Shifting into 5th on Highway

When I am on the highway, I usually stay around 70-73. The truck stays in 4th and feels/sounds like it should shift into 5th or even 6th and "settle" for a highway drive. However, it stays in fourth and it drives me a bit crazy because if it was a stick, I'd shift into 5th and cruise without that "should shift" feel/sound. Besides manually putting it into 5th or 6th, is there a way to program/tune the truck to shift automatically at a certain speed?

 

What size are your tires? Probably need to regear.

 

That is interesting. I am running 35X12.50XR20LT Open Country. Is regearing something I can do or is something I would need to take to a shop?

 

That depends entirely on your ability.

 

How do you determine it is in 4th gear? When you flip the lever to left, it goes into "upper limit is 4th" mode, even if it was in 5th or 6th.

 

If it's in 4th and you flip it over it won't change RPM, unless you are going slow enough for it to drop to 3rd, so if it stays the same then you are already in 4th.

 

Yeah, I almost added some info about that. I can follow instructions like a tutorial from YouTube, but I am no means an intermediate or expert mechanic.

 

Yes, that's what I did the other day on the freeway. When I heard what annoys me, I flipped to "manual" and it displays 4th.

 

RPM went up?

 

If I am remembering correctly, yes. Then RPMs lowered a bit when I put in 5th then quite a bit when in 6th. For reference: 4th RPMs = 2000 - 2100. 5th RPMs = 2000 - 1900. 6th RPMs = 1500 RPMs

 

So, it was probably in 5th, with torque converter unlocked. Maybe in 6th. Pretty common with heavy tires.

 

Sounds like you are similar to my level; comfortable with an oil change and spark plugs, but I'm not rebuilding transmissions. At my level a regear is 1000% going to be a shop job. It's to precise and easy to eff it up.

 

Ok, if your RPMs jumped when you flipped it to S mode then it wasn't in 4th. Flipping to S mode default shifts it to 4th. So it was running in 5th or 6th and you flipping it shifted it down.

 

You think it wants to shift - but it needs the torque with those big tires. I don’t run 6th gear anymore on skinny 35s.

 

There's a discussion, actually more than one about these transmissions. It has been found that until the engine or transmission reaches a certain temperature it will not shift into 6th. I know I've noticed this happens when my transmission temps reach ~100°F.

 

This.
@whatda
Are you driving around in S mode or are you in D? It should shift up to 6th in D on it's own. If you're at those highway speeds and you shift from D to S, it'll default to 4th. aka downshift to 4th.

To make sure you're not having issues with D, when you first take off from a stop, Put it in D and count your gear shifts assuming you're accelerating smoothly from 0-70ish and then let off the gas to count the last gear shift (should be 6th)

 

If it shifts into 6th in S mode, there is no reason it would not go to 6th in D unless you have a separate issue. Manual S mode only limits the maximum gear, it doesn’t put it into the selected gear directly when you switch it especially for upshifts.

 

Calibrated speedometer?

On the factory tires if torque converter is locked it turns around 1900 rpm @70 mph in 6th, about 2350 rpm in 5th, and about 3200 rpm in 4th. Full lockup in 5th and 4th only really happen in S5 and S4 respectively (unless Toyota changed it), so 4th in drive would be closer to 3500 rpm. On 35s just multiply those rpm by 0.91 if you're referencing gps or a calibrated speedometer.

My truck with factory size tires will handle any highway around here at 70 mph without ever downshifting from 6th. However it will downshift to 5th on many larger hills if going 75 mph. The extra wind is just that bad. If your speedo is not changed for the tires, 73 on the needle is really 80 on the sheriff's radar gun. It's gonna downshift.

Honestly if you're not going to regear, if it was my truck I would just drive in S5. With those tires it's 2100 rpm at 70 mph actual, only about 200 rpm higher than stock 6th, and the extra time the converter is locked will cool the transmission.

 

S mode defaults to 4th gear. If you’re driving in D at 70 mph in 6th gear and change to S mode, it will downshift to 4th every time. It’s programmed to do that. That does not mean you were in 4th while you were in D mode.

 

You added larger, wider, heavier tires with an aggressive tread pattern. He only real solution is to research, everything else is just a bandaid.

 

With 35 inch tires you would be best served to only use S5. Drive is pointless the gearing is not there to use 6th gear

 

76mph actual, 70 indicated on 35s, stock gears going up a slight highway grade in 6th with a locked converter. Amazing what a whopping 0 psi of boost does for gear holding.