FelixBabakuntos

If doing multiple drains and refills of the transmission fluid, how much should the car be driven between each refill? I want to make sure that the old and new fluid is well-mixed, so that on subsequent drains I'm not primarily draining the new fluid that I just put in.

Backstory: I purchased a 2005 LS430 Ultra Luxury with the harsh downshift problem as well as a very unresponsive throttle when pressing heavily on the accelerator. I had hoped that it would be a simple fix with a rebuilt ECU from SIA electronics, but their repair didn't help much if at all. I took the car into a transmission shop and they looked at the fluid and said that it seemed to be heavily contaminated with some watery liquid -- possibly radiator fluid. They dropped the pan and refilled with 2-3 quarts of Toyota WS, but again, there was little to no difference in the shifting after this. (Luckily, there were not a lot of metal shavings in the filter -- so I'm holding out hope that it's not too damaged internally.) They are suggesting a transmission rebuild or replacement.

I know 3 quarts is only about 25% of the total fluid, so I figure I should try draining two or three more times in order to have 60-70% new fluid. (See the old thread "Getting ready to do a drain-and-refill on my LS430" for the calculation.). If this doesn't work, then I'll have to decide what to do with the transmission. But I figure it's worth spending another $100 on transmission fluid in the off chance that this solves the problem and saves me a transmission rebuild (I was quoted over $4k!).

weldthedif

i would recommend buying about 12 quarts of WS fluid and doing this method. I used this and it worked 100%, and you will get most of your old fluid out.

FelixBabakuntos

Thanks, I just watched. So you didn’t drive between each refill, you just drained and filled the whole transmission as in the video?

Also, what was the transmission problem that you were having?

alextv

So you took this to a professional transmission shop and they didn't change the fluid by flushing. They must have tried to save you money because they thought transmission was gone. If it in fact does have radiator fluid in there radiator needs replacing. I have heard of this happening where it leaks into the transmission and surprised they didn't tell you it most likely needs replacing. Where else would the water come from. What I would do is replace the radiator which would most likely leak into any replacement transmission and do a full flush with good fluid. If then it doesn't work then it would need replacement but at least the source of fluid dilution would have been addressed.

FelixBabakuntos

Yes, they said it was unlikely to work but worth a try. (I had the transmission fluid in my car.)

Is radiator fluid able to leak into the transmission if the radiator breaks? I was under the impression that it must have been a previous owner who did something crazy and put the wrong fluid into the transmission — I’ve heard of this happening before.

alextv

I have actually heard of the radiator fluid leaking into the trans line. Replacement radiator is not expensive and easy to replace especially if it is the oem. I know it seems strange but others say it has happened. I can't think of anybody that would put anything different than correct fluid in trans as that is an expensive item. Radiator if oem is going to have to be replaced at some point anyway.

weldthedif

I changed my WS transmission fluid when i bought my LS in 2019. The car had 110k miles and no transmission issues. I was strictly changing the fluid as preventative maintenance, and the method i showed is the easiest and safest method to replace about 95% of the fluid in one go

bradland

A few things to consider-
A radiator failing to the point where it's mixing coolant and ATF is extremely rare. A vehicle would likely have close to 300k miles with the original (somehow) radiator.
This is not a one way street. If it were to happen the coolant would also be contaminated and there would be a milky mess inside the entire cooling system.
The Aisin A761E does not have a dipstick so filling any type of fluid is not a simple task. The fill hole on the side of the trans is in a very cramped space. Not really a situation where accidents just happen...

alextv

Agree on the extremely rare point but the age can happen even for a new one. These radiators generally fail from the plastic top. In this case the minute leak between the two systems could only occur when pressure builds in radiator and expels into trans line and not trans fluid into water. I have seen this happen with blown head gasket where water was in oil but not oil in water or so small it was not noticeable. I have always heard also that the fluids would mix back and forth but there are cases where that does not happen. That foreign fluid got in a sealed trans somehow.

Striker223

It can happen, and it may only leak in one direction depending on what side has more pressure etc. Open the actual rad cap and check if there is trans fluid on the top of the coolant.

I don't generally drive cars for the first two drain and fills, after the 2nd I'll go drive it around and bring it back for the last one.

FelixBabakuntos

Thanks, guys. I got the radiator replaced (along with the timing belt), since it was due anyway. (Roughly 170k miles.) Going to drain and fill again and see if there is any difference. I'm also sending my ECU back to SIA for further testing in case they missed something. If that doesn't work, I may see if someone I know with an LS430 can swap his ECU with mine to see if this solves the issue.

If I do indeed need to get a new transmission, do you all recommend a rebuild or a used transmission? From the two shops I've asked for quotes from, a used transmission with ~50k miles would be roughly $2,500-$3,000 to purchase and install while a rebuild would be $3,500-$4,0000. The rebuild would be warrantied for one year, however, while the used transmission would not.

alextv

To give this transmission a chance do more than the drain and refill as that is only 2 quarts. Do the method described above to remove as much as possible.

FelixBabakuntos

Quick update in case anyone else has the same problem.

I filled/drained one more time, and there was little if any change in the transmission smoothness. I was on the verge of giving up and getting a new transmission. I decided as a last-ditch effort to avoid spending $3000-4000, to buy another used ECU on eBay. I figured that even if this used ECU was also damaged, the transmission should perform badly in a somewhat different way and that this would be a good indication that the real issue was the ECU. But when I swapped the ECU, it turned out that everything with the transmission was solved. There is no harsh shifting, and there is no longer a long lag before changing gears when I aggressively accelerate. The car runs great!

I'm going to send my original ECU back to SIA and see if they can properly fix it this time. Luckily there is a warranty, so I don't have to pay for this (apart from shipping). But clearly since this is an ECU problem, their "fix" failed. Hopefully they will refund me if they don't solve the issue this time.

funcrusher

That sucks. I’ve heard good things about Relentless Motorsports. I’m thinking of sending mine out to him just as preventative maintenance

FelixBabakuntos

I considered it sending it to Relentless but they charge $400 while a used ECU in eBay was ~$350 with 30 day returns. So it made more sense to just buy an ECU with very little risk than to gamble $400. (I say “gamble” since at the time, I could not have been sure that it was an ECU problem.)