35's and 3.55's
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Joined: Aug 2006
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From: Northern California
Yes the TruTrac is an excellent limited slip. It doesn't use clutch packs like the stock one, so it will never wear out.
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Joined: Feb 2007
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From: Austin Texas
I am looking into getting gears as well... I want to upgrade to 35's and I know with my gryphon and intake/exhaust its gonna be a slug, I know i'm gonna need gears as well.. but my question is.. does this void the warranty?
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Joined: Dec 2008
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From: The Bayou State
I just answered a similar question, so I still have my spreadsheet handy. Here's a recap of cruise speeds at 70 mph with 325/60-20s.
3.55 - 1,699 rpm
3.73 - 1,785 rpm
4.10 - 1,962 rpm
4.56 - 2,183 rpm
Your factory gearing is around 2,000 rpm at 70 mph, give or take. 4.10s would get you close to stock, but there isn't much mileage penalty in going with 4.56s. If it were me, I'd go 4.56s, if I knew I didn't have plans to later go with 33s. I don't think we've seen the last of $4.00/gal gas prices.
3.55 - 1,699 rpm
3.73 - 1,785 rpm
4.10 - 1,962 rpm
4.56 - 2,183 rpm
Your factory gearing is around 2,000 rpm at 70 mph, give or take. 4.10s would get you close to stock, but there isn't much mileage penalty in going with 4.56s. If it were me, I'd go 4.56s, if I knew I didn't have plans to later go with 33s. I don't think we've seen the last of $4.00/gal gas prices.
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From: The Bayou State
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From: BC, Canada
here's a quote from Bill Cohron, the Gryphon tuning guru
I'll be putting this all together in the next few weeks, so I guess the seat of the pants will tell the truth
Originally Posted by Power Hungry
Just for reference, what Dave is talking about is a discussion I had with him about gears and tires. As I explained to him, our Expedition runs a 3.31 gear and we have 285/75-17 tires which come out to about 33". If you do the math, it's really close to a 3.55 with 35" tires, as far as RPM/MPH goes. We haven't had any problem form our Expy, which not only is undergeared, but also weighs more than the average F-150 and in fact I can stomp just about any F-150 in the area while breaking the tires loose from a dead stop.
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.
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.
I'll be putting this all together in the next few weeks, so I guess the seat of the pants will tell the truth
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Joined: Aug 2009
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From: Ogden, UT
k so what should i expect in a price range if i want to get a new gears i have a 2004 f150 with 35x12.50r18, i don't even know what gears i have but i bet they are stock so what would be a good brand to get and how much money should i be prepared to spend on them? just curious cause i have 105,000 miles on this baby and she still runs strong just would like to help the tranny out if i could...
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Joined: Apr 2009
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From: Madisonville, KY
k so what should i expect in a price range if i want to get a new gears i have a 2004 f150 with 35x12.50r18, i don't even know what gears i have but i bet they are stock so what would be a good brand to get and how much money should i be prepared to spend on them? just curious cause i have 105,000 miles on this baby and she still runs strong just would like to help the tranny out if i could...
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Joined: Aug 2009
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From: Ogden, UT
huh dang that is going to suck, idk for sure if it would be worth it then at least not know i don't even know how much longer i am going to keep this truck, hopefully upgrade here in a year or two, didn't think it would be that much, i guess we will see how much my tax return is lol, thanks though at least i have a idea what it would cost me, thanks
