I have the superchip, I took it off to run regular. What a mistake! I lost quite a bit of low and mid range power at part throttle. I hate driving a vehicle that has to be floored all the time to make it go!

I also have the 3.5 gears, I feel the truck needs 3.73s as it is only running 1800 or 1900 rpm at 70 mph. It is a little weak at those RPMs.

Chris

------------------
98 SC 4.6L stepside, Gibson headers, Gibson single exhaust, superchip, Intake mods, Piaa's, high end audio stuff.

 

Triton46,

Thanks for the lead on the gears but isn't the 8.8 Mustangs only. I have an extra 3.55 gear that came out of my Mustang but I looked at the gears, not at the same time, and if I remember it appears the truck is larger. Maybe I am wrong. Also I have a standard diffrential and the Mustangs are limited slip. Are they also the same gears?

But then what can I do to correct the speedometer after a gear change?


z-Man,

I changed the fuel filter about 5000 miles back.

[This message has been edited by LarryS (edited 05-29-2000).]

 

Larry-
P=passenger tire
SL is the speed & load rating (I think)

Also, a limited slip [differential] is independent of the ring and pinion gears- which is what you need to change. The thing to watch when getting "car" parts is the number of splines on the pinion gear. Most trucks and some Mustangs have 31- most cars have 29. Also note the direction of gear rotation. Front gears of a 4x4 are "reverse rotation"- you don't want those.

To correct your speedo after changing gears, all you have to do is get the correct "gear" for the speedo where it goes into the tranny. Very cheap; and any Ford parts dealer should be able to order one for you.

Y2K7700-
I was hoping you'd see my response. While I wasn't exactly near the limits of towing capacity of the Expedition, the hills, big tires and 3.55 gears meant all towing was done in 3rd. In 100+ heat, the engine got as hot as it was going to get. As an early skeptic in "magic" chips, I truly like the Superchip. A few more miles on my rattling Y2k F150, and it'll be chipped too- just like my '93 before it (which also had no tow pkg and pulled the boat w/5.0L engine).

 

Larry..
That tall of a ratio can work for you with a little more torque. I have a 3.31 in my '95 and it wanted to "search" more than I cared for. I installed a high end ignition, pulleys and intake mods and the searching is gone. Towing light loads the truck can still be left in OD. The problem is if you change the gear ratio too low, your revs will be high in 3rd. Letting it go into OD might bring the revs down too much, causing the lack of available power.
My ignition increased my mileage about 15%. It will pay for itself over time. The intake mods I performed myself and cost nothing. The pulleys were $100 from Ford. To be honest, I didn't notice any power increase from the pulleys....usually they help more at higher RPMS.
With a little more power and/or torque, you can tow the Mustang in 3rd, and still have the benefit of lower RPM and better mileage in OD.

 

Larry,

As far as I know, all 8.8" ring-and-pinion sets are the same (except for the reverse-rotation gears in the front axle of a '97+ F-150 4X4). All 4.2L or 4.6L F-150s have the 8.8" rear, the 5.4L models have the 9.75", and the F-250LD has a semifloat 10.25". If you have an extra set of 3.55s that were in a Mustang at one time, go ahead and drop them in! You just cut your costs in half!

My roomate just had 4.11s installed in his '90 Bronco (which has the 8.8) and he is installing the old 3.55 gears from that truck into his sister's '90 Mustang.

As for the speedo, all you'll need to do for a '97 is get the speedo gear for a truck with your tire size and 3.55 gears...since 3.55 gears are very common, it should be very easy to get this gear. I believe they cost about $12.

[This message has been edited by RPFB (edited 05-29-2000).]

 

I agree with what has been posted here. Don't blame the engine or the truck. You had a choice when you went to the dealer and what you have is what you bought. I don't think there is anyone here who has not added something to their truck, thats why we read these message boards don't you know. Change the rear, add a chip and do so for far less then buying another vehicle not to mention the loss on the trade in. HAVE FUN...

------------------
Black 1997 F-150 Supercab Flairside. 4.6L with Jocobs DIS, K&N Generation II, Cat back Exhaust (my own, nice rumble). 17" Off Road wheel pkg. Lots of body mods. 4 yrs old and still turns heads...

 

FYI,

The gears in the 8.8 front diff of the 97+ 4x4 are the same as the 8.8 rear. They used a flipped (upside down)differential. So when you turn it around it rotates the same way as the rear.

Regards

Jean Marc Chartier

------------------
00 F-150 XLT SC Flairside 4x4 4.6 w/5spd 3.55LSD
Warn XD9000i, skid plates, Draw tite class III,
Rancho RSX Reflex shocks,
Borla Cat Back
Modified Air Cleaner Outlet Tube
and air box, K&N air filter,
Superchips

 

I did not know that the 8.8 was in the trucks as well as the Mustang. I have compared my diffrential in my Mustang to my truck and they are the same. I appreciate this information.

