OD has left the house!

[Mojunk4Yard]

New to the forum... just read all Dodge van entries (I'm ) and no one quite hit on my '90 15 pax B350 5.9L van problem...

Installed a used tranny from the lcl junk yard (great guys - even said the buy it back at purchase price of $250.00) Very knowledgeable mech. said it should work fine... came out of Dodge pickup... (Dakota?). It's heavy duty... spline is larger than any of the other (3) dodge trannies I've messed with. It drives and shifts great... R,N,D1,D2,D3... BUT, NO D4!

Only other symptom is that in park, the reverse lights are frequently on. Playing with shifter a little turns them off. Oh yeah, the overdrive button seems to be supplying 12+ volts to tranny OD plug whether it's lit (depressed) or not... I detached it and drove it with no success.

The 90 models are supposed to be all mechanical except for the OD switch... Could it be a band setting? or other adjustment I'm not qualified/certified/or permitted (by Wife) to play with? LCL tranny shop is two weeks backfilled and the kids are ready to vacation! (Yikes)

Preciate any help or redirection to a thread I missed.

[alloro]

The backup light problem is an indication that the linkage is not adjusted correctly. Adjusting the linkage might also solve your O/D problem.

There is always +12v going to the O/D connector, the rest of the circuit supplies the ground to activate the O/D.

[Mojunk4Yard]

Thank you very much for the reply. I never considered the ground completing the circuit... But, either way, I guess unplugging the connector would have allowed the OD to operate normally.

I will mess with the linkage again.

Do you think that adjusting the reverse light / park, neutral starting sensor (ie. rotate clockwise/ccwise slightly) might also be a possibility? Or will I damage something. If I remove the sensor, can I see the internal linkages through the hole? (If I could, what then?)

Thanks, again.

[Mojunk4Yard]

Nuther question...

Just how does the OD (off) button work? It completes the ground, but just what does that cause the little chipmunks in my transmission to do?

Thanks

[Mojunk4Yard]

Most amazing! ... I started the van then disconnected the wiring harness from the reverse light sensor on the transmission and drove it. OVERDRIVE is ALIVE!

Now my brain hurts. Why? What is going on electrically between the OD switch (which now works too. Ie. will take it out of OD when depressed) and the reverse sensor / ground / what?

[alloro]

It might be a safety feature, where if your reverse light sensor is making contact then the O/D is disabled. This would prevent O/D from engaging during backup. Could be a bad sensor, a short in the wiring, or the linkage just isn't adjusted correctly.

By any chance the two connectors aren't interchangeable and backwards, are they?

[Mojunk4Yard]

No, the connections are not alike. I did finally find it in the Haynes manual. Says it is called the 'neutral start/backup light switch. (got a new one today... less than $9.00) three wires go to unit... the center terminal of the switch is a ground for the starter solenoid circuit when the tranny is in park or neutral. (allowing engine to start) The outer two terminals "make up the backup light switch circuit". Can't figure if they complete the ciruit? or what?

Crazy though,... why would this switch, when connected, keep the OD from engaging whether or not the OD wiring terminal is connected.? I'm thinking that there must be some sort of electrical explanation... ie. there is a short that is accomplishing the same inner workings (magic) as the OD switch does when depressed.

Gonna have to corner a tranny man. (that didn't sound right.)

Thanks, and I'm gonna try a few more tricks over the next few days with it. BTW... the van runs much more smoothly now that she shifts into 4th and I replaced the front wheel bearings.