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Rolling Chassis FAQ's

Old 08-28-2007, 12:22 AM
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Default Rolling Chassis FAQ's

hey I was searching for an answer to my question and I found this faq hopefully you guys find it helpful.
Old 09-03-2007, 11:20 AM
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Rolling Chassis FAQ's

Q: What is the largest tire that I can fit on my stock rims without a lift?

??? A: 295's are a safe bet. But some trucks with the plow package can fit 305's with minimal rubbing. Make sure the tire manufacturer says that it is okay for THEIR tire to go on the 7" rim that the Super Duty wears.

Q: What kind of axle do I have?

??? A: SRW Super Duty's from '99-'01 wear a Dana 50 in the front (4x4 only). The Dually's wear a Dana 60. In '02 the front axle was changed to a Dana 60 for ALL Super Duty's (SRW & DRW). All SRW trucks use a Sterling 10.5" full floating axle in the rear. Dually's use a Dana 80.

Q: How can I determine my gear ratio?

??? A: Refer to the specs sheets for available ratios for each engine. The easiest way is to find your ratio on the tag on the rear axle or axle code on the door jamb. Use this Code Sheet

Or you can determine your RPM at 60 mph, then use this calculator ?to help you. If you have stock 265 tires, then the tire height is 31.6.

60mph in OD w/3.73:1=1690rpm. w/4.30=1948 w/4.10=1857 This is assuming stock 265/75R16D tires.

Be advised that these are just mathmatical equations. True RPM will vary based on tire condition, inflation and the accuracy of your tachometer and speedometer.

Q: How do I know if my truck has a Limited Slip?

??? A: On the tag on the rear axle you will see the gear ratio. If you have an L between the first and second number, then you have a LS unit. You can also raise the rear wheels and spin one wheel. If the other wheel spins opposite then you have an Open Differential. If it spins WITH, then you have a Limited Slip.

Q: Why does my truck clunk when taking off from a stop?

??? A: Common problem usually lies with the slip-yoke on the rear driveshaft. Usually removing the driveshaft and lubing the slip yoke can relieve that problem. See this site for an excellent how to.

Q: What is the LOCK position for on my automatic hubs?

??? A: LOCK is used if the vacuum actuation fails. It will allow you to still lock in the front hubs. It can also be used in the event that you are stuck and cannot get any forward movement to lock in the hubs automatically. Some folks use it during inclement weather or frequent use to ensure that 4WD will be there when needed. Driving with hubs locked will cause no harm but can promote increased wear and the possibility of increased fuel consumption.

Q: My truck clunks over bumps, why?

??? A: Isolating sounds is difficult but you should document conditions and speeds in which it happens. Common sounds come from worn ball joints, loose sway bar links & bushing mounts, shock bushings, and cab mounts. Squeaks is usually a condition of missing or out of date spring isolator bushings.

Q: Are the rear springs different between the F250 & F350?

??? A: Not on the SRW trucks. The DRW truck has bigger capacity springs. Refer to the spec chart on the main page.

Q: What tire pressure should I run?

?? ?A: ?The recommended amount listed on the door pillar is the politically correct answer. different pressures are needed based on load and terrain. Higher TP for carrying heavy loads, lower TP for negotiating rough terrain. (4-wheeling, rock crawling etc.) Your tire pressure will vary based on ambient temp. Meaning, the outside temperatures affects your tire pressure. A tire's pressure can change by 1 psi for every 10 degrees Fahrenheit of temperature change. So if you put 60 lbs in on an 80? day and two days later it is 30?, your tires will be 5lbs. lower. It is also normal for a tire to lose 1psi per month. So make sure that you check your pressures regularly and check them when they are cold!

The chalk test is a simple way to determine if your tires are inflated properly. Draw a thick line straight across the treads. Now drive straight so that the tire goes around a few revolutions. Get out and inspect the chalk wear. It is worn off in the center but not the sides, then you have too much air. If the opposite, then you have too little air.

Here is the inflation table for 265/75R16E tires.

