Tires and Gearing info

[SOAZ]

Here are some RPM numbers with 4.88's in a 2001 Toyota 4Runner 3.4 Liter V6 and 255-85-16 Cooper ST's

 

[jim65wagon]

Here are some RPM numbers with 4.88's in a 2001 Toyota 4Runner 3.4 Liter V6 and 255-85-16 Cooper ST's

For some kind of apples to other foods comparison...the Tundra turns 1700 rpm at 60mph with 3.91 (stock) gears and 255/85s

 

[Redline]

I'm going to have to mount my STs and test my RPM on my '06 4Runner and stock 3.73 gears. Get ready for some low numbers

 

[SOAZ]

I'm going to have to mount my STs and test my RPM on my '06 4Runner and stock 3.73 gears. Get ready for some low numbers

ooh! Good stuff. That is the only thing I miss. Being able to go 85 and have the motor still sound like its barely turning. On the other hand if there was dust in the air it was enough to slow the truck down and kick it out of overdrive with that stock gearing and 255's. It was a :cow:

 

[Redline]

You are exactly correct. Even with my V8, if my foot is too heavy or the road a little steep, some wind, or speeds too high, my tranny will shift out of O/D for 4th/direct. If it doesn't downshift because I'm 'light footing it' I lose lots of road speed. But it goes very well in 4th, or 3rd if needed, on big hills towing the Chaser.

Lower gears would be nice, I'm thinking 4.56, and they or may not cost me some MPG. I’m still not sure I will do gears and lockers, I'm still deciding how bad I need or want them on this Mall Crawler.

ooh! Good stuff. That is the only thing I miss. Being able to go 85 and have the motor still sound like its barely turning. On the other hand if there was dust in the air it was enough to slow the truck down and kick it out of overdrive with that stock gearing and 255's. It was a :cow:

 

[slooowr6]

<hijack>
Please help me understand the way how O/D works on automatic. This is what I seen of my truck. Set crusing speed at 65mph.
on flat: ~1980rpm (Is this lock O/D?)
slight incline: ~2500rpm (5th?)
If I manually **** to 4th the rpm will jump to ~3000rpm.
Thanks -Alex
<\hijack>

 

[xcmountain80]

Here are some RPM numbers with 4.88's in a 2001 Toyota 4Runner 3.4 Liter V6 and 255-85-16 Cooper ST's

Those numbers aren't far off my 4.56's with 295.75.16 Nitto Terra's 33.27X 11.73


Aaron

 

[Redline]

SOAZ:

Here are some RPM numbers with 4.88's in a 2001 Toyota 4Runner 3.4 Liter V6 and 255-85-16 Cooper ST's

What is the overdrive ratio of your top gear in your tranny, and is it an A/T or manual?

Depending on your overdrive ratio I'm thinking my final drive ratio might not be too far off with 4.56:1 gears.

James

 

[SOAZ]

You are exactly correct. Even with my V8, if my foot is too heavy or the road a little steep, some wind, or speeds too high, my tranny will shift out of O/D for 4th/direct. If it doesn't downshift because I'm 'light footing it' I lose lots of road speed. But it goes very well in 4th, or 3rd if needed, on big hills towing the Chaser.

Lower gears would be nice, I'm thinking 4.56, and they or may not cost me some MPG. I’m still not sure I will do gears and lockers, I'm still deciding how bad I need or want them on this Mall Crawler.

I know what you mean. I never would have unless I broke the rear diff.
And I blame all of you Expo members too. ROFSheriffHL:
Peer pressure is a B@tch!

 

[Redline]

What car & transmission do you have? I'm assuming a 5-speed auto Toyota? But it doesn't matter much...

What you have described sounds correct.
Flat = 1980 O/D/5th locked
Incline = 2500 probably 5th-unlocked but it does sound like a big jump in RPM. (It could be 4th locked, and when you move the shifter it can change to unlocked 4th... but these are guesses as it's hard to drive another man's truck from here

Modern automatic transmissions with lock-up torque converters often drive like they have two more gears than they actually do. Usually the toque converters are capable of locking in both direct and overdrive. (Direct meaning no overdrive or under-drive gear is selected in the transmission. Direct is 4th in a 5-speed auto, 4th in a 5-speed manual, 3rd in a 4-speed auto. 1:1 ratio = whatever the ring & pinion ratio is in the differential).

Whereas with a manual tranny ‘the gear ratio is the ratio’ (unless you are slipping the clutch and modifying it), with an A/T in a gear with a lock-up converter, the RPM will reflect the changes between lock-up and unlocked. In the more common 4-speed auto you will have 'gears': 1, 2, 3-unlocked, 3-locked, 4-unlocked, 4-locked. The tranny won’t necessarily use each one of these 'gears' every time it climbs up through the gears, but it can. Often you will drive up to top/overdrive gear on the highway/freeway and then overdrive will lock.

With the Toyota 5-speed auto in my 4Runner, the torque converter has the ability to be partially locked or fully locked, so one can see different RPM for a given speed depending on the terrain, etc.

James

<hijack>
Please help me understand the way how O/D works on automatic. This is what I seen of my truck. Set crusing speed at 65mph.
on flat: ~1980rpm (Is this lock O/D?)
slight incline: ~2500rpm (5th?)
If I manually **** to 4th the rpm will jump to ~3000rpm.
Thanks -Alex
<\hijack>

 

[slooowr6]

It's a 5spd auto in a Tacoma.
Now it makes sense. I think/guess this is what happen.
From flat->long incline at 65mph.
5th locked(1980rpm) -> (SC kicks in) -> 5th un-locked.(2500rpm)
It's pretty cool that with SC the Tacoma never really need to shift out on 5th on long climb.
Thanks for the explaination!

