97 F350 3rd to 4th eratic upshift/downshift

[BleedBlue]

Just finishing up a complete exterior overhaul for my dad on his 97 F350 4x4 auto trans Stroke. Nothing mechanical just put a new dress on an ol' girl. Truck has 122k everything pretty much stock. I've had the truck for about a year doing my thing and am in the process of buttoning everything up to deliver it back to him. I changed the oil, replaced the air and fuel filters and loaded it up with fresh fuel. Drove the truck home Friday to make sure all the gremlins were worked out. All was good until I tried to maintain speeds between 50-60mph. Truck couldn't decide if it wanted to be in 3rd and run about 2100rpms or shift into 4th and run at about 1500rpms. If I accelerated it would shift up and rpms would drop if I slowed back down it would again shift up and down as if I was feathering the throttle. Also, it doesn't happen everytime. I couldn't really control anything to make it happen. I would just slow down and try again. On a side note I noticed the truck would not let me engage the cruise control when it was running at the higher rpm. When it acted "normal" I could set the cruise and everything was fine as wine. I checked the fluid level and added 1qt but otherwise it didn't seam to make a bit of difference. I saw a previous post with a similar condition and it mentioned something about brake lights/wiring maybe telling the torque converter to engage/disengage? All my lights seem to be working fine but any direction or advise would be greatly appreciated!! Thanks.

[bsanch1]

i dont know if this will help you much, but mine did the same thing. i noticed it would do it every time it rained, there were other times but nothing consistant. i figured it was temperature related or something. on mine the tranny wont shift into 4th until the engine temp. comes up a little bit. dieselsite.com has a 203* thermostat. i installed it for a different reason, but a weird side affect i noticed the other day was that while i was driving in a pretty bad storm is that it didnt shift wierd at all. first time! all i can figure is that the stock thermostat kept the engine temp too close to a permissive that allowed it to shift into high gear. the new thermostat rides almost in the center of the gauge, where the stock one barely touched the "N" in normal. its about thirty bucks. cant hurt. thats the temp that international designed it to run, but for some reason ford thought they knew better

[bsanch1]

oh yea, mine is a 96 automatic, should be the same

[jesilvas]

Originally Posted by BleedBlue

Just finishing up a complete exterior overhaul for my dad on his 97 F350 4x4 auto trans Stroke. Nothing mechanical just put a new dress on an ol' girl. Truck has 122k everything pretty much stock. I've had the truck for about a year doing my thing and am in the process of buttoning everything up to deliver it back to him. I changed the oil, replaced the air and fuel filters and loaded it up with fresh fuel. Drove the truck home Friday to make sure all the gremlins were worked out. All was good until I tried to maintain speeds between 50-60mph. Truck couldn't decide if it wanted to be in 3rd and run about 2100rpms or shift into 4th and run at about 1500rpms. If I accelerated it would shift up and rpms would drop if I slowed back down it would again shift up and down as if I was feathering the throttle. Also, it doesn't happen everytime. I couldn't really control anything to make it happen. I would just slow down and try again. On a side note I noticed the truck would not let me engage the cruise control when it was running at the higher rpm. When it acted "normal" I could set the cruise and everything was fine as wine. I checked the fluid level and added 1qt but otherwise it didn't seam to make a bit of difference. I saw a previous post with a similar condition and it mentioned something about brake lights/wiring maybe telling the torque converter to engage/disengage? All my lights seem to be working fine but any direction or advise would be greatly appreciated!! Thanks.

After you said this, are you sure it was switching between 3rd and 4th or 4th locked and 4th unlocked TC?

Originally Posted by bsanch1

all i can figure is that the stock thermostat kept the engine temp too close to a permissive that allowed it to shift into high gear. the new thermostat rides almost in the center of the gauge, where the stock one barely touched the "N" in normal

That is because your old thermo was stuck open. The stock gauge is nothing but on/off.

[retmotor]

Originally Posted by jesilvas

...That is because your old thermo was stuck open. The stock gauge is nothing but on/off.

On your Superduty?

The gauges on both my OBSs moved the needle depending on engine temperature.

[jesilvas]

They are the same on mine. But it's still not really accurate. I've got an ECT gauge.

[bsanch1]

im sorry. the old thermostat worked fine, but it was a lower temp thermostat. i think it was a 192? the new one is a 203. since the day i installed the old one it moved the gauge but it took forever to warm the truck up. i just thought that was how it was suppose to be. the new one warms up like i would expect any vehicle to. im not saying this is a cure for the shifting problem, but mine hasnt acted up since i changed it.

[Grebesbakery]

Mine has a similar problem with 3rd and 4th, between 30mph and 45mph. When driving around town, it will stay in 3rd until 45mph....then it will shift to 4th. But the second the speedo dips below 45mph it will down ship to 3rd. Very irritating, when its in 3rd it seems its revving (don't have a tac, its 95' e350) way to high for driving around town. Also my speedo does bounce a little....not as bad as some I have read about.

Is my tranny going or do I have some stupid sensor out.

[bsanch1]

Mine does that some tool if I try to hold certain speeds. I don't think its your tranny. I saw a few guys replaced the instrument cluster and haven't had a problem since. Make sure your fluid looks good and has the right level. If so change the cluster. That needle dancing its probably sending the trans some messed up signals