Don't change trans fluid?


Big-Al

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Had my mechanic tell me not to change my trans fluid in my 06 jeep with an automatic transmission because it's old trans fluid and a new trans-fluid most likely hurt the transmission.

Has anyone ever heard this before?

I will admit the trans fluid is past due. But it doesn't look or smell burnt. But how can new fluid cause harm?
 

MountaineerTom

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Had my mechanic tell me not to change my trans fluid in my 06 jeep with an automatic transmission because it's old trans fluid and a new trans-fluid most likely hurt the transmission.

Has anyone ever heard this before?

I will admit the trans fluid is past due. But it doesn't look or smell burnt. But how can new fluid cause harm?
I've heard it, but it's not true.
 
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Big-Al

Big-Al

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That's what I was thinking. I was planning on doing it myself this weekend. But I was told that this and I had to take a double look at the guy.
 

AjRagno

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I’m 255,000 on the 42RLE in my ‘05 LJ.

The original owner had the transmission dealer-serviced at 30,000 and 60,000 miles. I bought the Jeep with 76,000 miles and at 90,000 miles I dropped the pan, added a drain plug and replaced 5.5 qts of ATF+4. Since then I’ve generally alternated every 15,000 miles between draining the pan only or also replacing the filter.

My advice would be to buy the Dorman pan with a drain plug and replace the filter and whatever amount of ATF+4 drains at least every 30,000 miles.


Alternatively, you can replace the transmission roughly every 100,000 miles. Whatever works best for you.
 
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Badgerbiter

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Someone at NAPA recommended ATF 4 for my 2000 TJ. I read the opinion on this forum and switched to 4+. Immediate change in performance. No question better shifting and power to the wheels. Good information!
 

dcoop

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I had a Tranny go out, it was a 700r4. Was working fine. I was going to have flushed with the machine. My buddy told me to just change filter and replace whatever drains out cause the machine applies more pressue to flush than the tranny pump. I don't know if its true, But I did it anyway within a week it started not wanting to shift through the gears. Maybe a coincidence.
 

AndyG

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If anything actually happens, my friend who has owned several transmission shops say it is this: the high detergent concentration of all new fluid cleans plates that have varnished and the stiction of the varnish was actually working for the good of the transmission.

He contends its safer on high mileage trannys to do only the pan and fluid that comes out if it all hasnt been flushed regularly over time.

He won’t do a full flush on any transmission of questionable mileage.

He is an aircraft mechanic by trade and pretty sharp..... but this is me repeating his view, not a hard fact.

At the same time, it is hard to see how something getting cleaned and serviced can be bad.
 
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bromel

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There is a grain of truth to that theory. If your old fluid is so dirty, and your transmission is truly on its last legs, the old fluid will provide some friction for the clutch packs in the transmission to avoid slipping. Drain and add new fluid, and it may accelerate the decline and start slipping.

However, if your transmission has gotten to the point where old fluid is keeping it together, it's only got a few thousand miles left most likely. If you need to get another winter out of the old girl before a rebuild, maybe skip the fluid change. Otherwise I'd change it and if it begins to slip, well, you know you had to rebuild it anyway.
 
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JMT

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BugoutJeep

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First thing. Change your Auto fluid at least on time. We just ran into this with my wife's Tacoma, that it really looks like Toyota has been lying about their service intervals for their transmissions according to the spec sheet for the recommended fluid at the actual operating temperatures (which they hide in programming stuff along with the fluid level). Anyway, my point is that if these fluids breakdown they can cause malfunction in the transmission and possibly damage. The wife's Tacoma probably has slight damage to the shifting valves even though we changed the fluid before it was recommended, but not until after there was some minor damage to a shifter valve, which has a workaround for, but it's still kind of annoying.

Can you all actually find ATF+4? I have been searching locally and found a couple quarts at Walmart, not for this transmission but other Dodge stuff.
 

Jerry Bransford

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There is a grain of truth to that theory. If your old fluid is so dirty, and your transmission is truly on its last legs, the old fluid will provide some friction for the clutch packs in the transmission to avoid slipping. Drain and add new fluid, and it may accelerate the decline and start slipping.
Of course, which is another way of saying the transmission was on its last legs and about to fail anyway.
 
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