Greg88

Hey guys I have a line on a used moser 12 bolt true trac posi 4 channel rear end in a 94 Camaro. The owner says he thinks it's a 4 channel because it has a sensor in the housing. I am assuming that's for Traction control? My car is a 97 Trans Am with a 3 channel. I've read about converting the 10 bolts a little bit but is it the same with a 12 bolt?? Can it be done?

Thanks!
Greg

Injuneer

Sounds backwards to me.

If it's 4-channel (ABS + TCS) it would have a reluctor gear on the end of each axle (behind the backing plate) and a wheel speed sensor on each backing plate. Nothing on top of the diff housing. The two wheel sensors are used for both ABS and TCS, through the EBTCM (electronic braking/traction control module). TCS (RPO "NW9") was not available in 1994 models (even though the sales brochure lists it, and the factory service manual describes it).

If it's 3-channel (ABS only) there is a large reluctor gear on the differential carrier next to the ring gear, and a single sensor on top of the diff housing. No sensors on the ends of the axles. The single sensor is used for ABS, through the EBCM (electronic braking control module).

Greg88

This is a picture of the carrier. I see the ring there showing the Abs! So the only way to tell if this 12 bolt has TCS is from the sensors at the hubs? Or I guess if the rear end has the sensor in the housing then it only has ABS?

shoebox

If it only has a sensor in the pumpkin, it is 3 channel. If has a sensor at each end of the rear, it is 4 channel. Looks like a 3 channel.

Greg88

Here is a picture of my cars information. I have NEVER seen anything showing TCS when driving/spinning the tires. There is no button on the console to turn on or off the TCS. Although I know it does have the reluctor rings on the end of the axles and has the sensor. This is strange.

Injuneer

Did you buy the car "used", making it possible previous owner swapped in a 4-channel rear axle - rendering the ABS inoperative? Does your ABS work? When you hit the brakes hard on a wet road or on gravel, does the "LOW TRAC" light come on? Do the "LOW TRAC" and the "ABS INOP" lights on the dash turn on briefly when you firtst turn the key to run?

No "NW9" = no TCS

If your car had TCS it would have:

- a large black mechanism bolted to the top of the driver side valve cover.

- a "TCS" switch with lights to the left of the cigarette light on the console.

- a "TCS OFF" light on the dash, between the "AIR BAG"" light and the "1" on the tach, and it would light up when you first turn the key to "run".

- ABS + TCS has two brake lines running to the rear of the car. With ABS, there is only a single line running to the rear of the car.

Do your rear wheel sensors match this .pdf - item "C" is the reluctor wheel, item 75 is the sensor.

Injuneer

Item 20 is the TCS servo on the driver side valve cover:

Greg88

The ECU currently on this car is from an LS1 because I run the LTCC system. I am wondering if the TCS system has been removed from the programming.

I have not tried to lock up the brakes on gravel yet but I will. I know with prior experience if I forget to hook up the connectors for the front ABS sensors I will get a code showing ABS INOP

I definitely do NOT have that TCS servo on top of the engine!

I do not have the TCS switch on the console

I do have the "TCS off" light on the dash when turned to run.

Yes my sensors match item "C" and 75 item in the diagram


Here is a picture of the dash on the "run" position.

Any help is greatly appreciated! I just want to know what kind of rear end would be best? 3 or 4 channel.

Injuneer

Sorry, my mistake, totally missed the 24X. I shouldn't have responded.

Given the hybrid engine control system, and not knowing what it takes to interface the LS1 PCM to the LT1 EBCM (or EBTCM), there's nothing more I can contribute. Clearly your Service Parts tag does not have the TCS RPO code on it. To me, without the RPO, absence of the TCS switch, and absence of the TCS servo, you have ABS only, and need a 3-channel rear. But that's just a guess, due to the 24X conversion. Maybe EFIConnection, or whoever supplied the PCM programming can answer.

Greg88

Ok thanks so much for the help! I think I'll be going with a 3 channel and fingers crossed I'll be ok!

Greg88

So when I stomp in the brakes on gravel the LOW TRAC light comes on but not ABS or any pulsing on the brakes. Still good with a 3 channel?

Injuneer

The "LOW TRAC" light means the ABS has activated. Still trying to figure out how your ABS would even work with the 4-channel rear axle. Truly surprised that it works. Did you ever look to see if there is a sensor on top of the diff housing on your current setup? Something is screwy here. Absolutely no input from me on whether or not the Moser will work in your car. Don't know one way or the other at this point.

You can see the location of the 3-channel sensor in Shoebox's photo:

Greg88

I am positive that I do not have that sensor in the housing! I am dumb founded as well. Kinda sucks for moving forward with a new rear end if I don't know what I have!

The guy that owned the car before me told me he put the new gears (4.10) in the car but never mentioned the rear end being swapped!

terminal_crazy

Dumb question, but what would happen with just one of the rear channels of a 4 channel axle wired into a 3 channel system?
I'm guessing the no of pulses per rev are the same on both systems?

Mitch

Injuneer

The 3-channel reluctor is on the diff carrier, is about 8" diameter (similar to the ring gear, sitting next to it), and probably has well over 100 teeth, maybe close to 200 (look at pictures in post #3). The 4-channel reluctor is on the outer end of the axle is maybe max 2-1/2" diameter (hidden by backing plate in pic in post #5) and has far less teeth. They both turn at the same speed.

Must be some way to hook it up, maybe something like a Dakota Digital pulse conversion box. Otherwise his ABS system wouldn't work. I'm just not willing to go out on a limb and say "sure the Moser 12-bolt will work".