[dougsd]

Should I plan on swapping out 4 or 5 gallons? Trying to decide on how much to order.

 

[viper8315]

I did confirm I purchased 4 gallons and I performed the double drain and fill with no pan drop. I have an entire gallon left. If you look at Alisobob's picture, there is a lip around the drain plug so the pan still holds some.

 

[dougsd]

I raised the front end substantially and let it sit for 2 days while I drained the pan. I only ended up draining out around 7.5 quarts. So I pulled the pan and inner filter and ended up with 10 quarts total drained. I decided since I'm this far into it and I'm switching from Dexron VI to TES-295, I am going to take out another 6 quarts with the HOOT method.

DIY Detailed Hoot Instructions

Questions on the “Hoot Method” for flushing an Allison and changing to a synthetic fluid keep coming up. So I thought it might be handy to gather the wisdom and insight of several other DP posters as well as my own experience and present it here — with some pics. For those of you who are...

www.dieselplace.com

C4500 C5500 Allison Transmission Filter and Fluid Change

Drain and flush steps for allison 1000. Removing clips and lines to filter

mdt.volvospeed.com

 

[BoiseRob]

dougsd... just make sure the old o-ring from the used internal filter comes out before you install a new filter. Otherwise, you'll have to drain the pan and remove the original o-ring...

 

[viper8315]

Yes, what Boise said, and of course, exercise caution and don't run it too long. Don't want the pump to suck air.
Good luck! 👍

 

[dougsd]

I thought I would start with 3-5 seconds of run time and see how much comes out.

Yes, what Boise said, and of course, exercise caution and don't run it too long. Don't want the pump to suck air.
Good luck! 👍

 

[AlisoBob]

The Double Drain..... is WAY safer.

 

[dougsd]

But is double drain the better way to go if you are changing over from DEX VI to TES-295? From what I read, if doing apples to apples fluid change, just do a double drain. If switching from apples to oranges, do the hoot method.

A double drain leaves in the total system 3.5 gallons new (TES-295) and 1.5 gallons old (DEX VI), while throwing out one gallon of the new TES-295.

Is the total capacity of a shallow pan entire system 5 gallons even?

The Double Drain..... is WAY safer.

 

[viper8315]

I hear ya Doug,
However, as I put in the first post, "the man" (hzjcm8) said double drain is fine on a healthy trans. So I did that last year at about 12k miles. I'll do a single change this year and it'll be around 30k miles, and that'll get a good chunk of the factory stuff out. Is it over maintenance, sure, according to "the man's" advice. Is it still a free country for now, yup!
Also, based on Alisobob's findings, who didn't do the hoot method, you should be good.
At the end of the day, it's all in what you want. I was in your exact same shoes last year. I was all set to do the hoot method. After reading more of the Allison's engineer's posts, as well as learning about the risks of sucking in air, I changed my mind and did the double drain and fill.
I changed my mind because I wanted zero risk of sucking in any air. We're just trying to caution you on that risk, and if you accept it, then have at it. There is nothing bad that can happen from leaving in some of the factory fluid. Bad things can happen with inducing air though. Good luck!

 

[ChevyTech77]

Allisons run a LOT of line pressure. Even at idle in park/neutral. 6 speeds are less but still up there when in gear. No way would I be attempting to do what you posted here. At least without some help and the knowledge that I could easily cause a HUGE mess if something goes sideways. I’ve seen Allisons blow actual transmission flush machine hoses apart and they’re secured better than just hose clamps.

Double drain and fill is plenty, IMO.

 

[rockn69]

I thought I would start with 3-5 seconds of run time and see how much comes out

Let us know how that works out.

 

[dougsd]

I did it and it wasn't bad but I don't know if I gained anything by doing the hoot method over double drain method. Also I never notice a change in color after 6 quarts. If anyone decides to do it make sure you measure what you're losing out of the cooler return hole also. I had a drain pan there so I could measure it also as I replaced the fluid. I ended up with 2 quarts come out of the return hole and I'm guessing that was probably new fluid. If I ever did it again, I would just drain and drop the pan which removes half the volume or 2.5 gallons. Then do a double flush down the road. If what I lost out the cooler return hole was new fluid, I am probably not any better off by doing the Hoot method.

Still not sure if I have the cooler return line in completely. I wish I would have taken a picture before removing the line. What concerns me is the shiny area on the fitting. That could have been caused by me working the hose onto the line end but I'm not sure. I pulled and pulled on it and it wouldn't come back out. I drove it around for 10 minutes and it doesn't leak. If the fitting would go in further, I think the line going toward the front of the truck would be rubbing against the tranny.

