Redline
Likes to Drive and Ride
I posted in a couple of older threads but haven't received much input, and I'm hungry for responses 
I was considering only locking the read and forgetting re-gearing the diffs and the front locker. I have decided to discount that option and do a re-gear and lock both the front and rear while I'm in there.
Car:
2006 V8 4Runner
OME lift
255/85R16 tires
Skids, bumpers, armor, etc. = weighs 5,500 without passenger or a load, with passenger/load close to 6,000-lbs. Also tow a 2000-lb AT Chaser occasionally.
Typical cruise speeds is 65-70-MPH. Can I and will I drive faster on occasion? Surely, but rarely for an extended distance and then I'm willing to sacrifice noise/mpg if needed.
The car used to be pretty quick when it was bone stock, now not so much. But wait there's more... More than just the typical lift, tires, and weight. I live and travel at 5,000-ft and above, drive in the hills & mountains often, and we often have lots of wind. All of these factors impact performance.
For months I was convinced that 4.56 gears were the way to go. I think most of us are concerned about gearing rigs too low, but maybe we should be more concerned about gearing that is too high, as this is the problem with stock gearing and the reason to change from it.
When the 4Runner was bone stock it would turn 1900-rpm at 65-mph.
Now with 255s and 3.73s it turns about 1766-rpm. The RPM numbers don't tell the whole story because they don't factor for weight gain and the driving conditions. 4.11 gears would be closest to stock rpm, but that is not nearly enough change for the money nor all the changes made to the car. 4.56 gears will be available near the end of this month and 4.88s are already available, both from JT.
There is little difference between 4.56 and 4.88s. About 150-rpm at 65 in O/D, and about 180-rpm at 75-mph.
Overdrive ratio w/ 5-sp auto = .761:1
Stock final drive ratio is the typical: 3.727 (3.73)
For calculations I'm using a tire height of 33-in. A loaded tire may be 32.5-in. but it makes little difference in the numbers.
4.56 gears
In Overdrive:
@ 65 = 2160 rpm
@ 70 = 2327 rpm
@ 75 = 2493 rpm
4.88 gears
@ 65 = 2312 rpm
@ 70 = 2490 rpm
@ 75 = 2668 rpm
None of these RPM seem overly high to me, in fact the 4.56 rpm at 65-mph is a bit low and I wonder how well it will pull up hills in overdrive. The goal is to stay it overdrive as much as possible and not have to gear down to 4th or 3rd, at least at highways speeds, and to use small throttle openings. I'm a believer that less road speed (wind resistance) has a bigger impact on MPG than RPM. And when one increases their road speed to something like 75 the lower gears will buck the wind better than taller gears. Tall gears not being able to handle wind and even slight inclines is what I have now!
A couple years ago I re-geared my '05 Rubicon to 4.88s. That car had much less power, terrible aerodynamics and a 6-speed manual with a shorter/lower overdrive ratio. The shop that did the gears thought I was going too low, but I was not unhappy with the gearing. On the Jeep going to 4.88s made overdrive very close to where direct was with the stock 4.10s.
On the 4Runner with 4.88s @ 65-mph I will still be 200-rpm lower in overdrive than I am currently in 4th/direct @ 65. And possibly the most convincing argument for me in favor of 4.88s is that the engine rpm @ 65 will only be 400-rpm higher than it was when stock, 1900-rpm.
Arguments please.
I was considering only locking the read and forgetting re-gearing the diffs and the front locker. I have decided to discount that option and do a re-gear and lock both the front and rear while I'm in there.
Car:
2006 V8 4Runner
OME lift
255/85R16 tires
Skids, bumpers, armor, etc. = weighs 5,500 without passenger or a load, with passenger/load close to 6,000-lbs. Also tow a 2000-lb AT Chaser occasionally.
Typical cruise speeds is 65-70-MPH. Can I and will I drive faster on occasion? Surely, but rarely for an extended distance and then I'm willing to sacrifice noise/mpg if needed.
The car used to be pretty quick when it was bone stock, now not so much. But wait there's more... More than just the typical lift, tires, and weight. I live and travel at 5,000-ft and above, drive in the hills & mountains often, and we often have lots of wind. All of these factors impact performance.
For months I was convinced that 4.56 gears were the way to go. I think most of us are concerned about gearing rigs too low, but maybe we should be more concerned about gearing that is too high, as this is the problem with stock gearing and the reason to change from it.
When the 4Runner was bone stock it would turn 1900-rpm at 65-mph.
Now with 255s and 3.73s it turns about 1766-rpm. The RPM numbers don't tell the whole story because they don't factor for weight gain and the driving conditions. 4.11 gears would be closest to stock rpm, but that is not nearly enough change for the money nor all the changes made to the car. 4.56 gears will be available near the end of this month and 4.88s are already available, both from JT.
There is little difference between 4.56 and 4.88s. About 150-rpm at 65 in O/D, and about 180-rpm at 75-mph.
Overdrive ratio w/ 5-sp auto = .761:1
Stock final drive ratio is the typical: 3.727 (3.73)
For calculations I'm using a tire height of 33-in. A loaded tire may be 32.5-in. but it makes little difference in the numbers.
4.56 gears
In Overdrive:
@ 65 = 2160 rpm
@ 70 = 2327 rpm
@ 75 = 2493 rpm
4.88 gears
@ 65 = 2312 rpm
@ 70 = 2490 rpm
@ 75 = 2668 rpm
None of these RPM seem overly high to me, in fact the 4.56 rpm at 65-mph is a bit low and I wonder how well it will pull up hills in overdrive. The goal is to stay it overdrive as much as possible and not have to gear down to 4th or 3rd, at least at highways speeds, and to use small throttle openings. I'm a believer that less road speed (wind resistance) has a bigger impact on MPG than RPM. And when one increases their road speed to something like 75 the lower gears will buck the wind better than taller gears. Tall gears not being able to handle wind and even slight inclines is what I have now!
A couple years ago I re-geared my '05 Rubicon to 4.88s. That car had much less power, terrible aerodynamics and a 6-speed manual with a shorter/lower overdrive ratio. The shop that did the gears thought I was going too low, but I was not unhappy with the gearing. On the Jeep going to 4.88s made overdrive very close to where direct was with the stock 4.10s.
On the 4Runner with 4.88s @ 65-mph I will still be 200-rpm lower in overdrive than I am currently in 4th/direct @ 65. And possibly the most convincing argument for me in favor of 4.88s is that the engine rpm @ 65 will only be 400-rpm higher than it was when stock, 1900-rpm.
Arguments please.
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