Ok my 2000 w/ 5.4 4x4 has a set of 315/75r16's on it and as far as economical highway driving it just doesn't seem to work, as in I CAN NOT hold overdrive unless my rpm's are near 2200-2300 and thats about 120km/h plus. I was just wondering if I were to downsize to 33x12.5r16's or some other width of 33's would be better? I am sure if i got rid of the heavy front bumper and/or put a chip on it possibly improve its top end....

Also the transmission is strong, not the issue.... and the gears are 3.55 LS stock.

 

you could get a programmer and that would fix that shifting issues. or re-gear, or both haha

 

running 35's on 3.55's is part of your problem step up to 4.56's and you wont have a problem.........besides that I am running 33's 5.4 4x4 and hold overdrive fine


another thing is if you correct your speedometer your shift points will be correct

 

I am running 33s (285-70-17) on my 01 Expd with 3.55 LS, no problems. A 35 is a lot of tire for 3.55s.

 

Thanks guys, thats kinda what i had figured. I may not be keeping the truck for much longer and have the opportunity to sell my toyo mt 35's to a friend and get some toyo mt 33's for a good price. Appreciate the input, and regearing isn't really an option at this point even tho I work in a driveline shop lol. Financially not an option. But again thanks alot guys :P

 

Ok so i talked to the Tire Shop today, guess the 33x12.5R16's (305/70r16) are gonna be 1800bucks when it only costs 1500 for the 315/75r16's. So will the programmer be my best option for enhancing my overdrive issue. Regearing is out of the question as I am not planning to invest that much into the truck. Any other ideas?

 

try recalibrating the spedo. it shouldn't cost you more than $100 and could save you some serious cash.

 

k... i am failing to understand as to how the speedo will affect the lack of power to HOLD overdrive. It will shift in when it should... just as soon as it hits overdrive it starts losing power and eventually downshifts again... I will look into it just wanting direction for my best bet resolution to this problem. Thanks.

 

If you are not keeping it long just put stock size tires on and save more money.

 

Its down shifting because thats too much for those 3.55 gears to hold that high of speed at such low rpms. change your gears if your keeping it dude. Cost you a couple hundered bucks or get on Craigslist and get some cheap used 33in tires if your selling it.
Getting your spedo will help shift points but will not help the power. A tuner will add power and you may maintain O/D on flat ground but hit a hill and your down shifting again.


Change Gears or Change Tires

 

You will have to put gears in for 35's. I have 285's on mine and could tell a big difference in power vs my stock 265's with a 3.55 gear. IMO 33's are the limit with 3.55's. I am thinking of going to 3.73's to put me back close to stock.

 

if you work in a shop and can get somebody to install the gears for free, then a set of gears will cost about the same as a programer. the simplest solution is just to take it out of overdrive. you're gonna have troubles creating power even if you downsize to 33's. i've got a '98 4.6L with 3.55's and it wont hold overdrive at all.

dang it!! i must be getting tired cus i just typed up this whole long paragraph and at the very end i realized that the opening poster probably already knows this. jayphoenix, please do not be insulted by this post. i realized that you probably know how re-gearing benefits you but i had already typed out this long thing and hate to delete it because someone might gain from it.

if you already know how re-gearing benefits you, you can skip the last few lines in the next paragraph.

what a programer will do is it will delay the upshifting. what i mean is if before, your truck shifted from 3rd to 4th gear(overdrive) at 40 mph (the standard for my truck, not sure what that would be in km/h), you can set the tuner to shift into 4th at say, 48 mph. when you keep the stock shifting with larger tires, the engine will be at lower rpm's. if you delay the shift, that means that the engine will be kept at higher rpm's. if the shift occurs at 40 mph with stock tires, the engine might be pulling 1600 rpm's. with the new tires it might be pulling 1300 rpm's at 40 mph. these gas engines dont produce much power at low rpm's and the higher the rpm's, the more power produced. thats what you're doing when you change out the gears is allowing the engine to reach higher rpm's at slower speeds. for instance, lets say you have a truck with stock tires and a 3.55 to 1 axle ratio. if you were to switch to a 3.73 to 1 ratio, you would feel like the truck has more power, because the engine can now reach higher rpm's. when you get bigger tires, what happens is the engine rpm's go lower because the tires rotate slower at the same speed compared to stock. re-gearing helps bring the rpm's back up. i hope somebody finds this explanation useful and again, sorry about the long post when the OP probably knows this already.

Merry Christmas everybody!! hope you get the problem worked out man.

 

sharpshooter109 : Good explanation and the loss of power that I'd relize in my 5.4 Screw when going to a larger tire { my '09 has 3:55's with 255x70x17 tires} is exactly the reason I am having such a tough time in regard to going up to 285's
I am NOT willing to re-gear the truck { $$$ } just for the sake of looks { when you figure in the total re-gear costs, and also the larger tires cost } the total price for "looks " gets a little steep

 

i have a 5.4 with a superchips tuner and i can hold 70 just fine.

 

Ok, then ya have to add the tuner cost as well , more $$