Selec trac and Air lockers

Onno

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Hi,
I'm new at this game and might be obvious for others but I've ordered an Sahara with the Selec trac.
Now is it possible to put air lockers on this vehicle? Only front,or both Back and front without messing up the Selec trac system?
Asked Jeep Customer Service but they didn't give me an answer because I'm in New Zealand and not the U.S.
Here in NZ none off the Dealers could give me an answer, probably because we're still waiting for the first JL to arrive.
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mwilk012

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I’m assuming the only time it would possibly be an issue is if you locked the axles and kept it in 4H auto. Just don’t do that?
 

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**Edited for clarity**

The Traction Control system (which the Select-Trac transfer case is part of) utilizes the wheel sensors to read individual wheel speed. If one tires starts to slip (spin) the computer applies brakes to that wheel to slow it down and force torque over to the opposite wheel. Any changes made to the diffs or transfer case could possibly confuse the computer and cause Christmas tree lights on your dash (errors).

With an Air Locker in the unlocked (off) position the Select-Trac II system should work just like stock. They are an open differential when unlocked.

With Air Lockers locked in, the two opposite wheels will be locked in to each other, so the the computer will not read any difference between tire speed and should not be trying to apply the brakes at either side.

Now what is not known is what the computer will do if you have front and rear Air Lockers, both locked in and the tires are all going the same speed (relative to the wheelbase and track of the vehicle)..... It may try to throw warning light or it may not.
 
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SecondTJ

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I’m assuming the only time it would possibly be an issue is if you locked the axles and kept it in 4H auto. Just don’t do that?
Precisely. Don't use the lockers with 4Auto and there will be no problems.

The Select-Trac utilizes the wheel sensors to read individual wheel speed. If one tires starts to slip (spin) the computer applies brakes to that wheel to slow it down and force torque over to the opposite wheel.
What you're referencing is the electronic function of BLD (Brake Lock Differential), not Selec-Trac.
 
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Tech Tim

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What you're referencing is the electronic function of BLD (Brake Lock Differential), not Selec-Trac.
You are correct. Thanks for chiming in.

The original question was related to the Select-Trac T-case. As the BLD and Selec-Trac II work together as parts of the traction control system, any changes to the differential will possibly confuse the computer and throw errors.

I edited my post to be more accurate.
 

mwilk012

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The problem scenario I imagine is using lockers during a turn, where the system would be looking for a different wheel speed between the left and right tires, but they would be rotating at the same speed, slipping on the inside.
 

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The problem scenario I imagine is using lockers during a turn, where the system would be looking for a different wheel speed between the left and right tires, but they would be rotating at the same speed, slipping on the inside.
Exactly! There is still the sensor in the steering that is telling the computer the steering wheel is turning, but the wheels sensors are telling the computer the wheels are turning the same speed.

It will definitely drive smoother with front and rear Air Lockers, the traction control won't be trying to apply brakes, limiting forward momentum.
 

SecondTJ

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You are correct. Thanks for chiming in.

The original question was related to the Select-Trac T-case. As the BLD and Selec-Trac II work together as parts of the traction control system, any changes to the differential will possibly confuse the computer and throw errors.

I edited my post to be more accurate.
I think I understand what you’re trying to say, but it sounds like you’re describing the MP3023. I haven’t seen anything that suggests the MP3022 operates in the same manner.

Which leads me to believe that while Select Trac and the traction control system work together to maximize traction, they operate independently.
 

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Exactly! There is still the sensor in the steering that is telling the computer the steering wheel is turning, but the wheels sensors are telling the computer the wheels are turning the same speed.

It will definitely drive smoother with front and rear Air Lockers, the traction control won't be trying to apply brakes, limiting forward momentum.
The problem scenario I imagine is using lockers during a turn, where the system would be looking for a different wheel speed between the left and right tires, but they would be rotating at the same speed, slipping on the inside.
I highly doubt the system is “expecting” or “looking for” different wheel speeds,
4A merely switches between 2H and 4H, I don't see how it would interfere with air lockers.
it’s not that smart, it’s a retroactive system and we are over-thinking it. It may just be as simple as wheel slip detected—>then transfer 50% power to front wheels. If not, it will just stay in 2H. So if air lockers are on during 4A, nothing would activate and it will just be in 2H all the time — unless both rear wheels are slipping, same way you would be driving absolutely straight on flat pavement.

LSD and BLD would never come into play while air lockers are on. Both are retroactive/passive systems.
 
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IronScott

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I have similar questions as the OP. There are no good answers yet, evidenced by the contradictory statements given here (all by trusted advisors). Selec-trac with lockers seems to be an unknown quantity at this point. I want selectable lockers, front at a minimum and electric if possible, along with Selec-trac, but nothing is available and nothing rumored that I've seen. I'm sure the demand just isn't there yet but it is frustrating.
 

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**Edited for clarity**

The Traction Control system (which the Select-Trac transfer case is part of) utilizes the wheel sensors to read individual wheel speed.
I highly doubt the system is “expecting” or “looking for” different wheel speeds
I agree. What he is describing is the Grand Cherokee's Quadra-Trac II system with MP3023 not Wrangler's Selec-Trac with MP3022.

4A merely switches between 2H and 4H.
That's not accurate. The current MP3022 utilizes clutch packs instead of a center differential, which can vary torque distribution upto 50/50. 4-Auto can for example be in a 30/70 split, depending on slippage. While 4-High is locked into a 50/50 split.
 

mwilk012

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I highly doubt the system is “expecting” or “looking for” different wheel speeds,
4A merely switches between 2H and 4H, I don't see how it would interfere with air lockers.
it’s not that smart, it’s a retroactive system and we are over-thinking it. It may just be as simple as wheel slip detected—>then transfer 50% power to front wheels. If not, it will just stay in 2H. So if air lockers are on during 4A, nothing would activate and it will just be in 2H all the time — unless both rear wheels are slipping, same way you would be driving absolutely straight on flat pavement.

LSD and BLD would never come into play while air lockers are on. Both are retroactive/passive systems.
That’s oversimplifying things a bit. Systems like the selec-trac and BLD almost away rely on sensor inputs from multiple sources including steering angle and wheel speed. Automotive control systems are very complex.
 

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Here's a video covering the Select-Trac II system in a Liberty:


The JL does use a different transfer case than the Liberty and they still call it Select-Trac II. One could ASSume that the functions are very similar in operation even though they are using a different t-case.
 

mwilk012

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So another clutch pack to worry about and potentially replace (on top of my LSD clutch pack) when the it wears out after something 20k miles or whatever?

Ayayeh
If you wear out a clutch pack in 20k miles, something is drastically wrong.
 
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