2004 Dodge Diesel 4x4 ABS & Vacuum

[SDR]

:-{} :-{} My cousin owns a 2004 Dodge Diesel with all the good things. This past week we were out deer hunting and the hill became a little steep and a little slick and we came down the mountain road sliding backward. I had my window down and could hear the wheels were locked up at times while we were traveling backward. I told him not to stand on the brake, but to pump and maintain steering. My cousin's comment was that he had lost brake and I said "bull" they were locked up at times... ... ... . Oo. His position was that he knew the brake went closer to the floor going backward than it did going forward and he said this might be because diesel trucks do not develope the vacuum in inches that cars do. I said you had your hands full keeping the truck on the road going down hill backward and I don't know how in the *&%% one would know what the brake pedal was or wasn't doing in this quick situation. At the bottom of the hill the truck was still in drive and the engine was running.



The question's are

"Are ABS brakes working going backward down hill, as compared to forward?"

"Is there any know reason too have less brake pedal going backward?"

"Does the amount of vacuum play a big part in this scenario?"





PS we didn't hit any trees before coming to a safe stop!



Sheldon Ralston -- email address removed --

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************* I thank you ALL, I have enough information now******** Oo.

 

[BHolm]

Was it a 4x4 truck in 4wd? The ABS doesn't operate in 4wd as far as I know. Also, the brakes will lock when you get close to a standstill. If he locked them just as the truck stooped climbing the hill, then kept the pedal down the whole ride backwards, the ABS computer assumed the truck was stopped, all four wheels read zero.

 

[TowPro]

:-{} :-{} His position was that he knew the brake went closer to the floor going backward than it did going forward and he said this might be because diesel trucks do not develope the vacuum in inches that cars do.

this part is true, that's why they use power steering pump to run the power brakes! (vacuum don't run the power brakes)



Now sure about the ABS. The sensor is still going to give the ECM input because its counting pulses of the wheels, it don't know if your going forward or backwards. When the ABS kicks in, you pedel does go down further then normal, its kind of scary, like your brakes are going away. At least my 98 and 02 are that way.

 

[Bertram65]

Was it a 4x4 truck in 4wd? The ABS doesn't operate in 4wd as far as I know. Also, the brakes will lock when you get close to a standstill. If he locked them just as the truck stooped climbing the hill, then kept the pedal down the whole ride backwards, the ABS computer assumed the truck was stopped, all four wheels read zero.

ABS does operate in 4wd, but they will lock up at low speed, makes sense about staying locked.

 

[rbattelle]

ABS does operate in 4wd, but they will lock up at low speed, makes sense about staying locked.

I think ABS kicks off (wheels lock up) below 5mph.



Vacuum plays NO part in this scenario, because your brakes are not vacuum-assist. They're assisted by the power steering pump instead. In fact, if it's a manual transmission truck, there is NO vacuum system on the vehicle at all.



-Ryan

 

[FJfonda]

I think ABS kicks off (wheels lock up) below 5mph.



-Ryan

I believe this to be true -- I know mine will lock at slow speeds without the ABS coming on in both 2wd and 4wd. Tested many times plowing. I looked in the service manual but the ABS description section doesn't secify at what speeds ABS becomes active.