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Discussion Starter #1
My brother is a mechanic who studied at NTI. He told me that the reason you don't want to change fluid in high mileage transmissions is because the new fluid deturgent will eat away at the paper clutches that alot of newer model transmissions have. Mine is an 81. Do I have to worry about this. Should I not use new fluid for other reasons? My transmission pan gasket has failed and I'm replacing. Ive captured all the old fluid via extra large tote underneath. Do I use the old or get some new. Also If detergent is my enemy will using a cheaper fluid be better as they probably use less detergent. Also also why did they not have a drain plug?
 

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because you're suppose to drain the torque converter and drop the pan to clean the magnet and possibly change the filter. If that were true to never change the fluid how do you suppose you're suppose to drive for years to come on old ancient fluid. You always replace atf every 30k miles. Walmart Supertech Dex/merc.
 

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Discussion Starter #3 (Edited)
Ok so let me begin with the fact that I don't know anything about anything but my brother was talking about transmissions that have gone 80k without a fluid change. So the fluid that came out is grayish red. Do I put it back in or go with new? Also let me add that I never assume previous owner changed fluid when they were supposed to.
 

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A transmission is also composed of bearings, gears, valves, and other components that will last longer with new fluid. I used a Valvoline ATF that was backward compatible with Dexron II, which is what the manual said.
 

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the theory to which i subscribe regarding old fluid and fluid changes is that you do risk killing your transmission by doing a complete drain / refill. the reason is that old trans fluid stops carrying around the particles and debris and instead the debris will settle throughout the transmission. when you do a complete drain / refill the new trans fluid will grab those particles and start carrying them around again. and that will cause the transmission to fail.

the solution to this would be to pump out a few quarts of old fluid and do a partial refill. then after driving for a few hundred miles, do a complete drain / refill.

i have no documented evidence to support it. it's just one of those things i heard that make sense and i don't really know, so i'm inclined to believe it. YMMV
 

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85 Bronco, 309ci I6 w/4bbl, np435, 4" lift, 37" Irok NDs, 4.56 w/ Detroit Locker and tru trac
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Use new.

There are now newer transmissions out that are "sealed for life" meaning theres nowhere to easily add fluid or remove it. If it gets rebuilt, thats when new fluid is added.

My 96 C6 trans developed a hole and started puking fluid out. I was adding a gallon every week or so. The only time I would have issues was when i was running low on fluid. Fill er up, and she was good as new. That was with 160k miles on it.
 
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95 Bronco, 351W, E4OD, 4.56 gears, 35x12.50x15 Patagonia MTs. 94 Bronco 5.0/E4OD/1356/3.50 gears.
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As someone that's changed a lot of fluids, I reccomend changing the fluid. The additives oxidize and degrade with age, not to mention the detergents being utilized by debris. If you are afraid of the debris in the transmission, a remote filter may be a good addition? I don't run one, but I might if I have my transmission rebuilt.

I change my transmission fluid as soon as possible after aquiring a used vehicle.
 

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the theory to which i subscribe regarding old fluid and fluid changes is that you do risk killing your transmission by doing a complete drain / refill. the reason is that old trans fluid stops carrying around the particles and debris and instead the debris will settle throughout the transmission. when you do a complete drain / refill the new trans fluid will grab those particles and start carrying them around again. and that will cause the transmission to fail.

the solution to this would be to pump out a few quarts of old fluid and do a partial refill. then after driving for a few hundred miles, do a complete drain / refill.

i have no documented evidence to support it. it's just one of those things i heard that make sense and i don't really know, so i'm inclined to believe it. YMMV
I agree, killed my last transmission like that


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I agree, killed my last transmission like that


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No it didn't. Your transmission was already dead.


The only way changing transmission fluid will make a transmission stop working is if it was so worn that clutch material in the fluid is the only thing holding it together. At this point the clutches are shot and it's days are numbered anyway. I have a 05 Trailblazer that had one fluid change at 133k. At 220k I put in an aux trans cooler and filter. keep in mind this vehicle was used for towing and not babied. Not long after it stopped wanting to lock the TC. So I replaced a few quarts of the old fluid for new. And you know what happened? It got quieter, and the TC started locking again.

There's a few checks I do on old transmissions, If they pass I change the fluid. First Check the fluid, if there is significant clutch material or ANY metal (gold or brass) leave it alone and save for a new trans. Next, the operation test. If it has ANY slipping or shift flare leave it, the clutches are already worn. Find an empty road and floor it. Keep your foot in it. The engine should wind out before grabbing the next gear. Hard shifts or even a slam is good, it means the clutches are still grabbing hard. If RPM flares between shifts, or it slips at all leave it alone, as the clutches are already worn.

The Trailblazer despite having insane mileage on ancient fluid never had any operational problems, and even when held WFO with a loaded trailer never slipped. The fluid was dark but free of suspended particles so I was confident in changing the fluid.
 

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No it didn't. Your transmission was already dead.


The only way changing transmission fluid will make a transmission stop working is if it was so worn that clutch material in the fluid is the only thing holding it together. At this point the clutches are shot and it's days are numbered anyway. I have a 05 Trailblazer that had one fluid change at 133k. At 220k I put in an aux trans cooler and filter. keep in mind this vehicle was used for towing and not babied. Not long after it stopped wanting to lock the TC. So I replaced a few quarts of the old fluid for new. And you know what happened? It got quieter, and the TC started locking again.

