weird transmission issues

2016 Limited 4x4 5.7 non-flex fuel, 135k, farm truck so it gets off-roaded and beat like a rented mule every day.

Yesterday the transmission started doing something weird out of the blue. Going down the highway about 50 mph and slowly accelerating, the transmission won't shift smoothly from 5-4, it "hammers" back and forth. A slight adjustment in the throttle stops it. I am thinking now it might be slipping slightly in lower gears too. NO CODES. Transmission has been serviced twice, last time was in July. Vehicle is in excellent shape mechanically, MAF has been cleaned, new coils and plugs, new coolant, etc etc. My first thought is possibly a wiring issue under the truck, like maybe a weed or Sagebrush has messed something up, I plan to check that tomorrow. Has anyone experienced wear in the valve body at this mileage? TransGO has a couple update kits for the tranny to address wear in the boost solenoid and other places...

Only bulletin on it is to take it to the dealer and have the ECU re-flashed...and they'll try to sell me a new tranny I'm sure.

It's been used to pull trailers some, but by no means excessive or on a regular basis. It's never gotten hot. I'm kinda surprised its acting up really... Any ideas of things to check are appreciated.

 

Have you been doing a drain + fill of the transmission fluid at intervals over the time you've had the truck? The fluid doesn't last forever, and if you let it go too long you can have problems.

 

Yes, first at about 68k and second about 10k ago. No issues noted at fluid change. I hit something in July and punched a hole in the tranny pan, trans shop welded up the hole and serviced the trans, I have had zero issues until yesterday. Probably 20k miles put on the truck since that repair.

 

Gotcha. Yeah, that's a tough one. A high end scan tool that could look at shift times and trans in/output shaft speeds would be helpful to see if it's actually slipping, and/or see if it's a weird solenoid issue or something. I don't know.

Is your fluid that's in it now in good shape? Not brownish or burnt?

 

I had transmission replaced on 2011 Sequoia at 130k miles..bought it with 123k miles 6 months prior. Started getting "stuck" in gear (4th or 5th) while on highway, then went into limp mode eventually. Took it to trusted mechanic, and he found lots of metal shavings when he dropped the transmission pan. It's a 4.6l and previous owners would take it to Colorado on occasion from Central Texas to visit family there. They had lots of kids, so I'm assuming they would load it pretty heavily on their trips. This possibly overworked the tranny during multiple trips through mountains? Anyways, hope you don't have the same problem as ours, but I recommend dropping the transmission pan and looking for metal shavings. Good Luck!

 

Out of curiosity, I would plug a scangauge or ultragauge or use some other odbii/app and read the pan and torque converter temperatures. Make sure not much slippage , etc. going on. It may give you some ideas.

What kind of fluid did the shop use? I assume it's not low.

Also we assume not all of the 135K miles been driving slow in the farm in 1st-3rd gear & with heavy load ... Or has it?


p.s.
I've been waiting for the 5-spd manual NA 5.7L V8 but Toyota decided to go with the 10-spd auto TT-V6

 

Well if the transmission was equipped with a dipstick I could tell ya Most of the farm miles are more of a prerunner-type experience. Lotsa sand and terrain.

the complete lack of a code and the sudden onset of symptoms is making me think it’s gotta be electrical. I’ll find out tomorrow…

 

Get underneath and see if there are any drips anywhere... could be worn out , electronics or need of fluid...good luck OP!

 

Another thing to check is your ground wire for the transmission, its bolted from the tranny to the frame and people have posted about the rotting away and having shifting issues that are resolved when its replaced.

 

low fluid level or a plugged filter.

 

Well, everything looks beautiful from underneath. No stressed wires, zero leakage whatsoever, no corrosion, shifter connection is solid...I'm stumped. I tried disconnecting the battery and resetting the computers, we'll see if that helps. I wondered about the fluid level, but one would think that would have manifested itself as soon as I left the tranny shop in July, not waited until now to suddenly be real bad...

IF IT WOULD JUST THROW A CODE

 

You said you cleaned the MAF sensor. You could try cleaning it again, I know it does correlate with transmission signals for the ecu. Simple thing to try. Hopefully you get this resolved soon.

 

Got it straightened out. The winner is: ... defective spark plugs. When the trans guy took it for a test drive it finally threw a code, for a cyl #7 misfire (same problem I had dealt with a few weeks earlier, replaced all the coils, thought that was it). He verified that the coil was bad, then pulled the plug and found it gapped it over 100 thousandths. It wasn't that way when it went in. Friend with an F150 said the same thing happened to him once with OEM plugs. At any rate, another set of plugs and yet another new coil got me back on the road. Transmission has no issues.

 

Great news. It's such a good feeling when your mystery issue (that seems like it could be a big deal) ends up being something super simple/small. Glad that got sorted out for you