Hey Guys, Ive been doing some research lately and have read that the 45RFE is the same transmission as the 545RFE, except the 5th gear is not enabled. People are saying if you were to grab the TCM from a 2001 or 2002 Jeep Grand Cherokee, it would electronically enable the 5th gear. Ive been told to find part number RL041504AG. Has anyone had experience enabling the 5th gear? It all started when I read about it on DodgeTalk. The person in the post below claims that if you have the 3.7 engine you can flash it. Here is the post I'm reading from. How-To: 45RFE to 5-45RFE Transmission Upgrade - DodgeTalk : Dodge Car Forums, Dodge Truck Forums and Ram Forums What is your opinions on it? Id love to get some more MPG out of my trans.
Are the 45RFE and the 545RFE really the same?
- Thread starter chris03kj
- Start date
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uss2defiant
Full Access Member
hmmm I remember reading that there are two 2nd gears, a low and a high so technically there are 5 gears.
I may have misread that in the FSM.
I may have misread that in the FSM.
Hockeygoon
Full Access Member
You won't gain much in MPG as the gear you gain is not an OD gear. It might help your city mileage - but even then not by much.
Can't see that you would gain anything at all really over all. Ongoing discussion on one of the crappy Facebook sites claiming huge results , all total BS
Lets think about this for a moment, manufactures have to try and squeeze as much overall mileage as they can out of a certain model. IF this would of helped any on the KJ it would of been done.
Not really worth it but people like to pretend that it somehow does. Maybe on a V8 engine or higher displacement but can't see it on a 3.7
Lets think about this for a moment, manufactures have to try and squeeze as much overall mileage as they can out of a certain model. IF this would of helped any on the KJ it would of been done.
Not really worth it but people like to pretend that it somehow does. Maybe on a V8 engine or higher displacement but can't see it on a 3.7
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I see that all the time in computers, too. People will claim that by modifying one obscure registry key you can speed something up dramatically. If that were true, even Microsoft would have done it to begin with.
CactusJacked
Full Access Member
There's a lot more to this modification than what meets the eye....
[YT]MXW0bx_Ooq4[/YT]
[YT]MXW0bx_Ooq4[/YT]
:happy175::happy175::happy175::happy175::ROFLJest:
I want one! Or maybe two. Can you put one on each of the stranaflasters?
arty52:
CactusJacked
Full Access Member
I want one! Or maybe two. Can you put one on each of the stranaflasters?
Yes you can, but that may put excess stress on your ****** arm, so keep that in mind.
As long as its not your ****** berries
CactusJacked
Full Access Member
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The 45 program is 1-2-3-4OD with 2 prime being a kickdown gear. 545 program is 1-2-3-4OD-5OD with 2 prime being a kickdown. So if you switch to the 545 TCM you will gain an OD gear, but might not be worth the effort unless you do ALOT of highway driving at speed or have 4.10's or lower (numerically higher).
Thats the issue, most do not need nor would it do them any good since it could result in lugging the engine even more than it does stock. Those with larger tires would be dead on the highway and even if regeared to 4.10s, unless running a 29 inch tall tire, they would be lugging down quite a bit .
What works for some is not a good deal for all.
I saw where it was being discussed on facebook on one site, and the daydreaming Shade Trees Techs thinking it was so great:icon_lol:
colorado76
Full Access Member
Now if you do a 4.7 swap...it would be worth it for the mileage
Hockeygoon
Full Access Member
45RFE
Gear Ratios: 1st 3.00:1
2nd 1.67:1
2nd Prime 1.50:1
3rd 1.00:1
4th 0.75:1
Reverse 3.00:1
545RFE only:
5th 0.67:1
So fifth gear is actually a deeper OD.
So you basically repeated what I said but added gear ratios lol...?
Birdman330
Full Access Member
Hidden gears rarely add any actual benefits, when driving Semi I learned of the ''hidden split'' in 13, 15 and 18 speed transmissions that pretty much is only useful for steep inclines, the split actually hides between 5th and 6th gear. Otherwise you don't use the ''hidden split'' for anything else unless you're a ******** ''Cowboy'' or ''Super Trucker'' that needs to use 8 gears to leave a parking lot.
Most likely as it has been iterated before, Chrysler most like expiramented with having a 5 speed Automatic Transmission but it wasn't viable. Similar to the Gene Berg 5 Speed Manual Transmission for the Volkswagen Type 1 Sedan (Beetle), 5th gear was essentially too close to 4th gear making it pointless except for somebody who was die hard for a 5th gear. Air cooled boxers need rpms to keep temperature balance, too few rpms or too many causes the oil to get too hot. Of course that being said, Jeep decided a 6 speed manual transmission was viable so if anybody can figure that one out, I'll gladly listen to the explanation.
Most likely as it has been iterated before, Chrysler most like expiramented with having a 5 speed Automatic Transmission but it wasn't viable. Similar to the Gene Berg 5 Speed Manual Transmission for the Volkswagen Type 1 Sedan (Beetle), 5th gear was essentially too close to 4th gear making it pointless except for somebody who was die hard for a 5th gear. Air cooled boxers need rpms to keep temperature balance, too few rpms or too many causes the oil to get too hot. Of course that being said, Jeep decided a 6 speed manual transmission was viable so if anybody can figure that one out, I'll gladly listen to the explanation.
libertybob
Full Access Member
Thanks...
Thanks to all for the preceding discussion on 545RFE's. Always wondered if conversion was worth it, but when it leads to lugging of the engine, that kills the idea for me. Lugging an engine is not good and will end up costing far more than any savings in fuel cost. Good information!
Thanks to all for the preceding discussion on 545RFE's. Always wondered if conversion was worth it, but when it leads to lugging of the engine, that kills the idea for me. Lugging an engine is not good and will end up costing far more than any savings in fuel cost. Good information!
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