Overdrive/Trans Issue???

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charlestonfj60

charlestonfj60

Joined
Aug 31, 2006
Threads
265
Messages
882
Location
Mount Pleasant, SC
This has happened to me about 10 times.

When driving about 40-50mph and 2200rpms and in overdrive, the truck seems to drop down a gear or out of overdrive and runs at 3000rpms doing 60mph. It happened once on 1.5 drive and I ran the truck at 60mph doing 3000rpms. If I slow or go to "passing gear" has no effect. It hasent happen in a week or two but it did today on my way home from work. Is there a overdrive solonoid?

So whats going on?
 
Any strange noises coming from the transmission?
How does it drive with the OD off?
Have you drained the pan to see if there are any shavings?
You can pull the speed sensor on the left side of the tranny, its held in with one bolt, to check it for metal shavings. If you are not getting a check engine light then I doubt you will find shavings on the sensor.
 
I think I've experienced what you're talking about. The engine rpm's change, your speed remains the same, but the trans never changed gears? It's happened to me a few times, but I think only if I'm using cruise control.
 
The transmission is downshifting from overdrive to third gear.
This happens frequently when you go up a hill at highway speeds.
It is perfectly normal.
 
Ok after doing some research I think I understand what's going on...

4 sp w/ overdrive = 4 forward gears, the 4th being lower than 1:1 (ours is 0.753:1). Typically when in OD the torque converter locks up and the RPMs are very low. When you go up a hill the engine struggles to power it up the hill in such a high gear so instead of downshifting, the torque converter unlocks allowing the engine to rev much higher. Same speed, same gear, but higher rpm/power with some torque converter slippage.

I love learning new things :)

edit: re-reading you post, your issue is that it seems to be sticking in too low of a gear and you're wanting/expecting to upshift? That only happens to me when I'm in cruise control and general consensus on other threads is that it happens to everyone. Now if it's happening when not on cruise control... I don't know what to tell ya
 
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I live on the coast so its flat. It happens on a flat road running 20-25mph and all of a sudden it seems to down shift and runs at a higher rpms but same speed. I know its supposed to down shift when running up a hill to gain rpms but mine does it when on flat ground. It doesnt do it all the time, so trying to figure out whats the issue?

Also it doesnt happen with cruise control, I dont think. I dont use the cruise that much.
 
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Ok, so it happened twice on a 100 mile trip. The easiest way to explain what happens is that the trans doesnt want to go into overdrive. I found that the second time it happened, I pulled over and cut the engine off and it seemed to "reset" and all was fine for the rest of the 60 miles or so.

So why is it not going into overdrive sometimes???? Thanks
 
In your specific case IDK. However just generally the transmission shifts down whenever the torque demand is too high for a particular gear and rpm. Vice versa also; the transmission will keep shifting up if torque demand is low.

So you can easily have a situation where you are, for example, coasting along barely on the throttle and the transmission has shifted into top gear but every time you tip into the throttle a little it immediately downshifts. This just means that your speed is really too low for that gear and the part-throttle is 'fooling' the trans into upshifting prematurely by giving it a very low torque demand.
 
Sounds like the valve body is not working properly, may want to get a full fluid swap. If you decide to swap the fluid I would go ahead and drop the pan and clean the filter.
 
Torque converter unlocking. It helps maintain speed, since downshifting and running at 4300RPM is a bit on the wild side, it slips and allows a small increase in RPM's. Mine does it constantly, i I feather the throttle slowly it will unlock/lock each time. If I have time and traffic isn't dead stopped, I'll take a quick video. If you have O/D off and cruising at 50 and step on it (no downshift) you will hear the engine start to bog down slightly. With O/D on it will slip the TC and not bog.
 
When the issue happens it makes no difference when I push the OD button on or off. Or if I let off the gas to slow the RPMS. It will run like this untill I stop and turn the truck off. So whats the repair/fix to this issue?
 
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