2004 48RE tow/haul switch function

[MelvinPierce]

I have a 2004 HO with the 48RE. I have a question on how the tow/haul switch functions.



It has been downshifting, and holding, the transmission in 3rd gear.

I had the transmission and TC replaced, and now it is not functioning that way. At 60 mph, if I push the button, the rpm go up about 100 rpm for about a second, and then back down. TC unlocking, and relocking??



I put the tow/haul switch on, and did a max throttle run up to 80mph, shifted normally all the way up. Then, I removed my foot from the throttle completely. As I slowed down a little, it downshifted, and held that down shift until about 60 mph, then upshifted again.



I have been told that in the 2004 model year, you can have EITHER the normal, shift to third tow/haul, or it can be reprogrammed to act as a TC lock up.



Is this correct? How does the tow/haul work in the TC lock up mode?



I understand the newer trucks can choose the two ways at any time, but the older ones have to be programmed.



Any help would be appreciated.



Thank you. MP

 

[p-Bar]

I think my 04. 5 transmission works the same . With the transmission on "tow" the shift points are changed and the trans doesn't lock up and no overdrive . Some one correct me if I am wrong.

 

[Kry226]

On my 04, the T/H simply locks out OD and elevates shift points to hold gears longer. I have never noticed the downshift/upshift behavior you're talking about. I use T/H to get the load moving, and if on flat terrain, I'll hit OD at around 50-55 mph. When slowing, I'll use T/H again to manually downshift from OD to help slow the load.



I do believe that T/H programming changed around 04. 5.

 

[cerberusiam]

TH on the 03-04 trucks is just and OD off, nothing more. There is no way for the ECU to control holding shifts longer because shifts points are basically controlled by the TV cable and wheel speed.



Need to have an 05 or newer with enough electronic controls and ECU memory to add better shifting and lockup controls.



AFAIK, there is no flash for the older trucks to do anything more than tune the lockup and shifting a little better. You get one program for shifting and lockup and thats it. The TH just locks out OD until it is turned off again.

I put the tow/haul switch on, and did a max throttle run up to 80mph, shifted normally all the way up

That and your other descriptions do not sound normal. TH activated on the dash should lockout OD. That said it will do 80 in drive so maybe it never did upshift to OD and its fine.

 

[59Turbo]

My 04. 5 has the T/H button and when pressed it will delay OD until about 50 mph but it will go into OD for sure. I dont think the other gears are delayed. I'll have to try the next time I drive it.

 

[p-Bar]

My 04. 5 has the T/H button and when pressed it will delay OD until about 50 mph but it will go into OD for sure. I dont think the other gears are delayed. I'll have to try the next time I drive it.

No overdrive in tow haul mode. yes the gears are delayed. Give it a whirl

 

[AMcCormick]

I assume that the 04. 5 and 05 trucks are the same? If so there is for sure over drive while in t/h. I believe that the 06 trucks have both t/h and an o/d off function and the 03-04 trucks just had a o/d off? while the 05 just has the t/h which is great unloaded but not so great loaded. If I am driving in normal mode and shift into the t/h then yes the transmission downshifts then upshifts right back because there is no load if I do it climbing or loaded and accelerating it wil stay for a bit until it un loads a little. in t/h it will down shift coming to a stop. The t/h does not work for me if loaded. I am having a BD o/d lock out installed currently to solve this. From my research the t/h shift logic still works, which I like just not the o/d.

 

[cerberusiam]

I assume that the 04. 5 and 05 trucks are the same?

Any I have driven, no. The true TH function did not show up until 05. From all the info posted the 04. 5 ECU was not capable of handling the TH and was only OD off.



Possibly that has changed with new flashes???



You will like the BD box. Makes an 05 better than the 06+ functionality.

 

[AMcCormick]

Thats why I put the question mark in. I was not totally sure. The o/d lock out and a Colt Big Stick cam are in progress at Left Coast Diesel. I have a tow down to Long Beach in a couple days looking forward to trying the new parts out. So the original poster should just have a o/d off button? unless there is a stand alone controller with the new transmission?

 

[cerberusiam]

It is hard telling what is happening with different drivers. Some people think the TC lockup in drive is OD and since the OD shift lock is so quick they can't tell the difference, or, it could be the a wire was disconnectedborken when the trans was changed and the ECU is not getting the signal to drop OD. Light on the dahs will still work but the cluster has to notify the ECU and there is no communication on the correct wire or bus frequency. The communications from cluster to ECU are not monitored as well as they could be.



