CVT transmission flush damaging?

[cfahr]

I have a 2014 SEL hybrid. My service technician had said I should have my transmission fluid flushed and refilled. Am at 110,000 miles. Forward 3 weeks, I wanted to get it scheduled this week. Only time that would work out. They had no openings. Called another Ford dealership in area. Full also. Last one had an opening, but he told me don't have transmission fluid flushed, it can damage CVT transmissions. I told him that a flush was what the other dealerships were trying to schedule. He said he didn't know why they would say that, but he would check his information.  Came back and told me he was correct that it shouldn't be done to a CVT transmission. Who is correct, and why would dealerships have such conflicting information. Was not a misunderstanding of words since I discussed flush vs empty/fill.  Looked online and there are also conflicting statements concerning if a flush can be damaging to transmission. Mostly chemical and debris concerns. Suggestions? Thank you

[Billyk24]

The owners manual states "drain and fill" at 150,000 miles.  The electronic -not belt-CVT has a very small reservoir.    Your eCVT has no gears.    The flush method is for other types of transmissions.  The service tech is trying to drum up sales and money for the dealership. 

 

Edited August 11, 2021 by Billyk24

[hunt3rj2]

You could flush the HF35 transmission but why? The instant you release the drain plug a big gush of fluid carrying whatever wear metals are in there will come out. If you look at a teardown of the transmission there's no hydraulic control passages/clutches/fluid filters/etc like a normal automatic. It's more like a manual transmission, just some gears in there and not much else. The electric motors are responsible for changing the gear ratio, the rpm of MG1 changes the effective gearing depending on how fast the car is moving. I would do it at 100k but 150k is probably fine too.

 

The transfer shaft failures mentioned on the forum probably cannot be prevented with more frequent fluid changes. Only way to fix the issue is to catch it before the bearings fail and allow the transfer shaft to wobble in the transmission and grind away at everything else in the transmission. Then you have to rebuild the transmission with the updated parts listed in the TSB. Or a new transmission entirely.

[SnowStorm]

Further confirmation/correction/etc:

1. Ignore the dealers - go by the book.  Drain and refill at 150k
2. There is a filter in there.  I know, I tore my old transmission apart.  It's encased in metal and is, maybe, 5x6x1 inches.  You don't replace it.
3. IMO, its not the bearings that fail but rather is a press-fit ring that slips, allowing the shaft to slop sideways and start rubbing/wearing the case and, in mine, shearing off gear teeth corners.
4. Don't use engine braking.  I can't prove it but still feel my failure occurred at the end of a long run using engine braking - horrible clunk and nasty sounds.
5. Otherwise, drive normally and don't worry too much.  Aside from the transfer shaft problem, I think the HF35 is an incredible design - no clutches, no shifting, etc.

[Lacienega]

Good advise here. I used engine brake once on a pretty steep downhill and thought the rpms were way too high. Will not do it again. ( i used the transmission control switch on the side of the gearshift lever to activate grade assist, not the L gear)

Edited August 12, 2021 by Lacienega