With this in mind, I believe the 3.27 would be the best choice gear for me. I would still have good pulling power in 3rd with my trailer without too excessive rpm and my OD performance should be fixed. It wouldn't take much more gearing to get me over the overpasses without the converter unlocking as it makes it over occasionally now. Remember, pulling my trailer I am geared pretty good already with the 3.08 in 3rd.

There are plenty of 3.27 gears around as they are the takeouts from Mustangs. I will check with local Mustang performance shops and see what I can do.

[This message has been edited by LarryS (edited 05-30-2000).]

 

I just want to throw in my $.02... The one thing that I have noticed on my truck (See sig below) is that there seem to be 2 distinct TC unlock personalities. One for when cruise is on, which seem to cause it to unlock on roads where it doesn't when cruise is not used.

My S/C did make a noticeable reduction in TC unlock frequency, and made the truck all-around more enjoyable to drive.

------------------
2000 F-150 XLT, Reg Cab/Long Box, Styleside, Oxford White, Dark Graphite Int., 4x4, 4.6L, 3.55 L/S, Off-Road pkg (Skid Plates, Cab Steps, Heavy Duty Shock Absorbers, LT265/70R17SL), Class III Towing pkg with Heavy Duty Cooling pkg, 4 wheel disk ABS, Overhead Console, Factory In-Dash CD, Remote Keyless Entry, and Sliding Rear Window.

Added: K&N FIPK, Cabin Air Filtration, Ventvisors, Ford Bug Deflector, New: Ford Bedliner, SuperChip

 

JMC-I had heard that the part numbers for a R&P set for the front axle was different than the rear axle due to the rotation direction. If they are the same...great! I should be able to actually sell the 3.55s that I will be yanking out of the front axle of the SuperCrew I'll be getting (they are getting replaced with 4.10's).

LarryS-I'd pass on the 3.27 gears. You already have a set of 3.55 gears...just drop those in! You'd be much more satisfied with the performance of those gears, as going from 3.08 to 3.27 is not that much of an increase in gearing. Plus by using the 3.55s you already have sitting in a box, you don't have to haggle over buying another set of gears. Free is good! Also, 3.27 gears were not all that common on 8.8" Mustangs...They were only available as an option on AOD Mustangs until recently, when they have become very common ('99+ I believe), but those vehicles are so new that chances are, not many gear swaps have been performed on them. They can be found (my roomate found a set for his Mustang, but he was planning on swapping in a supercharged 5.8, so the more common 3.55 gears would have lead to many a melted tire!), but you'll have to look around for a while!

 

OK Larry, My 99 XLT SC with the 3.55LS does not lock or unlock much at all. Also, last October I towed a 4,400lb. 71 GMC truck on a 2,100lb. Car hauler trailer from Atlanta, Ga. to my house just south of Tampa, FL. I had no problems towing the weight up hills with OD off. ON I-75 I did about 60-65 MPH the whole way and still got 12.9mpg. This is not a weak engine. Total weight towed was around 6600lbs. along with the normal 1200lbs. I keep in the back of the truck I think it did rather well. My 98 with the 3.08 would not have done as well. Use the 3.55, I don't think the 3.27 will help as much.

 

RPFB, seacrow,

I agree with both of you that the 3.55 would do a better job of towing and getting over those overpasses without the converter unlocking. And too, I have the 3.55 just sitting in my garage waiting to be installed.

My truck pulls the Mustang in 3rd fair now, not good, but I feel a 3.27 would improve my loaded pulling in 3rd to an acceptable level and at 75 mph in OD, no load, all I need is a tad more to keep the converter locked. I feel the 3.27 would solve that problem. But you guys are right, the 3.55 would make for more torque, although slightly less economy, and it is free just waiting. I will have to make a decision but I do feel the 3.27 would get me by and yet keep the rpms at a little more acceptable level. Decision, decisions......

 

Think of it this way...if the 3.27 doesn't do the job...you have to reinstall all over again. Go with the 3.55 first, my mpg average 17 - 18 on the highway and 15 with mixed driving.

 

Triton46,

Good point. However, I plan to change out the gears myself so it will be mostly labor involved.

Chris,

With 31 inch tires you have slightly taller gearing with your 3.55 gear than I would with the 3.27 and my 28 inch tires.
3.27 x 336/28 = 39.24
3.55 x 336/31 = 38.48

If yours pulls good geared like that then the 3.27 would be the ticket for me.

 

RPFB,

Brain Fart Time. I apologize for the misdirection. Flipping the diff causes it to rotate in the opposite direction so the front are reverse cut gears. Sorry for the confusion I caused. Ok my foot is now out of my mouth.

regards

JMC

------------------
00 F-150 XLT SC Flairside 4x4 4.6 w/5spd 3.55LSD
Warn XD9000i, skid plates, Draw tite class III,
Rancho RSX Reflex shocks,
Borla Cat Back
Modified Air Cleaner Outlet Tube
and air box, K&N air filter,
Superchips