Ford 8F35 Transaxle Fluid Change at 150,000 miles? What's The Consensus?

[colinl]

Was just at the dealership getting another repair done and the service manager said 60K was way too early...

what they really mean is that they don't want to do it wrong and be liable for replacing it within factory powertrain warranty when it fails.

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[raceman94]

what they really mean is that they don't want to do it wrong and be liable for replacing it within factory powertrain warranty when it fails.

I was wondering about that or the other thought I had was that perhaps they already had such a huge workload, they just didn't want to take that job on?

I was thinking, 'geez, who would refuse to do a job and take my money?"

Gonna check out one of the others dealers closer to the city that I work in and see what they tell me.

 

[Scott Asheville]

Isn't there an old sixties song that goes "It's your thing, do what you wanna do. I ain't gonna tell you who to sock it to".

That is, IMHO, the best answer to 99% of the threads on MTC seeking advice. It's all about maintaining your vehicle in a way that makes you comfortable. For some of us that's never. For others, manufacturer's schedule. For still others, highly proactive preventative maintenance.

 

[JohnCondren1933]

I changed the trans, RDU and PTU at 28K. Both the RDU and PTU fluids were low and quite dark. The trans fluid did not look too bad. I used AmsOil in the trans and PTU, Motorcraft RDU fluid in the RDU. I will continue to do 30K changes.

Just changed the PTU & RDU at 11k miles.

PTU fluid is cheap & lots of suppliers, 75W85. Mine was dark and gunk on the magnet.

RDU uses proprietary fluid Ford charges $50 a damn bottle for & you need 1.5 bottles.
Said it didnt look bad at all, probably just change RDU with the transmission fluid, but the PTU just do it every other oil change it only takes .5 of a quart

 

[dalola]

RDU uses proprietary fluid Ford charges $50 a damn bottle for & you need 1.5 bottles.
Said it didnt look bad at all, probably just change RDU with the transmission fluid, but the PTU just do it every other oil change it only takes .5 of a quart

The RDU capacity is the same as the PTU, .5 Qt. You can get the correct spec Motorcraft oil from Rock Auto for under $30.

 

[mavhopefull]

I just called my dealer, and Ford's official recommendation is to change the 8F35 transaxle/transmission fluid at 150,000 miles, with the service costing around $260. Does this 150,000-mile interval seem realistic, or should the fluid be changed sooner for normal driving? I had originally planned on changing it at 30,000 miles. What is the general consensus for modern transaxles/transmissions? (not my transaxle in the pic).

If you're servicing your transmission, pay close attention to the fluid level! My services at 30,000 and 60,000 miles revealed a major problem: an approximate 1-quart volume reduction between those two maintenance events.

The culprit isn't a leak; it's evaporation and venting through the breather, leaving a tell-tale, heavy residue caked around the vent cap. The only logical conclusion is that the incredibly thin Ultra-Low Viscosity (ULV) fluid is simply too volatile and is boiling off.

The Bottom Line: At this rate of depletion, these transmissions are at high risk of catastrophic failure well before 150,000 miles due to chronic fluid starvation. This is a severe reliability issue that owners must monitor.

Watch the Maintenance Process:

I have documented this process, including the fluid changes for the PTU and RDU, in detail on my channel. I hope these videos are helpful for others looking to confirm this issue:

YouTube Channel: https://www.youtube.com/@dadsgarage.alwaysopen

 

[raceman94]

Interesting...and very concerning.

 

[dalola]

A significant issue I've tracked during transmission services at both 30,000 and 60,000 miles is concerning fluid loss. My measurements show an approximate 1-quart volume reduction between those two maintenance events.

The root cause appears to be evaporation/venting rather than a leak, as confirmed by the heavy, filthy residue I found caked around the transmission's top breather. My hypothesis is that the fluid's Ultra-Low Viscosity (ULV) formulation makes it inherently more volatile and susceptible to evaporation through the vent.

Frankly, I don't see these transmissions reaching 150,000 miles without a complete internal breakdown due to chronic under-filling. This fluid loss is a major reliability concern that needs to be monitored closely

ATF does not evaporate. Improper venting is a leak. If you are losing a quart every 30K, you have other issues.

 

[Equator Guy]

Replaced mine at 25K miles last weekend (drain/fill/check overflow). Great videos and write ups from members on this forum and YouTube. Used Forscan (which I previously used to disable Auto Stop Start and change speaker settings) to check transmission temperature before opening overflow hole. Cost of fluid was under $50 on Rock Auto. Used 4 quarts (bought 6). If you have the most basic tools and mechanical skills you can do it (I am proof).

