Tire size in fuel economy

[Randy Grant]

14 mpg in the Rubicon (no matter how you drove it) and 15 mpg in the TJ (3.07s and a 5 spd auto). The 3500 peeking from behind the TJ got 16.5 with the same 4.30 gearing as the Rubicon.
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Yea, but it looks like a brick and is shaped like a brick, and has the wind resistance of a brick.

 

[DevilDoc8404]

One thing I’ve noticed is after I had the transmission flushed and the spark plugs changed and tuneup done. I’ve been downshifting it out of ECO mode and the transmission is slow to shift from 6 to 7th gear and then from 7th to 8th.
Is there anything you can do with the transmission with a fancy computer like an auto shop would have?

 

[Wild one]

One thing I’ve noticed is after I had the transmission flushed and the spark plugs changed and tuneup done. I’ve been downshifting it out of ECO mode and the transmission is slow to shift from 6 to 7th gear and then from 7th to 8th.
Is there anything you can do with the transmission with a fancy computer like an auto shop would have?

Double check the fluid level. The trucks need the rear tires roughly 9" in the air to level the transmission,if you had a shop do it,odds are they did it on a hoist and never leveled the transmission.The 8 speed seems to be sensitive to fluid level and will act funny even if it's only down a 1/2 quart.
Did they replace the pan and filter? Personally i've never been a big fan of transmission flushes.If they didn't replace the pan,they didn't replace the filter,the filter is part of the pan
Read the first highlighted paragraph,then follow the steps from 5 to 13

 

[JD Martin]

Double check the fluid level. The trucks need the rear tires roughly 9" in the air to level the transmission,if you had a shop do it,odds are they did it on a hoist and never leveled the transmission.The 8 speed seems to be sensitive to fluid level and will act funny even if it's only down a 1/2 quart.
Did they replace the pan and filter? Personally i've never been a big fan of transmission flushes.If they didn't replace the pan,they didn't replace the filter,the filter is part of the pan
Read the first highlighted paragraph,then follow the steps from 5 to 13

Me either. I think a regular drain and refill is far, far safer than introducing pressure into the system to blow out all the old fluid. Yes, you're only getting maybe 50% of the fluid but that doesn't really matter assuming your fluid wasn't killed in the first place; you're still replacing the friction modifiers and additive packages as well as removing the majority of any debris and sludge in the pan and filter. Hell, for someone so inclined, you don't even need to remove all of the oil in the crankcase to get almost all the benefits of a full change just by swapping filters and topping off; I remember watching a Blackstone analysis experiment over 20k miles some years ago where they compared two taxi vehicles and the metals, acids and additives analysis was almost identical between the one that had a full oil & filter change and the one that just got a new filter and a top off from the oil pulled for the analysis samples (the other one also got the top offs from the samples).

Of course, I'd never do that myself because oil changes are cheap, Blackstone analysis on a regular basis are expensive and time consuming. The point is that people just think well if getting some out is good, going to extremes to get all out must be better. Automatic transmissions today have a lot of intricate parts and I would not want to be introducing artificial flushing power into it - not to mention the transmission today is considered a sealed unit and not even part of the maintenance schedule; only the transfer case is listed for checking/changing.

 

[DevilDoc8404]

I do a mix of both highway and city driving. I found out that I have a 3.21 rear end.
But my air intake sensor when it got put on the computer was registering -87°. I’ve changed it, but I have not seen any difference in fuel mileage, and I haven’t been back to see if that corrected the problem with temperature.

 

[Govtman]

Go back to stock tire size and see what you get in MPG. Bet you get a sugnificant gain. Driving around 55/60 0n the freeway is the sweet spot for most of these trucks too.

Saw a video about the design of Ram body was best up to 65mph, after that it is like it hits an air pressure wall, like a bullet or jet stacks pressure waives on its nose, and the gas mileage drops quickly above 65.