well guys iv got a 99 dodge 3500 4x4 and between 40 and 50 and sometimes at 55 to 60 it seems like it is coming in and out of lock-up sometimes it will jump rpms once or it may do it 5 times in a row before it desides to stay locked in. what could be the problem and how can i fix it please it gets on my nerves lol

you need to wire up a lock up switch (or a manual trans ). as for the cause...i've heard people say everything from solenoids to pcm to alternator.

Recalibrate the APPS and do the suncoast ground wire mod. Directions for both are on this site if you look.

Actually... Check for error codes first... You'll find that APPS sensor problems don't trip the CEL light...

Recalibrate the APPS and do the suncoast ground wire mod. Directions for both are on this site if you look.

I would try the calibrate the APPS but skip the wiring mod... If you think about it the truck ran fine for all these years and now needs a wiring mod... Doubt it... More than likely the APPS sensor is going bad in one spot and got a wild change in voltage which is being picked up by the PCM and it can decide if your accelerating or coasting... Hence the lock up and un locking...

After taking with Timbo he found that if you replace the APPS sensor typically the problem goes away...

Just my 2 cents...

Recalibrate the APPS and do the suncoast ground wire mod. Directions for both are on this site if you look.

The suncoast trick worked for me.Mine did the same thing.

Over the years I have found that the APPS calibration affects the issue he described in the first post only it is usually described as stacked shifting which is what mine did, it actualy would up and downshift in and out of od to 3rd multiple times at certain speeds and loads. The wire mod is to cure the tc lock unlock issue which is a problem they all came from the factory with and is an electrical noise issue and are 2 different scenarios/problems. I post this to kill 2 birds at 1 time. Most people are either so used to the tc lock unlock problem that they drive around it by adjusting the speed as you usually know at exactly what speed it does it so drive a couple mph faster or slower to avoid it, or they just don't realize it is a problem until they actually fix it while chasing other electrical issues. But when it does the stacked shifting you know you have a definate issue.

well the apps isnt but 6 months old. it has no codes at all. i read some ppl fixed the prob by wraping aluminum foil and electrical tape around the p-side grounds mainly the black and yellow to the alternator. i did that yesterday and it seems like it helped alot but it still done it twice lastnight but not near as much as it did before. so ill try the suncoast mod and see how it plays out. thanks for the tips

---------- Post added at 02:11 PM ---------- Previous post was at 12:02 PM ----------

well i just cleaned all the grounds. and did an apps re-learn for kicks and gigs...i dont have to drive it much today but i will be back to let yall know how it went. have not done the suncoast mod yet. that is the next step if it isnt fixed

---------- Post added 05-17-2010 at 12:29 PM ---------- Previous post was 05-16-2010 at 02:11 PM ----------

well after cleaning all the grounds and doing the suncoast mod yesterday and a apps re-learn to boot...went to a friends house last night on the way there had the radio on it done it prolly 25 times on the way...i was talkin to him and turned the radio off done anuther apps re-learn on the way home it ran like a champ...so once again im lost and have just about ran out of options..it has no codes and the apps is maybe 6 months old

Factory apps can go bad at any time.Check the tranny relay in the black box under the hood.Switch it with another and test drive it.

Hmm, my first post....I've dealt with the 40-43mph (4.10 gears) OD lock/unlock ever since I acquired this truck several years ago. I wrapped the alternator cables with aluminum foil and electrical tape and that worked for about 2 years, then it started up again about a month ago. Last night I did the Suncoast APPS grounding trick and it seems to have worked so far.

When I was having this same problem, cleaning all the battery terminal worked for me. Guess I was lucky

Well I changed the relay in the main fuse block and it seems to have fixed it. You would think that would throw a code but it didn't. Anyways thanks guys for the input

Yea... I see there is some common solutions that do fix the the lock/unlock problems...

I'm not sure if my problem is the same as you guys are talking about but my truck acts up at low speeds. It seems like it shifts between 1st and 2nd or maybe 2nd and 3rd when I'm under really light load like a going slow down a muddy trail (which is what I was doing when I really noticed the problem) This is really annoying and is it hard on the tranny?

Any codes? As slow speeds usually the TQ Conv is unlocked... By chance do you have a bad Trans Relay in the PDC?

Any codes? As slow speeds usually the TQ Conv is unlocked... By chance do you have a bad Trans Relay in the PDC?

Sorry this took so long to get back but I tried a different relay, still does it. And for codes it shows 0753, 1765, and 1693.

Here is part of it... http://mopar.mopar1973man.com/cummins/2ndgen24v/trans/trans.htm The P1765 was either the Trans Relay or a open/short condition for the TQ Conv... (Using a Mystery Switch?)

No mystery switch and it hasn't ever gone into limp home mode:shrug:

---------- Post added at 04:50 PM ---------- Previous post was at 11:06 AM ----------

Maybe there's a better thread for this but a new problem has developed. When I have the tranny in 1st gear it seems like it's locked up. It takes lots of power to move and when I release the throttle it stops short like the brakes are on. Also the OD OFF light was on and wouldn't turn off. I turned the engine off and restarted it and the light was off and the lockup was only momentarily a couple times and then it didn't do it any more. Any ideas what might be happening?

have you tried the suncoast fix? look at: http://forum.mopar1973man.com/downloads.php?do=file&id=18 or http://forum.mopar1973man.com/downloads.php?do=file&id=75

No mystery switch and it hasn't ever gone into limp home mode:shrug:

---------- Post added at 04:50 PM ---------- Previous post was at 11:06 AM ----------

Maybe there's a better thread for this but a new problem has developed. When I have the tranny in 1st gear it seems like it's locked up. It takes lots of power to move and when I release the throttle it stops short like the brakes are on. Also the OD OFF light was on and wouldn't turn off. I turned the engine off and restarted it and the light was off and the lockup was only momentarily a couple times and then it didn't do it any more. Any ideas what might be happening?

You may want to drop the trans pan and see if there are any signs of debris, sounds like a bearing siezed up and now it is possibly spinning in the housing.

DTT transmissions makes a filter for this purpose http://www.dieseltrans.com/. My truck came with it and the DTT trans. so I only speak of others that have used it successfully, along with checking for good grounds. Alternator interference is a major cause of the problem. ED

have you tried the suncoast fix? look at: http://forum.mopar1973man.com/downloads.php?do=file&id=18 or http://forum.mopar1973man.com/downloads.php?do=file&id=75

Did the suncoast fix this morning but it's still doing the gear hunt. No lockup today yet.