 

[MavChris]

Planning on doing a drain and fill on trans fluid when I change the oil at 35,000. I currently have 34,300. Reading on this forum it looks like when doing a drain and fill on transmission you will get between 4.5 and 5.5 quarts of fluid drained. The total capacity of system is around 9 quarts. Draining does not drain torque converter and this is why you only get around half of total capacity when just draining. Some will do the process twice to get mostly all the fluid changed. I'm planning on just doing once and will be happy if around half of the fluid is new. I have read horror stories about a total flush.

 

[JohnCondren1933]

Flushing before engine oil change is really simple, its just pouring a bit of new oil into the fill hole with the drain plug out, to "rinse off" the old oil residue & its suspended particles off the interior of the engine, before filling it with new.

Flushing a "hydramatic" style transmission is to flush out the old ATF fluid still in the torque converter, because when you drain a hydramatic style transmission you drain everything but the ATF left inside the torque converter.

If you change ATF regularly, the old ATF in the torque converter is not gonna hurt anything, but if its very old ATF, or you tow alot which generates heat which oxidizes ATF, or any doubt about ATF contamination from excessive moisture condensation where you take lots of short slow drives never bringing ATF up to 100C where water evaporates, THEN is when I believe you should absolutely flush the transmission to get all the old ATF out & replaced with new or youll contaminate the new ATF.

Disclosure:
my Mav hybrid has no torque converter & before this I had Honda CRVs whos CVT uses a friction clutch not a torque-converter so draining it removes virtually all ATF so no old ATF to flush, before that had Prius which as hybrid again had no torque converter.
So I haven't had experience with a torque converter drivetrain in years, but from what I understand its transmissions with torque converters that actually benefit from flushing to get all the old ATF out.

When you Mav owners talk about transmission fluid drain and refills, curious, is it also a good idea to get it flushed first hand? I’ve heard a while ago that flushing is not all it’s cracked up to be.

 

[Darryl]

Planning on doing a drain and fill on trans fluid when I change the oil at 35,000. I currently have 34,300. Reading on this forum it looks like when doing a drain and fill on transmission you will get between 4.5 and 5.5 quarts of fluid drained. The total capacity of system is around 9 quarts. Draining does not drain torque converter and this is why you only get around half of total capacity when just draining. Some will do the process twice to get mostly all the fluid changed. I'm planning on just doing once and will be happy if around half of the fluid is new. I have read horror stories about a total flush.

The horror stories of doing a total flush were based on the old days back in the 1990s and before. And they usually involved transmissions that had been neglected and were overdue. In those cases just a pan drain was done. The vehicle was driven a few thousand miles and drained again. But in today's transmissions with fluid changed at the recommended intervals, it's perfectly safe to to a total change. Having said that, if you change your fluid at 35,000 miles which is long before recommended, it perfectly fine to do a drain and refill because the fluid probably isn't very dirty or degraded

 

[Packer Bill]

The horror stories of doing a total flush were based on the old days back in the 1990s and before. And they usually involved transmissions that had been neglected and were overdue. In those cases just a pan drain was done. The vehicle was driven a few thousand miles and drained again. But in today's transmissions with fluid changed at the recommended intervals, it's perfectly safe to to a total change. Having said that, if you change your fluid at 35,000 miles which is long before recommended, it perfectly fine to do a drain and refill because the fluid probably isn't very dirty or degraded

Thank you for this info!

 

[FischAutoTechGarten]

My Maverick is 2 years old in January. It will also have 30k miles in January. I'm m probably going to wait for 45k miles to do ptu, rdu, and trans. My Maverick is not worked hard. Opinions?​

 

[Darryl]

My Maverick is 2 years old in January. It will also have 30k miles in January. I'm m probably going to wait for 45k miles to do ptu, rdu, and trans. My Maverick is not worked hard. Opinions?​

You're not hurting anything. But it's not necessary to change those fluids nearly that often. But as I said, you're definitely not hurting anything by changing those fluids more often than required. As a Ford tech, I personally follow the manufacturer recommendations for most vehicles. But in the case of the 8F35 transmission, I probably would do the initial fluid change at around 70,000 miles. Because some of the 6F35 transmissions fluid would look degraded if you went the recommended 150,000. The 8 speed uses synthetic fluid that doesn't degrade nearly as fast. But I still wouldn't go 150,000

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