Pros and Cons of driving in 4 vs D

Like I said, the torque converter will unlock a lot in 5th or just not lock at all, especially for those with big tires but even stock.

The truck drives just fine but for those of us who monitor trans temps the fluid temp will spike up beyond 200* which shortens the life of the fluid, and if not changed regularly the transmission

 

I think 4 is basically "overdrive off" or "tow/haul" setting. You'd use if high payload to prevent gear hunting and keep it out of overdrive and get more trans lockup. Can overheat a trans if not used in those conditions. I've done it on an old Ford Ranger one time and it was a big mistake

 

So I ended up putting in a Pedal Monster and holy shit what a difference. Feels like this is how it should drive. I'll report back later with MPG if anyone wants to know

Hate to give them free marketing but it's a game changer

 

have you heard of OTT

 

Yeah I'll probably do that in the future. But I'm trying to keep everything stock for now

 

Better handling includes responsiveness to gas pedal inputs. The truck is much more responsive to the gas pedal at higher speeds in 4 because there’s no need to downshift first from 5 for acceleration.

 

How do you "lug" the transmission in 5th? It will automatically (it is an automatic, after all) downshift to 4th once the torque converter has unlocked and measured torque or rpms determines the need. The transmission still heats up in 4th, but not as quickly. I monitor T1 and T2 on my ScangaugeII. T1 is the transmission itself, T2 is the torque convertor and it heats up much more quickly, but also cools more quickly once the load is reduced, like after topping a hill or slowing down.

I tow a lot, from a 5x8 enclosed trailer topping out at 1500-1600 pounds up to the maximum my truck is rated for, 6500 or slightly more with either a flatbed and tractor or a 6x10 tandem dump trailer. I never tow in 5th at all, even with the empty box trailer the truck shifts frequently and hunts between 4th and 5th (automatic) at highway speeds. I've generally come to drive around locally in 4th even on the highway at 50-55, but if on the interstate and not towing I use 5th. 4th gear is 1:1 and I find my throttle response is a bit better staying out of OD (5th). My gas mileage on a recent trip from NC to West Virginia pulling the 5x8 enclosed trailer was 14-14.5 going up I-77 at 65-70 mph and about 15 on the back roads at 50-55. Locally around my house I get about 16-17 in 4th without the trailer in mixed driving (35-55mph) and can get as good as 18.5-19 at 55 mph steady driving. In OD I get maybe another 1-1.5 mpg average. This is all measured on the Scangauge. Best gas mileage I've ever got was 21 mpg in 5th at 65 mph. Go 70 and the mileage starts dropping.

Highest I've ever measured trans temps was 220 on the T2 side (torque convertor) when it unlocked in 4th going up a hill. T1 has never hit 200 since I've had the Scangauge, which I installed when I bought the truck 7 years ago (It's a 2011 4x4 DCSB). Once the hilltop is reached, T2 drops pretty quickly, within a minute or so, to whatever T1 is at, usually 175-180 during summer. I run a slightly larger than stock tire and wheel, 265/70-17's, FWIW.

 

Do what works for you. I could care less. Some of us have 90 lb wheel and tire packages and live in hilly and/or hot areas. Driving in “4” the converter is nearly always locked at 50 +mph and the tranny runs cool.

EDIT: Lugging would be 5th gear, torque converter unlocked, low rpm and lots of throttle (but not enough to force a downshift). Tons of slippage and tons of heat. I’ve seen it over and over on my ultra gauge.

 

I drive mine much like a manual. In hilly terrain I drop to 4th, sometimes 3rd going up. Coming down 2nd, 3rd or 4th depending on the gear that holds it close to the speed limit or whatever speed is safe.

Even on level ground if I'm going to be driving a considerable distance and will never get over about 45 the truck just runs better and gets better fuel mileage in 4th.

Towing any real weight will be in 4th gear. On level ground with an empty utility trailer I sometimes use "D". It just depends on the road conditions. On open road when not towing I just drive it in "D".

Yes, it will. Eventually. The problem is that this is reactive. It only downshifts AFTER the engine starts to struggle and you lose momentum. If you proactively and manually downshift while the truck is still running in the rpm range where it gets optimum power, you maintain momentum up those hills. If you're in 5th and lose momentum the truck may well have to go all the way to 3rd to maintain speed. Downshift early and there is a better chance of getting up in 4th. This is especially relevant when towing but could be a factor at any time.

When tooling around town at speeds under about 45 the automatic is trying to get to OD. You don't need OD until you are at 55+. You have no power in OD at 45 mph or less. If for some reason you need to speed up to change lanes or something it can be a PITA. It's just better to leave it out of OD.

 

Ultra gauge or another type of OBD reader tool. You will also see and feel the rpm go down when it locks and up when it unlocks. It feels different than a gear change.

 

Add a supercharger and it doesn't matter.
Or 4.56 gears, gas and go.

 

You really gotta get an ultragauge, this will give you the info you need to decide on gearing. When loaded or towing going up and down hills I see the trans temp climb up. I put it in 4th and these cool off (as explained above with the locked and unlocked converter scenarios). Mind you I’m supercharged and lugging 33s. Whether on 4th or D it hauls, I just don’t want to change the trans fluid sooner due to higher temps cutting its life.