4x4Wire's TrailTalk Forums: Automatic transmission: Hot A/T problem-solving, and changing fluid & filter

Well, after months of experiencing overheating problems on my '89 A/T I seem to have found the solution and have come up with a working theory as to why this problem has been plaguing the operation of my vehicle on the highway.

Symptoms:
A/T Temp light repeatedly lit up while traveling at normal highway speeds in 4th gear (O/D on). There was no specific interval for this occurance, but it began to occur more frequently over a period of months. Occasionally, fluid would boil-over through the breather plug. Turning the O/D off and driving in 3rd gear would prevent the problem happening. There was also some lost power which was not immediately apparent due to the length of time it took for the problem to develop and other engine troubles.

Background:
This is a 4-gear non-lockup Automatic Transmission on an '89 Dodge Raider.
It was winter of 2002 the last time I had my transmission filter changed out by a transmission shop. Last Fall, I had a local transmission shop flush out my old ATF and replace it with Mobil 1 fully synthetic ATF. Expensive to say the least. I call it the "Keith Richards" treatement.

Until last Fall, I'd never had my A/T Temp light come on. Then, one day while driving through a headwind strong enough to fold my mirrors back and a tow strap tied around the front of my bumper, the A/T light went on. It would seem like that was an isolated event due to the conditions I described.
After the first few events, I did an ATF drain & fill in hopes that it might remedy the problem. No luck.
Earlier this year the A/T Temp light began popping on more and more frequently during long trips until finall it got to the point where I could only operate in 3rd gear at highways speeds to keep from overheating. Obviously, this was not a cost-effective/fuel-efficient means of travel. Luckily, the Mobil 1 ATF isn't as prone to breaking down as normal ATFs might be; it was not burned or discolored even after many overheating episodes.

After the last incident of it happening, I decided that I'd crack open the pan and have a look at the filter screen...

Once I got the pan off, I removed the bolts holding the screen to the valve body and popped it off. I was startled when about 1/4 of a quart more ATF spilled out. I hadn't expected that to happen so I got ATF everywhere. It was a mess.

Theory:
As it turns out, the flush & fill combined with the extra detergency of the new synthetic ATF must have washed out some deposits throughout the system. After a period of few months, these micro-fine particles eventually filled the pores in the filter screen making it difficult for fluid to pass through the mesh. With less fluid being able to flow at higher speeds and higher temperatures, fluid was not able to pass through the cooler at a normal rate. This is what led to the overheating.

The debris in the filter screen was not immediately apparent until I wiped a shop towel over a section and it became black.

I did a comparison between the old filter and new filter by pouring some used ATF on each filter screen using a turkey baster. The new filter allowed fluid to pass through while the old filter just let most of the fluid run off the sides. A subsequent test drive at highways speeds led to no overheating.

Anyways, problem solved: the Raider's runnin' well again. Hope this helps someone out someday. Happy driving!

-DougB

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LOST ARK
'89 Raider 3.0L V6 (6G72) w/ AW372L (A44DL) A/T
"The Millennium Falcon of automobiles"

Edited by PHIL (07/16/04 05:36 PM)

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