When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I have been fighting this off and on for a year or so. While driving the truck will start upshifting/downshifting very hard. Usually I notice it starting because the cruise control will kick off and not reset. The speedometer works normally and doesn't jump. It feels like it goes into a limp in mode- full line pressure. Sometime it will start working normally a few more miles down the road. Other times cycling the ignition switch will reset it. In the past I have replaced the VSS and MLP with no change. The local dealer couldn't find anything wrong but they did seem less than interested in working on something so old.
Is there a splice in the harness as it goes over the trans housing or some suggestions on where to look for a bad wire? I'm thinking it has to be electrical.
If it is bad wiring it is almost always on the passenger side plug as the wires go into the transmission shift/pressure (solenoid pack) plug. You would have to remove the back cover of the plug to see the wires as they go into the plug. This happens most of the time from someone leaving the shield off that protects the plug from the heat from the exhaust.
If not that I would suspect either the PSOM or the PCM Computer or the speed control module. You would have to monitor the signal as it goes into the PCM Computer to see if one of these items is at fault.
You should also check for any codes before you do anything else.
No codes present. I'll take a look at that pass side plug and look around for a wiring diagram. Guess I'll have to try to run some wires and monitor inputs to the PCM. Something has to be momentarily dropping out.
Didn't have time to check it out yesterday. I drove the truck yesterday and it acted up the first half of the day and drove great the second half. I'll slide under the Bronco after work and hope I find something
Thanks for the link. I had a loss of VSS a long time ago. That was fixed by a new sensor but hasn't resolved this issue.
I recommend opening the computer case & having a look at the capacitors.
I'm chasing a "no codes & erratic operation" as well right now, except my case is a fresh rebuild that was dyno tested. I've done all the plugs & MLPS. Mule kicks 1-2, sometimes (but not always) going into reverse. Sometimes a shudder after going into 2nd. 2-3 firm & 3-OD normal, but downshifts at the slightest drop in RPM.
Don't get anything but 111s & 512 (It sat for 5 months) even after clearing with the code reader...
So on a hunch today I opened up the PCM & I got green corrosion on the board under the 3 can capacitors.
When it acts up it is very hard upshifting and downshifting. Hard going into reverse as well. It actually stalled out when going into reverse the other day.
Starting working again on its own yesterday. Cleaned the solenoid connector today. See how long it stays working...