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Transmission Flush or Transmission Drain/Replace?

25K views 15 replies 10 participants last post by  rupertsilva10 
#1 ·
Whats the difference between a transmission flush and a transmission drain/replace on the Prius? I've heard of people getting their transmission fluid changed out around 60k miles and am trying to look into it.. but don't know what I should be getting?
 
#2 ·
A transmission flush is only worthwhile with automatic transmissions with torque converters and cooling lines to the radiator. That's because if you just simply drain the transmission, you're only removing 50% or so of the total system capacity. With the Prius, the majority of the fluid would be replaced with a drain and refill since there is no torque converter or lines to worry about!
 
#3 ·
Also automatic transmissions have little 'tunnels', valves and actuators that also contain transmission fluid, that often doesn't get completely removed. A flush also often uses cleaners to remove sludge and deposits still remaining in the transmission.

The purpose of the fluid in the Prius is simply to cool and lubricate. It has no responsibility for hydraulic controls like in a conventional AT. Draining the Prius AT is akin to changing the oil in your engine. Stuff comes out at the bottom, new stuff is added at the top (side actually), with few horizontal surfaces to trap and maintain the old stuff.
 
#4 ·
transmission juices

Listen to DanMan. Fluid flushes are some sort of evil dealer profit center in the case of Prius.

But meanwhile, fluid analyses have not been altogether yummy clean from Prius transmissions. A few of them have failed, and we don't know why. It would seem reasonable to drain and refill the type WS fluid every 60 k miles, even though not (yet) specified by Toyota. I appreciate that this might be overkill, but it will only add about 0.2 cents per mile to your total operating costs. You could save that amount by doing your own engine and cabin air filters. Let's spend our Prius-maintenance-pennies effectively.

DAS
 
#5 ·
Re: transmission juices

tochatihu said:
Listen to DanMan. Fluid flushes are some sort of evil dealer profit center in the case of Prius.

But meanwhile, fluid analyses have not been altogether yummy clean from Prius transmissions. A few of them have failed, and we don't know why. It would seem reasonable to drain and refill the type WS fluid every 60 k miles, even though not (yet) specified by Toyota. I appreciate that this might be overkill, but it will only add about 0.2 cents per mile to your total operating costs. You could save that amount by doing your own engine and cabin air filters. Let's spend our Prius-maintenance-pennies effectively.

DAS
Interesting.

I'm curious, are there any signs of impending PSD failure? And, what happens (internally) when it does fail?

Also, is there slippage or some other sort of empirical evidence? And does spent fluid get that burned smell as in a conventional AT?
 
#6 ·
It's all gears that mesh together. If gears are breaking, they crunch. I doubt you'd see any slippage. It either works or it doesn't, much like a manual transmission (assuming you have no problems with the clutch)
The Prius has no clutch, no hydraulic shifters, no torque converter using hydraulic viscosity to achieve engine to tranny coupling.
There is a silent chain that is supposed to last indefinitely. I suppose that might be able to slip.

A few Prius Classics had PSDs fail, but I haven't heard any HSDs have the PSD fail.
 
#8 ·
Dan, can an owner do the drain and refill? Or does it require the friggin' THHT to set some mode like the brake system fluid replacement requires? I don't mind doing it if I can, but I would think twice before spending $1-200 for the dealer to do it.
 
#9 ·
What do you mean, DAS?

KTPhil, anyone can drain it. I think it requires an allen key (hex) driver though to get the plug off. I think John has an article on it.

Just checked John's site. If it's there, I am not seeing it. He has an article on changing the engine oil though.
 
#10 ·
yea

anyone can change it if u can find some lovely ATF WS, its a 18 mm bolt i think, or 22 mm not sure, but drain it and fill it through the one on the side of the trans. Dont trust me on this, im the guy that drove hte prius without proper lubrication of the transaxle
 
#11 ·
KTPhil,

I had my dealer change the ATF (Type WS) in my 2004 at 61,000 miles. He only charged $85 and half of that was for the 4 qts of type WS fluid. In this instance the dealer charge was quite reasonable, but I had to explain to him that a "Flush" (at a much higher price) was not necessary in a Prius.

I also had a lab analysis done on both the used ATF and a sample of virgin Type WS ATF. It showed that at 61,000 miles the fluid was still sound, but just about used up. It is this lab analysis that has convinced the group that actively studies our trannys (particularly the gen1) that the HSD fluid should be replaced at 60,000 miles in the gen2 (2004-2007).

JeffD
 
#12 ·
jdenenberg said:
KTPhil,

I had my dealer change the ATF (Type WS) in my 2004 at 61,000 miles. He only charged $85 and half of that was for the 4 qts of type WS fluid. In this instance the dealer charge was quite reasonable, but I had to explain to him that a "Flush" (at a much higher price) was not necessary in a Prius.

I also had a lab analysis done on both the used ATF and a sample of virgin Type WS ATF. It showed that at 61,000 miles the fluid was still sound, but just about used up. It is this lab analysis that has convinced the group that actively studies our trannys (particularly the gen1) that the HSD fluid should be replaced at 60,000 miles in the gen2 (2004-2007).

JeffD
Can you post the actual analysis results please? Where did you have it done and how much was it?

Also, if anyone's actually done it I'd like to see a nice little step-by-step instruction set (pretty pictures are helpful too) to change that fluid. Certainly sounds simple enough, but I honestly don't know which screws/caps to open and don't wanna mess it up if I choose to do it myself. (about 4k miles until I hit the 60k mark)

It's probably overkill to do it at 60k, but for whatever reason the annecdotes have bugged me and I just don't want the PSD blowing.
 
#13 ·
#14 ·
efusco said:
JeffD Can you post the actual analysis results please? Where did you have it done and how much was it?

Also, if anyone's actually done it I'd like to see a nice little step-by-step instruction set (pretty pictures are helpful too) to change that fluid. Certainly sounds simple enough, but I honestly don't know which screws/caps to open and don't wanna mess it up if I choose to do it myself. (about 4k miles until I hit the 60k mark)

It's probably overkill to do it at 60k, but for whatever reason the annecdotes have bugged me and I just don't want the PSD blowing.
Evan,

As DAS said the data is available at Bob Wilson's site, but only the directions to do the ATF fluid change in a classic, not the current model. I don't think that doing the change at 60,000 miles is overkill (30,000 miles in a classic). There are two reasons for my opinion:
  • A 15% change in fluid viscosity is an indicator of end-of-life and that is what was shown in the analysis of my ATF at 61,000 miles

    The MG windings are exposed to the ATF fluid and as the metallic particulate count increases, I worry about a possible short circuit that would end the useful life of the assembly.
There is some anecdotal evidence that this has happened to a small number of high mileage classic Prii.

Besides, it was only $85 and my Prius deserves good care.

JeffD
 
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