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Car started shifting a bit hard or slipping do I need to flush, drain/replace or leave alone

Tiny
KIWASABI1
  • MEMBER
  • 2001 MITSUBISHI ECLIPSE
  • 2.4L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 208,000 MILES
Hey 2CarPros,

I have about 208,000 miles on my vehicle listed above, and I have flushed the automatic transmission exactly once. I estimate about 10 years and 80,000 miles ago. I've attached a picture of what it looks like now. There's a tiny bit of black carbon from the bottom of the dipstick, otherwise it's a little dark but still quite reddish, not totally burned by any means. My car has started shifting a bit hard or slipping a bit when going from 3rd to 4th gear (I think) around 40 mph or so. I noticed the dipstick reads at just above (or at) the lower hot line when warmed up. What would you recommend I do at this time? Topping it up to halfway between the bottom and top hot lines and seeing if there's any change in symptoms seems logical. What about using a product like Stop Slip in lieu of normal transmission fluid?

Technically I'm definitely due for a transmission flush. But I've heard that can actually make the problem worse on high mileage vehicles. Although it sounds like that's mostly if the fluid is burnt and full of metal shavings. Please advise on whether it's best to flush, drain/fill (which only replaces about half the fluid I've heard), or just top it up and leave it alone for now. Personally I don't like the idea of driving it as is until the transmission stops working.
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Tuesday, May 26th, 2020 AT 1:40 PM

20 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good afternoon,

I would not flush it at all. I would just change the fluid and filter. That is required to do to keep it working correctly

https://www.2carpros.com/articles/how-to-service-an-automatic-transmission

The flushing agents are too aggressive and can damage the clutches.

Roy

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Tuesday, May 26th, 2020 AT 2:54 PM
Tiny
KIWASABI1
  • MEMBER
  • 197 POSTS
So basically the fluid looks safe to change since it's not totally burned? And if it was completely black, would you leave it alone at that point? Some mechanics were saying you shouldn't even do the drain/fill at high mileage since the fluid is thick from old age and may be the only thing allowing the transmission to properly grip. What type of fluid should I get for my vehicle, and how much will I need? It looks like a gasket and filter will be needed as well.
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Tuesday, May 26th, 2020 AT 3:03 PM
Tiny
KIWASABI1
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  • 197 POSTS
Found the capacity and type in the manual:
Capacity (2.4L engine automatic transmission): 8.1 quarts
Type: Diamond ATF SP III or Diamond ATF SP II M

I was thinking of getting OEM for the fluid at least just to be safe. So with a drain and fill I've heard it only drains about half the fluid, so it would probably need about 4 quarts?
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Tuesday, May 26th, 2020 AT 3:28 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Okay, you never tell anyone not to change there fluid. They are telling you that just wait until it fails. That is like saying you have chest pains but do not worry about it until you pass out.

You can use the fluid from the parts store. Just make sure it has the designations for the fluids.

Roy
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Tuesday, May 26th, 2020 AT 3:33 PM
Tiny
KIWASABI1
  • MEMBER
  • 197 POSTS
Is there a heavier weight to either Diamond ATF SP III or Diamond ATF SP II M? Or one to get over the other when high mileage?
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Tuesday, May 26th, 2020 AT 3:41 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
No, do not use other than what is recommended. If you use heavier oil then it may damaged the front pump from making it work too hard.

It is already worn and if you do that, it may cause the pump to fail.

Roy
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Tuesday, May 26th, 2020 AT 3:53 PM
Tiny
KIWASABI1
  • MEMBER
  • 197 POSTS
I just talked to my local Mitsubishi dealership service department. The service manager said that when you have an existing problem (which I do), changing the fluid is 50/50 either going to make it worse or make it better. He said that the higher oil pressure of the new fluid is what causes existing problems to get worse.
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Tuesday, May 26th, 2020 AT 4:15 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Just what I told you.

Change the fluid and filter and use the correct oil.

