Harsh 2-3 Shift after Magnuson & ATF Cooler Install

Truck / setup

• 2020 Toyota Tundra 5.7 Crewmax ~53,000 miles, no racing, extreme towing, extreme duty anything. Pavement princess essentially.

• Installed Magnuson TVS2650 supercharger about ~2 months ago @ ~51,000
  
  • Ran the standard Magnuson tune that comes with the kit initially
    
• At the same time (while the truck was down) I also installed a Hayden 679 external transmission cooler + Toyota OEM hard lines, and did a transmission fluid drain & fill with Toyota OEM WS ATF.
  

When it started
For the first ~500–1,000 miles after the install, everything felt normal.

Then we did a ~700-mile round trip to visit family. On the way back, it randomly slammed/shifted harsh on the 2→3 one time. It wasn’t WOT — more like ~30–50% throttle. No issues the rest of the drive home.

After we got home, I found a way to replicate it, and now I can basically trigger it whenever I want.

Exact reproduction steps (100% repeatable for me)

1. Put the truck in manual/S mode
   
   
2. Hold 2nd gear around ~35 mph at a steady speed
   
   
3. Tap up to 3rd
   
   
4. As the trans is “deciding” to complete the 2→3 shift, roll into the throttle
   
   
5. It will slam into 3rd every single time
   

After I do that once, it almost acts like a learned behavior — it will then shift rough from 2→3 the rest of the drive, even with lighter throttle.

Weirdly, WOT shifts are smooth some of the time. Although sometime they're not, and it's extremely violent. The more common issue is mid-throttle / rolling into throttle during the 2→3 shift.

Things I’ve checked / tried

• ATF level checked twice — both times it was perfect
  
  • Slow drip at about ~105°F pan temp
    
• Typical ATF temp while driving is ~185–200°F (so it’s not like it’s ice-cold when it happens)
  
  
• Before switching tunes, I noticed something odd:
  
  • If I went into Tow/Haul and did a few pulls (WOT, then 3/4, then 1/2 throttle through the 2→3), it would smooth out significantly
    
    
  • Switching back to normal mode, it would sometimes “carry over” like it learned the smoother shift behavior
    
• About 3–4 weeks ago I got an OTT tune
  
  • It seemed fine for a while (although I wasn’t intentionally trying to trigger it)
    
    
  • But the harsh 2→3 behavior has now returned, and I can replicate it with the manual-mode method above
    

What I’m wondering / looking for help on

• Has anyone else had a harsh 2→3 shift after a Magnuson TVS2650 install (or any blower/tune change)?
  
  
• Could the Hayden 679 cooler be contributing?
  
  
• Would you recommend I remove/bypass the aftermarket cooler temporarily as a test?
  
  
• Any known fixes?

At this point I’m mostly looking for ideas and similar experiences. I can provide further details if I left anything out.

Thanks in advance — this one’s driving me nuts.

 

No the cooler wouldn’t have effected it, sounds like you might have a solenoid that is starting to stick or become an issue; I’m at the Dr right now but I can look through them and see which one attributes to the 2-3 shift… from my understanding the solenoids starting to fail on the AB60 is kind of common

If you have access to tech stream or a more sophisticated scanner like snap on/autel you can normally put the transmission in a sort of heightened detection mode to set a CEL, I’ve never tried it but I’ve read about it during my transmission trouble; also with techstream you can reset the learned shift points and gently drive the truck for a bit to have to relearn all the shifts, might help with the issue but won’t solve it

 

Forgot to ask, when you added the cooler and did the D&F did you use legit Toyota WS? Or did you just grab a off the shelf fluid?

 

Unfortunately, I do not have access to a tech stream or anything like that. I've been using the OBD Fusion app to monitor transmission temperatures, and there are no codes that are present according to that. I used legit Toyota WS, straight from the dealer. When we flashed the new OTT tune, I think it resets all the learned shift points at that time, and the problem came back shortly after.

