gear/locker help?
Mountain Pass
Joined: Jan 2010
Posts: 117
Likes: 1
Thats true, it is Eaton True Trac right? I thought it was through Detroit locker. From what I am reading, it is a LS unit that doesnt have wearable parts. It works like an open rear end until one tire slips, then it locks up. Am I right? I hate my open rear end, I get stuck in the snow sometimes because only wheel spins. I feel like My cousin Vinny...hahaha. No, I don't want a true locking "posi" rearend, just one that give equal power if one tire breaks free.
More Turbo
Joined: Feb 2006
Posts: 538
Likes: 11
From: Shiner, TX
Limited slip differentials don't "lock-up" when one tire starts spinning.
They're "locked" (by friction) until the friction coefficient or bias-ratio is overcome... like when you go around a corner on the street or when one wheel is on mud and the other is on pavement.
It's designed to slip when locked and not lock when slipping.
They're "locked" (by friction) until the friction coefficient or bias-ratio is overcome... like when you go around a corner on the street or when one wheel is on mud and the other is on pavement.
It's designed to slip when locked and not lock when slipping.
Thread Starter
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Senior User
Joined: Nov 2008
Posts: 306
Likes: 0
From: simi valley
need some help guys. got a new truck that was already lifted.he said it was geared but doesnt know whats in it. its on 40x15.50r22 and the speedo says 60mph when its doing 68mph gps and also its about 2000rpms.can anyone do the math and see what gears are in there? i have no idea how to do that.thanks
You Keep What You Kill
Joined: Dec 2006
Posts: 4,902
Likes: 2
From: Huntersville, NC
need some help guys. got a new truck that was already lifted.he said it was geared but doesnt know whats in it. its on 40x15.50r22 and the speedo says 60mph when its doing 68mph gps and also its about 2000rpms.can anyone do the math and see what gears are in there? i have no idea how to do that.thanks
Thread Starter
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Senior User
Joined: Nov 2008
Posts: 306
Likes: 0
From: simi valley
my bad.yes auto i just meant that i didnt know the trans name/number of it
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You Keep What You Kill
Joined: Dec 2006
Posts: 4,902
Likes: 2
From: Huntersville, NC
Miles Per Hour: 68
Tire Diameter In Inches: 40
Axle Ratio: 4.88
Transmission High Gear Ratio: .71
Calculated RPM's = 1,981
You can double check the RPM's by changing the value in the "Miles Per Hour" field. For example, monitor (write down) your trucks RPM's at 55 MPH, 60 MPH, 65 MPH, and 70 MPH. Then enter the various MPH values into the RPM Calculator to determine if 4.88 gears was the correct gear.
RPM Calculator
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Senior User
Joined: Nov 2008
Posts: 306
Likes: 0
From: simi valley
You have a 4R100 transmission with a "Transmission High Gear Ratio" of .71 which was used in the RPM Calculator below. I entered the following values into the form:
Miles Per Hour: 68
Tire Diameter In Inches: 40
Axle Ratio: 4.88
Transmission High Gear Ratio: .71
Calculated RPM's = 1,981
You can double check the RPM's by changing the value in the "Miles Per Hour" field. For example, monitor (write down) your trucks RPM's at 55 MPH, 60 MPH, 65 MPH, and 70 MPH. Then enter the various MPH values into the RPM Calculator to determine if 4.88 gears was the correct gear.
RPM Calculator
Miles Per Hour: 68
Tire Diameter In Inches: 40
Axle Ratio: 4.88
Transmission High Gear Ratio: .71
Calculated RPM's = 1,981
You can double check the RPM's by changing the value in the "Miles Per Hour" field. For example, monitor (write down) your trucks RPM's at 55 MPH, 60 MPH, 65 MPH, and 70 MPH. Then enter the various MPH values into the RPM Calculator to determine if 4.88 gears was the correct gear.
RPM Calculator
You Keep What You Kill
Joined: Dec 2006
Posts: 4,902
Likes: 2
From: Huntersville, NC
It appears that an aftermarket electronic device is needed to correct your speedometer. Here are a few that I found...
