Rough transmission shifting

My 2003 tundra is shifting rough once everything is warmed up after driving. The truck had the transcooler go bad over a year ago causing the fluid and coolant to mix. After that was repaired, the fluid and filter was changed at least once, maybe twice. Does the fluid need to be changed out again due to possible residual coolant mixed in the oil? I'd so, just a drain and refill or a complete flush of the transmission? Thank you in advance.

 

Twice is nowhere near enough if drained & filled.

It may be worth a shot, I would do at least 3-4 more changes. Unfortunately the damage may possibly already be done. Ymmv

 

I'm currently going through this. The pink milkshake might settle to the bottom, under the good fluid. When ever I checked my fluid on the dipstick it looked good. But then I drained it, and I had pink milkshake. Drain the fluid into a clean container. If it looks good, put it back in.

 

Do a full transmission fluid changeout via the tranny cooler lines. I can’t recall offhand but I think you need 10 quarts total. Also, use a synthetic fluid equivalent.

 

So not just drain and refill? Take the coolant line off and run truck while adding new fluid?

 

It’s a way to insure you’ve got most of the contaminated fluid diluted to the point it shouldn’t continue to cause an issue. You can also do the same with multiple drain and fills, but then you could be doing more damage until it’s diluted enough. Usually with the tranny cooler fluid change out method, you only run the truck long enough to drain 2 quarts. After you add 2 quarts, you can then run the truck again to drain 2 more quarts. It’s worth it if you’re not running synthetic fluid already.

 

Thank you. I read somewhere to have 10-12 quarts to make sure all the old fluid is flushed. Does that sound about right?

 

That sounds correct. I haven’t done it since 2003, so I can’t recall exactly. What’s most important is that you pull the correct atf radiator drain hose. I used Mobil 1 atf to replace dexron 3 fluid. I don’t know if your truck takes t4 fluid or not but a lot of people here have been using Valvoline MaxLife atf.

 

It's not until 05 that they use the 5speed trans that requires WS rated fluid.

Valvoline blue bottle stuff should be fine iirc. Maxlife is the red bottle.

 

The valvoline web page indicates maxlife is compatible with both t4 and WS. Is that not the case?
https://www.valvoline.com/en-thailand/our-products/automatic-transmission-oil/maxlife-atf

 

Yep. It's compatible with both.

I think the blue bottle is a couple bucks cheaper. And he'll need at least 3 gallon jugs (if not 4 or 5) for the full change. Since he has to flush so much, it may be worth the savings.

 

IDK, if it was me I’d pay the extra few bucks since the maxlife specifically states some of the additives are for slippage and shudder.

OP, also double check your fluid is at the right level on a flat surface after getting the fluid up to temp after a short backroad drive.

 

I hate to be the bearer of bad news, but if you've been driving around with coolant in the transmission for a year, I suspect the damage is already done. But flushing the fluid may be worth a try.

If you want to do it right, drop the pan, clean it, change the filter, then re-fill and begin the flushing process at the cooler line like is shown in this thread.

That's what I did when I had a pink milkshake on my '02 4Runner and it took 9 gallons before the fluid was running clean.

 

9 gallons.... What do we think about adding fluid by the other cooler hose while flushing? I'm thinking my long funnel will fit nicely in that rubber hose. Better than trying to get it down the loose fitting dipstick pipe. The trans fluid flush machines I used to use... Used the two cooler lines.

 

Yeah, 9 gallons. You really want to be sure you get all of the coolant out. I would think that adding fluid through the return line would go kind of slow, but I've never tried it. I've never used a flush machine, but I presume they pump the fluid back in the return line.

 

9 gallons sounds like the residue from the contaminated coolant is getting stuck to the internals of the transmission and is difficult to break free. Not a good scenario.

 

It's not so much that the ATF/coolant needs to break free, it's just that it's constantly mixing fresh ATF with contaminated. You just have to do it long enough to get the fresh-to-contaminated ratio down to almost nothing. I used clear vinyl tubing so I could easily see the fluid coming out. I flushed until there was no traces/streaks/etc. of contaminated fluid.

