Any thought on gears?

***88Racing*** · #1 Wed, November 11th, 2009, 07:55 PM

This a tough one!
You are not pulling anything big(load wise) or not putting bigger tires on. The bigger the ratio the more the economy is sacrificed.
My gut is telling me 3.73's.
My brain is telling me 4.10's.
Tell you what plug your numbers into the pegasus gear calcultor and see what that comes up with.
Just some thoughts.
JMHO
Lars

BlackSTX · #2 Wed, November 11th, 2009, 08:36 PM

Yeah, it is. I've been trying to think it out for a while. I have gone to a few sites and plugged in some numbers, and it appears 4.30's would likely raise RPM's at 55 mph in overdrive about 300 RPM's, which I don't consider significant for the driving I do. Since my daily commute is about 6 miles round trip, and the majority of driving I do isn't at expressway speeds.
I just want to get the mass moving quickly..... Something a relatively low horsepower 4.6L is a bit challenged in doing.

***88Racing*** · #3 Wed, November 11th, 2009, 09:24 PM

Well general rule is to go a step up. So if the info pointed you to 4.30 then go to 4.56. Or is this toooo radical?

JWBFX4 · #4 Thu, November 12th, 2009, 12:21 AM

I would think 4.10's would be a perfect fit. But IMO i would not go over 4.30's

But you will sacrifice some mileage at the higher speeds (interstate driving)

***Jackpine*** · #5 Thu, November 12th, 2009, 12:10 PM

And, Ford's torque control is going to get in the way if you go too high. Bill posted about this somewhere a long time back and I can't really think of a good "search string" to find it. Maybe if you search on all posts by "Power Hungry" and "gears" you may get lucky?

At any rate, if you put the gearing too high. the PCM won't see the need for power and will limit what you can get (at least that is what I understand).

Bill also published an Excel spreadsheet "RPM vs MPH calculator.xls", recently that you may be able to find pretty quickly if you look for it.

Personally, I would not go above 4.10.

- Jack

BlackSTX · #6 Thu, November 12th, 2009, 04:09 PM

Thanks for the info!

I'm guessing that 4.10's may win out, though I am curious about trying 4.30's. I'll admit, I don't know about the torque limiting effect of the PCM.

I believe it's always a bit better to wish you had a bit more gear than wishing you hadn't gone so extreme. I know 4.56's or better can get you up and running pretty quick, but there's certainly a down side with them. The answers I got on another forum some time ago was very extreme..... 4.88's.... really!

I couldn't even consider them to be serious, especially since I'm not planning on lifting my truck and running 36" tires, nor am I planning on taking it to the track.

I knew I'd get more logical responses here, not to mention some other info. worth considering, thanks!

***Jackpine*** · #7 Thu, November 12th, 2009, 07:15 PM

Quote:

Originally Posted by BlackSTX

Thanks for the info!

I'm guessing that 4.10's may win out, though I am curious about trying 4.30's. I'll admit, I don't know about the torque limiting effect of the PCM.

I believe it's always a bit better to wish you had a bit more gear than wishing you hadn't gone so extreme. I know 4.56's or better can get you up and running pretty quick, but there's certainly a down side with them. The answers I got on another forum some time ago was very extreme..... 4.88's.... really!

I couldn't even consider them to be serious, especially since I'm not planning on lifting my truck and running 36" tires, nor am I planning on taking it to the track.

I knew I'd get more logical responses here, not to mention some other info. worth considering, thanks!

With my tires, going one step up in gear ratio adds about 200 RPM in the 66 mph range. A bit more than that at 76, maybe around 250 RPM? I think anything more than that would make the engine sound like it was screaming at cruise speeds. I know I hate to listen to it when I have to drop into 3rd while towing at 65, sounds to me like the engine's running much too fast.

- Jack

dave-m · #8 Tue, December 1st, 2009, 12:44 AM

Quote:

Originally Posted by JackandJanet

And, Ford's torque control is going to get in the way if you go too high. Bill posted about this somewhere a long time back and I can't really think of a good "search string" to find it. Maybe if you search on all posts by "Power Hungry" and "gears" you may get lucky?

At any rate, if you put the gearing too high. the PCM won't see the need for power and will limit what you can get (at least that is what I understand).

- Jack

I think this may be what you're thinking about

Quote:

Originally Posted by Power Hungry

What many folks forget is that the PCM operates on a load-based strategy. The higher the load, the more power it will allow the engine to make. This is why 4.88 geared trucks often fall short in performance when compared to 4.10 or 3.73 geared counterparts.