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Should I change my transmission fluid

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djsj13

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I have a 1999 Mercury Mountaineer 5.0 rwd that’s completely stock with 394,000 original miles that still runs and looks amazing. My dad handed it down to me and I had to do some maintenance on it especially to the suspension but now I am having a hard 1-2 shift from the trans i have checked the fluid level and it’s good the fluid isn’t bright red but has good color and does not smell burned but the last time the fluid was changed was at 75,000 miles lol my dad never changed it after that and told me that he was told not to because it would just kill the transmission so my question is should I attempt to change or flush the transmission at this mileage knowing it hasn’t been changed for so long?
 
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C420sailor

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Man, that is some great mileage. That trans owes you nothing.

If it were me...id drop the pan and check the valve body, accumulators, check balls, all that, and re-fill. You’ll lose about half of the fluid (rest is in torque converter).

If it still doesn’t shift well, or it eats itself, it has absolutely earned a rebuild.
 
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crunchie_frog

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The 1-2 hard shift can be and is often caused by a broken accumulator spring, relatively easy to replace. I would do what C420 sailor recommends above just check the accumulator spring first ha ha.
 
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410Fortune

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AGREEED broken 1-2 accumulator spring I have seen that 3 times now in 4r70w's
So the good news is you will be dropping the pan so you can access the valve body and 1-2 accumulator
When you drop the pan you will lose 4-5 quarts of fluid and you can change the filter
You can also now add a drain plug to the trans pan so you can easily change out more fluid, Dorman also makes replacement pans that come with a built in drain plug.

So basically the worry with changing transmission fluid usually comes from the flush machines, they push fluid through the transmission and they run a cleaner...the cleaner and fluid being pushed through can dislodge bits of carbon or clutch/band material that can clog small passages inside the transmission. By just dropping the pan and changing 5 quarts of fluid and a new filter the chances of harming the transmission are about nil.

With your miles I would drop pan, check 1-2 spring, there are plenty of tutorials online about how to check the 1-2 accumulator and change the spring, use a floor jack to press the accumulator cover back on....quick repair.
Then change the filter and 4-5 quarts of mercon V
drive it a couple hundred miles, drain the trans pan again (this is why you add the drain plug) and change 5 more quarts.

repeat 3-4 times over the course of a year and eventually you will have bright red fluid again.
If you have fixed the 1-2 shift change the filter again, consider adding an in line magnetic trans filter to the cooler lines up front, and also consider adding a bottle of Lube Guard transmission additive
 
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fast_dave

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@djsj13

I'm going to drop an old school thinking your way, from a guy that at one time worked in an ATRA Approved Automatic Transmission rebuild shop.

Your transmission with 394,000 miles hasn't been serviced in 319,000 Miles.

And due to that, it's more than outlived it's effective service life of a maintained transmission.

You're in the red zone and are currently running on borrowed time.

IMHO - In it's current condition, you're asking for problems once you start changing the ATF fluid.

Even going the conservative route by pan draining & "hand pouring" ATF into your transmission, the high levels of detergent in new ATF fluid can (and do) reek havoc on automatic transmissions that haven't been properly maintained.

My advice would be if you really want to keep it;

A) Get a "good" AAA account with the long distance towing.

B) Try not to drive it "hard" and not more than 60 miles from where you live (or whatever the long range tow from AAA is).

C) In the meantime save money to have the transmission rebuilt.

Follow this advice, and you'll probably score "atta boy" points with your old man AND perhaps he'll help out with point A or C ;)

Your mileage may vary; good luck & welcome to the forum!
 
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C420sailor

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I keep forgetting you can get at the 1-2 accum without dropping the valve body. Easy day
 
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JohnH55

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I have a 1999 Mercury Mountaineer 5.0 rwd that’s completely stock with 394,000 original miles that still runs and looks amazing. My dad handed it down to me and I had to do some maintenance on it especially to the suspension but now I am having a hard 1-2 shift from the trans i have checked the fluid level and it’s good the fluid isn’t bright red but has good color and does not smell burned but the last time the fluid was changed was at 75,000 miles lol my dad never changed it after that and told me that he was told not to because it would just kill the transmission so my question is should I attempt to change or flush the transmission at this mileage knowing it hasn’t been changed for so long?
If you're not afraid of getting a new transmission than sure change it and see what happens. But if you don't plan on getting a new transmission than don't change it a drive it till it goes out completely. With that milage, the clutchs and bands are definitely worn out, so fluid is not going to fix that. I went through the same thing with a 5r55e, and just decided to get a new transmission there was no hope in saving one with high mileage.
 
