Read post #132.

Did you pull the oil sample before or after the hydraulic system flush?

 

This was my 7500/3 year fluid/filter dump. So this is the only fluid and filter that has ever been in the tranny. This is the original fluid that is the dirty fluid. The test will tell us how dirty is dirty.

Joe

 

Can we at least agree with the statement from above: If you are a do-it-yourselfer, you don’t want anyone else touching your car, you can change the trans filter without running this routine."

 

Sure, but that was not the point of the discussion at all (doing the computer controlled HSF when doing a drain and fill and not replacing the filter). And it wasn't what you said when you said the HSF and routine are the same thing.

 

Everyone can agree that Josh Holder said that at a Bash event in 2024. It would have been better if he has added "and it will not affect your warranty if you skip it and have a transmission problem later". But he didn't. He's not the one that makes decisions regarding warranty claims, and is probably not authorized to make a general comment about that.

We can also agree that the Warranty Manual says a couple of things:
1. GM cannot deny warranty coverage solely for the lack of receipts or for your failure to ensure the performance of all scheduled maintenance.
2. Damage caused by failure to follow the recommended maintenance schedule intervals and/or failure to use or maintain proper fluids, lubricants, or refrigerants between maintenance intervals recommended in the Owner's Manual is not covered.

In other words, they can't deny a claim simply due to failure to perform the required maintenance, but if that failure caused the issue, they can deny a claim.

And we can also all agree the HSF is step 1 in Service Manual procedure for changing the DCT external canister filter as required by the Owner's Manual. And, its important enough that there are extra instructions regarding the HSF if the filter is being changed beyond the scheduled change interval.

Another thing we can probably all agree on - the HSF is not only a step in the DCT Filter replacement procedure, it is also called out in many, if not most, diagnostic procedures for transmission related issue, in an attempt to remedy the issue. And, while it does not always resolve the issue, there are plenty of forum reports where it has resolved the issue.

The fact that it resolves the issue in some cases suggests that the "highway routine" alone is not sufficient to clear all the debris from the valves and lines, but the HSF sometimes is.

 

I changed my DCT oil and filter at 10,909 miles.
3,088 miles since the last fluid change one year ago at 7821 miles.
I ran the HSF procedure both times.
In addition, I changed the external filter one more time at 9410 miles.

Before changing the oil and filter and prior to running the HSF, I used a vacuum sample pump to withdraw an oil sample through the fill port. After discarding the used filter to install a new one and after running the HSF on this new filter, I took another oil sample before draining the unit.
Both the before and after samples were subjected to an oil analysis which included a particle count.

The particle count uses the ISO4406.99 reporting standard for fluid cleanliness.
The results listed in the report need to be converted into numbers that can be readily understandable. I will list them below.
Particle counts are listed on a per milliliter unit of volume.

 

Looking at it quickly it seems the first sample has manny more smaller particles than the second. Similar next size and same of the next size. So it could be the filters are letting the smaller particles build up and that could be if it filtered too small it blind off the filter immediately.

Another idea is the smaller particles will or will not be found in the next sample. I wish they told you either % or in ppm. The real question is how good or bad is this? The only way I think you could know if it’s dirty fluid that is causing these problems is to have a sample from a tranny that went bad. Then you could compare to something.

I kinda think what we learned is the filter is probably a 10 micron filter.

am I missing anything?

Joe

 

The particles they found are not normal metals they test for. If you look at the two columns they are listing the same metal counts. They say the particle count is outside or highest in red. Which is it and what is normal if it’s outside the range?

Can someone tell us what clutches are made of?

Joe

ps this is good stuff thank you!

 

Well it certainly shows that installing a new filter and running the HSF after reduces the particle count.

Makes me wonder what would have happened if you had just run car with the new filter and not run the HSF (since many DIYer's think they can skip it, its a relevant test):
1. sample before maintenance
2. change the filter, skip the HSF, run the car a little to circulate fluid, then take a sample.

It also makes me wonder what the results would be if the GM procedure is followed (since many/most do that):
1. sample before maintenance
2. run HSF - take another sample before changing the filter.
3. replace the filter, run the car a little bit to circulate the fluid, then take a sample.

 

Guys

I’m new to this all just bought a 2022 in march. Does any of this information say how dirty is too dirty? I guess it have to come from Chevy because they are setting up the service intervals.

