 2009 8:48 pm

jg45 wrote:

All I can say is that according to every diagram and schematic of the two I have found, they are the same hardware wise with the only difference being the software. As for the kickdown second gear. That is already turned on on our 45RFE's. It is spec'd for both the 45RFE and the 5-45RFE. You all really should look at this manual. I suspect one of two things, either the TCM I have does not engage 5th, or Jeep added some code to the later TCMs to keep them from engaging fifth on non OEM vehicles. I am probably going to purchase a different spec TCM and try it again, unless someone esle would like to spend the $50 and give it a shot. Even if I don't get fifth, the revised converter lockup is worth it to me. For my driving style and local terrain, the earlier TC lockup is a benefit.

Looking at the OEM parts books the internals for a 45RFE and 545RFE are different,and no they are not part# updates since those just change the last 2 digits in the part#'s.Yes the second 2nd gear is active in the 45RFE but only as a downshift at certian highway speeds and not for normal driving(acceleration) which is what the 545RFE TCM unlocked for you.Plus the 545RFE behind a HEMI uses higher line pressure and that is why you are locking up the TC earlier then normal.You may just needed a TCM update since my TC locks up at about 40mph in OD in my KJ,then again my JET chip increases line pressure to the 545RFE/HEMI specs.

jg45 · **Posted:** Sun Feb 08, 2009 9:57 pm

Here are a few facts. The 5-45RFE does not engage the second prime on upshift. It adds a .67 OD. That can be seen within in the first three pages of the document posted earlier. Also, the line pressure is higher for the HEMI, but that doesn't mean all 5-45RFE have the higher line pressure. The 2.8 diesel and 4.7 Grands use the same line pressures as the 45RFE even though they have the 5-45RFE. As far as a 45RFE being flashed to a 5-45RFE check out these threads for examples of people who have done it.

http://www.dodgetalk.com/forums/showthread.php?t=110994

http://www.dodgetalk.com/forums/showthread.php?t=208132

http://www.dodgetalk.com/forums/showthread.php?t=206535

http://www.dodgedakotas.com/boards/gen/23574.html

http://www.dakota-durango.com/forum/showthread.php?t=52534

Also, take a look at this parts list. It is the same parts for both transmissions.
http://www.eatmyshift.net/MONSTERFiles/chrysler/automatic-transmissions/545rfe-45rfe/index.html

tjkj2002 · **Posted:** Sun Feb 08, 2009 10:20 pm

jg45 wrote:

Here are a few facts. The 5-45RFE does not engage the second prime on upshift. It adds a .67 OD. That can be seen within in the first three pages of the document posted earlier. Also, the line pressure is higher for the HEMI, but that doesn't mean all 5-45RFE have the higher line pressure. The 2.8 diesel and 4.7 Grands use the same line pressures as the 45RFE even though they have the 5-45RFE. As far as a 45RFE being flashed to a 5-45RFE check out these threads for examples of people who have done it.

http://www.dodgetalk.com/forums/showthread.php?t=110994

http://www.dodgetalk.com/forums/showthread.php?t=208132

http://www.dodgetalk.com/forums/showthread.php?t=206535

http://www.dodgedakotas.com/boards/gen/23574.html

http://www.dakota-durango.com/forum/showthread.php?t=52534

Also, take a look at this parts list. It is the same parts for both transmissions.
http://www.eatmyshift.net/MONSTERFiles/chrysler/automatic-transmissions/545rfe-45rfe/index.html

Yes I know I know the 545RFE doesn't allow the second 2nd gear on upshift,though the 545RFE TCM on a 45RFE does.The 45RFE and the 545RFE are different internally,no way around that one and they are not getting the 2nd OD ratio,they are just feeling the second 2nd gear ratio.Plus a '02 45RFE comunicated differently then say a '04 45RFE or 545RFE.A 2.8 and 4.7 doesn't make near the power the HEMI does and do not require the higher line pressure to hold the clutch packs from slipping.

tjkoen01 · **Posted:** Thu Mar 12, 2009 7:40 am

It's been a few months, how are things working out?

45RFE -> 545RFE flash?

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