 

Yeah they should have reset the TCM when tuned; if you want to get techstream in the future it’s about $20 for the OBD II cable to usb off Amazon and then you can get the software from various places on here

 

I would try adding a 1/2 quart. I like a nice trickle, piss, not a slow drip. Easy to try...some of us add a little extra as the pan can accommodate it. Also have OTT see if the tune has too much torque reduction on upshift or increase in line pressure.

 

I actually just tried adding 1/2 quart this morning to see if that helped, and the issue still exists. I called John from IPT transmission and he's pretty convinced that I hurt the transmission and that it needs a whole new built performance transmission. $6,500 plus 1 month without the transmission. I wouldn't have done the supercharger if I knew it would've roasted the transmission in the first 1,500 miles, with almost no aggressive driving.

 

While John is very knowledgeable, I would honestly give new tune a try.

reach out to @snivilous .

I had IPT valve body installed, and the 1-2 shift was so harsh it felt torturous, I reached out to sniv and with a new tune running TRD shift map, it felt wayyyyyyyyyyyy smoother.

 

It sounds like a software issue more than an actual physical transmission issue. The fact that it went away with the tune until the truck re-learned that behavior makes me think the tune can be adjusted to hopefully fix it.

 

On your "truck / setup" portion you don't mention the OTT tune but rather say stock Magnuson?

You talk about the OTT tune in the "Things I’ve checked / tried" section

When did you introduce the OTT tune, before or after the Hayden install? or at Hayden install.

The timeline is not clear to understand what could be the root cause of this behavior?

I would avoid driving it until is clear what it is as you could further damage the transmission.

Can you put the Magnuson caned tune back on? That will tell if is the tune or not. Start with that?

Eliminate each new condition introduced, one at the time, if you can.

 

And also post this in the supercharger thread, better response there

https://www.tundras.com/threads/general-supercharger-thread.85513/page-975#post-4103863

 

It happened on the stock magnuson tune also. He's on the SC thread too.

 

OK, so it didn't happen before the Hayden kit install. So is not the tune, that we know now.

Something went bad during the install or coincidental something failed around the install timeline? You get any codes?

 

I'm not the OP. He stated no codes.

 

Have you tried the stock accumulator spring in the B3? accumulator. IPT doesn't put the stronger spring in as the 1-2 shift was a bit harsh for some.

 

I am watching this very closely because I am putting a Setrab trans cooler on my Magnuson 2650 actually next week and I don't want any surprises. Hopefully the cause can be identified?

 

I just swapped my oem cooler with new lines and magnefine filter. No issues. Most likely a tune issue.

 

Let me the the outcome after everything.

 

I haven't, so here's the funny thing, I found TRD shift map seems to feel the best, then I did a full transmission flush, and it feels REALLY good like borderline shifting like an 8hp good, but then I got P2757 while towing, clear the code and it hasn't come back.

Now I'm going down the road of working out the costs benefit of a full built AB60 vs the 8HP95 route.

 

Not to derail OP's thread...
I dealt with p2757 for years. It went away after I disabled flex lock and overfilled the pan with an extra quart after the trickle check. I know IPT says to overfill to alleviate issues with the ab60. We need a 8 speed!

 

@snivilous - how does one acquire the trd shift map referenced in this thread?

 

Send me a PM with your email and I'll send it over. It's also uploaded somewhere in the HP Tuners forum Toyota Repository thread but I'm too lazy to go searching through there.

 

TRD shift map can only be used (or should only) when sc’ed, right?

 

I don't know why it would matter. @Mdl knows more about transmission tweaking and results than I, he'd be better to speak to it. The shift points don't change with the TRD map, just the line pressure values.

 

So harsher/stronger lock ups; interesting that they didn’t adjust the shift points

 

The base line pressures are changed a little bit 1-8 psi increase as well as TCC offsets. Not much of a change but can help firm up from the added torque. They only changed the torque reduction on 1-2 and 2-3 upshift to firm it up. As well as the 2-1 downshift in shift schedule.
It's not a big change...