Stomis

I know there is calculators around but I cant make sense of them. I'm looking for some info on running these two different gear sets and how big of a difference they make in RPM's. I'd like to be able to cruise in overdrive with my RPM's at 2500 or below @ 75mph.

MudHippy

Try this one. I haven't found the other one I use yet.

http://www.marlincrawler.com/java/getspd_calc.html

still lookin', but here's another.
http://www.4crawler.com/4x4/4LoCalc.shtml

Stomis

Whats 5th gear transmission ratio in a v6 tranny? (w56?)

I was right in thinking it was .85

Well after looking at it I could go with 4.88's or 5.29's. The calc says that 4.10's and 31's to 36's should be 4.88s and 4.56's and 31's should be 5.29's. Guess its my choice..

MudHippy

These were the ones I found easiest to use. Finally found them.

http://www.richmondgear.com/01calculators.html

tc

Uh - no you don't. You will get worse gas mileage and it's going to be totally unresponsive to throttle. You will get worse mileage because you'll always have the pedal to the floor just dumping fuel into the motor in open loop.... keep the RPM's over 3000

Stomis

Ah alright see I wanted someone to tell me whats right with rpms because I used to have a commuter v8 that ran like 1800rpms at 75. I guess I'm gonna go with 5.29's then.

AH64ID

Check out this calc I made, super simple...

What speed to you normally cruise at?

But just from experiance 5.29 is as tall as I would go. I have 4.88 and 35's and its w/in 1% of OEM gearing... so its decent on the street but 5.29's would be much better.

SteveO

Here is some real world data.
My 4Runner is a brick in the air, and heavy to boot. When I go to the trails, I run 37" MT/R tires on 15x10 steel wheels, with 4.88 gears. On my last trip to Moab, I was loaded up to about 6000lbs.

Using a GPS to track my mileage and speed, I was able to pull in 20MPG crusing at 60MPH, with my RPMs at 1850, rolling on 37" MT/R tires.

When I put on my 35" BFG/AT tires, mounted on 15x10 wheels, my rpms go up to about 2k, somewhere around there. Since I drive this thing every day, around 90 miles a day, its kinda hard to check the mileage. Its not all highway miles as when I tracked with the MT/R tires.

With the 35" tires, I can maintain 75MPH, but I haven't really noticed how high my RPMs are, due to the uneven terrain that I ride on. I'll try and find a level spot and see what they are at 75mph. But, when I'm doing 60 and need to pull out to pass, I have plenty of power, and it does quite well when passing. There is a noticable power difference between running 35" A/T tires and 37" M/T tires.

WATRD

This might give you a ballpark idea of the difference:

SteveO

Cool chart. I wonder at what speed these chart was made from, and was it a 5speed that produced this data?

WATRD

The numbers represent approximately 65mph and are based on a manual tranny, but are representative of either transmission in a 1:1 gear configuration.

More details are here: http://www.wattora.com/index.php?page_id=14

4Crawler

iTrader: (3)

Just plug in the numbers:
- http://www.4crawler.com/4x4/4LoCalc.shtml#FindRPM
- Axle Ratio: 4.88 or 5.29
- Trans ratio: Whatever your OD ratio is
- Tcase ration: 1.0
- Tire size: 36

SteveO

Very cool, but I don't recall what my OD on my Auto gear ratio is..... .70????


edit: I think thats right. I know I do 1850RPMs (by the needle) at 60mph while in OD, and the computational number gave me 1861 RPM.
MPH: 60
Axle Ratio: 4.88
Trans Ratio: .70
Trans Case Ratio: 1
Tire Diameter: 37
Resultant RPM: 1861.258

Very cool little tool.

4Crawler

iTrader: (3)

Of course no calculator or chart will be of any use without that number

0.71 per this page:
- http://www.4x4wire.com/toyota/tech/a...ler/index2.htm

SteveO

After driving my rig now as a daily driver, I have been wondering if my final ratio in RPMs were close to stock. Using Mark Medina's calculators on 4Crawlers site, I have come up with the following:



The vehicle: 1999 4Runner Limited w/4spd Auto 4x4 w/Tow package
Given the constants:
Speed: 70MPH
Transmission Ratio: .71 (Overdrive)
Transfer case ratio: 1

Stock
Axle Ratio: 4.30
Tire Diameter: P265/70R16 (30.6x10.4x16)
RPM = 2343.6

Modified to crawler status
Axle Ratio: 4.88
Tire Diameter: 37" MT/R
RPM = 2202.5

Modified to commuter status
Axle Ratio: 4.88
Tire Diameter: 35" BFG/AT
RPM = 2328.3

From stock to rockcrawler there is a 6.5% change, not too bad, when moving from a 30.6" tire to a 37" tire.

From stock to commuter, there is a less than 1% difference in RPMs. This is a very nice change for 35" tires.

When I cruise to work the speed limit is 55mph. So, as I flow with the traffic, I'm almost always below 2k rpm. Pretty nice.

edit: to fix the trasmissions OD ratio

4Crawler

iTrader: (3)

Tire size may not be exactly what is on the sidewall and the tach may not be 100% accurate either.

AH64ID

The best thing to use for tire size is the rev/mile figure most mfgrs list these days.... the spreadsheet I linked to has a conversion in there for that, as well as being preloaded with toyota tranny gear ratios.. all you change is tire size, RPM, gear ratios...

UKMyers

If you can cruise in a Toy with 36's at 75mph your da man!!! I am running 37's with 5.29's and if I hold it on the floor in 4th gear for about 5 minutes I think I might be able to hit 75. I cruise at around 65 as long as it's perfectly flat and there's no head wind. This is with the 3.slow btw. Would be a different story with the 3.4 I suppose.

AH64ID

Yeah, with 35's I cant cruise at 75... but around town I can get 20mpg...

Stomis

Hmmm alright looks like I'm gonna go with 4.88's then.