Firstgenfanatic

I have a 1993 Dodge CTD with the A518 auto transmission. Just today i was driving the pickup on a long distance trip empty when the speedo needle started bouncing irratically until it dropped down to zero mph. Once the needle quite working the transmission shifted by itself from fourth to third gear. This situation randomly occured three times during my 300 mile trip. Roughly 150 miles of this trip was spent in third gear. Does anyone know or have experienced this problem? I am stuck out of town and need to fix ASAP. Thanks in advance

MBolivar

Check the connections to your crank sensor. If all are secure, your PCM could be going South.

Alwaysworking

also check you wires to the speed sencer, our ford had the gears that drive the speed sencer strip out then it wouldn't shift, just so more input

Chrisreyn

The only common points that I can think of between the Speedo and the OD would be the wiring harness along side the drivers side of teh tranny and the ECM.... being an intermittant problem I woudl think teh ECm isnt getting input or is going south..
As already suggested, check the connections and harness at the VSS and OD soliniod, and check the Crank Sensor..

zacks91

I had the same problem with my truck,the vss control the speedo and overdrive,change it and your problem will be solved!

zacks91

By the way I should have told you the vehicle speed sensor is in the back of the transfer case on a 4x4 I think it has a two wire connector. Hope this helps.

Firstgenfanatic

Thanks for the reply! This problem is frustrating for me because I have no service manual handy and also I am 300+ miles out of town. I limped the pickup 150 miles to my original destination @ 45-50mph!!!! This was the worst drive of my life. Because of this problem the cruise control stopped working as well. I figured the common denominator between the speedometer, OD, and cruise control not working is the VSS. I was hoping that another 1st genner on here experienced the very same problem at one time or another. Anyone know how much these VSS' cost at the Dodge dealership? I talked to a friend of mine on the phone who owns a 93' 1 ton..............he seemed to remember spending $60-$80 for this part. Any further troubleshooting help would be greatly appreciated! Is the VSS something easy to replace with simple tools? Thanks

Chrisreyn

https://www.dieseltruckresource.com/...d.php?t=198123

That should help you out on teh VSS and how it works..

chevummins

A handy trick I did on mine was to disconnect the VSS and then hook the cordless drill to the little four sided shaft and turn it. If the speedo picks up then your vss is good and then you need to look at the little right angle coupler and see if it is stripped out. In the end mine was BOTH!! Hope this helps.
-Greg

Firstgenfanatic

I checked my VSS with a hand drill and the speedo started to function correctly while my finger was on the drill trigger @ steady rpm. I did the same thing for the speedo reducer and VSS while they were coupled together.........same thing, the speedo worked great. Next I pulled out the unit that connects directly into the transfer case (has small metal pinion gear at one end). I couple this piece to the VSS and speedo reducer.........the speedo worked good, then started bouncing erractically. While spinning the small metal pinion by hand I heard some "clicks" coming from the speedo reducer (90* gear unit). Everytime I heard a "click" coming from this part, my friend told me that the speedo needle started to bounce. Further spinning caused the speedo to quit working. I took off the speedo reducer, popped off the 4 rivets and found that everything was intact except one of the smaller gear with the attached 4-sided shaft was slightly rounded. I installed this piece into it's female counterpart and found while spinning the assembly the shaft slipped and the final pinion was not moving. I believe this 4-sided shaft is too worn and rounded to accomplish a good engagement for gear movement. Does anyone know the part # for the speedo gear reducer (90* gear unit)? I realize this is a Dodge dealership item only. I've heard this part is $100+ ??? I tried filing the edges back to flat to achieve 4 sides...........too worn and not enough material left on the shaft. Anyone have similiar problems?

Dean Snow

https://www.dieseltruckresource.com/...d.php?t=198605

check that out. then read the rest of what im typing...


i had the same problem a while ago and i did a write up on it for people with this problem. If pounding it with a chisel or screw driver doesn't work in the tapered part where the 4 marks are at take some epoxy and shove in the hole where it needs pounded down at then stick the VSS onto the gear ratio reducer and let the epoxy make a new square in there and it will work out fine for you im 100% sure of it..

KRB

Thats a good write up and sounds like a great easy & cheap fix.

Does the VSS do anything for the odometer? Mine quit and new plastic gears still didn't help but my speedo never quit working.

Firstgenfanatic

Ok, I understand what your explaining. This is the order is which these parts are assembled: 1.VSS sensor plug------2.VSS sensor-----3.Gear ratio reducer------- and last, ??? 4.some metal part that has a metal pinion (attaches through transfer case hole-opening). My problem is between part # 3 and 4. I think you are refering to a issue between #2 and #3. Sadly, I'm pretty sure my only option is getting a new gear ratio reducer from the dealership. Does anyone have a FSM showing these parts or part numbers? I'd like to go to the dealership "armed" with this information to quickly find what I need.

Lil Dog

ON my 89, the 4 sided pin was rounded that went into the transmission and it would slip. I went to a speedometer shop that did installs on taxis. They had the replacement pin that went into the speedo reducer, cost like $1. I just took the reducer apart and the pin is only held in with a small spring clip.

IIRC you need a super thin wrench to pull it apart behind the mounting nut that goes onto the tranny. I justed used some welding rod and a vice to hold the nut and turned the 90° reducer with a wrench to disassemble.

Firstgenfanatic

I was able to locate a new speedometer gear ratio reducer at the Dodge dealership. The part# 4428549 (1.3 ratio) @ $101. bucks. Apparently the guy I talked to on the phone in parts explained that this item was recently ordered from a customer last week..........must be a common problematic part?