I’ve read a lot but haven’t found anything like that.

Joe

 

Considering that at 11,000 miles I have changed the external filter many times, ran the HSF twice before and changed the fluid twice, one has to ask why any supplemental cleaning process would be necessary. Does this imply that the filtration process on its own is inadequate?

Regarding your questions about letting the car run to 'circulate the fluid', understand that under most conditions, there is relatively little oil flow through the unit and the filter. The valve body receives pressure, but there is no gross oil flow through it. Most of the internal parts are splash lubricated - just like a manual transmission. The input clutches receive application pressure to hold engagement, but again, there is no gross oil flow. Perhaps you remember a method I explained on how to maximize oil flow through the external filter with the car stationary? The programming maximizes oil flow to the input clutches and then through the filter when it detects slippage. Slippage occurs during engagement from a stand still and when using the launch control. There is also minor slippage during shifts. Oil flow is controlled by a variable orifice valve that is under ECM control. So, the processes you describe will not work.

Of greater interest to me is what the before and after would look like running the HSF on the original filter on a car with 7500 miles and with no prior service - just like GM wants it done. We need a few volunteers!

 

Guys

From the lack of responses to my question “how dirty is too dirty” I’m guessing there isn’t info on that. I’m wondering if the problem is caused by initial “break in” debris, maybe?

Has anyone reported doing the service and still has blown a tranny? Or does the initial service fix any issues.

Joe

 

No one here knows, GM and Tremec do but you won't see it in print. The debris is probably the main source of DCT issues we see. "Blown"? I haven't heard of anyone actually blowing a DCT.

 

Reference published data on the cleanliness of hydraulic systems. You'll find a lot of information.

 

Thanks. When I said "run the car a little bit" I meant take it out and drive a little. What I was thinking is it would duplicate the condition that results when folks change the filter and skip the HSF. Yours shows a nice drop in particle count when the HSF is run in the sequence you described. What happens to those particles if the filter is replaced and the HSF is skipped? Obviously if you don't run the car the count stays the same. But does it drop after its run a few miles, or just stay high? Whatever filtering you get, a little or a lot, that's representative of the what happens when the HSF is skipped.

And, I also agree that what happens during the first 7500 miles is of great interest.

 

Thank you I mean broken or needing to be replaced. Just to help me understand what is the service interval once the first flush/filter change is performed. Is it every 7500 or 3 years filter/flush is that what everyone is doing?

Joe

 

Adding to post 175, I found the following that seems to say the max output rate of the pump is 70l/min, so if it was running at max capacity it could circulate all the fluid through the filter in less than a minute. Of course at idle, its not at max capacity. But again - by "run the car" I meant take it out and drive it to duplicate the conditions that would exist if the HSF is skipped after a filter replacement.

I should add - the service interval shown on this illustration is incorrect. Its a very old illustration, probably originated in late 2019 or early 2020. I do not know its origin other than I captured it from this forum. It's either a GM product or an independent publication. At that time there were other publications that also showed (or maybe estimated) the service intervals incorrectly. Go by the owner's manual for that.

 

this is true if you know what the tolerances are within the equipment. That’s why I’m asking how dirty is too dirty. It’s probably true that GM won’t print it because of lawsuits.

Are there any transmissions that failed after the first flush/filter change? This could be hard to know, but if they are still failing then the flush/filter change may not be the cure. Or if no more failures then the flush/filter change may fix it?

Sorry for all the questions I’m new and you guys have 5 years of info before me.

Joe

 

I don't know "what every one is doing", but here are the minimum requirements from the Owner's Manual - and the filter and fluid are on separate schedules.

Filter - change between 7000-8000 miles even if done earlier, then change it at 22,500 miles on the odometer, then every 22,500 miles (or less is ok here) thereafter. Or when you filter life monitor says to if you have one - but never go pasts the above mileages.

Fluid - change when the fluid life monitor says to, or 45000 miles, or at least every three years whichever is first. The fluid life monitor does not include time so you must observe that yourself.

Fluid and filter are to be changed every 24 hours of track use if you track.

 

I last changed my external filter 1500 miles prior to my most recent service which I detailed here with oil analysis reports. So, take this as the answer to your question regarding changing the DCT filter without doing the HSF.