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Reusing Mercon V fluid?

Havfun

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I have a 2010 Explorer EB V6 with 5R55S transmission. Mercon V in transmission that was replaced not long ago. Would it be acceptable to carefully drain the pan fluid into a clean bucket, lid the bucket (but not air tight lid) and then replace the fluid 2-days later? I've heard that newer low viscosity fluids should not be reused but I'm a little unclear if this would work out with Mercon V.
 


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Littleant

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Havfun are you doing repairs on the transmission??. I would add new fluid about 4-5 qt. The reason I say that because crap can happen, some thing gets into the bucket then ends up in the trans.
 




94Eddie

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I would replace the fluid. It is cheap insurance to possibly prevent a costly major transmission issue.
 




JK080

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You would probably be fine reusing the fluid but I would replace it with new fluid at this point.
 




BKennedy

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I did that once when I had a pan leak right after I changed the fluid. I was also using Mobile 1 ATF at the time so it was $14 a quart. I bought a new drain pan with a lid just for that. Now I just buy a gallon of whatever type ATF the car takes and change it, no matter how long its been. There are so many ways for that fluid to get contaminated while sitting in a bucket.
 




Havfun

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Thanks, folks, for the advice. I’ve already reused the fluid. Here’s the details. At a 140k miles with all working fine I did a complete transmission fluid change (DIY flush type). I dropped the pan which looked perfect, replaced the filter, filled the pan, ran the engine till a few quarts came out of the cooler lines, added more to the pan, drain, fill until the fluid coming out of the cooler lines looked like new fluid. It took 17 quarts of new Mercon V to complete the job. The trans felt like new which it also felt like before I did the DIY flush. So, this was for maintenance only.

Then, with about 11k miles on the new fluid I got a wrench of death which I diagnosed as a bad solenoid pack. I replaced the pack with a rebuilt unit. Since the fluid was almost new, I recaptured it into a clean bucket with a lid (not an air tight lid, just to keep debris from falling in). It probably sat around like that for a day. The rebuilt solenoid pack turned out to be defective and the car had some serious harsh shifting problem, worse than the original pack but no wrench of death. Got another pack this time from the dealer, and repeated the job the same way, reusing the fluid as explained. This pack worked fine and the trans was back to feeling like new. You can find all the details of the solenoid pack job here if you want details:
Wrench (of death), harsh shifting, P0798, P0968

Now with about 12k additional miles since the solenoid pack was replaced, it has developed a new issue. To recap, total miles are 163k with about 23k miles on the fluid which had about 5 quarts drained and reused twice. I should mention that this model has a tow package that includes a trans cooler and we don’t do any towing. Trans temperatures are very well controlled which usually means long fluid life.

The new issue started maybe 2-3 months ago. The car is driven about 250 miles per week. Maybe once a week or so it shows a slightly harsh shift. Not so harsh that I think it could damage anything, even with use, but not quite normal for this car either. My wife is the primary driver so I’ve only experienced this 2 or 3 times total. I’ve felt it at slower speeds like 25-40 mph and I’m sorry to say that it hasn’t happened enough for me to say whether its during an up or downshift or what gear. My wife confirms that she feels it about once per week so this is not a real serious problem (yet). So far it doesn’t seem to be getting worse or changing and the car feels great aside from this.

I don’t want to change the fluid unless it really should be done in order to solve this problem or there is reason to get rid of the reused fluid. I’m not even sure I should worry about it until it gets worse but I thought I’d check in and see what others think about it.
  • Any suggestions?
  • Is the reused fluid likely to cause this kind of problem?
  • If not, what should I be looking at to solve the problem?
Thanks for any help.
 




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