HR Backing plates

reddo · Post by **reddo** » Sun Sep 06, 2009 9:05 am

Hi All
Quick quizz.

Am fitting a HR disc front end shortly and gathering all the bits required to do the job properly.
This includes fitting the HR rear drum brakes

Do i need to use the HR rear backing plates when fitting Hr Ute rear shoes and wheel cylinders to my FB Van??

Or
Can i simply fit the shoes and cylinders to the FB backing plates.
I know the shoes and drums are wider .. and the cylinders have a smaller bore than the FB cylinders... just need to know whether to salvage the backing plates off the HR rear end and fit them to the FB housing.
I know some will say its quicker to just swap the entire rear end over but for now i will leave the existing housing and centre where they are..

Reddo

Trev · Post by **Trev** » Sun Sep 06, 2009 5:07 pm

Pretty sure they (HR backing plates) won't fit to the FB/EK housing, the holes don't line up, and you need to use them for the HR brakes to fit.
Go the whole HR set up

, Trev

.

reddo · Post by **reddo** » Sun Sep 06, 2009 7:37 pm

Thanks Trev..
I have about 3 HR rears at the mo.

Will sort em out send em off to get blasted and use the best of all i have,,
Leads me to ask..
can i run the 3.89 FB diff centre in the HR housing??
I believe they are all the same stud pattern

Reddo

mrs ratbox · Post by **mrs ratbox** » Sun Sep 06, 2009 7:59 pm

reddo wrote: can i run the 3.89 FB diff centre in the HR housing??
Reddo

yes, would you not be better off going a 3.55 centre for better highway gearing may suffer towing though

Finny · Post by **Finny** » Sun Sep 06, 2009 10:12 pm

This one I have actually done.

FB and EK backing plates won't work. I used the entire HR rear end.

Will need HR "U" bolts for the rear of tail shaft to attach it.
Also need a brake place to make a special FB body to HR rear end, hand brake cable.
Also isolation rubbers upper and lower for HR rear end.

Also male sure you have the 8 x HR Bolts for attaching the shockie plates.
And that you use the same type (HR Sedan for FB Sedan, wagon for wagon, etc)
The difference is in the number of leaf springs and therefore the length of the bolts.

jake08 · Post by **jake08** » Mon Sep 07, 2009 8:26 pm

FB and EK backing plates won't work. I used the entire HR rear end.

Will need HR "U" bolts for the rear of tail shaft to attach it.

I am doing this conversion soon- I assume the original tailshaft stays? (grey and crash box are staying) and I just need to change the rear uni?

Also I read somewhere that hr track is wider then ek- I think track is measured from centre of rim or tyre so I guess what I am asking is if there is a difference in width between the drum faces?
Sorry didn't mean to hijack the thread.

BTW I could be wrong but I think someone(ratbox maybe) mentioned on this forum that EJ backing plates will adapt HR cylinders to EK rear end?

reddo · Post by **reddo** » Mon Sep 07, 2009 9:09 pm

Hi Ratbox.

Wanting to stick with the old 3.89 at the moment as i tow a vintage caravan a fair bit.
3.55 would be ok with a bit of work done to the old grey .. like twin carbs, headers , cam perhaps.. but in standard form it would die in the arse on big hills.
I found that out when i fitted the 14" dragways with 60 series tyres... knocks the gearing around a bit ..especially when towing. Not too bad without the van on the back though.

EJ backing plates??
Would they be the same as EH??
I have a complete EH sedan rear end here.
Would also be interested to know if that ( EJ/EH backing plates / HR cylinders , shoes and drums on a FB/EK housing ) is a workable option .

Was sorta hoping that i wouldnt increase the wheel track too much by fitting the HR complete housing etc.
. Dont wanna stuff about with wheel offsets to avoid scrubbing tyres on gaurds etc.

Reddo

Finny · Post by **Finny** » Mon Sep 07, 2009 9:33 pm

Tailshaft doesn't need to change, just the items listed previously.

Not sure about track width

Have read that EH and later backing plates will suit, but haven't tried it.
Don't have front guards on, so not sure about scrubbing.

