I am looking at a '98 XLT with stock 16 inch rims and tires, 5.4, 4x4 with the tow package.

At 75 mph I'm at about 21-2200 rpms. What gears do I have (I'm guessing the 3.73's)?

How would I know if I have a limited slip rear end?

 

Mine registers 2025 RPM @ 70 MPH.

 

Anyone?

 

Check the tag on the drivers side door, it list all the info, in code of course.

for example a rear end code of H6 indicates the truck is equiped with a Limited Slip and 3.73 gears.

 

19-3.55 nls
17-3.31 nls
H9-3.55 ls
H7-3.31 ls
H6-3.73 ls

 

H6, Thank God! And I was wrong, it is 23-2400 at 75. Thanks!

 

I have a 01 Expo 4x4 with a 3:55 gear and was wanting to know what i can do as far as changing it out.. my milage is pretty bad.. 10 city and 14 highway with a tail wind.

 

waterrat - lower gears (3.73 or 4.10) won't do much for fuel economy but will give more power where you need it. Taller gears might help fuel economy but at the expense of power.

Really, the 3.55 is going to give the best fuel economy with acceptable power. I switched to 4.10's and am very happy that I did but I do a lot of towing and like performance (and don't care that much about fuel economy).

BTW, I get more like 18 on the highway at 70 running solo. It drops fast above that speed, though.

 

Ian-N I get about 10 when i'm running around 80 and i seem to of lost allot of power in the take off.. i have 20k on it now and it is in the shop due to a leak in the overflow tank for the Radi. it happened over the weekend.. everytime i stop it starts to run out of the seams.. go figure. and they can't tell me why i've lost power on the take off.. i can't fell anything until i reach 25oo rpm's. is that a common thing with these trucks?? I had an explorer before i got this one and pulled my boat with it as i do this one and i had a v6 in it, The expo seems to have as much take off power as the explorer.. any help would be graetly apreciated.. (spelling)

 

Waterrat, three words best answer your questions as to why you don't feel any power: Houston, Humidity & Hot.

I've got 3.31's in my '00 Expy 4x4 5.4L and don't get any better mileage than what you're getting. I'd love to switch to 3.73's but just can't justify the $1300 cost to do so.

 

A couple of questions:

Do you have an FIPK? They can cause drivability issues in hot weather.

Is the shop doing a pressure test on the cooling system? Symptoms like you are describing could come from a blown head gasket, although I have never heard of a mod motor blowing a head gasket (leaky head gaskets, yes but not blown).

If the truck ran better before, you might want to try resetting the computer by disconnecting the battery and turning on the headlights for a few minutes. Then reconnect the battery and see if it makes a difference.

Ian

 

I have no mods on the truck, I do however plan on gettign a K&N air filter in the near future, just the filter nothign else. I have a 100k warranty and do a lot of driving so don't want to give them any reason not to cover something.

 

I'd have to disagreee about the FIPK causing problems in heat. I'm in Dallas and before FIPK in the heat, like in traffic in 100+ degree weather, it would sit down and die. I mean I would have to stand on it hard to get it to move at all, untill I got rolling.

With the FIPK it does it but not near to the degree that it did. I say it's due to a much more open intake allowing accces to much more air. The hot air is still the same , it's just that it can pull more volume of air than with the stock air box that's restricted to what little air is can squeeze out of the dense hot air.

In the heat, they do that on purpose. Has to do with protecting from an unintntianl lean condition (which sounds backwards to me) or something like that, so it pumps the fuel to richen the A/F ratio.