Hi Guys, just wondering how do you tell the difference between a HR disc & drum diff. Is there a problem putting a drum diff behind a disc brake front end?
Thanks,
Dean.
HR rear ends
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JOD34N
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HR rear ends
I shoot little furry animals with a big Canon!!
Hr rear brakes
Hope I'm not going to step in and tread on toes here...... but
HR rear brakes fitted to vehicles with disc brake front ends are different.
The rear brake cylinders are much smaller - 9/16" bore - this is to prevent lock up of the rear brakes due to the larger piston areas of the calipers on the front........ and the system should be boosted.
The master cylinder is the same, but has the residual check valve removed - if you don't do this, you won't be able to release the brakes - the remote servo booster does not have a return spring in it's hydraulic piston arrangement - and as such, there isn't any mechanical force available to push the fluid back through the residual valve in the master cylinder.
The entire system is a "single line" system - hence the smaller rear wheel cylinders and associated shoes/components are necessary to complete the installation........
The rear shoes are different as well - because the smaller wheel cylinders have "button" ended pistons (as opposed to slotted pushrods for those fitted to drum brake front ends), - the shoes must be compatible - you will probably find it hard to acquire HR disc compatible rear shoes - I feel you may however still be able to get the wheel cylinders.........
If you find a set of shoes, don't ever let them out of your sight - you can have them re-lined - don't let them go.........
You may opt to fit a dual circuit system, or a proportioning valve - your brake specialist will probably be needed here to match whatever you intend to fit - under these circumstances, you can fit the standard HR rear brake assembly........
I know of instances where only the disc portion is boosted, leaving the rears un-boosted and have been informed that this setup works well, but to effect the two separate braking systems needs a "dual" circuit master cylinder......
Sorry if I have offended anyone here - but just thought I should step in.....
frats,
Rosco
HR rear brakes fitted to vehicles with disc brake front ends are different.
The rear brake cylinders are much smaller - 9/16" bore - this is to prevent lock up of the rear brakes due to the larger piston areas of the calipers on the front........ and the system should be boosted.
The master cylinder is the same, but has the residual check valve removed - if you don't do this, you won't be able to release the brakes - the remote servo booster does not have a return spring in it's hydraulic piston arrangement - and as such, there isn't any mechanical force available to push the fluid back through the residual valve in the master cylinder.
The entire system is a "single line" system - hence the smaller rear wheel cylinders and associated shoes/components are necessary to complete the installation........
The rear shoes are different as well - because the smaller wheel cylinders have "button" ended pistons (as opposed to slotted pushrods for those fitted to drum brake front ends), - the shoes must be compatible - you will probably find it hard to acquire HR disc compatible rear shoes - I feel you may however still be able to get the wheel cylinders.........
If you find a set of shoes, don't ever let them out of your sight - you can have them re-lined - don't let them go.........
You may opt to fit a dual circuit system, or a proportioning valve - your brake specialist will probably be needed here to match whatever you intend to fit - under these circumstances, you can fit the standard HR rear brake assembly........
I know of instances where only the disc portion is boosted, leaving the rears un-boosted and have been informed that this setup works well, but to effect the two separate braking systems needs a "dual" circuit master cylinder......
Sorry if I have offended anyone here - but just thought I should step in.....
frats,
Rosco
Last edited by rosco on Mon Aug 04, 2008 7:48 pm, edited 1 time in total.
G'day Rosco,
that's excelent information you have there, I've used Hr diffs & never noticed the difference except the need to remove the bit in the master cyl, once removed they worked ok (or so I thought)
I've also sold a few diffs over the years & never had anyone ask for a drum or disc one, never had any complaints off buyers either.
No one is too old to learn, (just some are too stubborn
)
Dave
that's excelent information you have there, I've used Hr diffs & never noticed the difference except the need to remove the bit in the master cyl, once removed they worked ok (or so I thought)
I've also sold a few diffs over the years & never had anyone ask for a drum or disc one, never had any complaints off buyers either.
No one is too old to learn, (just some are too stubborn
)Dave
trying to save some heritage before the scrappies crush it all...........
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mrs ratbox
As so well put by Rosco, did exactly the same on mine, except it was an EJ housing, was supposed to be EH but got jibbed. Nothing a centre change didn't fix. As for the shoes a simple fix, just by welding in a tab to fill in for running the button. Recommended by a brake place by the way.
Speed and Style........... One day I'll get the speed bit.