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2002 Forester
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Discussion Starter · #1 ·
I purchased a 2002 Forester used approx 63,000 miles. At around 67,000 I had HG Issue, replaced them, timing belt, spark plugs, water pump.

I am approaching 70,000 miles, I don't know if the tranny or dif have ever been serviced. I have always heard that if transmissions have a lot of miles on them without regular service, servicing them at such a late stage can lead to issues and you're better off leaving them alone. Is that true? When I put the car in reverse in the morning, I hear and feel a clunk. After driving a few miles, it goes in reverse smoothly. Its an automatic transmission.

My second question is if I top off the coolant, i.e. a few ounces do I have to add a little of the conditioner as well?

Thanks in advance for your reply.
 

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02 Forester L (sold) Manual
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1,220 Posts
Auto trans' should be serviced regularly per the manual. The fluid has a lot of work to do in those, is subject to a lot of heat, and will break down over time. A simple fluid replacement is a good idea. The "trans flush" that is sold nowadays I'm a little more suspicious of as it may dislodge matter within the trans.

The diff fluid in the rear is pretty durable and rarely gets changed. I'd do it at 100,000 just because it's easy and inexpensive.

The coolant 'conditioner' is just a fancy form of stop-leak IMO. Can't hurt, but I'd hardly call it essential. I don't bother with it.
 

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2002 Forester
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21 Posts
Discussion Starter · #3 ·
Auto trans' should be serviced regularly per the manual. The fluid has a lot of work to do in those, is subject to a lot of heat, and will break down over time. A simple fluid replacement is a good idea. The "trans flush" that is sold nowadays I'm a little more suspicious of as it may dislodge matter within the trans.

The diff fluid in the rear is pretty durable and rarely gets changed. I'd do it at 100,000 just because it's easy and inexpensive.

The coolant 'conditioner' is just a fancy form of stop-leak IMO. Can't hurt, but I'd hardly call it essential. I don't bother with it.
Thanks for the advice!
 

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04 Forester X, MT
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1,039 Posts
You should really change the diff fluid every year or two depending on your driving style. I opt for yearly because I do some towing. It holds less than 1 qt so it shouldn't be very pricey to change.
 

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2019 Crosstrek 2018 Forester XT
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Change the differential fluid. Do a drain and fill on the Auto Ttranny (I am assuming its an auto).

If your coolant already has the conditioner in it you don't need to worry about it. If it has none than add it as per the directions (into the radiator)
 

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06 Forester
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115 Posts
Auto trans' should be serviced regularly per the manual. The fluid has a lot of work to do in those, is subject to a lot of heat, and will break down over time. A simple fluid replacement is a good idea. The "trans flush" that is sold nowadays I'm a little more suspicious of as it may dislodge matter within the trans.

The diff fluid in the rear is pretty durable and rarely gets changed. I'd do it at 100,000 just because it's easy and inexpensive.

The coolant 'conditioner' is just a fancy form of stop-leak IMO. Can't hurt, but I'd hardly call it essential. I don't bother with it.
funny you mention this as my manual says absolutely nothing about replacing any of the diff or transmission fluids.
I agree on the partial transmission fluid replacement around 60k but diffs should be left alone unless you're tracking your car.
 

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2019 Crosstrek 2018 Forester XT
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diffs should be left alone unless you're tracking your car.
I don't understand why you would not replace it. But its a free country. Do an oil analysis and you will fine huuuuuge wear numbers on old oil which acts like liquid sandpaper on the gear surface.
 

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06 Forester
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I don't understand why you would not replace it. But its a free country. Do an oil analysis and you will fine huuuuuge wear numbers on old oil which acts like liquid sandpaper on the gear surface.
how many diffs have you heard of being replaced/repaired before 100k miles. I have not heard of any, unless it was a rally car or car being abused on a daily basis.
 

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02 Forester L (sold) Manual
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Changing the diff oil certainly isn't bad, but it's not critical like engine oil. I've had countless cars with very high mileage, most have never had the diff oil changed, and have never experienced a problem that wasn't the result of drag-race style abuse. Sure, I'd change it around 100k just for peace of mind and knowing even gear oil breaks down. But every year or two? Completely unnecessary.
 
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