There's a few checks I do on old transmissions, If they pass I change the fluid. First Check the fluid, if there is significant clutch material or ANY metal (gold or brass) leave it alone and save for a new trans. Next, the operation test. If it has ANY slipping or shift flare leave it, the clutches are already worn. Find an empty road and floor it. Keep your foot in it. The engine should wind out before grabbing the next gear. Hard shifts or even a slam is good, it means the clutches are still grabbing hard. If RPM flares between shifts, or it slips at all leave it alone, as the clutches are already worn.

The Trailblazer despite having insane mileage on ancient fluid never had any operational problems, and even when held WFO with a loaded trailer never slipped. The fluid was dark but free of suspended particles so I was confident in changing the fluid.
I disagree, had 60'000 km's on it. Japanese transmissions don't die at 45k miles.


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I disagree, had 60'000 km's on it. Japanese transmissions don't die at 45k miles.


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Changing the fluid on a 45k mile transmission won't kill it. Normal change is 30k, with synthetic 50-60k easy. Either you used the wrong fluid or there was an existing problem with the transmission. What kind of vehicle?
 

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Changing the fluid on a 45k mile transmission won't kill it. Normal change is 30k, with synthetic 50-60k easy. Either you used the wrong fluid or there was an existing problem with the transmission. What kind of vehicle?
Used the right kind and it was a 2006 mazda 3. Died 2 years ago when driving back up north


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2006 mazda 3.
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There's your problem. I have a CX-7 sitting in my driveway that ate a trans at 124k.


Ok not the same trans but mazdas of this era that weren't a basic rebadge of a ford cars seem to have tons of problems. And I'm bitter. Stupid POS.
 

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I have an '02 Ram 1500 that has a 210k. The trans fluid is supposed to be changed every 100k miles, according to manufacturer-stated intervals. When I bought this truck, the service records didn't indicate when the trans fluid was last changed (if at all), so I don't know if it has 110k on the fluid, or 210k. However, because it's so old, I have opted to ride it out until it dies. I have no current issues with the trans. There are tons of speculations on why changing very old fluid will contribute to a trans failure and all of them seem to have valid points. Bottom line: it can happen and usually does. However, my BKO has a fresh AOD and I do a fluid flush, regularly, at 25-30k. Complete system purge and refill. If you change your fluid regularly and don't beat the hell out of your trans internals with towing/hauling/temp-cycling, "budget" fluid is of no concern. You will be changing it out long before the fluid's "break-down" point.

My opinion: If you absolutely need your vehicle for a DD, your budget's tight, and it's not showing any signs of trans issues, don't touch old fluid. If your vehicle is not a DD, or a new trans is within your current budget, go ahead and change the fluid. Best-case scenario: you have successfully changed the fluid/filter and probably extended the life of the tranny. Worst-case: you smoke the trans (which probably needed to be rebuilt anyways) and have to source/build a new one.

Just my $0.02.
 
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You can make an educated guess on the condition of your trans and go from there. The only reason new fluid will cause harm is if the clutches are worn out and the trans is being held together by suspended clutch material in the fluid, which is pretty easy to spot by checking the fluid after it's been running. I had an 04 I got at 144k and had no service history on. I changed it and it was fine for the next 10k before it spun a bearing, I dropped in a new engine and sold that POS. Dodge is known for weak transmissions, but the good thing about the 454rfe is that it has not only a regular trans filter but a spin on filter in the pan.

When I dropped mine the fluid was as clean as on my other vehicles with auxiliary spin on filters. Personally unless I spot red flags of an issue or the car is literally scrapyard bound in a year or two I always opt to change the trans fluid. The reason why is simple. IME things tend to fail at the worst possible time. Provided theres not excessive clutch material or metal in the fluid, there's a low chance of making anything worse, and if it does, well it failed in the driveway vs out on the road somewhere randomly.
I can tell you the trailblazer was much happier once it got some new fluid mixed in.

Side note. You may notice that cheaper fluid comes out dark. black, or lacking color when it's used. This is really no concern. Transmission fluid isn't naturally red, it's dyed red for identification purposes. Cheaper fluids are often light on this dye to save costs, so they are more likely to turn dark or lose their color. More important is lubricity and viscosity.

Another side note. worn clutches is why those magical stop slip additives don't work. All those additives do is thicken the fluid, which fills in loose tolerances and makes the pressures higher. Sometimes the higher pressures will allow the worn out clutches to grab again. It's only a band aid though, once the clutches are worn out the only way to fix it is to replace them. And those additives will often cause other problems even if they make the clutches grab a little longer. Only use them in a trans that's going to the scrapyard, don't expect to rebuild it later.
 

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Discussion Starter #17
Update. During the removal of the pan I miscalculated the weight of the pan and took a fluid bath. So about 3 quarts of oil gone right their. Also while I was putting the pan gasket back on i realized two bolts weren't torquing down, they just kept spinning. So 200 dollars later and 2 new heli coils my transmission in back together. funny thing is it no longer has morning sickness. So i ended up taking some of yalls advice and putting some new and old back in. and ill just keep cycling until it looks good or i get it rebuilt. Thanks guys!
 
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So I take it you had someone helicoil the pan bolts? For the future you can do them yourself at home. Kits for a specific size are cheap and easy.

I just swapped another 4 quarts in the trailblazer. last one for a while, it's going to Tennesse on the 23rd. I'll swap the aux trans filter before then as well.
In your case I believe you should have a TC drain. If so I'd cycle some new fluid though it a bit then just dump and change it all provided no issues come up. I would to that on the TB but it lacks a TC drain.
 
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