Hi all, I have a 2003 2.8 Diesel Jeep Cherokee Extreme Sport auto, (European model I understand) It has three forward gears and an overdrive. the gear box seems to work fine except, When driving around town in the UK at 30 mph (speed limit 30 mph) the revs are about 1500 so the O/D never cuts in, so a lot of diesel is used. at 43mph I have about 2500 revs, when the O/D finally cuts in (43mph) the revs drop to about 1600. the O/D, never cuts in below 43 mph.
As per info from papaindigo, billwill and geodi, I have changed the two filters and renewed the oil in the gearbox, no change. I have yet to find anyone who knows anything about "Tuning the lower shift points" here in the UK, they seem keen on telling me the problem is the O/D gear is worn and needs replacing. I have no idea how to prove them right or wrong, before I pay them a lot of money to take the gear box out to find out if its worn or not.
Has anybody had any experience that could help.
Thanks.
William

I still think you need to find out what the shift and overdrive points are "supposed" to be on your transmission which I assume is the 42RLE automatic. What you are experiencing doesn't sound unusual but I don't know the specifics for that transmission. Check the owner's manual, check the FSM (download from Sir Sam's NOOB guide manual link), email/PM MrMopar64, or post that specific question for owners of the 2003 export model with that transmission.

Assuming the transmission shift points are controlled by a TCM it may be programmable but not by DCJ, that's an aftermarket issue and the only folks I know that do KJ TCM programming are GDE. Whether or not they are interested in doing it for this tranny you would have to email Keith at GDE and ask.

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Sold to LOST member my 05 Ltd, GDE Stg II turbo + TCM tune, SunCoast TC w. Transgo kit, Steiger window regulators, Samcos, Fumoto valve, 2nd gen filter head with Lub. Spec. bleeder, Hayden clutch & 11 blade fan, inverted spare, P-1 battery, BF Goodrich Long Trail TAs, Etecno1 glow plugs, timing belt at 50K miles/8 yrs

The trans in that vehicle is the 45RFE, so it's programmed (of that era) to operate as a 4spd.
I've not personally tried it, but if you get the TCM from an 05MY vehicle it might be even better for you and turn it into a 5spd.
From a communication standpoint i think it should work...

Thanks both for your time and comments. At the stage I am at, some of the jargon I am afraid goes right over my head.
(KJ TCM programming are GDE. Whether or not they are interested in doing it for this tranny you would have to email Keith at GDE and ask.)
Can I assume these are only contactable in the US, I not sure what (KJ TCM, GDE, email Keith at GDE ) is but I would need to find the equivalent in the UK I assume.
( but if you get the TCM from an 05MY vehicle ) not sure what a TCM or 05MY is,
If you would not mind giving me a simple explanation I will get to work as I am keen to solve this problem if it can be done on a budget.
Many thanks

KJ = Jeep Liberty model in US, Cherokee if memory serves in export market
GDE = Green Diesel Engineering, does deal in the export market but I don't know if or how they handle reprogramming export TCMs as that cannot be done by the tool mentioned below. Keith is to contact at GDE, see http://www.greendieselengineering.com/g ... ethod=home
TCM = transmission control module
ECM or ECU = engine control module or unit, programmable by GDE and can be done in export market if you rent or buy the programming tool
05 MY = 2005 model year. What MrMopar64 is saying is if you have the 45RFE transmission (there should be information in the FSM, factory service manual, that will tell you how to find out) then it "may" be possible to may be possible to install a TCM from an 05 MY KJ, which has the 545RFE transmission, in which case in theory that would transform your 45RFE transmission into a 545RFE, apparently the internal parts are the same with the shift points/gearing/overdrive controlled by the TCM. Whether or not this is possible I don't have a clue.

However, no one seems to be getting my underlying point relative to your overdrive question so I'll say it for the THIRD and last time. You do not have a "5" speed transmission hence you do not have a final shift/overdrive point at ca. 58-63mph depending on TCM programming. You have a 4 speed transmission that, obviously, will have a lower final shift point and generally, I presume, run at a higher rpm for the same mph. The question that remains unanswered and somewhat unasked is "Is ca. 43mph the proper speed for your transmission to shift into top gear/overdrive?". If the answer is yes your tranny is functioning properly; if the answer is no then there is a tranny function (not to be confused with the possible TCM swap upgrade) problem to be addressed.

