Thread: Diff locks and traction control

Originally Posted by PhilipA

That is why as I understand US army drivers are taught to left foot brake the Hummers which are fitted with Torsen diffs.

Regards Philip A

It (LFB )does help with otherwise unassisted ATB diffs installed. Used it many times in the Malaysian jungle. No doubt will need to use it in future in the Aussie bush too. But no doubt having traction control w/- ATB diffs, or full lockers, are more effective.

But this is only needed for that one ATB diff Achilles heel - cross axled (or wheel in the air).

<sup>I'm tremendously late to this thread. Oh well. I'll throw some recent learnings I've had on this subject for the heck of it.

So, I've got a TD5. It has the factory CDL, the factory traction control, plus front and rear ARB diff locks. Firstly - do the diff locks affect the traction control? Nope, if it's locked up then the TC just thinks no slip and does nothing.

Now to my learnings. On a recent trip to the Vic High country we went up Herne Spur which is pretty steep. A friend with a D2 was having a little visit from the Amigos, so his 1wd disco got stuck. I was asked to pull him up the hill as it seemed easier than going down. I did this no problems. We thought he was ok, so I unhitched him and continued to the next ledge. He got stuck again so reversed down to the ledge below. So, I got sent down again. This is where I had one of one of those moments we'd rather forget.</sup>

I decided it would be easier to drive down forward due to the steepness of it and turn around at the little flat bit. So, I disengaged the CDL for the u-turn.

I got to the ledge, turned around, hooked my friend up. I locked both lockers as it was straight and steep and I didn't know how much I'd have to pull the disco. And off I went.

We kind of got started and it was going ok.. but then it got a bit steeper and then the TC light came on. I could feel the front wheels spinning and I thought it was all four and maybe the car knew and was somehow running the TC.

Anyway.. we continued on for a bit and it was spinning more and I was slowing more and I could smell rubber smoke from the spinning wheels. Shortly after we failed to proceed.

So, I pushed the clutch in and then got a very big surprise.. virtually no brakes! I had to push with all my strength to stop the car rolling down the hill backwards. The strap was loose but I could barely hold this thing. I switched to the other leg. If I popped it in reverse with the engine stopped it still wanted to roll back. Also, then I didn't have brake boost to hold it. At some point through all this we unhooked the strap to the other car which seemed to be able to hold no problems.

After about 10 minutes the brakes cooled enough that they worked, then I had to work out how to get started. My mate was stopped on a water bar just behind me so I couldn't use that to get a start. The handbrake couldn't hold the car and I couldn't get my foot off the brake and to the throttle fast enough to get started. I didn't like the idea of clutch starting the car up such a steep hill.

So, for only the second time in my 12 years of owning the car I had to be recovered. A friend with a winch took the load and I started and then drove the car up.

Anyway, got to the top and was sitting there in shock while they recovered the other car. I was pondering how a defender with the ability to completely lock the drive train managed to work it's TC so hard that the brakes failed. It was about then than I noticed the CDL light wasn't on.

Yep, I'd disengaged it for the turnaround and forgot to lock it again. So, on the really steep hill.. with the weight transfer.. with the open centre diff the unweighted front two wheels just spun (despite being locked). So, the TC tried to brake the spinning wheels. It tried so hard as the back had all the traction and the front had none that it over heated the front brakes.

So, the lesson from this is that the number one thing to do before a big hill is engage CDL.

Personally.. if I had to buy traction control aids in an order this would be my running order.

1. Physical CDL
2. Electronic Traction control.
3. Physical read diff lock.
4. Physical front lock.

Clearly.. if you don't typically get a choice with number 2 as it's generally factory fitted. I put it higher up on my list because I don't think it works very hard at all if you have a CDL. Also, if you have a front locker engaged you can't really steer.. so I rarely use it. If the going is difficult I'll lock the centre (pretty much anytime off road), and then the rear. It's only if I'm in deep do do and if I'm in a situation where I can go straight that I'll lock the front. It's pretty uncanny how a bogged car will basically climb out of the mess and drive off with everything locked though.

Anyway, hope you all enjoy a laugh at my stupidity.

