Torque converter lock-up

[JKellis]

Yesterday my torque converter began locking and unlocking pretty much at random. I know this topic has been covered in many past threads and I have read many of them. What I am looking for is guidance for the electrically challenged that can walk me through the trouble shooting process starting with the most likely to the least likely. A few days ago my brake lights, turn signals and emergency flashers quit working. Turned out to be a blown fuse. If someone could point me to a previous thread that could help, I would really appreciate it.

 

[DavidC]

First thing to check is for AC voltage out of the alternator which if substantial can cause havic with the electrical. There are a few posts on here on how to do it, you will need a multimeter. All we have to do is find the posts.

 

[DavidC]

Here is one by Katoom.
https://www.turbodieselregister.com/threads/dead-pedal.268721/#post-2626603

 

[JKellis]

First thing to check is for AC voltage out of the alternator which if substantial can cause havic with the electrical. There are a few posts on here on how to do it, you will need a multimeter. All we have to do is find the posts.

Thanks. I have a multi meter and will check for AC voltage today. Right now I am cleaning the battery terminals and checking battery voltage.

 

[DavidC]

Good idea, another is to load test the batteries. If you do not have that tester Harbor freight carries one or maybe Napa, Autozone, Oreilly's will do it for you.

 

[DavidC]

If all of that does not work there is a thread or two floating around here on seperating the wires that cross the front of the truck above the radiator. They also make filters that may help but that would be a last resort.

 

[JKellis]

Good idea, another is to load test the batteries. If you do not have that tester Harbor freight carries one or maybe Napa, Autozone, Oreilly's will do it for you.

I don't have a load tester, but I can borrow one. The batteries tested 12.69 and 12.71 volts after sitting overnight.

 

[DavidC]

If you wind up with AC voltage you can verify whether it is a Denso or Bosch and buy rebuild kits. Geno's carries Denso I believe and some other places have Bosch. Maybe you will not have to go there but if it is the original or a store replacement it is possible.

 

[JKellis]

It looks like cleaning the battery terminals took care of the problem! Even though they did not appear the least bit corroded. The alternator is original and I will test for AC voltage later today. I have a good rewinder that I have used for years and I will let him rebuild the original alternator if it needs it. Thanks for all the good advice!

 

[DavidC]

Hopefully it stays fixed, not a bad idea to check for AC every once in a while as it really messes with electronics.

 

[AEdelheit]

I would suggest not driving the truck until its fixed, I snapped the input shaft on my 98.5 when the TC started doing that.

 

[BigPapa]

I would suggest not driving the truck until its fixed, I snapped the input shaft on my 98.5 when the TC started doing that.

Never heard that one before. What were you doing when this happened?

 

[JKellis]

Hopefully it stays fixed, not a bad idea to check for AC every once in a while as it really messes with electronics.

I just checked AC voltage, read a steady 0.078 volts. Should I go ahead and have the alternator rebuilt?

 

[DavidC]

I would if you can swing it. Help keep your ECM from going South on you, the less the better, I have read of a lot worse.

 

[Timd32]

There are also a bunch of known issues with the internal harness grounds. Not sure if you have had that addressed.

Some of this might be in the Perfect Collection or the Buyers Guide.

But they had a very interesting way how the factory grouped and bonded the grounds in the harnesses. See that from time to time as well.

Those books are available at the bottom of the page in the menu when on my phone.

 

[AEdelheit]

Never heard that one before. What were you doing when this happened?

Merging on the freeway about 3/8 throttle but if you think about it the TC rapidly locking and unlocking is a massive shock load to the input shaft, I had been working on trying to diagnose and fix the problem , probably drove it for a month before the input shaft broke. This was around 2005 so before it was a well known issue.

 

[cdefore]

Yesterday my torque converter began locking and unlocking pretty much at random. I know this topic has been covered in many past threads and I have read many of them. What I am looking for is guidance for the electrically challenged that can walk me through the trouble shooting process starting with the most likely to the least likely. A few days ago my brake lights, turn signals and emergency flashers quit working. Turned out to be a blown fuse. If someone could point me to a previous thread that could help, I would really appreciate it.

My pickup did the same thing a while back. Took it to a transmission shop that was supposed to be incredible and claimed knew “exactly how to fix it”. Long story short he put on a new tps and did the wire reroute “choke” that is a common fix for this problem. Claimed that electrical interference in the wiring sends a fluctuating signal to the tps which in turn tells the tcm funny stuff and causes the torque converter controller to lock and unlock. I believe some of this was true as I also had a pulse in speed when the cruise control was set which I attributed to the tps as this issue disappeared when the “fix” was installed. Anyway, the pickup ran and shifted normal again for about 10k miles then went right back to it. When it started doing it again it only did it when I drove it in the rain. I changed the abs sensor on the rear dif (found it to be cracked) and again the problem disappeared for a short time. The problem then reappeared about 3k miles later and before I could dig into it something went weird after I cold started it one day. I was letting it idle in my driveway to warm up and when I got in to leave my check gauges light was on and my amp meter was pegged at max. my edge monitor showed 89 volts which has to be the default max. But either way. Messed up. What I learned that day was (after 2 new batteries and an alternator rebuild) that my battery harness was apparently the culprit. I bought the replacement kit from Genos and while installing I made sure to clean all grounds really well. I could be wrong but I think that most of the electrical bugs that guys spend so much time tracking with an multi meter are more often than not related to corrosion inside your battery cables and bad grounds. I have now driven 25k ish miles with no troubles since the new cables. Just my experience. Hopefully this helps and you get back on the road.

Cd4

 

[Timd32]

Couple good things in this article from Fluke.

Besides the basic stuff that you covered. Yeah its never one deal as these system age its hard to pin point it to a single known issue.

Posted this before.

https://www.fluke.com/en-us/learn/blog/automotive/electrical-automotive-troubleshooting

 

[GW208]

I just checked AC voltage, read a steady 0.078 volts. Should I go ahead and have the alternator rebuilt?

I have an 01 with 138,000 miles on it and just in the last couple of days the torque converter has started with the lock/unlock problem between about 45 and 55 mph. After reading your post and the replies I checked for AC and I'm getting 175mv on the original Bosch alternator.

It looks like Geno's carries a rebuild kit with new bearings and brushes but not the diode assembly. Can anyone point me in the right direction to find a complete kit or is this something best left to a rebuild shop?

 

[Turbo Terry]

I would have a reputable shop rebuild it. Very interesting article by Fluke At least your automatic transmission shop would work on your truck .Mine said itwas passed their expertise and sent me on my way.