Finny · Post by **Finny** » Mon Sep 07, 2009 11:24 pm

Pic of the two diffs.
HR at the top and EK/FB at the bottom.

Doesn't look like a great difference, although I didn't measure them.

Also one other change when doing the swap, the Bump Stops are different, Need to remove one of them.

FB MAD · Post by **FB MAD** » Tue Sep 08, 2009 12:44 am

Not sure on the swapability of EJ to HR brakes on a grey housing ?? however without having had a go at seeing whether it's possible, I'd guess that it wouldn't be possible due to backing plate to housing face bolt pattern configuration difference and maybe? the axle housing end to wheel bolt up flange distance being different from FB/EK to EJ/EH?

According to what I've managed to research, the EJ/EH brakes are the same "Duo-servo" shoes and HD and HR are "Duo servo" with self adjusting mechanism.

Primary shoe length EJ/EH 7 27/32 inch.
" " " HD/HR 8 3/32 inch.

Secondary shoe length EJ/EH 8 31/32 inch.
' ' ' HD/HR ( front wheel ) 9 7/64 inch
" " " HD/HR ( rear wheel ) 9 13/64 inch

Lining width EJ/EH ( same as FB/EK ) 1 3/4 inch
" " HD/HR ( front wheel ) 2 1/4 inch
' ' HD/HR (rear wheel ) 1 3/4 inch

I'd take a guess that EJ to HR backing plates would be the same ? without actually having them to cross check that is, and the brake shoe length being the only difference ( along with the HD/HR self adjusters mechanism as well )

I think the EH or HD/HR drum to drum diff swap would be an easier option overall than trying to mod an FB/EK to fit EJ to HR brakes.

If you fitted an EH to HR diff and still wanted 3.89 diff ratio, there was a 3.90 ratio red motor type banjo centre available in the 4 cylinder Toranas that you could obtain and just bolt straight in to the EH/HR diff.

This ratio,although harder to find than the other ratio's, does appear from time to time on evilbay I've noticed.

FB MAD · Post by **FB MAD** » Tue Sep 08, 2009 9:19 am

http://cgi.ebay.com.au/HOLDEN-EH-HR-HK- ... 286.c0.m14

There's an example of the 3.90 red diff centre on evilbay completed listings although not surprised it didn't sell going by the asking price

.

reddo · Post by **reddo** » Tue Sep 08, 2009 8:06 pm

Hi all..
It seems like the only way to answer my question 100% is to pull the EH rear apart .. compare the backing plates with the HR rear plates and shoes etc..
Then whip the back end of the van up in the air and strip one side off back to the backing plates and compare all three model... housing stud pattern, backing plate configuration, housing width and then go from there.
The hard part will be not mixing all the odds and ends up...

3 housings , 6 backing plates, 6 drums, 12 linings ... ooooo bugger.

Now.. to get motivated.. beer... tape measure.. more beer... tools.. im gunna need tools... hmmmmmmmmmmmmmm .. beeeeeeeer

Reddo

mrs ratbox · Post by **mrs ratbox** » Wed Sep 09, 2009 8:58 am

not 100% sure if the HR brake components will go onto the EH backing plate (i think they should) but doesn't really matter as the axle flange bolt patern where the backing plate bolts to the housing is the same EH, HR

FB MAD · Post by **FB MAD** » Wed Sep 09, 2009 9:33 am

Reddo,

Forget the tape measure!!

A beer can's 130 mm long, use that as the measuring standard.

An FB/EK rear end backing plate-to-backing plate is 9.884615384 beer cans long.

There, I've helped ya research already........ hic

.

Get back to us when ya recover!!

Happy measur'in

FCOV6 · Post by **FCOV6** » Sat Dec 19, 2009 11:32 am

An old post but still may be helpful, EH up to VN rear brake backing plates use the same bolt pattern.Therefor you can use any brakes from EH to VN on diff including disc rears with no more than a rotor re drill.

fbekholden.com

HR Backing plates

HR Backing plates

tailshaft?