Originally Posted by Captain_Rightfoot

<sup>I'm tremendously late to this thread. Oh well. I'll throw some recent learnings I've had on this subject for the heck of it.

So, I've got a TD5. It has the factory CDL, the factory traction control, plus front and rear ARB diff locks. Firstly - do the diff locks affect the traction control? Nope, if it's locked up then the TC just thinks no slip and does nothing.

Now to my learnings. On a recent trip to the Vic High country we went up Herne Spur which is pretty steep. A friend with a D2 was having a little visit from the Amigos, so his 1wd disco got stuck. I was asked to pull him up the hill as it seemed easier than going down. I did this no problems. We thought he was ok, so I unhitched him and continued to the next ledge. He got stuck again so reversed down to the ledge below. So, I got sent down again. This is where I had one of one of those moments we'd rather forget.</sup>

I decided it would be easier to drive down forward due to the steepness of it and turn around at the little flat bit. So, I disengaged the CDL for the u-turn.

I got to the ledge, turned around, hooked my friend up. I locked both lockers as it was straight and steep and I didn't know how much I'd have to pull the disco. And off I went.

We kind of got started and it was going ok.. but then it got a bit steeper and then the TC light came on. I could feel the front wheels spinning and I thought it was all four and maybe the car knew and was somehow running the TC.

Anyway.. we continued on for a bit and it was spinning more and I was slowing more and I could smell rubber smoke from the spinning wheels. Shortly after we failed to proceed.

So, I pushed the clutch in and then got a very big surprise.. virtually no brakes! I had to push with all my strength to stop the car rolling down the hill backwards. The strap was loose but I could barely hold this thing. I switched to the other leg. If I popped it in reverse with the engine stopped it still wanted to roll back. Also, then I didn't have brake boost to hold it. At some point through all this we unhooked the strap to the other car which seemed to be able to hold no problems.

After about 10 minutes the brakes cooled enough that they worked, then I had to work out how to get started. My mate was stopped on a water bar just behind me so I couldn't use that to get a start. The handbrake couldn't hold the car and I couldn't get my foot off the brake and to the throttle fast enough to get started. I didn't like the idea of clutch starting the car up such a steep hill.

So, for only the second time in my 12 years of owning the car I had to be recovered. A friend with a winch took the load and I started and then drove the car up.

Anyway, got to the top and was sitting there in shock while they recovered the other car. I was pondering how a defender with the ability to completely lock the drive train managed to work it's TC so hard that the brakes failed. It was about then than I noticed the CDL light wasn't on.

Yep, I'd disengaged it for the turnaround and forgot to lock it again. So, on the really steep hill.. with the weight transfer.. with the open centre diff the unweighted front two wheels just spun (despite being locked). So, the TC tried to brake the spinning wheels. It tried so hard as the back had all the traction and the front had none that it over heated the front brakes.

So, the lesson from this is that the number one thing to do before a big hill is engage CDL.

Personally.. if I had to buy traction control aids in an order this would be my running order.

1. Physical CDL
2. Electronic Traction control.
3. Physical read diff lock.
4. Physical front lock.

Clearly.. if you don't typically get a choice with number 2 as it's generally factory fitted. I put it higher up on my list because I don't think it works very hard at all if you have a CDL. Also, if you have a front locker engaged you can't really steer.. so I rarely use it. If the going is difficult I'll lock the centre (pretty much anytime off road), and then the rear. It's only if I'm in deep do do and if I'm in a situation where I can go straight that I'll lock the front. It's pretty uncanny how a bogged car will basically climb out of the mess and drive off with everything locked though.

Anyway, hope you all enjoy a laugh at my stupidity.

Oops....

Originally Posted by Captain_Rightfoot

<sup>I'm tremendously late to this thread. Oh well. I'll throw some recent learnings I've had on this subject for the heck of it.

So, I've got a TD5. It has the factory CDL, the factory traction control, plus front and rear ARB diff locks. Firstly - do the diff locks affect the traction control? Nope, if it's locked up then the TC just thinks no slip and does nothing.