1494 / 35

1708 / 40

1921 / 45

2134 / 50

2348 / 55

2561 / 60

2775 / 65

2988 / 70

3202 / 75

3415 / 80

Be sure to obtain and read the tire manufacturer's inflation manual. Some things actually change based on speed and load. Check this thread for some relevant info on determining safe tire pressures.
Old 09-03-2007, 11:21 AM
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Engine & transmission FAQ's

Q: Gas or Diesel?

A: My standard answer has always been: "Get one of each, then sell the one you don't drive as much." My advice here is the same. Get what you like. If you are already informed as to the strengths and weaknesses of each then it comes down to two things. Your desire and your checkbook. This argument has been so beat to death that no matter what is said, the "other side" has a answer for it.

Some enjoy the quiet, relatively simple, able to idle forever and better stock acceleration of a gasser. Others love the low end torque, the growl at idle and the ability to extract massive power from a diesel.

A diesel powered truck can get 3-4 MPG more (average) than a similarly equipped gas truck. There are additional maintenance costs associated with a diesel that should be considered. Diesel engines have a long life expectancy compared to a gasser but gasser are generally cheaper to rebuild. Frankly, none of it matters if you are driving the truck that YOU like, gas or diesel. So, what's the answer to gas vs. diesel? Depends on your mission, your wallet and your preference.

Q: What kind of MPG?

A: Let's make this short, huh? MPG changes with the weather, load, driving style, state of tune etc. Here's what I've found to be solid, AVERAGE MPG for each unmodified engine. These are middle of the road figures that you can probably bank on to be safe.

V8 - 13.5 (5.4L)

V10 - 12.5 (6.8L)

PSD - 15 (7.3L)

PSD - 17 (6.0L)

Q: Killing the idling myth: You cannot idle a diesel for prolonged periods of times.

A: This can be harmful to the engine. If you must idle it for extended periods of time get either an exhaust brake or Auxiliary Idle Controller. Diesels run cooler at an idle and idling them for prolonged periods can lead to "wet-stacking". Here is a nice article on it.

Q: Why won't my truck idle or start without my foot on the gas?(V8 & V10's)

A: Idle Air Control (IAC) valve is usually the culprit. Check this thread for instructions on replacement & prices.

Picture of IAC location on the V8 & V10 engine.

Q: Why is my speedometer acting weird and the truck shifting really bad/hard?

A: This is usually traced back to the speed sensor located on the top of the rear differential. It is easy to find, just look for the wires leading to it. Remove it and replace it. It is only around $15 from your dealer. If it is covered in metal shavings, have your rear diff. inspected. The Ford part # is F85Z-2L373-AB

Q: Why is my OD light flashing?

A: This means that there is a fault somewhere in the transmission or related components. Have a dealer/mechanic run a diagnostic on it to see which code is stored in the computer. Also, see above. When the sensor acts up it can light the OD button

Q: Why is my OD light always lit?

A: This could mean that a wire inside the stalk has been cut or frayed. Remove the OD button assembly and inspect for wire damage.

Q: Can I change my own transmission fluid? Which fluid should I use?

A: Yes. See the technical article written by Mark Kovalsky You should ONLY use fluid that meets Mercon standards. Fluid that is dual use is not approved or recommended by Ford.

Q: I want to install a transmission temp gauge. Where to I access it from?

A: The port is on the Driver's side of the transmission, right above the pan. There is a black plug in the port. A spacer is a good idea as some sending units can bottom out in the pan due to a very shallow depth. Normal operating temps are about 40?-100? above ambient temps. But that can vary based on how you drive.

Q: How do I change the Cam Position Sensor in my PSD?

1. Make sure you have the correct part. This depends on the serial number of your engine which should be located on a sticker below the front of the plastic cover for the fuel bowl. Neither Ford or International calls it a "CPS", Ford calls it a CMP sensor and International calls it a CAMP sensor.

