Engine/Transmission (1998.5 - 2002) Top Speed w/ 3.55 vs 4:10's

[BigDan]

I was racing this POS F150 Super Crew yesterday and lost:{ I had to let off when I hit my redline at 100mph. What is your top speed w/ 3. 55's??? I have a 02HO EZ w/ 4. 10's. I only ocassionally tow about 8K. It accelarates fast but it takes a wile to shift, sooo many times so I'm always left in the dust. Would 3. 55's give me a quicker ET's. What RPM do you run at when going 70mph. With the 4:10's im right in the sweet spot when towing 2K at 62mph. Would I even feel a difference when towing w/ 3. 55.



Thanks

BigDan



P. S I might upgrade to 33"-34" inch AT's

 

[Snow man]

I have 4. 10's and an auto, my factory tires were 265/75/r16. Mine pulls hard to 105mph,then defuels slowly,topping out at an indicted 114mph. now my 285 tires makes the actual speed around 120-122mph,plenty fast for me,my RPM's are at 3550 according to the tach,I never let of at redline unless im ready to slow down. The auto has a . 69 4th gear ratio,this must be the difference.

 

[sdalton]

115 mph easy with 3. 54 gears and only mod is a BHAF. It will not go any faster. It is like it suddenly hit a brick wall.

 

[Puffin Smoke]

My ECM cuts me out at 117 MPH. Fastest ET time with 3. 55's is 13. 72 and 98. 25 mph.

 

[Jetpilot]

At 115 the speed limiter will stop the truck from accelerating, as stated above it is like hitting a brick wall. Now if you cut the speed limiter wire you can in theory go faster. But, at the track this weekend I was running 115 at 3400 rpm with 3. 54 gears and 265 tires. The truck will continue to accelerate slowly above 3400 but not much.



The only fix I see is bigger tires, taller gears, or a p-pump .



Doug

 

[emjay]

Here's two simple (if you have a calculator ) formulas for figuring RPM and speed based on O/D ratio, R/P ratio and tire diameter:



MPH = (RPM/OD/RP) x TIRE_DIAM x 0. 002975



... and... .



RPM = (MPH/0. 002975/TIRE_DIAM) x OD x RP



Tire diameter is in inches. So, at 3000 RPM with 30. 5 inch tires, you get 111 MPH with a 3. 54 RP and an OD of 0. 69. With 4. 10 gears, your speed at 3000 RPM is 96 MPH.



Note that "what-if" comparisons are easy as scaling one parameter, such as tire size. For example, say you wanted to switch to 35" tires from the 30. 5" tires in the first example. All you have to do is divide the new tire size by the old tire size and multiply by the speed; 35/30. 5 = 1. 15, then 1. 15 x 111 MPH = 127 MPH. You can use that same scaling factor derived from the differences in tire sizes to determine effective gear ratio, for instance 4. 10/1. 15 = 3. 56. So 35" tires and 4. 10 gears are nearly equivalent to 3. 54 gears and 30. 5" tires.



Since you must have a computer to read this, you may already have a spreadsheet program that you can enter this stuff into (like I did) so you only have to think hard once

 

[TPCDrafting]

stock 12 valve, 5 speed and 3. 54 governs at 3k rpm at 95 mph.

 

[Chipstien]

Speedometer reads about 117 and factory tire are 265's but I have 315's which is about a ten percent difference so... ... ... ... ... around 124MPH.

 

[K_Arts]

I am running 265 tires, 3. 54 Rear end. . and I can bury my speedo at 120 with the truck still pulling and plenty of RPM's left.



If my speedo went past 120 I could give you an exact number.



Kev

 

[BigDan]

Thanks for the info so far...



Q. You guys that seem to have a higher top speed, are you sure you are actually going as fast as your speedometer says. All of the othere veichles I've owned if you change the rear gear ratio it gives you inacurate speed readings. Like in my camaro I went form a 3. 27gear to 4. 10 and it now says I'm going 90mph when I'm really only going 60mph.



Q. Same goes with tire size I had changed tire sizes quite frequently on my Toyota anywear between 30"-39. 5" every time I changed tire size is changed my speedometer.



Q. Do the 3. 54 gears provide faster accelartion in a 6speed then 4. 10's



Q. How come it seems that some people with the sme trucks can go faster then 114mph with 3. 54's. Was a governer only installed on some trucks.



Q. Who as gone down in gear ratio. I hear that everybody who has 3. 54's love them and hate 4. 10's and vise versa. Did you like the taller gear overall.