Now to my learnings. On a recent trip to the Vic High country we went up Herne Spur which is pretty steep. A friend with a D2 was having a little visit from the Amigos, so his 1wd disco got stuck. I was asked to pull him up the hill as it seemed easier than going down. I did this no problems. We thought he was ok, so I unhitched him and continued to the next ledge. He got stuck again so reversed down to the ledge below. So, I got sent down again. This is where I had one of one of those moments we'd rather forget.</sup>

I decided it would be easier to drive down forward due to the steepness of it and turn around at the little flat bit. So, I disengaged the CDL for the u-turn.

I got to the ledge, turned around, hooked my friend up. I locked both lockers as it was straight and steep and I didn't know how much I'd have to pull the disco. And off I went.

We kind of got started and it was going ok.. but then it got a bit steeper and then the TC light came on. I could feel the front wheels spinning and I thought it was all four and maybe the car knew and was somehow running the TC.

Anyway.. we continued on for a bit and it was spinning more and I was slowing more and I could smell rubber smoke from the spinning wheels. Shortly after we failed to proceed.

So, I pushed the clutch in and then got a very big surprise.. virtually no brakes! I had to push with all my strength to stop the car rolling down the hill backwards. The strap was loose but I could barely hold this thing. I switched to the other leg. If I popped it in reverse with the engine stopped it still wanted to roll back. Also, then I didn't have brake boost to hold it. At some point through all this we unhooked the strap to the other car which seemed to be able to hold no problems.

After about 10 minutes the brakes cooled enough that they worked, then I had to work out how to get started. My mate was stopped on a water bar just behind me so I couldn't use that to get a start. The handbrake couldn't hold the car and I couldn't get my foot off the brake and to the throttle fast enough to get started. I didn't like the idea of clutch starting the car up such a steep hill.

So, for only the second time in my 12 years of owning the car I had to be recovered. A friend with a winch took the load and I started and then drove the car up.

Anyway, got to the top and was sitting there in shock while they recovered the other car. I was pondering how a defender with the ability to completely lock the drive train managed to work it's TC so hard that the brakes failed. It was about then than I noticed the CDL light wasn't on.

Yep, I'd disengaged it for the turnaround and forgot to lock it again. So, on the really steep hill.. with the weight transfer.. with the open centre diff the unweighted front two wheels just spun (despite being locked). So, the TC tried to brake the spinning wheels. It tried so hard as the back had all the traction and the front had none that it over heated the front brakes.

So, the lesson from this is that the number one thing to do before a big hill is engage CDL.

Personally.. if I had to buy traction control aids in an order this would be my running order.

1. Physical CDL
2. Electronic Traction control.
3. Physical read diff lock.
4. Physical front lock.

Clearly.. if you don't typically get a choice with number 2 as it's generally factory fitted. I put it higher up on my list because I don't think it works very hard at all if you have a CDL. Also, if you have a front locker engaged you can't really steer.. so I rarely use it. If the going is difficult I'll lock the centre (pretty much anytime off road), and then the rear. It's only if I'm in deep do do and if I'm in a situation where I can go straight that I'll lock the front. It's pretty uncanny how a bogged car will basically climb out of the mess and drive off with everything locked though.

Anyway, hope you all enjoy a laugh at my stupidity.

Sorry but the first rule should never be disengage cdl off road , I never do for anything off road F/R diff locks OFF yes but never cdl off road , You can turn a car around no probs with cdl in

Originally Posted by Captain_Rightfoot

Anyway, hope you all enjoy a laugh at my stupidity.

Nope, a good lesson for us all.

Originally Posted by Captain_Rightfoot

Anyway, hope you all enjoy a laugh at my stupidity.

Anyone here that has done any reasonable amount of off-road and is honest would have to admit we've all had our "stupid" moments.... some of us more than others

Originally Posted by Captain_Rightfoot

1. Physical CDL
2. Electronic Traction control.
3. Physical read diff lock.
4. Physical front lock.

I reckon you have that exactly right...... while 3 locked diffs is awesome.....centre and rear locked and traction control on the front makes steering somewhat easier than all 3 locked, which can be handy at times

As Bohica said..... good lessons here for all of us.

