2002 Grand Cherokee 4.7 TCM Ordered!
#11
08-17-2011, 11:22 PM
Ok I just was reading through the 12 pages that moparman1991 had from the link he posted, this makes sense on how this can be done. On page five a user named sjonnie posted this,
"The 45rfe transmission actually has 3 sets of planetary gears and 6 possible forward gear ratios, check out this masters thesis on the 45rfe. The 2nd overdrive gear 0.67:1 just isn't programmed into the TCM. Program it in and you get a 545rfe, pretty sweet huh?"
MoparMan1991 this seems like a great idea, I read through there and having the extra ratio and what sounds to be a better torque converter management opens lots of possibilities. Like some of the guys on that thread putting in 4.56's then the jeep tcm bringing them back to the great highway mileage with the towing power they wanted. This is so cool, you need to give us every detail when you are done!
"The 45rfe transmission actually has 3 sets of planetary gears and 6 possible forward gear ratios, check out this masters thesis on the 45rfe. The 2nd overdrive gear 0.67:1 just isn't programmed into the TCM. Program it in and you get a 545rfe, pretty sweet huh?"
MoparMan1991 this seems like a great idea, I read through there and having the extra ratio and what sounds to be a better torque converter management opens lots of possibilities. Like some of the guys on that thread putting in 4.56's then the jeep tcm bringing them back to the great highway mileage with the towing power they wanted. This is so cool, you need to give us every detail when you are done!
#13
08-18-2011, 12:37 AM
I am one of the many who have put the Jeep GC TCM onto my Durango. I had mixed results, and took it off because my MPG and driveability was better with the Dodge TCM. But before you think the TCM swap isn't a good idea understand what my circumstances were. (I posted plenty about this on that website that gets censored out by this website.)
My Durango has a 3.55 axle and I am running 29" (as measured on the truck) tall tires. With the 4 speed TCM I run about 2300 RPM at 75MPH. With the 5 speed TCM that dropped to a little over 2000 RPM. My usual commute takes me over a hill with a noticeable grade.
With the 4 speed TCM I can usually hold the speed with some additional throttle pressure. The tranny stays in 4th gear and very rarely does it feel the need to drop out of TC lockup. With the 5 speed TCM the engine wasn't running far enough into the powerband to hold the speed. I would continually lose speed until I had to give a lot of throttle to get the speed back up. This would drop it out of TC lockup and into third gear where I would drive most of the hill doing 3500 RPM (and higher).
When I change the axle gears to 3.92 I'm going to try the TCM again. I think I'll have better results, as the engine speed will be closer to 2400 RPM and into the engine's powerband at my usual driving speed.
If your Durango has 3.55 gears and tall tires I feel the TCM swap will be less than pleasing if you have any hills to climb in your normal driving. If all you do is drive on flat ground, then it'll probably do you good. If you have lower axle gears (3.92, 4.10, 4.56) then I think it'll be a winner in most cases.
The Jeep TCM holds TC lockup better and longer than the Dodge TCM, but it activates around 50MPH, while the Dodge TCM activates around 40MPH. It takes more throttle pressure to unlock it when driving.
My Durango has a 3.55 axle and I am running 29" (as measured on the truck) tall tires. With the 4 speed TCM I run about 2300 RPM at 75MPH. With the 5 speed TCM that dropped to a little over 2000 RPM. My usual commute takes me over a hill with a noticeable grade.
With the 4 speed TCM I can usually hold the speed with some additional throttle pressure. The tranny stays in 4th gear and very rarely does it feel the need to drop out of TC lockup. With the 5 speed TCM the engine wasn't running far enough into the powerband to hold the speed. I would continually lose speed until I had to give a lot of throttle to get the speed back up. This would drop it out of TC lockup and into third gear where I would drive most of the hill doing 3500 RPM (and higher).
When I change the axle gears to 3.92 I'm going to try the TCM again. I think I'll have better results, as the engine speed will be closer to 2400 RPM and into the engine's powerband at my usual driving speed.
If your Durango has 3.55 gears and tall tires I feel the TCM swap will be less than pleasing if you have any hills to climb in your normal driving. If all you do is drive on flat ground, then it'll probably do you good. If you have lower axle gears (3.92, 4.10, 4.56) then I think it'll be a winner in most cases.
The Jeep TCM holds TC lockup better and longer than the Dodge TCM, but it activates around 50MPH, while the Dodge TCM activates around 40MPH. It takes more throttle pressure to unlock it when driving.
Last edited by modain; 08-18-2011 at 12:39 AM.
#14
08-18-2011, 03:43 AM
#17
08-18-2011, 12:39 PM
#18
08-18-2011, 02:53 PM
It will function on a 2000 Durango or Dakota. But since the truck's communication bus is still CCD it won't work properly with the TCM, as it is a PCI bus. The tranny will function with the new programming, but the PRND3L indicator won't work right and there will be a constant MIL showing.
To use the Jeep TCM the truck requires the 4.7L engine with the JTEC PCM (three plugs with separate TCM). This includes 2001-2002 Dakota, 2002 Ram (with 3.7L and 4.7L), 2001-(early)2002 Durango. Late in the 2002 model year Dodge went to the NGC PCM (four plugs) in the Durango. This is a combined PCM/TCM package and it already has the 5 speed programming in it.
In 2003 (and beyond) all 3.7L and 4.7L trucks have the NGC PCM with the 5 speed programming.
Last edited by modain; 08-18-2011 at 09:09 PM.
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