So I think this thing contributes to both RABS-II and provides speed info to the PSOM as a result of the magnetic pickup.

What I'm wondering about is how it works: Is it counting ring gear teeth or something else? That would explain why you have to recalibrate if changing your diffy ratio, as the number of teeth would change, but I'd like to be sure I have this right for my 1996 F-150 ...

 

Posted by Bill aka subford: https://www.ford-trucks.com/forums/1...l#post14385171

The VSS is not counting the number of teeth on the ring gear, it's a separate piece called a "tone ring".

When you change the rear gear ratio it does not require you to re-calibrate the PSOM. The number of tone ring teeth remain the same.

 

rla2005: Many thanks for the reply. I was concerned about this because I have a 2.47:1 gear I'd like to install and didn't know if it would work.

So apparently the tone ring just unbolts from the old ring gear and goes back on the substitute? That would certainly save me some worry.

 

2.47?? Really, why on earth would you put that gear in?

If you are swapping complete carriers just make sure the donor has provision for the tone ring. Reference the tooth gear on the left side of the carrier:

 

rla2005: I'm doing a fuel economy trial and I wanted to try this gear, vs my 2.73:1.

I've just looked at the 2.47:1, and it has 10 bolt holes on the reverse side. If that's for the tone gear, I'm in good shape.

 

Most folks find the 2.73 ratio to be too tall if you use the truck as a truck. I cannot imagine what you will end up with if you go even taller.

Now that I see what your end goal is I suggest you stop before you make a huge mistake. What kind of MPGs are you getting now and under what conditions?

 

I use the truck as a daily driver mostly. I've only seriously loaded it down with wood, soil and bricks a half dozen times in five years. The ZF-S542 has better gearing for hauling, so for the amount I've done, it's worked fine.

First, I've had this part on the shelf for over two years. The only real mistake I could make right now is that of never using it.

The truck is getting really excellent fuel economy right now, as much as 30-32 mpg at highways speeds of 55mph.

I'm trying to accomplish something extraordinary:

Coast to Coast Fuel Economy Challenge

Accomplishing this goal requires taking a few chances and risking failure. My next two ventures are the installation of an Isky Mile-a-Mor (331-M) cam that has just arrived, and also this ring and pinion gear set that I've had for quite a while.

Every half-mile per gallon is a big win for me. The gains I see will never pay for themselves at the pump, but this is a "proof of concept" that has implications for a big percentage of the 100+ million trucks and SUVs on the road, with average of 10+ years old, that account for a very large share of emissions and low fuel economy.

I want people to enjoy their trucks however they want, and if a few people take an interest in this project, then that's great too.

 

I wish you the best in this project but I have to throw the BS flag for the claim you are getting 30-32 MPG on the highway under normal driving conditions. The hyper-milers have several tricks to attain these questionable MPG numbers that may or may not translate to real world driving.

Good luck and happy hyper-miling!

 

Do you have any pictures or lists of mods you've done to your truck to achieve the 30 mpg? I know on the ecomodder forum, there are a few small trucks that are getting 30ish MPGs after extensive mods, but a 90's F150 would be doing very well to get past the mid 20 range.

 

rla2005: I understand your skepticism. Exceptional claims require exceptional proof. I'm aware of the hyper-milers, but what I'm working on doesn't depend on any of that pulse-glide stuff. For people that do serious work with their truck, I understand that they'd immediately drop a 3.55:1 in it. The original 2.73:1 is already an excellent fuel economy diffy, but it's not for serious hauling or towing. I'm not opposed to downshifting to get the crawl / RPMs I need though! My best MPG results are from a relatively flat interstate route with good pavement. I do benefit from the "corridor effect" mentioned in this list:
100+ Hypermiling / ecodriving tips & tactics for better mpg - EcoModder.com

DIYiT: It's quite a long list, but nothing inside the engine yet. Aerodynamic mods include a tonneau cover worth 1.5-2 mpg, a very curious looking front air dam and rear bumper mod worth about 2.5-3.5 mpg, running the tires with all the pressure they can stand, reduced exhaust backpressure with a Flowmaster Series 50 muffler and Magnaflow Heavy Metal Cat, a 3.8L Taurus electric fan, a Meziere 3365 electric water pump, a Delta Current Controls Fan/Pump controller, Mallory HyFire 6a multi-spark discharg, Accel Super Stock Coil, new O2 sensors, K&N low restriction air filter, Mobil 1, ScanGaugeII ...

I'm also going to upgrade to four-hole injectors vs the single pintle OEM parts. Hoping for slightly better atomization.