Just changing the trans will not change the functionality of the TH switch. If the trans has an issues it can seem like it but it doesn't.



At one time Dodge claimed the ECU's were not capable of taking the code for OD off on the 04's and 05's. It has since been suggested it was not in Dodges best interest to offer that functionality. Not that it could not be done but rather the cost benefit was not there so they "Dodged" the issue.



If the ECU was not flashed then its not the computer controls it is a communicatin failure somewhere. TH on anything previous to an 05 was OD off only, and, the ones I drove it did not change the shift patterns for towing. Same sloppy operation just no OD. That could have been updated in flashes for that year at a later date though.



What the OP was suggesting as TC lockup is not correct either. TC lockup was there from the start, crappy as far as that goes, but it was there.

 

[p-Bar]

This has been interesting read. My 04. 5 works when in "tow" mode my trans will not go into OD and the shift points are definetly changed higher rev before going into the next gear. I don't notice the converter locking up either.

 

[JMarketos]

My 0. 02:

At one time I knew the information solid, my problem is whether I can remember it correctly...

I was tempted to chime in when I first saw this post, but I held off because my truck is an 05 and the OP question was 04, and I wasn't sure if my info was relevant, and I didn't want to muddy the water. So now here comes the mud...



My truck has the BD overdrive lockout module installed. (did it myself a few years ago). To my knowledge, that module is specific for the 05 trucks, will come back to this later.



My truck has a Gearvendors overdrive unit mounted at the rear output of the transfer case. Effectively, that makes it like having a 2-speed rear axle (and yes, I cannot engage the GV OD while in 4WD because of how it's installed).



My 05 truck (I'm going to say all 05 48REs) absolutely yes do end up in 4th gear (OD) whether they are in TH mode or not. TH mode changes the up/down shift decisions, but the trans still ends up in top gear. For example, on a long flat stretch, start from 0 with TH-OFF and accelerate to 70MPH, set the cruise, end up with engine tach reading xxx RPMs. Stop, turn TH-ON, repeat the process, cruise at 70MPH you will end up with same tach reading- trans is in 4th gear, TC is locked.



05 TH mode does change one thing about lockup- in 3rd gear.

This is where my memory is a bit fuzzy. #7 AMcCormick will be able to confirm this once he gets his BD OD lockout module installed:

If I remember correctly:

When TH is OFF, then the TC does NOT lock in 3rd gear.

When TH is ON, then the TC does yes lock in 3rd gear.

Explanation I have read is that was done to reduce slippage and preserve trans fluid temps when the drivetrain is heavily loaded.



The BD OD lockout box uses the same TH button on the end of the shifter- it looks for the user to press the button TWICE in quick succession. Thus (with BD box installed), when you start the engine fresh, TH is OFF. Press the TH button once, and TH mode comes on. Press the TH button again twice quickly, and the BD lockout feature is engaged. Doing that, you also just went out of- and back into TH mode again. So you're in TH mode with BD 4th lockout active. etc. (The BD box comes with an LED that you install wherever you want it, which lights when 4th gear is locked out. ) In my experience, I don't fool much with changing the modes while the vehicle is moving- I try to anticipate what state I'm going to want, and set that before I move off.



So the presence of vehicle TH option, plus the BD OD lockout module, gives you a matrix of 2x2, which results in 4 possible states. Assuming a fresh start with TH-OFF and the BD 4th lockout OFF (inactive), here's an effort to list the 4 states:



X means a single push of the button. XX means two quick pushes.



[1] (no pushes) TH-OFF and 4th lockout-OFF. TC is unlocked while in 3rd gear. Trans will progress to 4th gear.

[2] X (TH-ON, 4th lockout-OFF) Trans will progress to 4th gear. While on the way up, TC will be locked when in 3rd.

[3] X + XX (TH-ON, 4th lockout-ON, BD light is lit) Trans will stay in 3rd, not shift into 4th. TC is locked while in 3rd.

[4] XX (TH-OFF, 4th lockout-ON, BD light is lit) Trans will stay in 3rd, not shift into 4th. TC is unlocked while in 3rd.



Difference between state 3 and state 4 is- in state 4, RPMS for a given vehicle speed will be a bit higher due to TC slippage. Also, when in state 4 going (for ex. ) about 55MPH, and take your foot off the accelerator, you'll see the RPMS drop off due to TC slippage. Do similar in state 3, you'll see RPMS remain constant as with a standard trans, because TC is locked up.



