Speedo / Auto no shift

[MICHAELSILVTYLER]

Hi,
I have 1993 6.5 TD. The transmission stays in 1st gear and won't change. Had several business look at and don't know where to start. The speedo also does not work. Is it a sensor and if so which one is it

[More Power]

There's a vehicle speed sensor on the trans tailshaft (if 2WD) or transfer case (if 4WD), that sends a signal to the vehicle computer, VSSB - speedo, cruise control module.....

More info on wires & such for a 1995 model can be found in Ron's article on the BD Torq-Loc (http://www.thedieselpage.com/reviews/torqloc.htm).

MP

[cruzer]

Michael, I had the exact same problem a couple of yrs ago on my C2500. It was the back sensor that was bad. After replacing I still had the same symptoms as b4. I then disconnected the batteries to reboot computer. All was good then.

[RaptorMan555]

Hey I have a 92 C3500 that the speedo still won't work aftera new speed sensor. Also the tach goes haywire sometimes. Any ideas on this one?

[Hye]

On my '89, the speedo problem was the unit in the dash. It was intermitant for several years before it quit completely. I got a used cluster from a junkyard. $25 All the guages, temp, batt, oil, speedo, etc. unplug from the cluster circuitboard. The speedo replacement from a gasser plugged into my diesel dash cluster.

[JohnC]

A common cause of this problem is a bad contact in the ignition switch. It powers both the trans and the speedo. Check the trans fuse for a reliable power supply. If it drops below about 9 volts, especially when first turning the key on, the trans will end up in limp mode until you cycle the switch.

Most likely you're stuck in second, not first. If you can go 40 mph it's not first. If it's stuck in second that's the "limp" mode. There should also be some diagnostic codes stored in the PCM.

[MICHAELSILVTYLER]

I am finally starting to get somewhere. I added new earth straps from steering column to engine bay firewall and another from there to engine block. After removing earth lead from battery and then putting back on I noticed when truck on stands the speedo fluctuating. Took truck for run and hey presto the transmission shifts. Now all I have to do is get speedo working and the fuel gauge is also on full empty deflection.

Any ideas???

[MICHAELSILVTYLER]

Help still diagnosing this dang thing. i was searching around the other day and i found that I have 7 volts?? on the extental case of the TCM. has anyone ever seen this. i think i may have a stuffed TCM!!!

[Iain]

Not sure if this will help or not, I have a 1994 6.5 TD that was doing a similar thing. Speedo and tach would flicker and jump around and the truck would be stuck in second gear in limp mode. It was eratic and would only act up on heavy loads (pulling a steep hill, etc). Other than that it would drive fine and shift o.k. TRake it for a long trip and it may or may not act up. I spent 2 months trying to figure it out and took it to a reputable performance transmission shop. They pulled the tranny and found that the lock up on the torque converter was not always locking up and it was badly burned due to slipping. They replaced the TC and went through the rest of the tranny, replacing a few seals and some other minor odds and ends and now it shifts great.

You may want to check your trans and see. I found metal flakes in my trans oil pan prior to taking to the tranny shop.