Ok, so my 91 B250's (5.2 engine) overdrive is not working. The voltage regulator in the ECU went out last last year, but I was able to bypass it and just use an old school regulator to charge the battery. From what I've read, the 4th gear (or overdrive) is electronically triggered by the ECU, and so at that point I assumed the whole thing was just starting to die.

I bought a new ECU and just installed it into the van, but sadly that didn't fix the issue after a quick test drive. In a way, I'm sort of relieved since I can get my $260 back from autozone, but also a bit ticked off since I've got to find out what else is causing the problem. Gears 1-3 shift perfectly fine, so I don't think the transmission is totally shot.

I don't want to take the beast down to a transmission shop just yet, so I thought I'd ask the epic dodge forums this question:

What/where else should I check for this no-overdrive issue?

Many thanks
-Nat

 

speed sensor on trans

 

x2 on nibroc's post.

Should be getting a code 15 too if the vss is done for. The reed switch inside the VSS has a certain amount of cycles. Mine started going at 190k miles. Full replacement at 200k was necessary.

This will not illuminate the check engine light

 

In the older, hydraulic trannys, OD was always the first gear to go. Especailly in heavy, non-aerodynamic cars and trucks.
IIRC, the only electronic circuit in your transmission is the TC lockup, so the ECM has nothing to do with shifting - it is all hydraulic.
Also, I dont think you even have a speed sensor. You have OBD 1, and a hydraulic transmission, so I really don't think it is there.
You do have control solenoids in that transmission, and every tranny ever made has probelms with these:
http://www.rockauto.com/catalog/moreinfo.php?pk=320331

Instead of throwing parts at this problem, you should
1. Drop the transmission pan
2. Is the fluid anything but reddish-pink. No - Then you need a rebuild. Yes go to step 3.
3. Is there slime or sand in the bottom of your pan. then you need a rebulid. If No go to step 4.
4. Is there any metal, or pieces of shavings in the pan. If yes, then you need a rebuild. No--then go to step 5,
5. Replace 4th gear solenoid. If it doesn't fix it, pay the $60 for professional diagnosis and band adjustments. Go to step 6
6. If your van has over 120k miles, expect needing a rebuild.

Good luck

 

It will be a part around the transmission, not knowing exactly another thing to look for is the connection which makes the transmission change gear. should be one for up and one for down. there are posts way back about these.

Another question seeing as you have one of the few B250 with O/D what kinda mileage do you get with the ability for overdrive, I ask as later models dropped the overdrive and I am curious

Thanks

 

Ouch, was hoping not to hear that. It's actually funny because the odo says it has 119,775 miles, but it's never worked so the true miles are unknown.
Transmissions are a bit out of my league (I was hoping it was electrical), so perhaps I'll just have a shop look at it and cross my fingers.

Thanks for all your help, guys.

 

as said before try the speed sensor that is on drivers side of tranny