MODIFY YOUR GM CAR
FOR WINTER DRIVING Uni-Quad Uni-Quad

Adding SECOND GEAR START WITH GEAR INDICATOR to your GM car

DISCLAIMER

This information is provided for only the purpose of increasing safety in winter driving.

This device is not guaranteed to prevent wheel slip.

The page author will not be responsible for any damages caused by any of the following:

One of the reasons that modern vehicles have so much trouble in winter weather is that the engines are so powerful that they easily cause the wheels of the car to spin on snow or ice. The high torque multiplication of first gear contributes to this.

The Second Gear Start modification will not totally prevent wheel slip. The driver's skill and the slipperiness of the surface are also factors in wheel slip. But this device will greatly help the driver to control wheel slip.

Unlike devices in other websites that propose using such wiring, this has been tested in a 2002 Pontiac Bonneville SLE owned by the page author, and has been shown to actuate the transmission as described.

This should work in any GM-designed car with a 4-speed automatic transmission made since 1994 and controlled by the GM Powertrain Control Module (PCM).

This has not been designed for cars made by other companies and sold in the US by GM.

This has not been designed or approved in any way by GM. It is in no way connected with GM or its subsidiaries.

The instructions for using this device are given first, followed by the theory of operation, and then the construction details.


USING SECOND GEAR START WITH GEAR INDICATOR

Instrument panel with second gear start Here is how to use Second Gear Start With Gear Indicator:


A WORD OF WARNING

It has come to the attention of the page author that some law enforcement officials mistake devices such as this one for illegal RADAR or LIDAR detectors. Instead of realizing that there are other legal modifications people can make to their cars, they wrongly assume that any device such as the Indicator Assembly is an attempt to disguise an illegal detector.

States with such backward laws include Virginia, the District of Columbia, and Quebec.

It might be a good idea to print the Quick Reference Card above and keep it in the car as evidence that this is not an illegal detecting device.


WHY THE PAGE AUTHOR BUILT THIS

The following events resulted in the page author building this device:

  1. The previous two cars the page author owned had some form of Second Gear Start.
  2. Second Gear Start worked quite well with slippery conditions on the other two cars.
  3. One time, the page author was caught in an ice storm where almost all of the cars slid off the street into curbs and ditches. With Second Gear Start and antilock brakes, the page author still had complete control of the car. But he did turn onto a quieter street to avoid being hit by other cars.
  4. The city relocated the page author's driveway to add curbs and sidewalks on the street.
  5. The new driveway has a sharp uphill section just before the ridge preventing drainage into the driveway.
  6. The page author agreed to the design of the driveway because his car had Second Gear Start.
  7. The President's Cash for Clunkers program depleted the market of cars with Second Gear Start.
  8. The page author had to quickly buy a car because of the sudden loss of use of the previous car.
  9. The new car couldn't get out of the driveway on days when ice storms happened.
  10. Due to financial agreements, the page author loses a lot of money if he trades the car now.
  11. The page author decided to research adding Second Gear Start to the car.
  12. The author added gear indications for saving gas when he discovered how easy it is to do.

THEORY OF OPERATION FOR WINTER DRIVING

The theory of the operation of this device is based on the principle of the weakest link in a chain. But instead of a chain, there is a drive train with two places where slippage can occur. Which one slips depends on the amount of torque needed to make each one slip.

Known values for the 4T65 transmission:

Let's assume the following:

Now look at the table of operation of this transmission:

GearTC Slip
Torque
TC
Ratio
Gear
Ratio
Output
Ratio
TC & Gear
Output Shaft
Slip Torque
Low | High
Engine
Torque
To Slip TC
Engine Torque
To Slip wheel
 Low | High
Which Will
Slip First
  Low | High 
1n22.921 5.8425n | 4n n0.856n | 0.685n wheel | wheel
2n21.568 3.1365n | 4n n1.594n | 1.276n TC | TC
3n21.000 2.0005n | 4n n.2.500n | 2.000n TC | TC
4n20.705 1.4105n | 4n n.3.546n | 2.837n TC | TC
Rn22.385 4.7705n | 4n n.1.048n | 0.839n TC (?) | wheel

The idea here is to make the torque converter (TC) the weakest link in the chain. It will slip first, before the road wheels do, if the engine torque needed to slip a wheel is larger than n. Notice that in the table, the engine torque needed to slip a wheel is greater than n in all gears except first gear (and reverse, if the ice is very slippery).

The way to do this is to start the car moving in second gear. This way, the road wheels are much less likely to slip under acceleration. But you must take it slow and easy to realize this benefit.

Note that slow and careful driving is also needed here to prevent damage. You can't drive at normal speeds or acceleration rates, or you can heat up the transmission or strain certain parts of the drive train. Your Check Engine light will come ON if you are overdoing it.

One problem with the other devices seen in various websites is the tendency of such devices to cause the Check Engine light to come ON. This device will not cause the Check Engine light to come ON unless the driver is abusing the engine or drivetrain.


THEORY OF SAVING GAS WITH THE SHF INDICATOR

Here is a table of the SHF indications and gas mileages for each gear:

Gear Used SHF ColorGear RatioSteady Speed MPG
1DARK2.921:17.24
2RED1.568:113.5
3YELLOW1.000:121.2
4GREEN0.705:130.0

MPG figures are based on a highway gas mileage of 30.0 MPG.

Gear ratios are for 4T65 transmission.

The driver uses the SHF indicator and throttle control to get into the highest gear available as soon as possible.

Note that the transmission will not shift into 4th gear until the car is going in the range of 45-50 mph.


THEORY OF OPERATION OF THE CIRCUITRY


CONSTRUCTION


TABLE OF OPERATION

Here is the table of gear selections and indications with 2GS switch OFF and ON:

NO RELAY     RELAY
bar
Gear
Shift
Pos
PCM
Gear
Sel
2GS Switch OFF 2GS Switch ON
Trans
Gear
Lights Trans
Gear
Lights
SHF 2GS SHF 2GS
bar
Drive 1 1DARKDARK 2REDWHITE
2 2REDDARK 2REDWHITE
3 3YELLOWDARK 3YELLOWWHITE
4 4GREENDARK 3YELLOWWHITE
bar
3 1 1DARKDARK 2REDWHITE
2 2REDDARK 2REDWHITE
3 3YELLOWDARK 3YELLOWWHITE
bar
2 1 1DARKDARK 2REDWHITE
2 2REDDARK 2REDWHITE
bar
1 1 1DARKDARK 2REDWHITE
bar
bar
Gear
Shift
Pos
PCM
Gear
Sel
2GS Switch OFF 2GS Switch ON
Trans
Gear
Lights Trans
Gear
Lights
SHF 2GS SHF 2GS
bar
Drive 1 1DARKDARK 2REDWHITE
2 2REDDARK 2REDWHITE
3 3YELLOWDARK 3YELLOWWHITE
4 4GREENDARK 4GREENWHITE
bar
3 1 1DARKDARK 2REDWHITE
2 2REDDARK 2REDWHITE
3 3YELLOWDARK 3YELLOWWHITE
bar
2 1 1DARKDARK 2REDWHITE
2 2REDDARK 2REDWHITE
bar
1 1 1DARKDARK 2REDWHITE
bar

Credits:

I give many thanks to the people who helped me research the design of this project.


Links: