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When should I change the transmission and transfer case fluids?

GaTechTJ

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In the 2000/2001 service manual I downloaded from this board, it doesn't list changing the transmission fluid in a manual transmission in the Maintenance Schedules.

It says to drain and refill the fluid in an automatic transmission every 37,000 miles.

Once a month it says to check the fluid level of the transmission and add as needed.
 

Sancho

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An old wive's tale and bad rumor.
You bring up a good point on the old/failing transmissions.

My 1st grade understanding is.... the old transmissions have leaks, worn out clutch packs, and what-nots that screw up the pressure needed for the auto shifting. The dirt and particulate help clog/seal those old leaks.


I dont know if it is true or not... but there is some logic behind it.

Any evidence or experience as to why it is a wives-tale?
 
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CMBD

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I understand that the OP is seeking guidance on a manual transmission. And I work really hard to be a good positive person. Like if there is nothing nice to say I struggle not to say it. But sometimes not speaking my mind makes me grumpy, but the me being good here is not quoting all the absolute garbage reasons to not service your auto trans in this thread.

I have a degree in automotive/diesel/automatic transmission repair and was a Ford factory trained auto trans tech and level 1 Master Tech for nearly the entire 1990s... for f*cks sake baby Jesus on a f*cking pogo stick the people who keep the "don't service your auto trans because..." nonsense alive should be hunted down and repeatedly punched in the 🍆 until they stop posting it or can no longer reproduce.

There. I said it😁
 

Big Dan

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You bring up a good point on the old/failing transmissions.

My 1st grade understanding is.... the old transmissions have leaks, worn out clutch packs, and what-nots that screw up the pressure needed for the auto shifting. The dirt and particulate help clog/seal those old leaks.


I dont know if it is true or not... but there is some logic behind it.

Any evidence or experience as to why it is a wives-tale?

Thats the thought process. The auto transmission is already on death's bed and the crap in the tranny is the only thing keeping it shifting for a little bit longer. A good condition transmission won't have a problem with a fluid change.

Separately (for others), as already mentioned, a transaxle is the transmission and axle connected together as found on transverse engine, front wheel drive vehicles.
 
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txbemis69

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I just had my Jeep transmission rebuilt. The guy has built hundreds of transmissions. He swears up and down to not change the transmission fluid.

I had my Duramax in for maintenance and asked the mechanic about it. He said now all they do is change the external filter and top it off.
I don't know enough to argue about it one way or the other. I will try to share his position. Most everyone here is going to know the mechanics of a transmission better than me.

He says the friction material on the bands wears off and becomes suspended in the ATF. If the material is off the bands and no longer in the fluid then the trans will not function as it should.

Apart from the trans mechanic, a high school friend of mine worked rebuilding transmissions since he was a kid, and retired doing it, recommended adding friction modifier to ATF.

I admit, not changing the ATF goes against everything I have been told.

the guy i bought my jeep from (used jeep dealer) said to never change the fluid in my 42rle transmission. said it would screw it up. a year later the transmission front seal started leaking so i had seal replaced and told transmission guy what i was told about never changing fluid. transmission guy called bull shit and recommended regular maintenance of transmission.
 

eastbloc

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I tend to do few things at once, this way i know it gets done and i don't have to keep up with every single thing separately.
5000: engine oil and tire rotation
15000 : both axles and transmission
greasing ball joints and driveshafts is done during one of the two
 
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pagrey

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Personally I'd change the fluid in the transmission and the transfer case once so I had a solid baseline. Beyond that if you don't really use your Jeep hard you can ignore those probably for a long time after you have known good fluid. A little like @eastbloc says engine oil and axles are more important, don't let those get away from a regular schedule. Don't forget brake fluid and power steering fluid while you are pondering those precious fluids.
 
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MikekiM

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True. And to clear up one thing that might have been said just out of habit, our Wranglers don't have transaxles like my old 1966 VW beetle did. I.E. a transaxle has the transmission and axle combined together which isn't the case with any of our Wranglers. :)

My bad on the use of the term transaxle.. I know better. Though not by much.

The thought a mechanic recommending not changing any fluid…. Self serving me thinks.

