Well I pulled my beast of a jeep to the sand dunes over the past weekend with my newly aquired 99' F350 with the V10. On the e-way I was running about 75MPH and turning 3700RPM! I guess the V10 doesn't like 4.30 gears and 265 tiny tires. My question is, I have a 4" lift already, how much of an improvement will I notice when I put on some 35" tires? Running at this high of an RPM range I totally had no pulling power once I got rolling. What's the powerband like on these motors? Almost forgot, 5.1, yep that was my mileage for the trip, pretty pathetic huh? Any suggestions or comments are welcome, I'm a noob...

 

I don't know what transmission you have, but I have a 5spd manual and 3.73 gearing. At 75 mph, I'm turning my engine at 2,500rpm. You need to hit overdrive or get it out of 2nd gear. That is way too high of a rpm for it to be normal.

 

I'm running 4.30's and 35" tires, turn 2500 in Overdrive at 75mph.

 

I running a 3.73, auto trans at 70mph at 2000 rpm. 13 mpg empty. When I tow my 7300 lb trailer I get 9 mpg. OH yea almost forgot OEM tires.

 

Trans in mine is an auto. I completely ran the truck out of it's powerband, at 70mph, I'd hit the gas to the floor, not a darn thing would happen. Guess bigger tires are on the immediate horizon... anyone else with v10, 35's, and 4.30's?????

 

I took my first road trip with my Automatic V-10, I dont know what gears it has, but at 70 MPH the engine was turning 2000RPM's, so they must be 3.73's?. Stock everything.

I was damn happy getting 15.9 MPG, empty with the A/C running. This was on I-15 from Victorville to Saint George Utah, hills, flats, mountain passes.

 

15.9 mpg - I wish...(i never really looked)

Also with V10 and 35" (2WD) auto, no idea what gears, but from LA to Vegas @ 85-90mph I stop once for gas RPM's ?

I just love my truck... 2001 48kmiles 6" lift V10 FM-40 and big tires!!!!


as far as driving in trafic...when i have to...i put it in second gear, and race up the car in front of me!!! hehehehe i like to see how high the RPM's well go.

 

Your trans isn't making it into overdrive. Check your overdrive lockout.

I plugged your numbers into the formula:

RPM = (MPH X GearRatio X 336) / TireDia

and got this:..... (75 x 4.30 x 336) / 31.5 = 3440 rpm.

The difference between 3440 and 3700 could be torque converter slip, not sure.

If you were in ovedrive, the numbers would look like this:
(75 x 4.30 x 0.78 x 336) / 31.5 = 2683 rpm, assuming your overdrive ratio is 0.78.

The equation suggests that you may actualy have 4.56 gears in the truck. I substituted 4.56 for 4.30 in the equation and left out the 0.78 overdrive gear and came up with 3648 rpm. That's close enough to 3700.

Did you buy the truck used? If you bought it used with a 4" lift on it and stock tires, it sounds to me like someone had bigger tires on it, re-geared it for the bigger tires, then took them off and sold it with the stock tires on it.

You may want to drive the truck again and make sure it is shifting into overdrive and take another careful tach and speedo reading and plug those numbers into the equation and see what you come up with. It would also help to know your exact overdrive ratio, since not all trans' OD ratios are the same, can vary from 0.70 to 0.80.

It is also possible that the speedo was corrected for the bigger tires and may be off now. In that case, the results of the equation will be off and there's no telling by how much.

You may also want to pop off one of your diff covers and count the ring gear and pinion gear teeth and divide the ring gear teeth by the pinion gear teeth and that will give you your actual gear ratio.

On the question about switching to 35" tires, there is an 11% difference between the stock 31.5" tires and the 35's, so your rpm's will drop by about 11% at any given vehicle speed with the 35's and whatever gears are in your truck now, so your rpms would be about 3300 instead of 3700 at 75 mph in direct gear (overdrive off).

 

i was about ready to say tcc maybe not activated...

 

Wow, thanks for the insight. I'll definitely pull the diff covers and recheck the gears, I bought it used so who knows. Thanks for all the help from everyone, it is greatly appreciated, thanks again and keep the comments coming, maybe 37's are in my future...

 

dude if your not happy with your pulling power now..( i think thats what i got from your confusing post).. than higher gears or taller tires are only going to make it worse.... sounds like the V10 might not be for your needs.....YOu said you "had no rolling power" .. not sure what that means but the higher rpms your at the more power you had available.. go with taller tires and youll have less power.

 

Umm, I'm gonna have to disagree with ya there Tex... All engines have a specifiic power band where they make their optimum power. I think 3700 rpm would definitely be out of the SD's torque/power band. By using bigger tires you can lower the engine R's, and put the motor back into it's power band. Call me crazy but, most trucks don't like to constantly run at 3700RPM, unless it's an F1 race car which doesn't make power until well over 8k RPM... Thanks for the input though...

 

Hey Sparky, I got a question for ya. How's the passing power with your setup on the e-way? How's it do pullin' a load? thanks for the input guys! This board rocks, Judd

 

First you never need to pull diff cover to count gears and get the ratio... it is either 3.73:1, 4.10:1, 4.30:1, 4.56:1, or 4.88:1 yes there are others 3.55:1 and several 5.??:1 variations but rarely put in these trucks without serious other mods.

Get both rear tires off the ground and set firmly on jack stands. Block BOTH front wheels front and rear, let off parking brake, shift to neutral, chalk mark top of one wheel, chalk mark horizantal on drive shaft. Watch drive shaft as wheel is rotated one complete rotation, drive shaft mark will pass by 3.55, 3.73, 4.10, 4.30, 4.56 etc times.

If no limeted slip rear end, this can be done with only one rear wheel raised. Think safety and DO NOT try this with engine running or in gear!

Power band on the V10 is very linier, nice gentle, and flat all the way to 4800RPM then gradual drop by a few FtLbs to 5500. 80% torque at 2500rpm, peak around 3600 to 4200RPM no serious drop until after 5200rpm. This motor had the flatest powerband of any motor I have ever seen in a gas engine!

I have locked out overdrive and down shift to 2nd climbing steep long pulls with heavy loads up Arizona, Utah, Colorado, and California Passes and been able to keep above 60mph @ 4700RPM with a 5900LB load.

This motor was designed and geared to pull freeway speeds with medium loads at 1900 to 2300 RPM in OD. Your "beast of a Jeep" doesn't qualify as a HEAVY load in my opinion. 75 MPH at 3700 rpm is right smack in the best powerband for this motor.

Give us more detail of tire Diameter, 2x4 or 4x4, hubs locked? 265s don't mean much, could be 29 to 31 diameter depending on brand and amount of wear, what gears really, what status of auto trans setting (OD in or out, gear?) Can you tell if your torque converter is locking and unlocking normally? How many miles, any engine mods, chiped, exhaust, FIPK or other air mods etc, etc? How much do you think trailer and beast Jeep weigh, trailer brakes biased on maybe... lots of hill or flat? Grade and brand of fuel, last time fuel filter changed.... Bunch of reasons a 99 V10 could be lacking in power but I will guanentee you 35s or 37s will make it worse!

 

tHE v10 Redlines at 6k rpm due to smaller pistions.. running at little over 50% of redline is acceptable for long periods of time in any gas eng... and try and keep your posts professional