Hope this is of help to some. I might have the bit about the TC lockup in TH-ON vs TH-OFF exactly backwards, but I don't think so. Someone please do yell at me and I'll edit this post if I've got it @$$- backwards.

=

To my knowledge, the "4th gear still comes, even when TH-ON" was specific to the 05 models, and was changed again for 06-onward, back to "TH-ON means top gear is locked out" after many customer complaints, hence why BD aftermarket made the module to give the 05 owners same capability everybody else had (to lock out top gear). Installing the BD lockout on 05 gives you the choice of TH and TC lockup or not, along with choice of top gear or not, which results in a nice selection, if not a bit complicated.

=



Now for some banter- (my truck is 48RE with stock wheels & tires and 3. 73 axles)



imho, the "difficulty" with this setup overall is that there's a fairly big difference between 3rd and 4th gear in the 48RE trans. I happen to remember that 3rd is 1. 00 ratio (straight through). I don't recall exactly what 4th (OD) is, but it's a big step different from 3rd. 0. 72 or something like that- on the order of 28% different from 3rd. The bottom line is- if you lock the trans in 3rd, it's not practical to travel at modern highway speeds because the engine RPMs are near redline. 4th gear was chosen largely for economy in unloaded or lightly loaded condition. Towing heavy loads in 4th, I discovered the engine will do it, but often runs at high boost and relatively high EGTs. (and resulting relatively less than ideal MPGs... ) Note if you happen to have 4. 10 gears, that doesn't fix the issue- that big difference between trans 3rd and 4th still remains. The 4. 10s just shift the overall engine RPMs (in whatever gear) upwards a bit, so the highway towing might be a bit easier. Note that the difference between 3. 73 and 4. 10 is 10%. (3. 73 + 0. 37... )



In the stock configuration (before adding GV and BD lockout), I discovered one more associated "don't like that"... When towing on highway, using cruise control, running in 4th gear (usually around 1700-1800 RPM), and come up on a grade or hill- cruise control will add boost more and more... (cruising along in 4th... ) At some point, what I found to be typically around 25PSI boost to 27PSI boost and the vehicle has slowed to a certain point, the trans will downshift. The result is a (rather harsh) blip to near redline, and boost spikes well above 30PSI. I have read elsewhere this situation can be a cause of the burst end tanks on the plastic intercoolers. My truck was one that came stock with the plastic intercoolers . I did not experience failure of the intercooler, but I really didn't like the RPM jump on downshift, so I learned to watch the speed and boost gauge, and I would manually take it out of cruise as boost approached 25+, to avoid the "self downshift under power".



The Gearvendors box is nothing more than an additional overdrive. Key there is- the GV unit doesn't have nearly as much difference ON/OFF as there is between the stock 3rd and 4th gears. The GV has about half the difference. So, whereas I used to run around 1700 RPM in 4th stock, now with the trans in 3rd + GV OD-ON, the equivalent RPM is about 2000-2100, which is much better for this particular engine. It runs at lower boost and lower EGTs, and towing MPG (towing a 20 ft Haulmark, about 7K) went from about 10-11MPG stock, now to about 14-15MPG with the GV and BD. (and please note, that towing comparison was BEFORE I installed the Banks stuff with new intercooler. it might be even better now with the bigger IC- I just haven't towed anything yet to find out !)



Lastly, one additional benefit of the GV box is that (when empty), I can run in stock 4th + GV, which results in about 1500 RPM at highway speed. Again, I have not yet had the occasion to take a run of atleast couple hundred miles to hand calculate the MPG, but it seems to be improved over the ~ 19-20 MPG stock 4th. With the GV OD 1500 RPM highway, the overhead console reports MPG that is... wayyyy above 20 MPG. But I'm not even going to post what numbers the overhead indicates. I'll post real hand calculated #s when I get them. Might be next summer!



OK, so that's my blather. Hope this helps to make everything clear as mud.

I'll crawl back under my rock now...

Best to all.

 

[cerberusiam]

The 05 algorthms lock the TC in drive TH on or off. Feeling the lockup TH off on a stock trans takes a bit of practice and familiarity with how things sound but it is there.



With a built up trans there is no question, even with TH off its noticeable. Now with TH on, a built trans, TQ management removed and 1/2 to 2/3 throttle on a slight grade you feel EVERY shift and lock sequence AND hear the turbo barking. :-laf



Under certain conditions its shift to drive, 1 count, lock TC, 1 count, unlock TC, 1 count, shift to OD, 1 count, lock the TC, WOOF! :-laf



But thats an 05. Every 04 I have driven\ridden in has never been that aggressive or tight on the shifts and lock sequence. Not that they can't be made that way but ti takes building and an added compoent like a Co-Pilot or other box.

