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Axle gearing and engine 'rattle' questions


Armatron

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I have a 98 ranger with the 4 cylinder. I paid $100 for a set of tires/wheels from a lincoln aviator and gave away my stock wheels w/ worn out tires. Since I very rarely drove the truck (I rode a motorcycle most of the time..) the horrid gearing didn't really bother me much.

However, I've sold the bikes (insurance was ridiculous and I'm between jobs atm..) and am now driving the truck more often... and am fed up with the gearing. I believe it has 3.08's. I've seen the 'gearing chart' but does that apply to 4 cylinders? This motor really doesn't have much power.. what is the ideal gearing? The tires are 245/65-17 and make 5th gear pretty much impossible to use. I'm really not interested in an explorer swap - I never go off-road and am looking for least expensive solution.


Also, since I've bought the truck it has an odd 'rattle' when you really push the gas. It's worse with cheap gas, the a/c on, and/or in the summer. When it gets really bad it's throw an EGR code (or it may be an o2 sensor.. actually I think it was the o2 sensor, but can't really remember..)
It's best described as sounding like a couple of pennies in a metal can sitting in the glovebox. I actually thought it was something rattling in the glovebox but couldn't find anything. It doesn't sound like detonation or engine knocking - although it is much less noticeable when using mid-grade or premium.. Is this any kind of known problem? I spend a lot of time searching on the 'original' forums a few months ago and didn't find anything.


Thank you very much in advance!
 


mjonesjr

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the gearing chart is a "rough" estimate.......

use this formula to find out what gearing you should go to:

NTS/OTS x SG = New gearing (round to the next largest gearing number ie: if you come up with a 4.21, then round to a 4.56)

NTS = New Tire Size
STS = Stock Tire Size
SG = Stock Gearing

here is the formula for my truck:
35"/31" x 3.73 = 4.21 (so i rounded up to 4.56 since there is no 4.21 gear)
 

MAKG

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The truck is detonating, probably due to a lean mixture. Fix it before you start going after gearing. 3.08 is pretty high, but you may care a whole lot less if your engine is running correctly.
 

Armatron

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The truck is detonating, probably due to a lean mixture. Fix it before you start going after gearing. 3.08 is pretty high, but you may care a whole lot less if your engine is running correctly.
Hmm.. I've replaced the plugs/wires, pcv valve, and cleaned the IAC...


Any other suggestions as to how I can correct the lean issue? AFAIK I can't adjust the timing either on this motor... it uses coils or whatnot.
 

Armatron

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the gearing chart is a "rough" estimate.......

use this formula to find out what gearing you should go to:

NTS/OTS x SG = New gearing (round to the next largest gearing number ie: if you come up with a 4.21, then round to a 4.56)

NTS = New Tire Size
STS = Stock Tire Size
SG = Stock Gearing

here is the formula for my truck:
35"/31" x 3.73 = 4.21 (so i rounded up to 4.56 since there is no 4.21 gear)
I'm assuming you meant STS intead of OTS in the formula?
Using this: http://www.miata.net/garage/tirecalc.html to convert my stock tire size (205/75-14) and new tire size (245/65-17) I end up needing 3.48's.. so I'm guessing I'd be best off with 3.73's.. I have the 4cyl, so I'd rather go with the RPM's being a bit high than low.

Okay.. is it easier to just buy the gears:
http://cgi.ebay.com/ebaymotors/FORD-OEM-373-3-73-GEARS-UPGRADE-FORD-RACING-7-5-V-6_W0QQcmdZViewItemQQcategoryZ33731QQihZ006QQitemZ160146747371QQrdZ1QQsspagenameZWDVW
or an entire new axle? I know with LS rear ends it's an "art" to install them correctly - I don't care about having LS with this truck... do you still have to set the backlash and stuff with non LS rearends?
 

Wicked_Sludge

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its an "art" to install and properly set-up ANY ring and pinion.

your cheapest option is to pick up a whole used axle from the junkyard. lucky for you, 3.73 is a common factory gearing, so it shouldnt be hard to find an axle.
 

Dave R

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With a 29.5" tall tire I'd recommend 4.10 gears. They will only 'cost' you 216rpm more (2346 vs. 2130) at 60mph in 5th but you'll be a lot happier in the long run.

The differential isn't that difficult to set-up but the gears require quite a bit of patience. Since the diff has to be removed to install the gears you might as well upgrade that at the same time. I'd recommend a Torsen geared posi.
 
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Armatron

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Hmmm.... a guy local to me has an apparently fairly badly wrecked 2007 that came with a 3.0 v6. I had him read the tag off the axle, it looks like a 3.73 7.5.... However, apparently one of the axle shafts broke in the wreck. The housing/gears didn't leak and he said don't appear to be banged up... he wants $25 for it. Opinions?
 

Dave R

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I'd vote a definite no. Since something had to hit the axle hard enough to break it, you can bet there is additional damage.

Though it would be a cheap set of gears.

Your call.
 

Armatron

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I found a guy with a good 3.73... and he only wants $50, and will give me the leaf springs as well... and has a sawzall to cut it all off with. Downside is that it's a 4 hour round trip, not counting at least an hour to get the rear end off.

Bleh...
 

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