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Sold to LOST member my 05 Ltd, GDE Stg II turbo + TCM tune, SunCoast TC w. Transgo kit, Steiger window regulators, Samcos, Fumoto valve, 2nd gen filter head with Lub. Spec. bleeder, Hayden clutch & 11 blade fan, inverted spare, P-1 battery, BF Goodrich Long Trail TAs, Etecno1 glow plugs, timing belt at 50K miles/8 yrs

Thanks papaindigo, you are right, I am letting my inexperience and enthusiasm take over. I seem to have spoken to so many people and had so many conflicting answers I did loose site of the main objective. I have spoken to my local Jeep agent in the UK and they are really only interested in new car sales. I have sent several E-mails to Jeep US but no reply, I cant get a FSM for this model for some unknown reason I only have the user manual that came with the car it says the O/D should cut in around 31 to 33 mph and that is what I have been working on. I will post that specific question for owners of the 2003 export model with the same transmission so as to get confirmation.
Thanks,

You can get the 03 FSM, parts fiche, and export diesel manuals here http://colorado4wheel.com/manuals/Jeep/KJ/

As to the shift question you might PM or email forum member MrMopar64. Does the owner's manual speak to overdrive or torque convertor lockup? That speed seems way low for overdrive even for a 4-speed

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Sold to LOST member my 05 Ltd, GDE Stg II turbo + TCM tune, SunCoast TC w. Transgo kit, Steiger window regulators, Samcos, Fumoto valve, 2nd gen filter head with Lub. Spec. bleeder, Hayden clutch & 11 blade fan, inverted spare, P-1 battery, BF Goodrich Long Trail TAs, Etecno1 glow plugs, timing belt at 50K miles/8 yrs

HAS ANYONE READ MR MOPAR'S SUGGESTION ABOVE???

It has long been known the older 45RFE transmission has the ability to be a 5 speed by changing the TCM to a 05/06 TCM

Joe

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Atlantic Blue 06 CRD Limited (his)
Joined by a 2000 XJ Classic (hers)

Thanks all, I must admit some of what is being said is going right over my head, but I am trying to learn. I have down loaded the Tech. Manual but is does not give shift speeds, the owners manual says Overdrive should cut in just over 30mph. regarding the Torque Converter, the owners manual says," A feature designed to improve fuel economy has been added to the Auto. transmission, a clutch within the torque converter engages automatically at calibrated speeds. " but no mention of what speeds. I have just had the car re-mapped but that has made no difference, if still changes up to O/D at 43mph. so more work to be done. regarding
Joe Romas suggestion HAS ANYONE READ MR MOPAR'S SUGGESTION ABOVE??? It has long been known the older 45RFE transmission has the ability to be a 5 speed by changing the TCM to a 05/06 TCM
I have looked at the cost of a new TCM for a 05/06 and these are about £100 in the UK, if this would work it could be a very simple and cost effective solution, could anyone suggest where I might go to research this information. According to the Tech. manual the 2003 Jeep Cherokee 2.8 diesel has the (AUTOMATIC TRANSMISSION -545RFE DESCRIPTION The 545RFE automatic transmission is a sophisticated, multi-range, electronically controlled transmission which combines optimized gear ratios for responsive performance, state of the art efficiency features and low NVH. Other features include driver adaptive shifting and three planetary gear sets to provide wide ratio capability with precise ratio steps for optimum driveability. The three planetary gear sets also make available a unique alternate second gear ratio. The primary 2nd gear ratio fits between 1st and 3rd gears for normal through-gear accelerations. The alternate second gear ratio (2prime) allows smoother 4-2 kickdowns at high speeds to provide 2nd gear passing performance over a wider highway cruising range. An additional overdrive ratio (0.67:1) is also provided for greater fuel economy and less NVH at highway speeds. The hydraulic portion of the transmission consists of the transmission fluid, fluid passages, hydraulic valves, and various line pressure control components. The primary mechanical components of the transmission consist of the following: ² Three multiple disc input clutches ² Three multiple disc holding clutches ² Five hydraulic accumulators ² Three planetary gear sets ² Dual Stage Hydraulic oil pump ² Valve body² Solenoid)
If it was possible to change this gear box from a 4 to 5 speed by simply changing the TCM I would like very much to research the possibility. Any information would be greatly appreciated.
Yours.
William

A simple flash at the dealership can do the same thing,no need to buy another TCM.It's the same flash for early WJ's with the 4.7/45RFE to unlock the 2nd OD like the later models of WJ's.

That just isn't enough information.
What are the exact operating conditions that allow it to go into lock-up?
Assuming normal operating temp but then there are the following factors interlinked whether the unit is
under exactly what conditions will it go into lock-up?
These depend on TPS (whether electronic or hydraulic as this is a line P issue) - so how heavily loaded is the throttle?
-I am not talking about kick-down.

How many engine rpm are you doing when it does go into lock-up?
Best description is with a "normally" loaded vehicle with no extraneous passengers and heavy fuel load and the like.
Is it 2000rpm at light throttle or even a number of % throttle application would help.

Sorry but if you want help we need details of when it actually happens and even then can't promise anything from afar.

I can only assume Lock-up is when it goes into overdrive, (O/D) When engine is warm and driving on flat road, with light throttle, from third gear the engine gets up to 2500 revs and at these revs in third gear I will be doing 43 mph and then O/D cuts in and the revs drop to about 1700.
This means the car is in 3rd gear for almost all of town work.

You can be in OD without the TC being locked.