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410Fortune

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Not much choice here
Has to check 1-2 accumulator
so you are going to lose some fluid!
I guess you could always put the fluid you drain through a paint filter and re use it! HAHAHAHA
 
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Josh P

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If you do drop the pan and change the fluid, I wouldn't drive any farther than you are willing to walk after that.
 
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C420sailor

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You may get lucky. I’ve heard 4R70Ws don’t really burn through frictions if they are treated well and aren’t run hot. They’re pretty beefy transmissions.

If it was a 5R55E I’d say to not even bother, just rebuild it.
 
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crunchie_frog

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You may get lucky. I’ve heard 4R70Ws don’t really burn through frictions if they are treated well and aren’t run hot. They’re pretty beefy transmissions.

If it was a 5R55E I’d say to not even bother, just rebuild it.
My bet would be there is little chance that changing the fluid will cause issues, especially just dropping the pan. The 4R70W is extremely durable.
 
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collinstm57

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Just replaced my 5R55S with a reman. The O/D went out trying to pull a trailer. If it were one of the 5R55 series definitely - replace with reman.

These were a very well known weakness. Gave Explorers a bad rep.
 
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djsj13

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Just wanted to update everyone on what I decided to do. I took my mountaineer to my friends new shop because he offer to help me and since he’s a BMW master tech I thought that couldn’t hurt. We got the mountaineer up on the lift took the pan off the transmission and to our surprise the fluid was really clean and still had good color to it with no burn smell. When we inspected the pan it was really clean even the magnet had very little metal on it my friend looked at me and he said there’s no way in hell this transmission has 395,000 miles on it it looks way to clean but I reassured him that it did and that the fluid has 295,000 miles on it lol as for the harsh 1-2 shift we removes the 1-2 accumulator and the bottom spring was broken and luckily the bore where the piston goes was not scarred at all. I called all the Ford dealerships trying to locate the springs and piston but no luck. I was able to find a company locally called Transtar and he said he had all the parts so I went there and he had the piston the piston cover the upper white spring but the bottom spring he had was purple while my application calls for a pink but he reassured me that it would work and not be any issues. I picked up a motor craft filter and factory gasket to all the parts back to the shop and we installed them and put the pan back on refilled the transmission with 5 quarts of mercon v and when I drove it the shifts were perfect and the transmission feels great it even now has more response than it did before especially going into overdrive where it used to drag a little now or goes right into it with no hesitation. I know it’s to soon to celebrate because I haven’t put enough miles on it yet so I will keep everyone posted but on a positive note my friend thinks it’s going to be fine because of the cleanliness of the fluid that came out he also said that the fact the mountaineer has a huge external trans cooler and that the vehicle was never used for towing and wasn’t driven hard might be the reason for that. I do have one more question if anyone might have the answer for I’m curious about using the purple bottom spring instead of the pink I saw a chart and it said 96-98 use the purple spring and 99 use the pink spring does anyone know why Ford did that or what the difference is? I have Googled it and can’t find any info but like I said it shifts great and feels perfect when driving. Also I want to thank everyone that responded to my first post for all the helpful info
 
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C420sailor

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I took my 1-2 and 2-3 springs out for snappier shifts under WOT. Some people like it, others don’t.

Regardless, I wouldn’t worry about the spring color.

The 4R70W will tell you it needs fresh fluid by giving you that torque converter shudder around when OD engages. Mine felt like driving over rumble strips. New fluid and it was gone.
 
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djsj13

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I took my 1-2 and 2-3 springs out for snappier shifts under WOT. Some people like it, others don’t.

Regardless, I wouldn’t worry about the spring color.

The 4R70W will tell you it needs fresh fluid by giving you that torque converter shudder around when OD engages. Mine felt like driving over rumble strips. New fluid and it was gone
I took my 1-2 and 2-3 springs out for snappier shifts under WOT. Some people like it, others don’t.

Regardless, I wouldn’t worry about the spring color.

The 4R70W will tell you it needs fresh fluid by giving you that torque converter shudder around when OD engages. Mine felt like driving over rumble strips. New fluid and it was gone.
i have heard of taking out one spring but both? Now you got me curious lol so are the springs just there to take the harshness out?
 
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C420sailor

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On the 1-2 piston you remove bottom springs only. Sorry, should’ve been more clear.
 
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