Engine/Transmission (1998.5 - 2002) Another T/C Lockup Question

[Dirks]

I think I might be chasing ghosts but I will need you all to test the theory on your trucks:



When I'm driving down the freeway, the tach is about 2,000 rpm (which for my 4. 10 rear end and tires is about 60 mph), I'll experiment with the lockup by just tapping the brake pedal with my left foot while maintaining some accelerator pedal to hold my speed. Of course, the lockup immediately disengages but here is where I have the question. About half the time and depending on how much throttle I have, the T/C does not go back into lockup for quite awhile. Is this normal or should the T/C go back into lockup each and everytime shortly after tapping the brake pedal?



I had thought it is the latter (i. e. , lockup within seconds after brake pedal release) but I need to know what other drivers experience on their trucks to see if I'm just chasing a ghost. I have replaced the APPS, installed a filter on the APPS signal coming from the ECM to the PCM, changed the AT filter to check for anything lose on the valve body, and it only seems to be a bit better.



What do you all with auto trannies think?

 

[MLeppen]

After you unlocked the converter did you release pedal then apply?

My 1999 will do just what you describe especially with a trailer. Mine won't lock when accelerating heavy in OD with more than 10 psi boost, if I ease off as to unlock the converter then re apply pedal it will lockup.

 

[macdaddy]

There's a TSB on this, you'll have to do some homework on this one. I had it done on my 99 back in 2000. I found it in a dated issue of the TDR. I tried to find it for you but my TDR issues only go back about a year, sorry.



The bulletin calls for a different valve body separator plate, which helps with MUCH quicker lockup anytime you let of the throttle and then get back into it. It also really firmed up my shifts as well. My 99 had this same problem on the stock 47RE only a little different as it did not seem to matter what I did with the brake.



I made an attempt to dig through some of my old issues, just don't have it.



Mac

 

[Dirks]

Thanks to both MLeppen and macdaddy for the feedback.



MLeppen: To answer your question, I left my accelerator pedal in the same position after tapping the brake pedal to release the lockup. It doesn't go back into lockup until I have let up on the accelerator pedal and then slowly reapply some accelerator pedal. If I accelerate moderately to hard, it will not go back into lockup.



macdaddy: I'll do some diggy also but thanks for your input. If you happen to come across anymore info like the TSB number or issue of TDR, please post again. Thanks!



It is good to know that what I'm experiencing seems not to be an eminent failure of a component but another (what seems like) difficiency in the DC 47RE design. I looked up the separator plate in my 1999 shop manual and found that they refer to it as an "overdrive separator plate". A quick look into this seems to imply that the transmission valve body has to be removed and disassembled; not something I'm willing to tackle in my driveway.



Since I already have the BD T/C and someday plan on installing an exhaust brake, it looks like I probably should include on the list of mod's an after market valve body to match my T/C. I would expect that the replacement valve body would cure the lockup symptom I'm experiencing.



For now, it is good to know that the symptoms are typical to some of the 1999's. I look forward to some additional $$$ for upgrades one of these days.

 

[Dirks]

Correction;



I looked a little deeper into the shop manual and found that the separator plate is called the "upper housing separator plate" in the valve body.



In addition, the TSB's that cover this issue are the following:



21-19-99

21-02-00

21-08-00



They all involve replacement of the separator plate to increase fluid flow to the T/C lockup clutch.



Thanks again for the info you all...

 

[y-knot]

I would think that you might want to include a transmission controller, especially if you plan to run a exhaust brake. The leading competitors all have their own versions to compliment their brand of transmissions and transmission packages. The controller by-passes the factory settings and allows for aggressive control. I would never recommend using any controller or home brew version such as the "Mystery Switch" with out first up-grading to better then stock components. The stock transmission with new TC or with out is not up to the demands imposed by such aggressive TC lock-up and extended lock-up conditions. The need for a controller multiplies it self it you plan on running a exhaust brake, the the combination of TC lock-up/brake application, all in one convenient package is priceless.

I have been testing the Dodge 48RE/47RE for the past three years, it is a very stout and reliable transmission, in a gas engine equipped truck. But when partnered with a diesel, it exceeds it's operating limits. The transmission was originally paired with a 160HP Cummins, and slowly thanks to the HP wars, it is now behind a 300HP-600ft/lb engine. It's dependability is marginal at best, there is a huge difference between the transmissions ability to live in the gassers vs the diesel. Modifying the TC lockup, and even up-grading the TC with out upgrading the rest of the transmission package, only leads to it's earlier then already boarder-line pathetic transmission life. The TC was designed to do what it does, so the transmission will live. You tap the brakes, it dis-engages. it does this first for safety, but also to keep the transmission from seeing a heavy load upon applied throttle. Everything that people find annoying about the transmission is there to help it live. Heat is the number one enemy of any transmission, and by UN-locking the TC the added rpm helps circulate more fluid, there by helping to cool the transmission. Also, by UN-locking the TC,the rest of the transmission has a chance to survive. The clutch packs and bands are just not capable of sustaining long term life in stock form, with out the constant UN-locking. The Overdrive unit which is located at the very end of the transmission in the tail section, is particularly susceptible to failure. The stock programing helps protect this area, with slow lock-up engagement and quick unlocking. Without total transmission up-grading, from TC to tail-shaft, the transmission just will not last . Of-coarse everyone will do what they see fit, thats natural, just keep in mind what your working with.