Think of it this way: say you have a quart bottle of acid. You dump two ounces out and replace it with two ounces of fresh water. Keep repeating that process over and over and eventually the acid-to-water ratio will be so low that the fluid in the bottle is safe to drink. But if I'm going to drink it, I'm going to be damn sure I repeat that LOTS of times.
Incidentally, that's why I'm a proponent of transmission flushing (not with a machine, just using the transmission to pump the fluid) as opposed to the "spill & fill" one gallon at a time regimen. With the "spill & fill", at each change you're just getting slightly less dirty fluid.

 

That makes sense if the new fluid was getting completely mixed with the old fluid.

Draining 2 quarts out of 12 quarts at a time would leave you with 83% mixture.

0.83^number of iterations =

0.83^18 = 3.5% for 9 gallons
0.83^6 = 32.7% for 3 gallons

I just assumed it really wasn’t mixed much at all until you put it in gear and started driving.

 

On a spill & fill it is.

I think the numbers are even better than that for flushing because you're pushing virgin fresh fluid through the system (assuming you dropped the pan, cleaned it, changed the filter, and refilled with fresh fluid)
and not recirculating the mix.

If the engine is running, the transmission is circulating fluid throughout the transmission. A flush is done with the transmission in Park.

 

A little will remain in the valve body, until you garage shift through PRNDL and activate lock up.

Anyway, dropped my pan and cleaned it out. Had some aluminum metal shavings and a pretty big chunk. Also, some sludge from the strawberry milk shake that was solidified on the bottom.

I thought may as well put this filter and fluid in that I already bought. And, I'm happy to say it shifts better than ever. No longer slamming into 2nd. There is still a little metallic ping shifting into 2nd, but it's smooth. Sounds like slop in the drivetrain. Whatever, I'm happy. I can drive it like this until it explodes.

 

@mbreed2 how many quarts did it take to get it clean? These transmissions are tough. Maybe you'll be ok.

 

I'm at 7 gallons so far. Milk shake is gone but it's still cloudy. Like @tvpierce has said, it will probably take 9.
I did a drain and fill, then dropped the pan and cleaned it. Changed the filter and put the pan back on and filled it up. Since then I have flushed about 5 gallons through the cooler lines.

 

When does this probably typically surface? I’m at 140k miles

 

More based on time I would think. Maybe 10 years. Someone said if your radiator plastics has turned brown, it's time.

 

I finished today. I put 9 gallons through. It's running clear now. May have been good at 8. Did the last one for good measure.

 

Do you still have your old radiator? If so, would you mind investing a few minutes to remove the ATF cooler to perform an autopsy. You just have to pry open the tabs that hold the plastic tank, then you have full access to the ATF cooler. I think it would help folks in the future to see how it failed. I bet you'll find it failed at the o-ring seal. It's the weak link, and a really bad design because that joint has to seal both ATF and coolant.

Here's mine from the 4Runner. The 2nd and 3rd pics show the failing point.

 

I didn't get a new radiator. The radiator is new. I pressure tested it and it's good. I think whoever had it before replaced the radiator and traded it in. I'm gonna pull the drain plug in a few days to check the fluid, to be sure.

 

Check your overflow tank. Since the ATF is oil, it floats in water/coolant, so will tend to be at the top of the radiator, and be bled off into the overflow tank. (That's if there is/ever was any ATF in the cooling circuit.)
Did you have the ATF cooler lines removed when you did the pressure test? That's where you'd see the failure -- as coolant forces itself past the o-ring and out the nipple of the cooler.

 

OP, don't know if you got this fixed, but here's a video of the method using the transmission coolant lines

https://www.youtube.com/watch?v=RumPXivBlk8&t=729s

 

@tvpierce that's a good idea. I thought about isolating the radiator, but I didn't have caps for the upper and lower hose connections.