Ford Part #'s: Before engine serial #375549 F6T012K073A
Serial #375549 and above F7T012K073A

International Part #'s: Before engine serial #375549 1821720C98
Serial #375549 and above 1825899C93

2. Remove the #9 fuse under the hood (not in the dash).

3. You may want to remove the belt for easier access, but it's not necessary.

4. Disconnect the CMP sensor electrical connector. The sensor is located towards the bottom left on the front of the engine. You'll see the single wire bundle going to the sensor.

5. Remove the old CMP sensor using a 10mm socket. Be careful not to round off the bolt (there is only 1). It's on there real tight and is tough to get to.

6. Take the new CMP sensor and coat the seal with either motor oil or Vaseline and intall it. Install the bolt and reconnect the wire connector.

7. Reinstall the #9 fuse under the hood and you should be ready to go.

KUDOS to user "johnsdiesel" for the CMP sensor write-up!
Old 09-03-2007, 11:21 AM
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Interior & Misc.

Q: Why won't my "Door Ajar" light & dome light turn off?

??? A: The switch is dirty. The switch that controls the door ajar light is an integral part of the latching mechanism. Get some WD-40 or similar product and liberally spray inside the latch. Open and close the door a few times. The problem should be gone.

Q: How do I turn off the Belt Minder feature?

??? A: The instructions are outlined in your manual but here they are anyway.

??????????????? 1. Set Parking Brake & put truck in Park.

??????????????? 2. Turn key to ON but do not start. Wait for the seat belt light to go off.

(NOTE: This could take 30+ seconds before the light goes off. Be patient.)
??????????????? 3. You have 60 seconds to complete the next task.

??????????????? 4. Buckle and unbuckle the seat belt 3 times ending with the belt UNbuckled.

??????????????? 5. Turn on the headlight and then turn them off.

??????????????? 6. Buckle and unbuckle the seat belt 3 more times ending with it UNbuckled.

??????????????? 7. Watch the dash as the seat belt light will illuminate.

??????????????? 8. Within 7 seconds of the light going out, buckle then unbuckle the seat belt.

You're done!

Q: How do I get rid of the key buzzer?

??? A: Easiest way is to remove the ignition assembly. This is done by looking under the steering column and using an awl or something similar press the detent ball under the ignition. The assy. can only pull out when the key is in the ON position (not started.) You will see some brass contacts. Tape over them and the buzzers will stop.

Also, some models will let you just push the seatbelt latch and that will disable the buzzer until you turn off the truck. Once restarted you must do it again.

Q: How do I modify my fog lights to: 1. Keep fogs on with brights? 2. Use the fogs when only the parking lights are on? (newer trucks are equipped with that feature)

?? ?A: Check these threads.

Q: Will aero style mirrors swap with Trailer tow mirrors?

A: Yes. Simple swap. Remove the sail panel (black panel on the interior at front part of door.) Remove bolts that hold on mirror assembly. Access wiring harness (if equipped) by removing door panel.

Q: How do I remove the front door panel?

A: Slide the electric window controller on the door forward and up. (A flat, wide screwdriver will help this process.) Once removed, remove the screw underneath. Remove the reflector lens at the bottom of the door to expose the other screw. Remove it then lift the panel straight UP to remove. Be careful. See this page for pictures.

Q: What is that hook thing under the cup holders for?

A: Trash bag holder! BUT some Super Duty owners out there have found some other uses! Such as, a CB radio mike holder, purse holder and one guy cut it up and made an electric trailer brake module holder!

Q: Can I swap with other grills from the Super Duty's and Excursion line? How do I remove the grill?

??? A: YES. How? Simple. Pop the hood. At the top of the grill you will see 4 screws. Remove them. At the bottom of the grill are 4 clips (sometimes 2). Using a large flat-blade screw drive, carefully lift the lower edge of those clips and pull the grill toward you to remove. Re-install in reverse. Before putting it back on let me suggest that you put a screen behind your grill. Heck, why not!? It's off! It'll stop bugs, rocks, leaves etc. from prematurely killing your A/C condensor PLUS it looks better (IMO) when approaching a SD/Ex truck with a black screen behind the grill. It blocks the look of the bug filled condensor.
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