Transmission Overdrive Problem

frontshadow

Registered User
I've a '95 SC with about 58K miles. Bought it new and have serviced the transmission every 20K miles.....filter and complete flush each time. I own/run a Lube shop so we do the service ourselves and am always careful to preform correctly.

Recently, the car started to "drop" out of overdrive for no apparent reason. Yesterday, I spent some time "testing" the situation and noticed that it will occur at almost any speed, up to 80 miles per hour at least. It might happen two times in a mile or it might not happen for 20 miles or so. I thought it might have something to do with temperature however it will do so warm or hot. By the way the engine temp never gets above NORMAL and generally is about mid way between dead cold and NORMAL.

When the overdrive drops, the speed is constant, the tach is constant, and the car does not have to be in a load condition. By that I mean that, it is not going uphill nor having to accelerate to keep speed constand. In fact, I experienced it going down hill. It also occurs with or without the use of cruise control.

I notice that the OVERDRIVE OFF lite does not lite or flicker however it does work as normal when the switch is depressed. When depressed , naturally the car will drop to Drive from Overdrive.

The transmission shifts from first to second to third and overdrive smoothly and normally. No signs of slippage nor early/late shifting. When the car does drop from overdrive, and then allowing the engine to coast (remove foot from accelator) for just a second or so, the tach will then drop (of course), overdrive will again engage itself, and everything is normal. The trans will stay in overdrive while accelerating back to prior speed. Naturally if you "stand" on the accelerator, the trans will downshift out of overdrive until acceleration is stopped, at which time it will return to overdrive again....

Today I decided to change plugs and wires...it was time anything. My thinking was that perhaps a slight missfire/miss might be occuring and triggering the trans to drop overdrive. I haven't noticed any hesitation or miss at this point. Tomorrow I plan to install a new filter and completely flush the transmission again. The fluid remains clean and does not smell burnt.

Could this be a solenoid or sensor failure? Help!
 
you might wanna drain the fluid, add some LUCAS TRANSMISSION FIX, see if it helps, my guess is that the computer transmission might be messed up and probably needs some re-learning, try unplugging the battery overnight and let the computer learn everything again. see if it helps.
 
Does it slip when this is happening or does it just downshift to 3rd at random?
I have had my 94 do both and it wound up being the MLPS sensor on the trans.
The 94-95 models have a MLPS that is notorious for going bad,
If you do a search for it you will see a lot of the 4R70W SC's have had to replace theirs.
 
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