Roy
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Tuesday, May 26th, 2020 AT 4:29 PM
Tiny
KIWASABI1
  • MEMBER
  • 197 POSTS
I had a free inspection done by a well reviewed transmission shop. They told me there's nothing wrong with the transmission, and had me do a transmission fluid drain/fill (not a flush). They found an old code for my throttle position sensor stored since before I replaced that with an OEM one, and said they thought that was causing the hard shift/sliding between 3rd/4th. Hopefully that issue will sort itself out between the fluid change and computer relearning the new TPS and when to shift (although should have happened by now, maybe I will try resetting the computer again as I'm not sure if the mechanic who swapped me TPS ever did, the computer could still be running off some flawed data of the old TPS).
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Friday, May 29th, 2020 AT 7:19 PM
Tiny
ASEMASTER6371
  • MECHANIC
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Okay. No, the TPS has nothing to do with slipping between gears. The TPS only sends a signal to the ECM for proper shift points only.

There is no resetting for a new TPS. Live data is what the ECM sees all the time whether it is the old one or new one.

Roy
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Saturday, May 30th, 2020 AT 4:25 AM
Tiny
KIWASABI1
  • MEMBER
  • 197 POSTS
Thanks for clarifying Roy. Based on what you said, the faulty old TPS could have caused shifting issues though by providing incorrect shift points? But not the new (well used but tested working) properly functioning one.

I'll see if the drain and fill fixed the issue then and report back in a few days or week.
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Saturday, May 30th, 2020 AT 1:54 PM
Tiny
ASEMASTER6371
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You are welcome.

Always glad to help.

Roy
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Saturday, May 30th, 2020 AT 1:59 PM
Tiny
KIWASABI1
  • MEMBER
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Based on what you said, the faulty old TPS could have caused shifting issues though by providing incorrect shift points? But not the new (well used but tested working) properly functioning one.
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Saturday, May 30th, 2020 AT 2:01 PM
Tiny
ASEMASTER6371
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Did you verify the signal voltage?

Roy
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Saturday, May 30th, 2020 AT 2:05 PM
Tiny
KIWASABI1
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We calibrated the new one to.58 (the acceptable range is.535-.735). The guy who sold it to me said he tested it first with a multi-meter. Mostly I've just tested it by driving it, which it has been perfect. The old one was getting all kinds of dead zones when I tested that one which corresponded to the bucking acceleration.

Anyway, I've got an ELM OBD2 Bluetooth scanner. For whatever reason I can't get the TPS voltage off of it, but I can get the throttle open % and see the graph. So I can verify no dead zones that way. So I'll double check that as well.
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Saturday, May 30th, 2020 AT 2:09 PM
Tiny
ASEMASTER6371
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You need to back probe the signal wire and check the voltage sweep.

I am looking for actual voltages and not concerned about the TPS itself to see if it a wiring issue.

Roy
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Saturday, May 30th, 2020 AT 2:22 PM
Tiny
ASEMASTER6371
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I attached the diagram again for the TPS. Monitor the yellow wire with the key on. Then go from 0 to 5 volts.

Roy
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Saturday, May 30th, 2020 AT 2:28 PM
Tiny
KIWASABI1
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Alright I'll get that done. I will say that the TPS voltage itself is not holding completely steady when the car is running, but it is when it's stopped. So when it's running and idling it bounces between.58 and.60. Now this is an improvement compared to the last one I had, which was bouncing between.60 and.725 or so. I was going to attach an extra ground wire to the TPS to see if that fixed this. I was instructed to just leave it alone though since the car was functioning properly. But now I'm reconsidering it.

Anyway I know you're talking about testing the wiring connector, not the TPS itself. So I'll have my mechanic check that for me and re-evaluate adding an extra ground wire.
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Saturday, May 30th, 2020 AT 2:28 PM
Tiny
KIWASABI1
  • MEMBER
  • 197 POSTS
Oh I see, so you're talking about the TPS voltage. Okay, yeah my mechanic's scan tool is capable of displaying live TPS voltage, but mine isn't. So I'll check that out. Basically we're just checking for dead zones right?
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Saturday, May 30th, 2020 AT 2:29 PM
Tiny
ASEMASTER6371
  • MECHANIC
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Yes, you need a voltmeter to do it manually.

You are looking for a clean sweep of the voltage from idle to wide open throttle with the key on, engine off.

Roy
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Sunday, May 31st, 2020 AT 12:34 PM

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