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IWANNARAMU
Prospective Buyer
 
2/21/2001
10:04:26
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 Subject: Need info from 4.7 4x4 quad owners!
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Message:
Ok I test drove a 4x4 club cab with the 4.7 and what the dealer said were 3.55 gears (a little box above MPG figures with tow and capacity rating said 3.55 so I assume that is what the truck had.). WOW, FAST TRUCK!! I ask the dealer if with the extra weight of the quadcab if I should go with the 3.90s. Since I dont tow or haul alot, except ass!, he thought I should stay with 3.55s for better milage and top end. What do you guys with these turn for RPMs at 55 and 65 MPH in OD with either of these gears? Do you think the truck I drove actually had the 3.55s? I did not take a RPM to MPH reading to verify the gears. Any and all info is appreciated! The 4.7 KILLS the 5.9!
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Dan Gruber
Unregistered
2/21/2001
12:36:28
| RE: Need info from 4.7 4x4 quad owners!
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Message:
Even though I own a club cab, the info you're asking for is applicable to both the club cab and the quad cab, so here's my input. Hope it helps.
I have a 2000 4X4 club cab with the 4.7/auto/3.55 LSD combo, and the 31 inch tires. At 55, my engine turns in the neighborhood of 1700-1800 rpm (give or take 100 rpm), and at 65, I sit right around 2000, give or take 100. These are based on my memory...I haven't gone out and written down exactly what rpms the engine runs at different speeds.
The only thing I wish my truck had come from the factory with that I don't already have is the 3.90 gears, and here are my reasons:
1. At 55 mph, almost any movement of the gas pedal causes the torque converter to unlock, if not drop into 3rd gear. If you spend any time at all driving around 55 mph, that gets annoying. The extra revs provided by the tighter gearing would limit this.
2. Between 2100-2300 rpm (70-74 mph, right where I like to cruise on the freeway) is a natural resonance within the 4.7. Almost all engines have this...it is just a combination of air flow and backpressure in the engine that cause it to become a little louder at a given rpm. This is noticeable with the stock exhaust, but a little loud with the 3 inch exhaust that I have. Ususally causes me to speed up to about 75, where the exhaust becomes much quieter. The 3.90 gears would drop the speed of this resonance down to the 60 mph area, where I usually spend little to no time. Depending on how you drive and if you're planning on getting an aftermarket exhaust, you may want to take this into consideration. I generally love the sound of my 3 inch exhaust and it's normally not a big deal, but it can become a little tiring on long drives.
3. Towing capacity jumps by nearly 1000 pounds by getting the 3.90 gears.
Bottom line: You are unlikely to see a huge mileage penalty by getting the 3.90's, maybe 1 mile per gallon. In my mind, that is a more than fair trade for the increased tow rating, better acceleration, and less transmission "hunting" at highway speeds. Go with the 3.90 gears.
Dan
2000 CC/SLT+/4X4/4.7/3.55LSD
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