1999 F350 CC V10, RWD, DRW - gear change 4.56 or 4.88
#16
12-28-2016, 06:13 AM
Join Date: Dec 2006
Location: Cincinnati
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Yes.
That tire size is shorter than what is usually on these trucks. They are usually equipped with 235/85/16 or 265/75/16, which are very close in diameter. The 215 is smaller diameter so the tire is spinning more revolutions per mile and making you "think" you are traveling farther than you are. So any mpg calculations are going to be skewed because of the different tire size.
The speedometer will also be off by about 3 mph too fast @ 60 mph. So if you are keeping up with other traffic that IS traveling at the correct speed limit, your truck will be turning more RPMs than stock due to the change in effective final drive ratio which will also reduce fuel economy.
Your truck should have a vehicle certification label on the driver side door jamb that will have the original tire size on it.
That tire size is shorter than what is usually on these trucks. They are usually equipped with 235/85/16 or 265/75/16, which are very close in diameter. The 215 is smaller diameter so the tire is spinning more revolutions per mile and making you "think" you are traveling farther than you are. So any mpg calculations are going to be skewed because of the different tire size.
The speedometer will also be off by about 3 mph too fast @ 60 mph. So if you are keeping up with other traffic that IS traveling at the correct speed limit, your truck will be turning more RPMs than stock due to the change in effective final drive ratio which will also reduce fuel economy.
Your truck should have a vehicle certification label on the driver side door jamb that will have the original tire size on it.
LT215/85R16 is the factory tire size
#18
12-28-2016, 03:01 PM
#19
12-29-2016, 03:25 AM
All
I have a 99 F350 CC Dually V-10 w/ 4.30's in it right now. Over the winter I want to change the gear set, It is only RWD and I only use it to pull my Bumper tow 30ft Jayco Jayflight (9000lbs) I already have a 5 Star tune and will be doing banks headers this winter as well. Other than tune truck is completely stock. Taking a long camping trip come April and am looking for a little extra power. I would like to be able to use the OD more instead of dropping into 3 just as soon as you start up a hill. Only seeing 8 - 8.2 mpg anyways so what are your thoughts.
Thanks
Angelo
I have a 99 F350 CC Dually V-10 w/ 4.30's in it right now. Over the winter I want to change the gear set, It is only RWD and I only use it to pull my Bumper tow 30ft Jayco Jayflight (9000lbs) I already have a 5 Star tune and will be doing banks headers this winter as well. Other than tune truck is completely stock. Taking a long camping trip come April and am looking for a little extra power. I would like to be able to use the OD more instead of dropping into 3 just as soon as you start up a hill. Only seeing 8 - 8.2 mpg anyways so what are your thoughts.
Thanks
Angelo
First of all, if you're asking that question, the answer is "go big or go home".
Secondly, you already have 4.30's right? Then you will probably not be able to feel ANY difference if you move to 4.56. It's just too close.
I say: go 4.88 or bigger. No matter which ratio you choose, it's going to cost you $600-$900. That kind of money isn't for subtle changes.
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