Originally Posted by Captain_Rightfoot

<sup>I'm tremendously late to this thread. Oh well. I'll throw some recent learnings I've had on this subject for the heck of it.

So, I've got a TD5. It has the factory CDL, the factory traction control, plus front and rear ARB diff locks. Firstly - do the diff locks affect the traction control? Nope, if it's locked up then the TC just thinks no slip and does nothing.

Now to my learnings. On a recent trip to the Vic High country we went up Herne Spur which is pretty steep. A friend with a D2 was having a little visit from the Amigos, so his 1wd disco got stuck. I was asked to pull him up the hill as it seemed easier than going down. I did this no problems. We thought he was ok, so I unhitched him and continued to the next ledge. He got stuck again so reversed down to the ledge below. So, I got sent down again. This is where I had one of one of those moments we'd rather forget.</sup>

I decided it would be easier to drive down forward due to the steepness of it and turn around at the little flat bit. So, I disengaged the CDL for the u-turn.

I got to the ledge, turned around, hooked my friend up. I locked both lockers as it was straight and steep and I didn't know how much I'd have to pull the disco. And off I went.

We kind of got started and it was going ok.. but then it got a bit steeper and then the TC light came on. I could feel the front wheels spinning and I thought it was all four and maybe the car knew and was somehow running the TC.

Anyway.. we continued on for a bit and it was spinning more and I was slowing more and I could smell rubber smoke from the spinning wheels. Shortly after we failed to proceed.

So, I pushed the clutch in and then got a very big surprise.. virtually no brakes! I had to push with all my strength to stop the car rolling down the hill backwards. The strap was loose but I could barely hold this thing. I switched to the other leg. If I popped it in reverse with the engine stopped it still wanted to roll back. Also, then I didn't have brake boost to hold it. At some point through all this we unhooked the strap to the other car which seemed to be able to hold no problems.

After about 10 minutes the brakes cooled enough that they worked, then I had to work out how to get started. My mate was stopped on a water bar just behind me so I couldn't use that to get a start. The handbrake couldn't hold the car and I couldn't get my foot off the brake and to the throttle fast enough to get started. I didn't like the idea of clutch starting the car up such a steep hill.

So, for only the second time in my 12 years of owning the car I had to be recovered. A friend with a winch took the load and I started and then drove the car up.

Anyway, got to the top and was sitting there in shock while they recovered the other car. I was pondering how a defender with the ability to completely lock the drive train managed to work it's TC so hard that the brakes failed. It was about then than I noticed the CDL light wasn't on.

Yep, I'd disengaged it for the turnaround and forgot to lock it again. So, on the really steep hill.. with the weight transfer.. with the open centre diff the unweighted front two wheels just spun (despite being locked). So, the TC tried to brake the spinning wheels. It tried so hard as the back had all the traction and the front had none that it over heated the front brakes.

So, the lesson from this is that the number one thing to do before a big hill is engage CDL.

Personally.. if I had to buy traction control aids in an order this would be my running order.

1. Physical CDL
2. Electronic Traction control.
3. Physical read diff lock.
4. Physical front lock.

Clearly.. if you don't typically get a choice with number 2 as it's generally factory fitted. I put it higher up on my list because I don't think it works very hard at all if you have a CDL. Also, if you have a front locker engaged you can't really steer.. so I rarely use it. If the going is difficult I'll lock the centre (pretty much anytime off road), and then the rear. It's only if I'm in deep do do and if I'm in a situation where I can go straight that I'll lock the front. It's pretty uncanny how a bogged car will basically climb out of the mess and drive off with everything locked though.

Anyway, hope you all enjoy a laugh at my stupidity.

Nope. We've all done stupid, I'm sure. I certainly have. Top Gear's unofficial motto was, 'Clever people doing stupid things.'
As you said, no need to unlock the centre diff on gravel to make a turn.

This experience would tend to prove that the ETC on pre D2A also measures differences between axles. Logically with both front and both rears locked then the only difference can be the difference between the axle speeds which applied the brakes on the front.

Perhaps it is the difference in the D2A ETC computer and D2.
Regards Philip A