 

[JMarketos]

Honestly, not sure I understand what #13 is communicating.
I think it's stating that 4th gear, TC is ultimately locked whether TH-on or TH-off.
I'd agree with that. I'd also re-state my experience that 3rd gear, TH state determines whether the TC locks or doesn't. Maybe that action is part of the feature set of the BD box ? I'm not sure (because with the 05, you can't hold it in 3rd gear in stock form !!)

 

[cerberusiam]

TH state determines whether the TC locks or doesn't.



Maybe that action is part of the feature set of the BD box ?

No and no.



The 05 algorthms lock the TC in drive, TH on or off. Feeling the lockup in drive, TH off, on a stock trans takes a bit of practice and familiarity with how things sound but it is there.



The BD box only taps into the OD sense circuit, nothing else. In order to control lockup it would need to tap the lockup sense circuit and override the ECU.



OD locked out and TH off is stock mode shifting and lockup.



The BD box does not change shift points either. It would need to tap into the TTVA motor and\or gov pressure circuit to accomplish that. Thats what the Shift Enhanser does.



TH off operations on these trucks are in reality NVH mode, slop and slide on everything until you fix the issues.

 

[JMarketos]

One more try-
As tone is difficult to interpret from text, let me state that I'm not trying to challenge or dispute cerberusiam. Simply that I wasn't sure that I understood what reply #13 was communicating.

But please if we quote, let's use the full context, which was:

"... re-state my experience that 3rd gear, TH state determines whether the TC locks or doesn't. "

I don't dispute anything that's being said about what happens when the 48RE is in 4th (top) gear.

I know from direct experience with the BD OD lockout box, keeping the 48RE in 3rd gear, in that condition there's a difference whether TH is on or off- in one case, the TC is locked (when driving in 3rd gear), in the other case the TC is unlocked (when driving in 3rd). It's verifiable on-the-fly by the tach reading, I remember learning this from a tech support telephone call to BD shortly after I installed the unit (years ago). I had called because I didn't understand the operation I was experiencing.

[edit]- After some further thought, I wonder if cerberusiam is trying to convey that the trans doesn't know whether the BD box is locking out 4th gear, and that the end result is same as far as the ECM software is concerned- TC ends up locked whether TH is on or off ? I will take my truck out and make the 3rd gear experiment again, to re-familiarize myself with what happens. (Use the BD box to lock out 3rd gear, and drive that way, and observe what happens with 3rd gear locked out and TH off, and 3rd gear locked out and TH on).

 

[cerberusiam]

I know from direct experience with the BD OD lockout box, keeping the 48RE in 3rd gear, in that condition there's a difference whether TH is on or off- in one case, the TC is locked (when driving in 3rd gear), in the other case the TC is unlocked (when driving in 3rd).



[edit]- After some further thought, I wonder if cerberusiam is trying to convey that the trans doesn't know whether the BD box is locking out 4th gear, and that the end result is same as far as the ECM software is concerned- TC ends up locked whether TH is on or off ?

Sorry, let me try to clarify.



To the first statement, my experience is the TC does lock in drive with TH off. The caveat to this is with a stock transmission, TC, and line pressures it is very very difficult to feel the TC lock and the conditions have to be right. Frequently it will shift to OD before the TC locks. With a good TC and shift kit it is much more obvious. The lockup points are different TH on\off but I am feeling the TC lock in drive with TH off, with or without the BD box activated.



Second statement, exactly. That is what I am saying. The BD box does its own thing completely independent of the ECU. If its wired correctly the ECU has no idea the transmission is not in OD or out because on the 48RE there is no way for it to tell if the OD clutch engages. The BD box simply interrupts the ground sense circuit and feeds the ECU a false message saying everything is cool.

 

[AMcCormick]

so do the 06 and up trucks lock in 3rd while in t/h?

 

[JPul]

Andy,



My 06 locks in 3rd in TH somewhere around 30-35 mph depending on throttle and keeps it locked until 50-55 depending on throttle and then makes a pretty solid shift into OD. Not much if any TC slippage after this shift.



Regards, John

 

[WalterJ]

Greetings Cerberusiam;



My '04. 5 TH in 3rd is 750 RPM higher than in OD. The shift points are about 300RPM higher as well. Yes it locks up with TH on, otherwise I'd be burning up the TC clutches on every trip in the mountains with my 15K# 5'er, eh?