Welded diff + ABS ?

[tossaxe]

Hello,

I've aquired s13 open diff internals, got them welded and put in my s14 zenki sr20det. Now ofcourse my ABS light is on and not working too well.
Is there a way to still make the ABS work?
Or short some wires on the diff housing so that ABS would still work at least on the front?

[oni jake]

In short answer. No, you cannot make ABS work with a welded diff. The entire perimeters of the ABS program needs to be reworked to accommodate 2 wheels locked. No company or person, that I know of, can do that.

Disconnect fuse to ABS, pull the gauge cluster bulb, and work on taking all of that crap out.

[tossaxe]

What I needed to hear. Thanks ;)

[Darren]

abs and welded diff are contradictory, do what jake suggested

[jr_ss]

In short answer. No, you cannot make ABS work with a welded diff. The entire perimeters of the ABS program needs to be reworked to accommodate 2 wheels locked. No company or person, that I know of, can do that.

Disconnect fuse to ABS, pull the gauge cluster bulb, and work on taking all of that crap out.

S-chassis' only have one speed sensor for the rear, located on the snout of the differential, so he shouldn't have an issue with it...

[oni jake]

S-chassis' only have one speed sensor for the rear, located on the snout of the differential, so he shouldn't have an issue with it...

Dude, post something worth a damn instead of getting your post count up. Contradicting what I said with no logical reasoning doesn't help anyone. If by your logic there isn't a problem with running a welded diff on a ABS S-Chassis, then post possible reasons why his ABS malfunctioning light is on.

S-Chassis have 3 wheel speed sensors. Two in the front, measuring directly off the hub, and one in the rear measured off of the differential. Through magic and math, the ABS computer adjusts hydraulic pressure to each individual caliper. This MAGIC and MATH part relies heavily on the preprogrammed information of chassis weight, dynamics, and a whole bunch of other stuff that requires years worth of education to understand. When you lock two tires, (make them work simultaneously), the dynamics of wheel braking change outside of the program. ABS turns off because the computer believes there is a malfunction in the system somewhere, effectively rendering the system useless.

If you want more information in regards to ABS on S-Chassis look at the FSM under BR, Braking System, starting on page 22.

[rwtf]

:drama::drama::drama:

[jr_ss]

Dude, post something worth a damn instead of getting your post count up. Contradicting what I said with no logical reasoning doesn't help anyone. If by your logic there isn't a problem with running a welded diff on a ABS S-Chassis, then post possible reasons why his ABS malfunctioning light is on.

I corrected you, because you stated that ABS system would see that there would be "two" wheels locked, however there is only one sensor for both rear wheels...

It is possible that the sensor in the diff he has is faulty, causing the light to come on. Perhaps a poor electrical connection....

There are very few reasons the ABS light can be on, it's either mechanical or electrical, my guess is on the electrical side.

However, before you try anything, you should pull the negative battery terminal to clear the codes. Disconnect it for atleast one minute and see if it clears.

Me, a post whore, good god you're an idiot...

[godsmack]

ok i'm confused with this one. i don't know much about abs but what part of the diff is the sensor reading?

[jr_ss]

ok i'm confused with this one. i don't know much about abs but what part of the diff is the sensor reading?

The pinion gear has a ring on it inside the diff that the sensor reads as it spins. If it sees the rear wheels spinning a percentage faster than either one or both front wheels under braking conditions it activates the ABS. It is a very simple system, far less advanced than the newer abs systems out there.

[oni jake]

I corrected you, because you stated that ABS system would see that there would be "two" wheels locked, however there is only one sensor for both rear wheels...

It is possible that the sensor in the diff he has is faulty, causing the light to come on. Perhaps a poor electrical connection....

There are very few reasons the ABS light can be on, it's either mechanical or electrical, my guess is on the electrical side.

However, before you try anything, you should pull the negative battery terminal to clear the codes. Disconnect it for atleast one minute and see if it clears.

Me, a post whore, good god you're an idiot...

I love this. You have been trailing recent posts nit-picking a selection of words and posting nothing useful to anyone.

This what you sound like, "HAI GUIZ! I read watched a 2 minute youtube video on ABS systems and pulled the diff out of my 240sx once, so I am now the all-knowing authority figure on Zilvia. I hand out bad advice and ride the coat tails of other people's posts all the time, and no one knows the difference so I carry on with it."

And serious thought: you honestly think, sitting back all fat like in your computer chair huffing about your response to this post, that the S-Chassis ABS system cannot tell the difference between a open and welded diff with 3 sensors measuring 4 wheels? A welded diff LOCKS the rotation of two wheels changing the circumstances of how a car reacts to braking; throwing the static perimeters the ABS computer needs to properly work out the window. So I said before, if you want to actually educate yourself and help others on Zilvia, try reading the ABS section in the FSM then come back posting about how wrong I am.

[jr_ss]

I love this. You have been trailing recent posts nit-picking a selection of words and posting nothing useful to anyone.

This what you sound like, "HAI GUIZ! I read watched a 2 minute youtube video on ABS systems and pulled the diff out of my 240sx once, so I am now the all-knowing authority figure on Zilvia. I hand out bad advice and ride the coat tails of other people's posts all the time, and no one knows the difference so I carry on with it."

