Hi guys! I have a 95 F150 with the 4R70w transmission. I was coming home on an hour long drive and my truck shifted very abruptly going up a steep hill. (I was doing 65-70 mph). Then the overdrive switch on the shifter started blinking OFF. About 10 miles down the road, I stopped my truck and did a restart and the light turned off. I could kind of smell transmission fluid when I stopped. A few miles more down the road and my truck stopped shifting over 60 and then later it would not shift over 50 mph. I limped the truck home my shifting it from N to D which help get it into gear when I lot it. Transmission fluid level is good too.

The transmission was rebuilt 15,000 miles ago and I did have this same issue before when the transmission filter came loose.

Does this sound like the same problem?

Any help would be appreciated!

 

The blinking O/D light means there is a code in the computer. Pull the codes to see what the computer thinks is wrong.

 

The flashing is gone now. I'll still check. It's OBD1, so do I need a special tool to read the codes?

 

If there was an issue to trigger the O/D light to flash it will be stored in Continuous Memory (CM aka Stored Codes). Therefore regardless if the O/D light is no longer blinking or the Check Engine Light is off there will be a code stored in memory.

You can use a paper clip to pull the codes: How To Run a Self test

Or do yourself a favor and purchase a code reader such as the Equus/Innova 3145. It's a worthwhile investment.

 

I bought the Innova 3145 and it didn't work and tried it multiple times. So I found a local repair shop that had an OBD-1 reader. He didn't tell me the code number but told me two codes showed. They were transmission temperature switch and transmission oil temperature over heat. Both descriptions fit code 68.

So other than the obvious fact that my transmission is overheating. What would a temperature switch be?

The code 68 description is transmission temperature switch circuit failure; circuit open.

 

A 1995 F150 will not get a code 68.
It will have three digit codes.
If the code reader did not work take it back.
The Innova 3145 is a very good code reader and I have used it on 1995 F150 with the 4R70W transmission many times.

 

ok I figured it out. The extension cable I bought with the innova was bad. So I ran the codes and it gave me 565 O. That code in the book is canister purge solenoid circuit fault. I'm going to look up what that means.

Do you happen to know what it means off the top of your head?

 

This was from the KOEO

The KOER test was good. No fault codes.

 

How about the "C" codes?

DTC 565 indicates a failure in the CANP (Canister Purge) solenoid circuit.
Possible causes:
-- Open harness (VPWR or CANP).
-- Damaged CANP solenoid.
-- Shorted (power to ground) harness.
-- Damaged Powertrain Control Module (PCM).

 

So does that code sound like it could affect my transmission shifting?

Nope gave 111 for C.

 

No it does not.

 

At this point you should probably just drive it again til you get the flashing light. The hard shifting is not a problem but a deliberate feature intended to protect the transmission. Aside from being a little harder on u-joints it won't hurt a thing. If it were my truck I'd go for an easy ride and see if the fault comes back. If not then put a little more load on it, maybe drive up the same grade you were on when the problem first happened.

I know the code 68 you got was erroneous, as mentioned above, but since you asked... there is no temperature SWITCH in a 4R70W that I am aware of. It is a PTC thermistor which is an analog device so it will provide an actual temperature value to the PCM (Powertrain Control Module).

 

I still drive the truck quite about although I haven't gone over 50 for extended periods of time.

Today, I disconnected the cooler lines and checked the flow of the fluid through it. It worked pretty well. However the fluid might be the problem.

Here's a picture of new fluid next to what's in my trans:


I'm not sure what qualifies as burnt and therefore ineffective fluid, but the current fluid looks aweful black compared to the new. The current fluid also smells bad.

What do you think? Could burnt fluid be the culprit after all?

 

I've seen worse and while fresh fluid would certainly help with shifting, that old stuff wouldn't have degraded transmission operation enough to cause your OD light to flash. There's another problem somewhere...

 

I bought a new shift solenoid. I'm going to install it and see what happens. No codes came up for it, but the symptoms match.