2002 Tranny NOT holding a gear!!

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Nov 3, 2009 | 01:29 PM

BIGDOGDIESEL

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Joined: Nov 2005

Posts: 25

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From: South Texas

2002 Tranny NOT holding a gear!!

What's going on all you BLACK SMOKE LOVERS!! I guess it is true once you go black you never go back!!! Anyway having trouble with the rig around 40-50mph. The tranny can not decide what gear to be in from 2nd to 3rd at the higher speeds 4th unlocked. I had the tansmission governor solenoid replaced 40k ago and no problems till NOW!!! Anyway all these freaks in New Mexico want at least $90 for a diagnostic fee. If there is any insight out there let us all know.. Thanks fellas!!

Nov 3, 2009 | 02:19 PM

jrs_dodge_diesel

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Joined: Nov 2003

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From: League City, TX

Understand that the overdrive lockup clutch is controlled electrically by the PCM.

The effect that is occuring is known as a "ground loop". Ground loop cause unwanted electrical "noise" on electrical and signal lines. The lockup clutch is controlled electrically and a noisy control line will make it "hunt".

http://en.wikipedia.org/wiki/Ground_loop_(electricity)

Dirty connections, corrosion, and loose connections all contribute to ground loop. Fixing it is easy though. Generally involves cleaning ALL ground connections affecting the transmission and controlling it. Batteries, frame connections and the PCM on the firewall all need to be cleaned.

IMO tin foil shielding and power filters are simply band-aids that mask the underlying problem if left unchecked. And like I said before a simple cleaning with a wire brush and a piece of sandpaper will normally fix the problem with the lockup clutch.

Here is one of my posts from another thread involving the same issue.

Quote:

Originally Posted by jrs_dodge_diesel

There are 6 key spots to clean. Each negative battery terminal (1,2). There is a wire that runs from each negative battery terminal to the body of the truck with an eye terminal (3,4). Not only did I clean the connector, I took some sandpaper and took the sheet metal to bare metal to give a better electrical connection. The most critical wire to clean is the one on the PCM (Powertrain Control Module) which sits on the firewall, on the passenger side (5,6). The PCM is what controls the lockup clutch. There is a ground wire on it that runs to the firewall. On my truck, I did not like the amount of corrosion I saw on my PCM ground wire, so I replaced it. Made a new one with soldered eye terminals to minimize corrosion. I also sanded the firewall and PCM where the ends connect.

I had the lockup issue and it immediatly was solved after cleaning the grounds. Best of all, this fix is free!