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2014 Chevy Silverado 3500 HD, LML 6.6L Duramax
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Discussion Starter · #1 ·
2014 chevy silverado 3500 HD 6.6L Duramax / 6 speed Allison...

While getting some brake work done, I was thinking of having the transmission flushed. But the mechanic told me that if it's never been done before, I could have a blown transmission within a week. I guess a flush would clean all the goop out and unplug any small cracks in gaskets and seals. Anyone have advice on how I should proceed? Looking to get the service records from the previous owner. You think a basic fluid change should be fine without doing a flush?

Thank you
 

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How many miles on the fluid? If fluid miles are not known, truck miles?
 

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Simple drain and fill is the safest, and all that is needed. Unless things have changed, Allison always recommended drain and fill. If that's not enough to make you satisfied, drain, fill, drive for a short while (or a long while), then drain and fill again.

Don't overfill. At 170*F the proper level is about 1/4th of the way up into the "hot" hash area on the dip stick. Many of us use a TES-295 rated ATF.
 
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Discussion Starter · #5 ·
Simple drain and fill is the safest, and all that is needed. Unless things have changed, Allison always recommended drain and fill. If that's not enough to make you satisfied, drain, fill, drive for a short while (or a long while), then drain and fill again.

Don't overfill. At 170*F the proper level is about 1/4th of the way up into the "hot" hash area on the dip stick. Many of us use a TES-295 rated ATF.
Thanks, that's really good information...
 

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Now would be the perfect time to switch to Transynd or any other TES-295 fluid as recommended by Allison for your transmission. A list of those approved fluids is here: The Mobile Delvac 1 is a popular choice.


Since you just got teh truck this thread may be of some interest to you as well:

 

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Allison doesn't recommend a full flush.
 
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Personally i would drain the oil then drop the pan and change the pan filter and also the spin on filter and refill with TES-295 fluid. Others might say to just change the oil and the spin on filter. Once again personal choice.
Use only Allison filters!
If dropping the pan there is a magnetic inside of pan to clean off.
There is also a donut (washer) magnet above the spin on filter to take down and clean off and reinstall or put new one in.
Write date and mileage on spin on filter so you know next time when it was serviced.
 
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Good Info BrokenBackJack, I do the same thing only I drain mine twice, the second time after driving about 50-100 miles. Allison says Do Not Flush.
 

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2014 Chevy Silverado 3500 HD, LML 6.6L Duramax
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Discussion Starter · #10 ·
Good Info BrokenBackJack, I do the same thing only I drain mine twice, the second time after driving about 50-100 miles. Allison says Do Not Flush.
Do you have a link where Allison suggests not to flush? I am printing everything to give to my Mechanic. (Chevy Dealer)

All this info is great!! I will get some decent fluids and just do a drain, change filters, etc... then drain again after about 100 KM.

Thanks!!!
 

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Check into Transyd or Amsoil Torque Drive for fluid, Dexron VI is crap. And don't forget to use Original Allison filters.
 

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Oh, the things I forgot (I'm old and getting even older) but as others mentioned...
  • Allison spin-on filter
  • Look for the magnet on the filter and re-use. If missing, buy a new one.
  • Yes, like others, I also get Delvac TES-295 from Summit.
  • Don't flush (although "Hoot" or "passive" fluid exchange is acceptable; but still not necessary).

I'm in the camp that doesn't think dropping the pan and replacing the internal filter is necessary. Allison once recommended (and still?) doing this only if the pan was dropped for other reasons.

Beware that you're not likely to get any of this advice from a dealer. They tend to blindly follow their party (GM) line.
 
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A few thousand miles after I had my trans built I dropped the pan and replaced the internal filter, spin on filter, cleaned the magnet, and drained and re-filled the fluid twice. Just to make sure all the clutch dust from break in was out of there. Personally if a truck had over 100,000 miles on it and I was unsure of the maintenance schedule that's exactly what I would do and then replace the internal filter only every 100,000 miles or so. Even though it's unnecessary.
 

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Had a high mileage honda when i was younger. Took it to a lube place, asked if I wanted my trans flushed, I figured sure. Car had 200k on it and I had no idea when or if it had been done before.

Car almost didn't make it the 15 minute trip home. Moral of the story? Whether or not you can or cant flush...don't. Drain and fill. You wont get every bit of crap out (convertor keeps a ton inside it), but you will get the bulk of it. Thats why lots of people drain twice (1st drain, drive a bit, park, 2nd drain) if they want to get as much out as possible without a flush.
 

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FWW I have an LBZ w/ 518k miles I've flushed the Allison twice once about 200k and the other at 400k. Original trans. I change the spin on's every 50kish. I use factory recommended trans oil.
 

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Don't flush the transmission. Older transmissions have established a status quo with the fluid and contaminates it has in it. Flushing everything out can lead to transmission slippage, even failure. Just drain the transmission (as much as will come out), replace the filter, and refill. I also recommend a TES-295 approved fluid per Allison standards.

If you want to have a more complete fluid replacement, do the fill-drive-drain-fill process. You don't have to perform the second drain and refill immediately, it can be done after a few thousand miles.
 
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I’ll beat this dead horse:
No flush. Ever. A flush shouldt ever be needed if properly looked after And if it were, rebuild it.
But yes, now is a perfect time to. Drop the pan and replace the internal filter. Wipe the pan and check the magnet for metal.
I used Mobil delvac tes-295 approved. You can get a hell of a deal at summit I still believe.
The double drain isn’t a bad idea but not necessary. That’s the only flush I’d do.
 
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