Thanks

BigDan

 

[Jetpilot]

Dan,



I know that when I was at the Atlanta drags this weekend when I would go through the traps my speedo was showing right at 115 and this is also the speed that the time slips showed. The 3. 54 auto trucks with 265 tires will be right at 115 when it reaches 115 mph so the ecm will start to defuel the engine..... There is also a speed limiter wire that when your truck hits 115 mph it will defuel the engine but much more aggressively to prohibit speed in excess of 115. But if one were to cut the speed limiter wire they could continue to accelerate faster than 115 but at a much reduced rate.



You are correct that changing tires size, gears, etc. will alter the top speed obtainable. This is one reason that I just installed 285 tires on my truck. I want to be able to go faster than 115 on the track without the top end defuel from reaching 3400 rpm. Based on these tires I should be able to obtain a true speed of approximately 125 when reaching 3400 rpm.



Doug

 

[Greg Boardman-RIP]

Jet Pilot,

Doesn't the Edge Comp Drag "clip" the limiter wire? I know that I fuel all the way through OD on WOT.

 

[Jetpilot]

The difference between the normal comp and the drag comp is the drag com does not defuel above 2700 this will hold full power until engine redline of 3400. Now above 3400 the ecm will cut down the fuel to the engine. The drag comp does nothing for the speed limit defuel as far as I know.....

 

[rkressg]

100 :{ I can only get 97mph out of my truck. That is where it defules in 6 @3200 rpm :-{} :-{}

 

[Greg Boardman-RIP]

Originally posted by RGilbert

100 :{ I can only get 97mph out of my truck. That is where it defules in 6 @3200 rpm :-{} :-{}

If you put in some DDII injectors, You will be up to 100+ mph no problem. Go ahead and finish what you have started The dark side is stronger than a mere mortals willpower.

 

[CRegal]

Big D...



If you plan on running a larger tyre in the near future, Don't do away with your 4. 10's. Alot of guys I know running the 3. 55's have problems towing if they goto larger tyres. Your sweet spot is around 2200 rpm for towing, so depect what speed u want to run at that giving rpm. Of course u can start adding more fuel via fueling boxes or injectors and change your optimum power range.



I have 4. 10's with my 6 speed & I only git up to about 108 & that is it. (stock tyres) Now depicting how fast u reach that speed is a bit different of course... . Bomb the fueling & there wont b ANY f150 near you till u hit that wall.....

 

[Snow man]

I just upgraded my Comp to the drag comp,I did pick up 4 mph when flat out,but it pulls much harder from 2700-3200. According to Edge the drag comp fuel hard to 3200-maybe there are different versions fo the drag comp,but when i asked i was told that at 3200,the fuel cut back to where the normal edge comp fuels at.

 

[Roger rodbolt]

3.54

Originally posted by CRegal

Big D...



If you plan on running a larger tyre in the near future, Don't do away with your 4. 10's. Alot of guys I know running the 3. 55's have problems towing if they goto larger tyres. Your sweet spot is around 2200 rpm for towing, so depect what speed u want to run at that giving rpm. Of course u can start adding more fuel via fueling boxes or injectors and change your optimum power range.



I have 4. 10's with my 6 speed & I only git up to about 108 & that is it. (stock tyres) Now depicting how fast u reach that speed is a bit different of course... . Bomb the fueling & there wont b ANY f150 near you till u hit that wall.....

Big Dan,

I've ran both 3. 54 and 4. 10 gears and much prefer the 3. 54. Every ISB horsepower and dyno chart that I've seen shows a rapid loss of horsepower after 2800rpm. With stock tires and 4. 10 gears 2800rpm equals 88mph, you need over 3400rpm to do 108mph while the 3. 54 does 102mph at 2800 and 125mph at the same rpm that the 4. 10 will do 108mph.



For towing I have changed the torque curve so my sweet spot is well below 2200 rpm but even on a stock engine, 2200rpm in fifth gear is 59mph and 80mph in sixth gear which is nice in most towing situations. All calculations assume a stock tire to be a 265/75-16. JMHO Larry

 

[jwilliams3]

Stock tires on my 99 were 245's, I switched to 265's and I can hit 120 on the speedo, I figure this to be about 126mph (someone correct me here!)



--Justin

 

[Roger rodbolt]

Originally posted by jwilliams3

Stock tires on my 99 were 245's, I switched to 265's and I can hit 120 on the speedo, I figure this to be about 126mph (someone correct me here!)



--Justin

Justin,

Your auto equipped truck has a faster overdrive then a 6speed, . 69 versus . 73, if I remember correctly, so my numbers do not work for you. The factory tach is are accurate (if you read the hash marks correctly) but the speedometer and odometers are generous. A GPS with steady driving on the interstate will give decent numbers. There are several good sites with calculators for tire diameters, and all sorts or gearing calculations, try:



http://www.4lo.com/



The 3. 54 may not be the best ratio in an auto equipped truck especially if you tow. The greater overdrive really drops the rpm and strains the trans. HTH's Larry

Larry