I've got an '01 Scab 5.4 with 3.55LS and I'm considering a gear change. Right now I have P275/60/17 BFG(30") on it and turn about 2,000 at 70 mph or so.

I guess what I am asking is it worth it and would the people that have done it do it again?

Also, what is the downside to this if any?

 

I have the 4.6 and went from 3:55 to 4:30 gears and it was the single most significant performance change I did. Most are happy with the 4:10's.

Upside: I actually improved fuel mileage even with corrected speedometer. Truck is much faster. I tow and it made a significant difference there. I burn rubber at will.

Downside: I burn rubber sometimes even when I don’t want to. Increased rpms at highway speeds (not bad though). My 4:30's make a little noise (4:10’s make less). When towing at high speed and under load, I have noticed an annoying drone from my Flowmaster (but I am looking into another system anyway). You will have to correct the speedometer through the computer.

All and all a very good performance upgrade.

Have fun…

 

But, since no one would answer my post I guess I will have to ask someone that has done it for sure. WLF do you have to buy a special ring gear for the wheel speed sensor? You said you corrected your speedometer so I guess your speedometer works still. I have nothing to offer accept my thanks which is worth nothing I know. Thanks

 

Silver&Blue,
I must have missed your post somehow.
The gear is an aftermarket one that is not available thru Ford. It is a 23 tooth gear. I purchased mine thru Mustangs unlimited. There was no special adapter needed to use the gear. It is very easy to install.
On the 97 and 98 you will find the speedometer gear on the drivers side rear of the transmission main housing towards the top. There is a small nut holding it in. I didn't even have to disconnect the wire. Just removed the nut, pulled off the assembly, pulled out the old gear and then installed the new one. The speedometer worked just fine from there.
I hope this helps.
Find the calculater here
http://www.finer.com/Internet/pages/speedo.htm

 

I have the 4.10's and it made a huge difference in the performance of my truck. I would have gone to 4.30 if it was available for the 9.75/8.8R axle combination on my truck.

My gears are completely quiet.

On a '99 up truck, you have to correct the speedo with a computer update. You can either try your dealer (good luck) or talk to Mike T about a superchip. I have a flipchip to correct my speedo.

Ian

 

Thanks guys, what kinda mileage are you guys getting with those low gears. I do so much hiway driving that I don't think 4.10 will do me anygood in the mileage field. But it is in the back of my mind.