 

[Redline]

3.73 @ 70-mph

I didn't do a proper test. Didn't even mount my Cooper STs today. But I did put my Maxxis Bighorn MTs on the crawler tonight and went for a short drive, at 70-mph my RPM is about 1900-1950 (just under 2000) with the stock 3.73 gears.

Looks like with your 4.88s you are about 900-1000 RPM higher at 70-MPH with the same size tires.

I'm going to have to mount my STs and test my RPM on my '06 4Runner and stock 3.73 gears. Get ready for some low numbers

 

[madizell]

It's a 5spd auto in a Tacoma.
Now it makes sense. I think/guess this is what happen.
From flat->long incline at 65mph.
5th locked(1980rpm) -> (SC kicks in) -> 5th un-locked.(2500rpm)
It's pretty cool that with SC the Tacoma never really need to shift out on 5th on long climb.
Thanks for the explanation!

Perhaps my Nissan Frontier differs from the Tacoma enough not to be a direct comparison, but when mine shifts from 5th at around 1,800 or so rpm to 2,500 rpm, it is downshifting to 4th. I don't see more than a few hundred rpm difference at best as a result of torque converter changes within any given gear, and those changes are a sliding scale, not a leap from one range to another. Since it won't use "overdrive" in combination with any other gear but 5th, I assume that it is essentially a 5-speed auto transmission, with 5th gear ratio being less than 1:1, hence "overdrive." I have been able to verify 4th versus 5th on the Nissan because of the O/D lockout button, which forces the transmission to stay in no higher gear than 4th (otherwise shifts normally but won't use 5th), and the dash display changes from "D" to "4", showing which gear it is in. Or, if it has already shifted down and you engage the lockout button, nothing happens in the transmission but the dash display changes from D to 4, suggesting to me that the shift was a gear change, not a converter spooling up. Most small displacement engines won't pull a long incline without gear changes because of lack of torque. I know mine won't, 265hp notwithstanding.

 

[Redline]

Sounds just like a Toyota, and most other 'Overdrive' transmissions to me. Every automotive O/D I'm aware of works basically as you have described. Wether the O/D selector is actually a physical gate using the shifter (like new Tacomas/4Runners) or on a button on the dash or on the shift stalk (your Frontier, full-sized trucks). In most (all?) applications overdrive is taller than 1:1.

Gear ratios in the 03-up 4Runner & 5-sp Tacomas:

1st: 3.520
2nd: 2.042
3rd: 1.400
4th: 1.000
5th: 0.716
Reverse: 3.224
Ring & Pinion 3.727

Some of the new 6-speed trucks have two overdrives. Example: New 2007.5+ Dodge/Cummins with 68RFE trans:
1st: 3.23
2nd: 1.84
3rd: 1.41
4th: 1.00
5th: 0.82
6th: 0.63

I can't find my reference to state the blow affirmatively, but from memory the above new Dodge 68RFE trans not only locks-up in direct & overdrive, but in lower gears too, which makes the standard, turbo-exhaust brake work much better.

I have strayed a bit off topic.

Perhaps my Nissan Frontier differs from the Tacoma enough not to be a direct comparison, but when mine shifts from 5th at around 1,800 or so rpm to 2,500 rpm, it is downshifting to 4th. I don't see more than a few hundred rpm difference at best as a result of torque converter changes within any given gear, and those changes are a sliding scale, not a leap from one range to another. Since it won't use "overdrive" in combination with any other gear but 5th, I assume that it is essentially a 5-speed auto transmission, with 5th gear ratio being less than 1:1, hence "overdrive." I have been able to verify 4th versus 5th on the Nissan because of the O/D lockout button, which forces the transmission to stay in no higher gear than 4th (otherwise shifts normally but won't use 5th), and the dash display changes from "D" to "4", showing which gear it is in. Or, if it has already shifted down and you engage the lockout button, nothing happens in the transmission but the dash display changes from D to 4, suggesting to me that the shift was a gear change, not a converter spooling up. Most small displacement engines won't pull a long incline without gear changes because of lack of torque. I know mine won't, 265hp notwithstanding.

 

[slooowr6]

Perhaps my Nissan Frontier differs from the Tacoma enough not to be a direct comparison, but when mine shifts from 5th at around 1,800 or so rpm to 2,500 rpm, it is downshifting to 4th. I don't see more than a few hundred rpm difference at best as a result of torque converter changes within any given gear, and those changes are a sliding scale, not a leap from one range to another. Since it won't use "overdrive" in combination with any other gear but 5th, I assume that it is essentially a 5-speed auto transmission, with 5th gear ratio being less than 1:1, hence "overdrive." I have been able to verify 4th versus 5th on the Nissan because of the O/D lockout button, which forces the transmission to stay in no higher gear than 4th (otherwise shifts normally but won't use 5th), and the dash display changes from "D" to "4", showing which gear it is in. Or, if it has already shifted down and you engage the lockout button, nothing happens in the transmission but the dash display changes from D to 4, suggesting to me that the shift was a gear change, not a converter spooling up. Most small displacement engines won't pull a long incline without gear changes because of lack of torque. I know mine won't, 265hp notwithstanding.

Sorry to keep dragging this thread off topic but I really want to understand how this works. My original understanding is just like yours. But the truck's reaction tells my other wise. This why I'm confused.

Truck is using cruise control and set at 65mph.

1) On flat: 1980rpm.
2) On the incline: throttle slowly passed 27% SC starts to engaged jumps to 2500rpm.

If I manually shift to 4th while in cruise control by moving from D to 4. The rpm jumps to 3000rpm.

So I'm guessing, On flat it's 5th+lock converter. On incline it's 5th+unlock converter.

Ok, back on original topic. I'm 80% sure that I'll get the Dunlop RVXT 255/85/16, 32.8".