Lost OD a4ld

[nmos]

Last week my wife came home in our 92 Ex with about 230K and told me it wasn't feeling right in OD. Sure enough it wasn't shifting into OD at freeway speeds but seems otherwise normal in Drive when warm. When cold it does feel a little sluggish in pretty much every way and for the past couple of years there has been some 4-3 flair. I should note that TCC lockup seems good in 3rd. I tried flushing the fluid and adjusting the OD band without any noticeable change. I put a probe on both the TCC and 3-4 wires near the PCM and the PCM seems to be sending the correct signals at the correct time. With the ignition on but engine off I can hear the TCC and 3-4 relays faintly click when I ground their wires. At lower speeds (say 45-50) especially on a slight down grade it does appear to shift from 3 - 4. At this point all I can think of to do is to pull the VB, replace the 3-4 solenoid as well as any seals that are easily accessible and generally clean things up. I've never been into a VB before and it looks like there are a lot of opportunities to screw things up so I'd like to keep it as simple as possible. My questions are:

1. Is it likely that replacing the 3-4 solenoid will correct the OD problem?
2. What other parts will I need? I know I'll want new fluid, a new pan gasket, and filter. I know there is a low/reverse servo that has a seal that may be worth replacing. What other seals/gaskets do I need? Can I get them as a kit?

--
Ray

 

[BrooklynBay]

Test the overdrive solenoid with a multimeter. Sometimes it could be a sensor related issue. Do you have a check engine light, flashing O/D light, a lack of cruise control or ABS?

 

[nmos]

Cruise control works and the check engine light is off and I don't think it has an O/D light. The PCM appears to be sending the 3-4 shift signal at the correct time. When you say to check the solenoid with a multimeter, what should I be checking, resistance? Do you know what sort of value I should be looking for?

One thing I noticed is that if I'm going down a slight hill around 45mph in OD and then shift to D the rpm rises as if it had been in 4th. On the other hand at higher speeds shifting from D - OD and back has no effect at all. Does this suggest a vacuum problem? I did replace the vacuum modulator last year in an attempt to correct the 4-3 flair but didn't notice any leaking at that time.

 

[BrooklynBay]

Check the resistance of the solenoid's coil through the 3 prong connector. It should be between 25-40 ohms.

 

[1Byounkin]

i have all the same problems with the OD, but mine has never work before and after the rebuild. I have no CEL. The ohms on the solenoids are 30ohms on both. In the koeo test I saw 12v in the 3 prong connector. But no volts in the OD solenoid when driving. Yes the TCC locks up. What else does the PCM need to shift? I checked the TPS, VSS, MAF all good.

 

[BrooklynBay]

Check the coolant temperature sensor. The computer won't let it shift into overdrive if it thinks that it's too cold.

 

[1Byounkin]

The Coolant temperature Sensor reads good. The Temperatures to the ohms move like they need to do. Found that chart that shows the ohms to temperatures.

 

[BrooklynBay]

Was the wiring from the PCM to the transmission checked?