32" Tires/ MPG loss and gear hunting

Any tunes that you recommend for the issue I'm having? I feel like 3rd gen owners usually use tunes to kind of do the opposite...keep the truck at lower gear/higher rpm for longer. I am trying to get it to come up out of the lower gears at highway speed and reduce my rpm.

 

Your tires are larger, so its changing the gear ratio, so yes your transmission is going to act differently. But you are also introducing a large amount of air resistance to the mix.

Get a tune, regear, or live with the change.

 

Any tune recs for increased mpg//lower rpm?

 

KDMax 10.0 is probably the absolute best tune for our 3rd gens. @TWTaco It’s about $400 so it’s way cheaper than getting new gears.

 

No need for a regear unless they’re 35’s. Waste of money. Tune will do him just fine

 

Seems like this tune, as with the others I've seen, is actually aimed more towards keeping RPMs higher. The opposite of what I want to do. No?

 

It keeps gears better so you’re not constantly gear hunting. The shift points are buttery smooth. Night and day difference.

 

I got the kdmax 9 on my truck. I tow a small boat and trailer, I get 19mpg towing it at 70mph.

 

The tune will keep RPMs higher while accelerating instead of shifting up while accelerating and lugging. But once up to desired speed on the highway it is much better at keeping your truck in 5th and 6th gear, where the stock tune will constantly stay in 4th or even decide to shift to 5th then 6th, bog down and downshift to 4th again screaming RPM's.

Message @PapaRee for any info you need and read the 1st page of the KDMAX forum. Absolute best thing you will do to your truck. I started with 33's and stock tune, then went to OV tune when they first started tuning our trucks. It helped significantly but I ended up re-gearing to 5.29's and switched to KDMAX. Absolutely love how my truck drives now and I get EPA rated MPG's.

But as others have stated definitely start off with the KDMAX 10 tune. I doubt you'll need gears with the tune on 32s.

 

You say they are lighter, did you actually weight your tire/wheel combos on a scale? You when from a 16" rim to a 17" rim, your tire might be lighter but the wheel might have made up for that weight.
The type of tire, compound in the tire and tread design all have an effect on that MPG.
Lifting the truck changes the aerodynamics at higher speeds with can affect the MPG.

I used to have a excel spreadsheet and documented my MPG until I realize how sad it was making me. Truck stock got about 22MPG
3" Lift, loss of about 2 MPG on when I was on highway driving but didn't notice the loss on the day to day around town. I was able to combat some of this loss just by reducing my speed buy 5-10 MPH on Highway
Wheels, 31s to 33s another 2 MPG which affected the around town driving by about another 2 or so MPG
At this point I was around 17s for awhile
Changed 33" tires from Toyo ATs to Cooper ATs XTLs on paper these tires matched size and weight. I lost about another 1 MPG and I assume it was tire compound because these tires road so much smoother and quieter on the Highway.
So 16s MPG
Then armor my girl up regeared to 4.88s lost some more
I think I was around 14s

I'm now on skinny Mickey Thompsons AT in 35s and I getting 12 on a good day.

So if you really want to maintain your MPG don't change it up from stock.

 

Yes, I'm sure. Thanks though lol. Also, you have a 2nd gen.

Why does no one believe that my MPG loss is coming from my auto trans shift point issue with the larger tires lol... I would bet my life savings on it.

 

Sent you a PM Adam. I think we have the fix for you.

 

From my experience, I totally understand and agree with you. Stock gears don't work well with this 3.5 engine. It doesn't have enough torque to hold low rpms. Re-gearing gets it back to what most normal vehicles would be so it can be in the correct part of the power band for specific speeds and to maintain 65 on flat ground. That being said, the tune should fix this issue your having. Start there as it's much cheaper and increases torque at lower RPM to hold 5th and 6th gear. If it doesn't work (highly doubt it) then a re-gear will fix your issues of running over 3000 rpm to maintain 65mph.

Again, these trucks just don't have any torque down low. Very difficult for these trucks to maintain highway speed below 2000 rpm. With my 5.29's and 33's in 6th gear, my rpm's at around 1900 at 60mph and 2400 at 75 mph. It effortlessly maintains speed at these rpm's.

 

Thanks for believing me haha. Did you do your tune and gears at the same time? How do you know the tune would help if you have both that and gears?

 

I went to a 75 from a 70. Simultaneously with a 2.5" lift, a pedal commander, new plugs and filter. My mileage went up.
Myth or not I like to reset the ecu when making changes so it can relearn from what is and not try to readjust from what was.

 

Haha no doubt. I tried tuning with my E-load 33's I had at the time first before re-gearing. It made a huge difference and my avg fuel economy went from 17 to 20mpgs. This is when OV tune first started tuning our trucks. OV tune developed VF tuner that anyone can purchase and tune their truck. The KDMAX group used VF tuner to make their own tune that is night and day better than the original OV tune that came out maybe in 2019 or so?

So I'm confident it will be better. Like you noticed increasing a 1/2 in ruined how your transmission works, imagine how 33's are that are even heavier. Since I live at high elevation with mountainous terrain, re-gearing was very appealing to me. The combo of a tune and re-gear makes it a totally different driving experience. If I lived flat terrain, I would not necessarily needed to re-gear.

I have a 1.5 in lift, sliders and a skid plate for reference. Not too much weight. But it is a DCLB which is about 150lbs heavier than the 4 door short bed.

 

Reset ECU by disconnecting battery?

 

It is where that rotational weight is. The poster noted a larger circumference and this is correct. The distance the weight is from the centre of rotation is a very large factor and could well negate having a lighter tire.

 

Yes by disconnecting negative battery terminal for up to 30 min, some say.
Not sure about all models but pulling ecu fuse(s) or efi relay will work too.
Saw one method of DISCONNECTING BOTH battery terminals and holding the cables together for 15min. (Haven't tried)
I just unplug negative terminal and go do something else for awhile.

 

cap discharge, its a system reset that many dealers will do with weird problems.