Load Sensing Valve
- Alister McBride
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Cheers, alister
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- Holmz
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Alister McBride wrote: Hi all, mine is basically out of adjustment but rear brakes are still on too much. Can someone post a pic of their rear brake proportioning valve setup so i can compare... Preferably if you've done the swap to a commodore unit. TIA
Cheers, alister
In general:
1) at low braking, (snow, ice, dirt, sand): then the brake force should in proportion the weight on the axel.
2) at high braking: then there is also the weight transfer... and the front always get a boost in the force that they can tolerate before lock up.
So the rears are only on too much if the rears are not the loaded axel, or there is some obvious "too much" that is not solely the measured temp.
And the fronts probably get more cooling than the rears...
Balance bars, manual proportioing valves etc are common in race cars, but the theories of the concepts apply everywhere.
I am interested in that commodore unit too.
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- Alister McBride
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Has anyone got a pic of their setup, want to make sure mine is on the right way around and and piping hooked up correctly...?
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- Peter and Sandra OKA 374
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OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 1100w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.
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- Alister McBride
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Cheers, alister
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- Peter and Sandra OKA 374
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The original cable between diff and arm was 130mm eye to eye and I made a new longer one at 230mm eye to eye as my springs are set at maximum "arch" (were a bugger to get back in!) as the truck is permanently loaded all of the time so needed more braking on the rear.
OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 1100w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.
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- Peter Davis
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Mine is seized with obviously full braking to rear. Will need a new one if the anti seize doesn't work. Still to change front chassis hose as access isn't easy. Very little room for spanner to move being the middle hose under the pedals.
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- Peter and Sandra OKA 374
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There isn't much inside the valve, just a floating piston and a couple of seals so if the bore isn't corroded then it should be rebuildable but given they are freely available for Holden 1 tonners probably easier to fit a new one.
OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 1100w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.
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- Alister McBride
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Peter Davis - mine is an XT and it doesn't have the mounting bracket either. I imagine it's to avoid having the mounting bolt heads interfere with the longitudinal cross-member which holds the divorced t-case in the LT...
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- Peter Davis
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- Peter and Sandra OKA 374
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Did yours have the sloping ends where it bolted to a flat sloping mount at each end ? 374 has right angle mounts with rubber donuts at each end
OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 1100w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.
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- Peter Davis
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- Peter and Sandra OKA 374
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OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 1100w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.
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- Alister McBride
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- Peter and Sandra OKA 374
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In that valve there is a floating piston which under normal conditions has equal pressure from both front and rear brake systems on each side, ie: one side has the front fluid and the other the rear fluid. If either system loses fluid the piston will move to that side as the pressure is higher on the "good" side which shorts the wire to ground and brings up the brake warning light on the dash.
Alister to decrease the rear braking the brake proportioning valve arm needs to drop downwards at rest. You can adjust the bolt but it is easier to shorten the cable connecting the arm to the rear diff. You can replace the cable with a piece of chain which makes it easier to get the right length by shifting from link to link to get it right.
OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 1100w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.
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- Ralley
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Rob
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- Alister McBride
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- Peter and Sandra OKA 374
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If corroded internally they will also not work as fluid bypasses the buggered piston seals.
Years ago I had an old Volvo which had a similar valve to the front one to operate the brake light if one circuit had failed and the seals between the front and back systems had worn to the stage where fluid freely passed between the two effectively removing any bias front to back.
I only found the problem when the plastic switch decided that it could no longer handle the hydraulic pressure and blew out making a huge mess and no brakes!
OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 1100w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.
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- Alister McBride
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That would make quite a mess in the cab... I hope it's not that! Considering it's been like that for years i doubt it's the problem. Possibly the new (second hand) rear proportioning valve is buggered, maybe moving but not proportioning... may have been sold like that. Next step, take it off and pull it apart i guess.
Thanks Peter's and Rob for the help!
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- Peter and Sandra OKA 374
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The bolt adjustment changes the tension on the spring which in turn changes the amount of pressure on the valve piston, you may need to screw the bolt in to lessen the pressure as well.
OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 1100w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.
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