4spd 2.7 Highway help

Hey guys, i need some insight and tips here. So this is whats going on:

I just recently entered a serious relationship, and my girl lives four hours away, through a lot of mountainous interstate roads...

2015 ACLB 2.7L 4spdAuto with 265/75/16 tires on alloys off a 2016, and a better flowthrough glasspack exhaust. Getting 21mpg on daily commute to work, having issues with mpg and gear selection at highway speeds....

Im literally at wits end with the trip because although i can handle 18mpg going 70mph in a 4spd 4 banger, the constant shifts down to 3rd are driving me crazy because not only is it guzzling more gas when not necessary, but it for some reason wont upshift to 4th and OD again on its own most of the time. I can go over a mountain and it will take until halfway coasting down the other side to realize it can go down to OD, so i end up taking cruise off, and resuming to that it shifts at a reasonable time.

What can i do? Can i do headers and a CAI to add maybe 10hp and will that be enough to hold 4th at least on average grades, instead of it dumping into 3rd and ramping up over 3200rpm?

What do i do to fix the laggy upshift after breaching the crest of a mountain? Do i just keep manually stopping and resuming cruise to make it shift up?

Finally, whats the best speed for these trucks with this drivetrain to get the best mileage and reasonable shift patters? i just spent over a hour searching old threads and all im getting is the same old "trade it in for a 4.0" and "dont use cruise" etc. Can i get some real answers from people with the same drivetrain?

If a few performance mods and 10 or so hp boost would help hold 4th and OD instead of dumping to 3rd, that would be huge. Or if someone knows that speed this truck likes to cruise at that would be helpful for the gas conservation as well. Im putting on thousands of miles a month to see my girl, so 2mpg saved is a lot of money when im burning 50 gallons twice a week.

One more thing: how feasible is a turbo or supercharger upgrade? im broke, and trying to save for a future with my girl, but if a turbo is an option for under 2 grand, i might consider it if it would help the powerband or cruising/mpg issues. Any thoughts and advice welcome.

Thanks guys. This forum has made a huge difference with a lot of questions ive had! Keep being awesome.

 

You got a few options a) trade it in b) tell friend to move to flat lands c) what is the altitude of the mountains your going up? The 2.7 was designed to be a work horse.Not designed for cruise control on high mountainous regions. You could try bringing it to dealer and having them reprogram the ECU to accommodate your driving. It’s a shot in the dark but might be worth it.

 

Is the dealer reprogram even a possibility? I didn’t think that was even an option, especially since it has 6.5 years and 95,000 miles of drivetrain warranty left...

 

How much of a difference is that really going to make with shift patterns and mpg though? If all it does it significantly reduce my off-road ability and don’t help the gear selection then it’s probably not worth it.

 

Yeah, I'm sorta'f in that situation with my 2013 reg. cab, 2.7, auto., 4X4. Except for me, the mpg. is not as important. I talked with my mechanic about changing my gearing & his first response was, lets see about reprogramming the trans. shift points. I don't understand how this may help, but I'll give him a chance. I hope you come up with something, but to me it seems anything that would help with your mph. will make the shifting problem worse. Good luck to the both of us.

 

Best you can do is ask them. I don’t see how any ECU air/fuel trim (aka volumetric efficiency) is going to significantly effect your off road capabilities. You have a second gen engine, therefore it was design to give you better torque at low RPM’s. Trimming your volumetric efficiency will make you run a little richer and it could help you out with cruise on the mountains. I mean you could change the thermostat to a cooler temp and probably get the same results without reprogramming anything. I have the 4.0 no problem with any mountain or hill in cruise control. Then again I don’t know the altitude of the mountains your driving on. Believe it or not that significantly effects volumetric efficiency.But to really see where the problem lies you would have to monitor the vehicles inputs an take a snap shot of these measurements while the symptoms are occurring.
I’m just throwing ideas out there based on the repairs I’ve encountered on the 2.7 engine.
I wish you luck and kindly keep me posted.I’m pretty sure one day someone else will pull into my garage with the same problem.

 

believe it or not, higher RPM in lower gear isn't necessarily burning more fuel. Although it makes more noise, the engine isn't working as hard to do the same amount of work.

That being said, the 2.7 was never meant to win any races, it's engineered for torque and reliability, and it'll excel at both of those. A re-gear is most likely going to be your best next step.

 

Don't bother with the thermostat, modern EFI engines don't care. You may actually force the engine to stay in open loop which causes it to run richer, making your fuel economy issues worse.

 

This will serve you well if you dont have to worry about smog

https://www.lceperformance.com/ProductDetails.asp?ProductCode=1041055

 

I also agree with downsizing the tires to the 245/75/16s.

That would be effectively regearing the truck just slightly, and the reduced mass will also give you a little performance back.

 

Can't really do anything but it's supercharger. Cruise control is stupid in my truck will downshift for everything when if pedaled gently will pull great. Again, a workhorse, not a sprinter. Sorry for just confirming

 

Your probably right “WILL”. However, these vehicles are over geared as it is. Usually in my experience when cruise fails to shift, its a reprogramming of shift solenoids and cleaning them out or replacing them due to dirty tranny fluid.
Not saying this is Cedar’s issue but not totally ruling it out either @95k for mileage. All I can do without seeing the vehicle is through things out there that I’ve come across and hope that the least costly works.

 

Good point, I forgot how much better my shifting was after I did a good drain and fill

 

Maybe I wasn’t clear - I have 95k remaining on my 100,000 mile warranty. I bought the truck this summer with 4,989 miles on it, four years old lol. It’s up to 8,650 miles now. It’s possible a tranny fluid drain and refill could be useful but I find it very unlikely there’s a fluid issue or a solenoid problem with such low mileage on the truck.

 

I’m in New York State... have to comply with Cali libtard emissions... is this not legal for me then?

 

If you have to worry about Carb/smog, check these out, they're doug thorley and carb/smog compliant

https://www.urdusa.com/thy-509-y-c-doug-thorley-header-tacoma-05-2-7l-tri-y/

 

This i am not sure of, sorry..

 

1. Downshifting doesn't "use more gas than necessary". RPMs don't determine fuel usage.

2. Is this not normal operation? No engine is going to traverse mountains without downshifting. Furthermore, does cruise control not intentionally hold lower gears on downgrades to keep speed under control?

If you don't like the decisions made by autopilot turn off autopilot.

 

Trade it for a V6. I always thought that the modern Tacomas are just too big/heavy for a 4 cylinder, especially up hills. A manual trans helps a bit though. You are gonna spend money on NA power mods and they aren't gonna make that big of a difference. A supercharger gets you power but that ain't gonna help too much with fuel mileage.

 

Sorry about that .I can’t reside myself to the fact that I need reading glasses. Now if this vehicle is still under warranty bring it to the Stealership and bitch ! Let them figure out what’s wrong with their puppy.