 

[AlisoBob]

If I ever did it again, I would just drain and drop the pan which removes half the volume or 2.5 gallons. Then do a double flush down the road.

I bought my LML with 14k miles on the clock. As I do with any used vehicle I buy, I swap out every filter and fluid (Regardless of mileage)

I did a double dump, added a deep pan, tossed in a few extra magnets, and added a Suncoast filter lock.

At 64k miles ( + 50k miles) I did a single dump and refill.

At 114k miles (+100k) I dropped the pan, to start the sequence all over again. The thing was spotless.

So, for the cost of a few gallons of Delvac 1 ( A TES-295 fluid), a hand full of spin on filters, and a internal filter... I had outstanding performance over 100k miles of use.

I plan on doing the exact same thing again......

 

[ChevyTech77]

I did it and it wasn't bad but I don't know if I gained anything by doing the hoot method over double drain method. Also I never notice a change in color after 6 quarts. If anyone decides to do it make sure you measure what you're losing out of the cooler return hole also. I had a drain pan there so I could measure it also as I replaced the fluid. I ended up with 2 quarts come out of the return hole and I'm guessing that was probably new fluid. If I ever did it again, I would just drain and drop the pan which removes half the volume or 2.5 gallons. Then do a double flush down the road. If what I lost out the cooler return hole was new fluid, I am probably not any better off by doing the Hoot method.

Still not sure if I have the cooler return line in completely. I wish I would have taken a picture before removing the line. What concerns me is the shiny area on the fitting. That could have been caused by me working the hose onto the line end but I'm not sure. I pulled and pulled on it and it wouldn't come back out. I drove it around for 10 minutes and it doesn't leak. If the snap fitting would go in further, I think the line going toward the front of the truck would be rubbing against the tranny.

View attachment 1084835

If that line wasn’t locked in there correctly, it would have popped itself out by now. You’re good.

 

[pullin15]

Hi all, I'm one of those that has dealt with occasional hard down shifts to first. Although less frequent than the beginning it still happens now at 24k. I finally decided to try switching to TES-295 fluid (double drain/fill, no pan removal).
On the first drain, i got out 6.4 qts . Since checking trans levels can be difficult, i typically just add the same amout i took out assuming the original level was correct. However, when i checked the level, i had to to add an additional quart (7.4 qt total) to get to the hot level (doing the hot level check per manual).
So, now im questioning was it a quart low the whole time? Can that explain the hard shifts?
Or does it sound like im checking the level wrong? I only question this because the fluid is so clean it is really difficult to see where the level is at.
Any thoughts/advice appreciated?

 

[Cbrick]

Same happened to me when I double drained mine, initial drain was around 6 quarts, I refilled with the same amount and ended up about a quart low. I’ve also had the occasional hard downshift to first, it seems to be getting better the more miles I put on, I really only notice it when I’m braking hard. The hard 3 to 4 is what really bugs the shit out of me on mine.

 

[pullin15]

Thanks for the info. So if I'm hearing you correct, it sounds like adding more fluid did not eliminate the hard shifting. My main concern is if the low fluid has caused any damage. I talked to two different dealers about the hard shifting and the both said it's normal and never bothered to check anything.

 

[Cbrick]

Correct, my trans behaves the exact same now as it did before I swapped to Delvac. That includes driving around 50 miles a quart low, I haven’t noticed any difference in shifting, temps, or metal on the filter magnet.

I honestly think it’s just the way it’s programmed, it’s annoying because my deleted LMM was much smoother. Not concerned though, after driving my brother’s Ram and feeling the 68RFE slip it’s way through the gears.

 

[Ditda]

So since I'm so trusting of the Duramax/Allison combo, and its my third one, I bought a used hotshot '18 GMC 3500HD dually for ranch use and some side-gig transporting. Minor detail is that it has over 200k on it now. Bought it LA and drove it 1k to Far West TX, then to Bama and back for Thanksgiving, so almost 4k in the last month and no real issues but since I can only see past oil changes in the logs, getting ready to change the tranny and transfer case fluid so I have a baseline.

Thanks for the above info gents and pics @AlisoBob. Also read a bunch of the posts from @hzjcm8 and @viper8315 so decided to drop the pan, change filter and gasket, add the Mobil 1 Delvac and change the spin-off filter.

If it's nasty inside the pan will post pics.

giddy up.

 

[Ditda]

Sorry for the delay, ordered the incorrect gasket initially. So truck is now at 203,xxx miles and the drained ATF fluid looked pretty good while the front diff fluid look like grey water...glad I changed both. Here are some pics for y'all to see. So while it looks like the previous owner didn't change the front of rear diff fluids, the tranny fluid looked normal and I didn't see any sediment or metal in the pan.