Your new rear is 3 channel, however you can make it work on your 4 channel car if you put the axles, backing plates, and sensors from your 4 channel rear on the three channel rear.

 

That's correct and what I said earlier. Channels refer to the number of ABS sensors. Cars with TCS have 4 seperate brake lines to each wheel as well as 4 seperate sensors at each corner of the vehicle.

A car without TCS has 3 seperate brake lines and 3 sensors. The 2 in front and a single sensor in the center top of the axle.

The reason the TCS cars have 4 channels is because the braking system is capable of applying brake pressure to each individual rear tire to control wheel spin.

Since the major parts between the 2 different style rear ends is just the sensors, you should have been able to remove the c-clips and pull the left and right side axles out of the housing, remove the backing plates and then install them onto the new rear axle from the 3 channel car. The 3 channel rear will have the sensor on the top of the pumpkin as well as the 2 on the ends that came from your original rear.

Does that make sense? Assuming you did swap axles and endplates and plugged both of the rear ABS sensors back in, the computer should not know the difference.

 

man do you use instant messanger at all? if you do my aim is onfirebird00, i understand what your saying, and i did all of that, but what i dont understand is, i have the top module for the pumpkin its plugged in, but its just flopping around, its not actually set in it. the old rear had it set in the top of the pumpkin. do i just leave it?

 

Let me get this straight. We are talking about your Firebird Formula, right? It has the TCS button by the cig lighter, right?

So stock, your rear had the 2 sensors on the end of the axle and no sensor on top of the pumpkin, right?

 

ok let me describe the two

the stock rear on teh firebird has tcs, yes it has the button. it has a sensor on top of the pumpkin that actually goes into it. after that, there are no more sensors. i know my car has abs, because prior to the swap the abs has kicked in. there was one main brake line that plits into two one to each axle.

the new rear end has no hole on top of the pumpkin for the sensor, but it does have a clip for wires. the new rear end did not have tcs. the new rear end also had gears n the ends of the axles, assumingly for teh ebrake.

for my swap i changed over the axles, as well as the backing plates so that i could use my e-brake and my calipers. i did not change over the wiring harness. the brake lnes are the same ones that were on the car since day one. therefore, i never unplugged or plugged and sensors, other than the one on top of the pumpkin to get the rear end off of the car.

i plugged the sensor, the one that goes into the pumpkin, on top, into the wiring harness and it is dangling near the sway bar, because there is no hole to plug it into.

 

OK, what year is your Formula? If it has TCS, but only one sensor on top of the pumpkin, then I have never seen that before. That means your car has a 3 channel TCS system.

If your new rear end had the gears on the axle ends (actually reluctor rings that send a pulse to the magnetic ABS sensors) then it must have been a 4 channel rear. If the car it came off of did not have TCS, then I don't know why it would have the a 4 channel rear in it.

Since your original rear had a big reluctor ring mounted on the ring gear inside the pumpkin (remember seeing that?) and your new rear does not have that big ring (I assume because it doesn't have the hole on top for the sensor to mount in) then you are essentially putting a 4 channel rear into a 3 channel car and the ABS won't work at all.

If your original rear did not have the sensors mounted into the backing plates then there was no need to swap axles and endplates. Sorry.

When you had the cover off the new rear, did it have the big reluctor ring attached to the ring gear? If so you could drill a hole into the top of the axle to mount your sensor.

Have any of these rears been swapped before or gears been swapped in these rear ends? I don't understand how they could be this mixed up unless these are from LT1 cars that may be different, but even those should be the same as the LS1 rears. I just don't understand it.

Here is a pic of a 3 channel rear end. It's called a 3 channel because the front 2 wheels are 2 channels and both rear wheels only get one channel. That's why your rear brake lines share a single line and then split in two for each side. A car with a 4 channel setup has 2 rear brake lines all the way from the front to the rear.

 

the old rear has that ring the new one does not. its actually a v6 firebird and its a 2000. the new rear is off of a 1999 formula. is there any way for me to get the abs working again aside from putting the old rear back in?

 

Here's a better pic of a 3 channel rear end.


If this is what was originally in your car, then this is what you need to get. There is no easy way to add that big reluctor ring. That's why most folks say you can't use a 4 channel rear in a 3 channel car. You can however put a 3 channel rear into a 4 channel car.
That's what I did. I have that big old toothed ring and sensor on top, but I'm not using them. I have my 2 sensors on the axle ends that I'm using. Swapping axles and endplates is pretty easy so that's why folks say you CAN put a 3 channel into a 4 channel car as long as you swap axles and endplates.