E4OD, 4R100 Transmission from PATC, E4OD, 4R100
<TABLE border=0 cellSpacing=0 cellPadding=0><TBODY><TR><TD>Electronic Ratio Adapter (ERA)
[***************]Now You Have the Solution to Your Speedometer Problems.....<!--webbot bot="HTMLMarkup" startspan --> <FORM id=form2 method=get name=form2 action=https://www.vermontsecure.com/cart.asp><INPUT value=79 type=hidden name=cID> <INPUT value=1 type=hidden name=AddItem> <INPUT value=#69. type=hidden name=Sku> <INPUT value="Electronic Ratio Adapter (ERA)" type=hidden name=ProductName> <INPUT value=169 type=hidden name=PriceEach> Qty <SELECT name=Qty> <OPTION selected value=1>1<OPTION value=2>2<OPTION value=3>3<OPTION value=4>4<OPTION value=5>5</OPTION></SELECT>
<INPUT value="Add to Cart" type=submit name=Submit></FORM><!--webbot bot="HTMLMarkup" endspan -->[/COLOR]
</TD><TD>
</TD><TD>
</TD></TR></TBODY></TABLE>
#69. Any change in a vehicle's tire size or rear axle ratio will cause the speedometer reading to be inaccurate. The Electronic Ratio Adapter (ERA) is designed to correct this problem. With the ERA, you simply hook up four wires, set the DIP switches according to the calibration table included with your order, and you are ready to go.
What does the Electronic Ratio Adapter do?
The automotive industry has a great variety of part sizes, types, shapes and descriptions, but regardless of make, model or year, a few things are standard. One of those standards has been the number of revolutions a speedometer cable will make for each mile travelled. Nowadays, electronic pulses have replaced the rotating cable, but the same principle applies. The Pulse Ratio (the number of pulses per mile travelled) remains the same, regardless of speed, since the same distance is travelled and the same number of pulses have occurred each mile no matter what the speed was during that mile.
However, this Pulse Ratio can be made to vary from the true when modifications are made which change the number of electronic pulses per mile on a particular vehicle. This is most commonly caused by changing the tire size (increasing the outside diameter of the tires will cause the tire to travel further before making a complete revolution), but other modifications could have the same result. When the Pulse Ratio is thrown off, the speedometer/odometer will be inaccurate and corrections must be made.
This relative difference between true speed and the speed indicated on the speedometer is called the Variance Ratio, and it is corrected using the Electronic Ratio Adapter. Cost $169.00
EDIT: However, looking at the price of these units, you would do better by getting a SCT X3 tuner that probably does what these units do and a whole lot more!
E4OD, 4R100 Transmission from PATC, E4OD, 4R100
<TABLE border=0 cellSpacing=0 cellPadding=0><TBODY><TR><TD>
[***************]Now You Have the Solution to Your Speedometer Problems.....<!--webbot bot="HTMLMarkup" startspan --> <FORM id=form2 method=get name=form2 action=https://www.vermontsecure.com/cart.asp><INPUT value=79 type=hidden name=cID> <INPUT value=1 type=hidden name=AddItem> <INPUT value=#69. type=hidden name=Sku> <INPUT value="Electronic Ratio Adapter (ERA)" type=hidden name=ProductName> <INPUT value=169 type=hidden name=PriceEach> Qty <SELECT name=Qty> <OPTION selected value=1>1<OPTION value=2>2<OPTION value=3>3<OPTION value=4>4<OPTION value=5>5</OPTION></SELECT>
<INPUT value="Add to Cart" type=submit name=Submit></FORM><!--webbot bot="HTMLMarkup" endspan -->[/COLOR]
</TD><TD>
</TD><TD></TD></TR></TBODY></TABLE>What does the Electronic Ratio Adapter do?
The automotive industry has a great variety of part sizes, types, shapes and descriptions, but regardless of make, model or year, a few things are standard. One of those standards has been the number of revolutions a speedometer cable will make for each mile travelled. Nowadays, electronic pulses have replaced the rotating cable, but the same principle applies. The Pulse Ratio (the number of pulses per mile travelled) remains the same, regardless of speed, since the same distance is travelled and the same number of pulses have occurred each mile no matter what the speed was during that mile.
However, this Pulse Ratio can be made to vary from the true when modifications are made which change the number of electronic pulses per mile on a particular vehicle. This is most commonly caused by changing the tire size (increasing the outside diameter of the tires will cause the tire to travel further before making a complete revolution), but other modifications could have the same result. When the Pulse Ratio is thrown off, the speedometer/odometer will be inaccurate and corrections must be made.
This relative difference between true speed and the speed indicated on the speedometer is called the Variance Ratio, and it is corrected using the Electronic Ratio Adapter. Cost $169.00
EDIT: However, looking at the price of these units, you would do better by getting a SCT X3 tuner that probably does what these units do and a whole lot more!
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