torque convertor unlocking going down grade..

[ff43sc]

I have 95 k2500 6.5L F. 4l80E tranny, My truck while traveling down highway works fine until i start going down even the slightest hill, then the torque convertor unlocks and if i have the cruise on will accelerate then drop rpms, then accelerate, then drop rpms every few seconds. Once I'm back on flat ground or uphill, it locks back up and is fine...if I'm running flat grade or uphill it doesn't do this, tranny was rebuilt last year, (tranny shop says everything with tranny is fine..throttle pedal assembly was also replaced. is there a control on injection pump or elsewhere that could tell computer to unlock or does this sound like a cruise issue. If a cruise issue could it cause the unlocking problem when cruise is off? I wonder if the computer could be malfunctioning? any ideas? thanks,
k2500, 205,000 miles...

[MTTwister]

You should do a search on this - if IRC, the converter will stay locked if your into the pdeal about 10% - pretty tough to do on a downhill run. Otherwise, it unlocks.

However - your year would be a good candidate for the BD torque loc , or similar mod. It applies full line pressure to the Torque converter in a certain mode. For '96 on up, this throws a hard code and ya go into limp mode, but pre- 96's I believe it works quite well. I remember looking into this while researching the "Cheap TCC lockup" One discussion:

http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=005837
and -
http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=006718

Neither of these really talks about downhill lock up tho'. But - the search feature should pull up some reference. Good Luck

[rjwest]

" CHEAP " TCC lock method still allows TCC to unlock when coasting.

I have had several discussions with BD on there Torque Loc.

( DOES NOT WORK ON 1996 K3500 1996 )
There have been other posts also which indicate problems on 1996 and newer.

BD still sells unit for 1996 " as will work "

BD problem occurs when you let off on Accelarator
( ccoast ) above 30-40 mph in 2nd or 3rd gear(and some times 4th).
PROBLEM:
TCC remains locked as commanded by TorqLoc...
Transmission controller commands TCC unlock, than checks Input shaft speed to be less than output
speed( per gear ratio), This sets a " Fault " code which commands " Limp" mode. IE Full pressure shifts.

There are sw's on the TorQ-Loc to set TCC release at a higher speed, This may allow unit to release
sooner and prevent " Limp" mode, ???

In my application, there were too many occurances of " Limp" mode ( requires IGN OFF/ON cycle to clear) to make the TorQue usefull.

I suspect that it will not work reliably on any 6.5l with OBD2, Seems to work on older Trucks,pre 1996

[Barry Nave]

rjwest
Do you still have the unit,send it back or sold it?

[HowieE]

rjwest

How about e mailing me your phone number, howie.braith@verizon.net. I would like to discuss the BD Torq Loc in greater lenth with you.
I have one on a 97 and have met with BD's and had long discussions with other BD employees and met with the teck who designed it about the problems on the newer trans.
My problem is not while coasting but rather while accelerating with the BD on it will set the limp mode, 0742 code,. Never had any problem decelerating.

[rjwest]

Still have it. were you the person who enquired before, Lost phone number, qwestav@attglobal.net
( slightly out of control,)


Howie will send email....

[MTTwister]

HowieE - in one of the links above, I put out a theory on why the thing may not work on OBDII. It commands full line pressure to ( ?something?) which in the OBDII world might be the cause of the higher level code, and limp mode.