And serious thought: you honestly think, sitting back all fat like in your computer chair huffing about your response to this post, that the S-Chassis ABS system cannot tell the difference between a open and welded diff with 3 sensors measuring 4 wheels? A welded diff LOCKS the rotation of two wheels changing the circumstances of how a car reacts to braking; throwing the static perimeters the ABS computer needs to properly work out the window. So I said before, if you want to actually educate yourself and help others on Zilvia, try reading the ABS section in the FSM then come back posting about how wrong I am.

Yep, you caught me, I ride coat tails around here, bet you feel proud of yourself don't you... :blah:

Typical immature douche bag response...

You are comparing a system that is more advance than what the S-chassis has. The ABS ECU see's ONE sine-wave from the rear differential, whether it is a 1/1.5/2way LSD or open-diff has no effect on the system. You don't speed up the differential by locking the two rear wheels together. There aren't TWO different sensors on the rear diff like the J30's. I understand what you are saying about the logic in the computer to compensate for two wheels vs one. However, the system is archaic at best, it activates both rear wheels simultaneously. IF it were a more advance system, it would have two seperate wheel speed sensors, brake fluid lines and two sine waves going back to the ECU, then yes you'd be right and I'd admit defeat.

Do you honestly think that people haven't installed other types of LSD's into the S-chassis ABS differentials before?

OP, was your light on after the diff install, before you started driving? Or did it come on after you drove? The ABS system does self checks after start up at low speeds, to identify any potential problems within the system. If it see's a problem, bad wheel sensor, no wheel speed registering, etc., it will shut off the ABS system, and pop the ABS light on your dash. Do you have an FSM?

[KiLLeR2001]

Man this oni jake fella sure is try-harding today. I'd love the explanation of how the rear ABS sensor can tell the difference between a 2way, 1.5way, welded and open.

[oni jake]

Yep, you caught me, I ride coat tails around here, bet you feel proud of yourself don't you... :blah:

Typical immature douche bag response...

You are comparing a system that is more advance than what the S-chassis has. The ABS ECU see's ONE sine-wave from the rear differential, whether it is a 1/1.5/2way LSD or open-diff has no effect on the system. You don't speed up the differential by locking the two rear wheels together. There aren't TWO different sensors on the rear diff like the J30's. I understand what you are saying about the logic in the computer to compensate for two wheels vs one. However, the system is archaic at best, it activates both rear wheels simultaneously. IF it were a more advance system, it would have two seperate wheel speed sensors, brake fluid lines and two sine waves going back to the ECU, then yes you'd be right and I'd admit defeat.

Do you honestly think that people haven't installed other types of LSD's into the S-chassis ABS differentials before?

OP, was your light on after the diff install, before you started driving? Or did it come on after you drove? The ABS system does self checks after start up at low speeds, to identify any potential problems within the system. If it see's a problem, bad wheel sensor, no wheel speed registering, etc., it will shut off the ABS system, and pop the ABS light on your dash. Do you have an FSM?


edit: Came back after thinking about this. I realize we're not communicating about the same thing anymore. We're two dudes on the internet playing up to our imaginary stereotypes. In fairness, I apologize for sounding harsh. I'm terrible at the internetz, I just wanted a solid answer because you have trailed my last few posts.

You say the 3 channel system will work with a welded diff, I believe it will not. Where you say the 3 channel system is archaic and cannot physically detect a change in the vehicle braking dynamic through its 3 sensors, I say it can and was hoping you would prove that part specifically. From my understanding, ABS modules are programmed to handle a specific vehicle under specific conditions. Locking your rear end physically changes the braking dynamic. That in itself should be great enough for the ABS module to realize something is wrong and throw an error code. The FSM only explains how the sensors communicate with the ABS module (i.e. what you just posted).

[jr_ss]

edit: Came back after thinking about this. I realize we're not communicating about the same thing anymore. We're two dudes on the internet playing up to our imaginary stereotypes. In fairness, I apologize for sounding harsh. I'm terrible at the internetz, I just wanted a solid answer because you have trailed my last few posts.

You say the 3 channel system will work with a welded diff, I believe it will not. Where you say the 3 channel system is archaic and cannot physically detect a change in the vehicle braking dynamic through its 3 sensors, I say it can and was hoping you would prove that part specifically. From my understanding, ABS modules are programmed to handle a specific vehicle under specific conditions. Locking your rear end physically changes the braking dynamic. That in itself should be great enough for the ABS module to realize something is wrong and throw an error code. The FSM only explains how the sensors communicate with the ABS module (i.e. what you just posted).

I believe it see's the rear axle as a single unit so it does not detect a difference in wheels speeds out back, just a difference of wheel speeds between the front and rear. I say archaic because it isnt an advanced system that see's and also monitors wheel speeds and fluid pressures at individual calipers like on newer ABS modules. It can only modulate the pressure at both rear calipers, with those pressures being identical at each caliper because of the single brake line that runs to the rear brakes. I'm not saying that the computer doesn't have the logic and algorithm's in it to account for both wheels, as it most likely has to, to send adequate fluid pressure to the brakes in the rear while also modulating the front wheels. However, locking those rear wheels, shouldn't push anything outside of those parameters because it still see's the same sine-wave from the rear differential, unless there is an issue with his sensor, or possibly the gearing changed, making the rear differential read outside of the typical tracking window the ABS ECU is accustomed too.

