Torque converter problems (P2757) S/C'ed 2017

Hey folks,

So here is my story. Magnuson supercharger installed at 63,000 miles. Currently sitting at 71,000 miles. The truck has saw about 4000 miles of towing during that time. No mods other than s/c'er. The last 1800 miles was a trip from VA to AZ, 95% of it on I-40. My husband and I made the drive together (29 hours straight through). While I was sleeping, he woke me up at one of the refuel stops because the CEL came on. I pulled the laptop out and used VCM Suite included with the Magnuson kit to look. P2757 has shown up as a PERMANENT code since installing the S/C'er. I didn't pay attention to the fact that it was also listed as a pending and current code. CEL on and traction control disabled.

Cleared it, it came back. Cleared it again, it came back, etc. Husband driving. He was in a rush, put it in drive with tow/haul on and proceeded to cruise at 80-85mph (trailer weighted around 1500 lbs). Seems this truck has the tendency to just unlock the torque converter and remain in 6th gear rather than downshifting to 5th and locking up TC. I already knew from monitoring trans temps in past that the fluid pan temp would raise to around 215-220 and fluid temp at TC would peak at around 260 deg F if allowed to remain in 6th gear with high load and TC unlocked.

I slept for about 6 hours and I'd hate to know how long the truck stayed in 6th gear with TC unlocked and with high load, but suffice to say, it was A LOT.

When I took over driving again, what I immediately noticed:

- P2757 cleared successfully, but returned pretty quickly (along with Traction control disabled)
- when TC locked in 4th, 5th or 6th gear (and confirmed with VCM logging), when giving more throttle, I could definitely see about a 50rpm rise (mind you - TC is in lockup mode) - i.e., TC clutch slipping slightly
- slight rattling noise heard in P and N and slightly louder in gear and stopped. Noise goes away at any speed other than idle and stopped
- watching fluid temp at pan and torque converter while it was slipping in lock-up mode, I noticed that both temps were sitting at around 208 deg F (normal is for both to stay 185-188 when TC locked). As said, this is when TC clutch was in lock-up mode but was having that ~50 rpm slip. Temps stayed 185-188 remainder of trip with me driving. I drove like I had an egg between my foot and the throttle.

I drove the last 1000 miles, being extremely careful not to allow the TC to remain unlocked at all (manual downshifting to 5th and 4th on all inclines) other than the brief second it remains unlocked when downshifting. DTC never returned (pending or current). I didn't push it or test it out until about 100 miles from home here in AZ. TC clutch remained very solidly locked anytime I was increasing load in 4th thru 6th gear up to the point where ECU commanded TC to unlock. I.e., no slipping when in lockup mode.

Transmission shifting is no different now. Shifts butter smooth. Nothing abnormal to report. Fluid was changed at 65,000 miles (2000 miles after S/C'er installed and towed 3500 lb trailer from AZ to VA). Fluid analysis looked pretty good per Blackstone.

So it's apparent that the torque converter was overheated and the clutch began slipping (but doesn't slip now). Rattling noise remains.

I will be doing fluid flush using cooler lines, dropping pan and replacing filter in the upcoming few days. Will also send fluid for analysis.

Is it reasonable to think I can get by with just changing the torque converter for a new one and the entire transmission isn't toast?

Think with above information that there is any hope of salvation with frequent fluid changes?

Any info as to what I should expect is helpful.

Thanks
Travis

 

1500lb trailer shouldn't have caused any issues. Maybe 7500lbs. You need to find a qualified tech that can diagnose before swapping out parts. Only time I had a rattle in a transmission was during TC lock up, tech said it was a check valve in valve body. Rattled another 75K miles and I sold car.

 

+1

I have what sounds like worn converter bearings on my old 4runner (328K) but also need to find someone who is willing to repair vs. just replace the trans, uggg.

 

I'm in agreement with all said above.

However, that was a long post. To summarize:

1) for a fact, the TC got very, very hot for long periods of time
2) while TC clutch was locked (as confirmed by my observation and the VCM program), saw ~50rpm rise when adding throttle - it definitely was slipping and I know this for fact
3) P2757 DTC confirmed this multiple times - this code is a 2 trip detection logic and it tripped the CEL when the TC clutch was slipping while in lockup. This happened at least 5 times.
4) being gentle with the throttle and manually controlling gears to keep the TC clutch locked resolved the issue for the remaining 1000 miles

I'm telling you - he was downright ROUGH on it for the first 800 miles. It was partly his driving but moreso the (IMHO) horrendous programming for the transmission, although I guess Toyota didn't factor in the extra 150hp and tq added by a supercharger. This truck will allow the torque converter to remain unlocked in 6th gear at high load indefinitely, which causes a constant 260 deg TC fluid temp and 215 pan fluid temp.

I think the TC got so hot the clutch was slipping after hours of operating at high load in 6th gear with it unlocked and (maybe) in lockup here and there periodically. I was sleeping but everytime I woke up, I'd tell him to ease up on it or use manual mode to downshift so it would lock the TC.

Bottom line is something happened and I'm fairly certain the above is what it is. Maybe not, but a 260 (or higher) TC temp is not good for long periods of time.

I'm just wondering if the rest of the transmission is FUBAR if the TC got overheated and started spitting debris into the fluid, thereby starting an endless cycle of wear and ultimate decimation.

I think there has been permanent damage done to the TC due to overheating and it should be replaced but I REALLY don't wanna put that kind of time, money and effort into it.

Mechanical parts like this are susceptible to overheating and damage, especially after adding the power of a supercharger without knowing exactly what's going on and some crappy programing.