Jason

 

That's why he has TCS with a 3 channel rear, it is a peculiarity to a V6.

You are the second person who has done this recently, Sp00rkz pm'ed me about the same thing. Sorry we didn't understand clearly that you were a V6 car.

 

well i should apologize for not making it clear, thanks for all the help, i appreciate it. those pictures look exactly like the old rear.

 

You might be able to find someone locally who has a 3 channel and needs a 4 channel. You might be able to swap. A rear from a manual V8 with no TCS would give you a posi 3.42 rear that would work just fine.

Check these forums for a 3 channel rear.

Why did you swap in the first place?

I got lucky and found a local guy with a 3 channel 3.73 rear. Paid $500, but I needed it fast, so I couldn't shop around much.

 

well the old rear was whining really bad, i mean realllly bad, it was so loud it would give me an earache after driving. we concluded that the gears were shot after we found tons of metal shavings. i bought the new rear from a guy off of this site for 20$ and its posi with 3:42's. im happy with it and i cant complain at all, so ill just have to live without abs[no big deal]

 

20 bucks!? That's the kind of deal I needed. This is my only transportation so beggers can't be choosers. I did go from 3.42 to 3.73 and it's does get up to speed quicker, but next time I'll go to 4.10.

Anyway, I'm not too famuliar with the V6 brake system, but the V8 cars had a dynamic proportioning valve meaning that the rear brake bias was integrated into the ABS system. If you deactivate the ABS on a V8 car the rear brakes will get too much pressure and the rear will lock up very early and make it dangerous to drive.
You might try hitting the brakes hard on a wet road or on some loose gravel and see what happens. If the rear gets loose way too early you can add an adjustable proportioning valve to the rear brake circuit. That's what a lot of racers do on these cars who don't want to run the ABS system.

How they work:
http://frrax.com/rrforum/index.php?act=ST&f=2&t=4937&
http://www.chevyhiperformance.com/techarticles/71398/
http://www.stoptech.com/tech_info/wp...formance.shtml

Here's a pic of an adjustable valve on a F-body. This guy is using it with a line lock, but I don't know why. All you have to do is add the valve between the master cylinder and the old ABS brake system block on your car. As you adjust the **** it reduces pressure to the rear brakes. This will allow you to adjust the brakes so that the front and rear lock up at the same time or maybe have the fronts lock a liitle sooner than the rear. You'll need to threshold brake as well. You can't just hold the pedal down and let the ABS work. You'll have to feel the tires locking and then reduce pedal pressure to get them turning and then cycle the brakes manually. Like a poor mans ABS. With practice you can stop the car as quick or even quicker than an ABS system. It does take practice though, which is what most people don't have.

I thought about deleting my ABS as well because I don't like the feel of it. I'm good at threshold braking plus I like sliding the car a little on certain occasions. I decided not to do it because I didn't want to hurt the value of the car, plus the traction control comes in handy if I want to pop the fuse back in to get it working.

 

thanks for all the information, youve gona above and beyond to be extra helpful and i truly appreciate it. im definatly going to look into that. i do like the feel of the brakes without the abs, its not so touchy feely, but as you stated i dont want to hurt the value of my car, so taht might be up my alley.

 

hey couple quick questions:

what would i have to do to get the reluctor ring into the differential, like on the original rear? is it just a bolt off bolt on jobber?

and second, im pretty sure my gear ratio was lower than 3.42 on the original rear, and the new one is at 3.42 so is my speedo going to be off and if so how much? can a dealership correct this? thanks

 

It looks like the reluctor ring is made onto the carrier, so I think you'd have to swap all the internal parts from the original rear to the new rear. That's at least $200 to have someone shim it and you might as well put new bearings in $80. Then you wouldn't have the posi anymore, etc... So I don't think you want do that.

If you have the old rear, count the teeth and see what the ratio is. Also take a close look to see if the toothed ring can be seperated.

You might want to look on the V6 Firebird sites for specifics on the rears as well as what transmission gears ratios they used. Most of my knowledge is on the V8 cars.

I'm going to check with my dealership about resetting the speedo.

 

thanks again for the help!