[godsmack]

that is why i started to get confused. with one sensor in the the diff you can not possibly be able to tell the speed on both tires. i read up in the fsm on this matter now and jr ss is correct with what is being said. even if the diff is locked the sensor is only reading the input to the rear. so with that being said you can have abs with welded diff as long as you have the same gearing and properly working sensor.

[oni jake]

I believe it see's the rear axle as a single unit so it does not detect a difference in wheels speeds out back, just a difference of wheel speeds between the front and rear. I say archaic because it isnt an advanced system that see's and also monitors wheel speeds and fluid pressures at individual calipers like on newer ABS modules. It can only modulate the pressure at both rear calipers, with those pressures being identical at each caliper because of the single brake line that runs to the rear brakes. I'm not saying that the computer doesn't have the logic and algorithm's in it to account for both wheels, as it most likely has to, to send adequate fluid pressure to the brakes in the rear while also modulating the front wheels. However, locking those rear wheels, shouldn't push anything outside of those parameters because it still see's the same sine-wave from the rear differential, unless there is an issue with his sensor, or possibly the gearing changed, making the rear differential read outside of the typical tracking window the ABS ECU is accustomed too.


One thing I think you are overlooking is that hydraulic pressure is applied in the path of least resistance. This is why ABS systems came about. The S-chassis is a 3 sensor system, and it is also a 3-channel hydraulic system. When the brakes are applied, the caliper with the least resistance is going to lock first. Pressure will NOT be a applied evenly to the rear calipers and both wheels will not lock simultaneously.

The ABS module is programmed to take that into account and tries to guess which side the tire slippage is happening by measuring the wheel speed of the front two wheels and the static drive train together. This is what I was referring to when I was talking about the physical braking dynamic is changed.

I tried google searching for a definitive answer and only found out dudes with jeeps have similar setups and similar problems when they put in a welded rear end to go muddin' and other hill billy shit. If someone else out there has a welded diff (not a 1.5, not a 2-way) in a S14 ABS model and ABS still works, I'll shut up and admit your greatness. I just can't find it.

[godsmack]

^if that rear tire locks so will the otherside so the abs will have a correct reading. both will lock because of having a welded diff. if one stops they both do. it doesn't compensate for which one locks up first it compensates for the rear showing a lock up and then adjusts the pressure going to the sensor in which this would be the rear in general which is one line with a T.

[jr_ss]

One thing I think you are overlooking is that hydraulic pressure is applied in the path of least resistance. This is why ABS systems came about. The S-chassis is a 3 sensor system, and it is also a 3-channel hydraulic system. When the brakes are applied, the caliper with the least resistance is going to lock first. Pressure will NOT be a applied evenly to the rear calipers and both wheels will not lock simultaneously.

The ABS module is programmed to take that into account and tries to guess which side the tire slippage is happening by measuring the wheel speed of the front two wheels and the static drive train together. This is what I was referring to when I was talking about the physical braking dynamic is changed.

I tried google searching for a definitive answer and only found out dudes with jeeps have similar setups and similar problems when they put in a welded rear end to go muddin' and other hill billy shit. If someone else out there has a welded diff (not a 1.5, not a 2-way) in a S14 ABS model and ABS still works, I'll shut up and admit your greatness. I just can't find it.

It's not about who's right or wrong man. It's an internet chat forum, and we are having a heated discussion. I have nothing against you other than my opposing ideas/understanding of the S-chassis ABS system.

I will agree with you that putting in a welded differential will change vehicle and possibly change braking dynamics, but not as drastically as you may think, especially with a welded diff.

The braking system will send fluid aft, in the path of least resistance, as you stated, but fluid pressure will equalize before enough pressure has been applied to the pistons to lock the rear breaks. Once fluid has filled that caliper with the "least" resistance, it will start to see resistance as the piston is pushed, allowing the opposite caliper to "fill" and start to apply pressure to the back side of that piston.

Regardless of which one locks first, and however minuscule the time delay/difference is, the ABS system is/was designed to pulse the brakes, and prevent the tires from reach the full lock and skid situation. It allows the driver to still have some control over the vehicle to prevent/avoid that possible collision that surely would've happened had the brakes locked.

IN his case, he has a welded diff. The rear shafts, even though they are independent of each other, are now locked as a single unit. If one break is applied, it slows down and "stops" the opposite wheel as well because there are no longer planetary gears to allow different wheel speeds.

Either way, this discussion has wandered from the main purpose of the thread. I honestly believe the problem lies within the electrical side of things in/on/around the rear diff. IF the OP were to ever come back and try some of the diagnosing we could further assist him.

I don't know everything "Jake", there is always learning to be had, but I'm not some forum retard that just posts random shit. I do have a bit of knowledge about cars and the inner workings. If your assumption was that I was singling you out, I wasn't and I'm sorry you took it that way.