I have a 98.5 that just within the last couple of weeks started to surge in and out of lockup on the TC, it even shifted clear out of OD like I had pushed the button a few times. Tonight on the way home it never did lock up the TC, it just stayed in OD. The tranny is full, no burnt smell no foam, it supposedly only has about 10,000 miles on it. I have cleaned the battery cables, checked the connection at the tranny, all grounds that I can find are good. Now I was almost positive that it was a connection, because it would come out of lockup when you hit a bump in the road, but now, I'm at a loss, everything I can find is tight. I just started a new job, no money very little time to spend on this but I have to have it to get to my job, any help would be so much appreciated.

Thank you so much everyone!
Jeromy

 

Is it brake pedal bounce? It sounds like it but could be electrical noise. A noise filter from DTT is reasonaly priced and is a good addition to all auto trucks.

 

Is it the 98.5 12v? Might be a faulty Throttle Position Sensor.

 

It is a 24v.

 

As stated, a noise filter is a good idea as well as wrapping the ground wire from the alternator with foil and elect. tape.
HTH
James
transbuilder since '74

 

I have another question, not sure if related but it might be. On the passanger side of the truck there are 3 connection blocks the one to the right as you are looking at them (driver side) has an orange wire, I cant see a tracer, its dark, but it has been cut and a green wire spliced and run back through the loom to about the center of the engine compartment. Then it comes back out of the loom and runs down somewhere to the fuel filter area, any ideas? Its dark so I cant see for sure where it runs to exactly. I checked all the grounds again and scraped to bare metal then reconnected them I'll see if that helps. I only found 2 on the fenders one that runs down to the bumper, one that runs to the alt loom, one that runs back into the wire loom on the firewall it is split right off of the battery from one into two. I cleaned and retightend the three that I could get to easy. The main grounds to the block are tight from both sides. I'll see how it runs tomorrow. Exactly where do you install the noise filter and how expensive are they? I see DTT has them any where cheaper?

Thank you!!

Jeromy

 

I finally found it this weekend, I think. On the passenger side battery there is one small wire that splits into two, one of the grounds must have been loose there, I clipped them and redid the connection. So far it is shifting like it is supposed to. I see more on Monday.

Thanks all!!

Jer

 

I thought I found it, but after about 80miles on a rough road, it is doing it again. Now it is back to doing it when you hit a bump. I'm at a loss, did anyone know what the wire that was spliced was for, or if that has nothing to do with the problem?

Jeromy

 

Drive the same road that it acts up on again. This time lift your brake pedal with the left foot and hold it. Does it still unlock/down shift?

 

checking the brake switch is a good idea. The noise filter is also a "must do" on most of our trucks as it is a not if but when kinda thing. Also the batteries need to be load tested after being isolated from each other as they are the source of a lot of maladies. I tend to be suspect of batteries that are near three years old or more. Also always replace batteries as a PAIR. Just order the noise filter from DTT and solder it in per the instructions. The time you may spend trying to find another source will just cost you time, and I know the DTT filter works. Contact me in a PM or by email if I can be of help.
James
building transmissions since '74

 

No luck with the brake pedal, I'll just have to take your advice inarush76 and order the filter. I'm not sure how old the batteries are but I will try to get them as well. Thanks so much for all the help.

Jeromy

 

About 6 months ago, I had my 99 start acting up again after almost a year of flawless shifting. I went strait to the batteries and found one getting week. I replaced it, and she was back to normal. Two weeks ago, same thing all over. Replaced the other battery, and all is well. These trucks need two good batteries, clean cable connections, and good grounds. I also have the DTT filter and the TPS jumper wire in place.