I just did the diff’s and the transfer case and transmission are the only fluids I am unsure of. Could be 5k or 50k. I would rather change both and have a baseline and peace of mind.
 
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BlueC

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In the 2000/2001 service manual I downloaded from this board, it doesn't list changing the transmission fluid in a manual transmission in the Maintenance Schedules.

I change my manual trans fluid(s) every 50,000, and that's with any/every vehicle. I base that off of a conglomerate of factory service schedules. I've seen Honda say every 90K, Ford say "lubed-for-life" (BS), Dodge I think I've seen 30K and 60K intervals for trucks. Much of this depends on vehicle type and usage, i.e. heavy and/or towing. Also, like my other service intervals, a nice round number like 50,000 is easy to spot on the odometer.
 

cpwolf

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I understand that the OP is seeking guidance on a manual transmission. And I work really hard to be a good positive person. Like if there is nothing nice to say I struggle not to say it. But sometimes not speaking my mind makes me grumpy, but the me being good here is not quoting all the absolute garbage reasons to not service your auto trans in this thread.

I have a degree in automotive/diesel/automatic transmission repair and was a Ford factory trained auto trans tech and level 1 Master Tech for nearly the entire 1990s... for f*cks sake baby Jesus on a f*cking pogo stick the people who keep the "don't service your auto trans because..." nonsense alive should be hunted down and repeatedly punched in the 🍆 until they stop posting it or can no longer reproduce.

There. I said it😁

Thank you! My brother was an AIr Force C130 mechanic, then lead tech at Off Road Unlimited in Houston for a long time, hard Guy as well.

This is one of the things that makes him crazy. Seriously, people think floating material/whatever in the Transmission is a good thing? It blows my mind.

I’m not sure any fluid is a forever in a vehicle, that I know of.
 
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MikekiM

MikekiM

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I understand that the OP is seeking guidance on a manual transmission. And I work really hard to be a good positive person. Like if there is nothing nice to say I struggle not to say it. But sometimes not speaking my mind makes me grumpy, but the me being good here is not quoting all the absolute garbage reasons to not service your auto trans in this thread.

I have a degree in automotive/diesel/automatic transmission repair and was a Ford factory trained auto trans tech and level 1 Master Tech for nearly the entire 1990s... for f*cks sake baby Jesus on a f*cking pogo stick the people who keep the "don't service your auto trans because..." nonsense alive should be hunted down and repeatedly punched in the 🍆 until they stop posting it or can no longer reproduce.

There. I said it😁

No further responses needed.
download.jpeg
 
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BlueC

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I’m not sure any fluid is a forever in a vehicle, that I know of.

Due to the cleaning nature of various vehicle fluids, I don't see how any could be "forever" or even "lifetime" as I've seen suggested in some Ford service schedules.
 

rouxbicon

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Due to the cleaning nature of various vehicle fluids, I don't see how any could be "forever" or even "lifetime" as I've seen suggested in some Ford service schedules.

I think most vehicle manufacturers (at least the US big three) consider modern manual trannys and diffs to be lifetime lubed. The owner's manuals for our TJs make no mention of changing the manual tranny fluid, and specify 12000 miles for the diffs only if we tow or offroad frequently.

On the flip side, a vehicle's "lifetime" means different things to different people. Participating in this forum suggests that we're driving vehicles 16-26 years old, which is past what many people would consider a vehicle's lifetime. I for sure wouldn't want to still be running any of the 20-yr old original fluids in my TJ.

Except I suppose the clutch hydraulics, which are still original...
 

BlueC

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On the flip side, a vehicle's "lifetime" means different things to different people. Participating in this forum suggests that we're driving vehicles 16-26 years old, which is past what many people would consider a vehicle's lifetime. I for sure wouldn't want to still be running any of the 20-yr old original fluids in my TJ.

The definition of "lifetime" is key. The last Ford I had (late '90s vehicle) specified that differentials were "lubed for life", but the factory maintenance schedule ended at 120K, so that indicated to me that Ford designated the lifetime of the vehicle to be around 120K. When I sold it, it had 245K on it, so more than double the factory schedule or expected "lifetime", with all major parts being original and in good condition. I changed the gear oils on 50K intervals in that one.

I disregard any suggestions of "lifetime" fluids.