 

I'm not too experienced with superchargers, nor do I own anything supercharged, the closest thing I owned was the MR2 turbo, but that was a manual, and loads of fun, but anyways... I've been reading on the Lexus forums about the SC400 and the people who run superchargers usually have issues with the TC as it is the weakest link, just before it takes the whole transmission with it.. I understand you can get them rebuilt and beefed up to handle the additional power, but I'm sure your main concern is the overall health of the transmission..

 

just something to note- regardless of supercharged or not, towing in "D" auto the trans will be shifting around, TC locking and unlocking. Towing in "S" where you select the gear is best and will keep the TC locked up better. I have noticed this myself when towing even light loads on the highway (1000-1500lbs). So, when towing you would usually keep it in S4 or S5 depending on speed, even if it is in tow haul mode, use S vs D for better trans lockup and lower temps.

 

Great post with good factual information.

Here is my take.

The high temp warning light for transmission is 302F. I'm fairly certain this is on TC temp.

Those pan temps are about 10-15 degrees hotter than would be expected on a 2017 with aux trans cooler, towing a load. The SC might add a few degrees to this however.

The unlocked TC was likely dumping heat into the system.

I don't believe the trans temps were a sign of impending doom. 2019+ units run 40F higher by design (no aux cooler and major change to transmission shifting map that chases lock up like a fiend.)

So I think the unlocked TC is an issue but not the issue. In other words...in another 10,000, 20,000+ miles it would have shown up as an early failure (if driving in same conditions).

I think there may have been mechanical damage somewhere else to cause TC to slip (great job getting data to find this...super cool).

Something broke downstream of filtration and hurt the TC and the clutches.

 

If the truck is acting weird and slipping I'd pull the converter or take it to a shop and have them inspect it. IPT makes upgraded converters you could swap in if you wanted at that time. A few weeks ago I got my trans very hot by being retarded in the sand, and got the TC to ~285F and had a nearly catastrophic failure. No light on the dash, dash gauge barely starting to move, etc. But it began slipping way worse than what you're describing. I swapped the fluid hoping for an easy fix but it didn't help, so the truck is at the shop right now getting a fully built IPT trans and TC put in since the shop thought my issues were more than just a TC. I would start with swapping fluid and see what happens, and next step would be talk to a transmission shop and get their two cents if just swapping the converter will fix it.

 

Thanks for replies! I called the Aamco shop in Flagstaff, AZ (2 hours away but closest place to me with transmission shop). After finding out about s/c'er, they just flat out refused to touch the truck. Contacted another shop, which I will take in on Friday for diagnosis. I didn't tell them about the supercharger, but guess they'll find out on Friday. There's only 1 other left in Flagstaff. After that, I'll be driving 4 1/2 hours to Phoenix and hoping and praying it doesn't leave me stranded before then. Babying it for now. It drives fine, shifts smooth, torque converter clutch doesn't slip when locked up - nothing abnormal other than the rattling noise at idle, which has worsened somewhat. But I'm convinced it's the torque converter with the code, the slippage and the noise.

IPT sales a high stall torque converter, which is the last thing I want with the extra power (and heat). I sent Level 10 an email asking about their Bulletproof TC because the one listed on their website does not list the AB60F transmission as one of the transmissions it is compatible with and doesn't say anything about whether it's a high stall TC or not. Anybody know the answer to those questions before Level 10 gets back to me??

Thanks

 

https://www.importperformancetrans.com/index.php?l=product_detail&p=5423

 

Roger that - I know a shift kit is likely in the future, but that's not really what I'm looking for at this time. No shifting issues currently. Only torque converter. And I might consider the IPT. I just don't want or need the extra revs to potentially heat the torque converter up because that's what caused this problem in the first place. I just don't know if the Level 10 TC is a high stall TC as well.

This $2000 ordeal is gonna break the bank as it is. Plus I don't have to pull the transmission out to replace valve body. Maybe later...

 

Absolutely, I can't remember the last time I drove my truck in "D". Especially on low speed, curvy roads,(towing or not) the transmission will shift needlessly and constantly in 'D', only creating additional heat from an unlocked Torque Converter. It's no wonder vehicle manufacturers have had to include software in the transmissions to down-shift on their own, with a brake-tap, while ascending steep enough grades. The drivers of today wouldn't dream of touching the gearshift except for P-D and R!

 

I don't tow or haul heavy loads, and I no longer drive in "D".

I stay in S-4, and manually up shift to S-5, and sometimes S-6 as needed... whenever I come to a stop, I manually shift to S-4 again.

 

We might be twins!

 

Any updates here?

 

I'm memory (mammary?) serves a supercharger install should include edited ECU tables for both fuel AND transmission control. Transmission edits include shift point and pump pressure regulator mapping.

Any chance this trucks ECU is lacking pump pressure edits to account for the increase in force application?

 

Need that update... don't leave us hanging.

 

OP was last eeen on February 5th...

 

Hey - sorry y'all. Update is this: had IPT torque converter installed at trans shop in Flagstaff, got the truck back and still making the exact same rattling noise at idle. And what exactly was making the rattling noise, you ask? Because it very obviously wasn't the torque converter.

The friggin supercharger coupler. I removed the supercharger snout myself and replace the stupid $80 to fix it. The torque converter was fine all along. It did get hot enough for the clutch to slip, but apparently Toyota threw a very durable one in my truck.

So yeah - been happily cruising along for the past 20,000 miles. UNTIL a few days ago I started getting this very distinct jolt when the torque converter disengages at low speeds in 6th gear (around 40-45 mph range). I have a fluid sample on it's way to Blackstone to see if there might be coolant in the fluid (also have small amount of coolant loss). This seems to be a fairly well documented issue on these vehicles, but it's strange that my issue just started at 87,xxx miles.

 

Any more updates?

Any idea what was specifically changed and can those altered parameters be added to an older truck via vftuner or the OV tune?