Chev EK

[EK283]

Thanks for all the comments guys.

So i started the fault finding on the dragging brakes and i have discovered it was pilot error on my behalf and not anything faulty, (although my money was on the booster !!)
What has happened is the measurements i made on the bench were correct but when i set everything in place the measurement i took was from the pushrod end, Well the pushrod doesn't contact on the end now does it, no, it makes contact on the outer edges so pushing the master cylinder in about 1mm too much and blocking the bypass port.
In the Fraud range of master cylinders they do not have a circlip at the back of the piston assembly and have to be preloaded accurately, i have also measured exactly where the piston needs to be and have gone off that measurement whilst adjusting the booster pushrod today.

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The bypass port is a very tiny hole that lets the fluid come back into the master when the brakes get hot and the fluid starts to expand. If for any reason the port is blocked it will pressurise and keep the brakes engaged until the fluid cools and shrinks and at this point release the callipers.
Another byproduct of this is the pedal will go rock hard and it feels like the booster is not working,which is what i initially thought. In actual fact because the master is pressurised hydraulically there is no play for the pedal to move hence not allowing the vacuum valve inside the booster to operate. This is why it feels like no brakes but in reality they are not boosted and you need to press real hard for it to stop.

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You can see the small port hole in the above shot, and you can also see the piston covers half the fluid porthole, this is now at its correct position for it to operate.
All fixed now, and i will test it next week.

Greg

[Errol62]

Good news.


FB ute fixer upper, EK van on rotisserie

[Harv]

Sounds familiar - had to do the same mating the XA/B/C master to the Gemini booster. The pushrod I used was not adjusted able, so weld an extension and grind to suit. Hoppers had some good advice - gently probe that bleed port with a bit of fuse wire to make sure it is not covered.

Cheers,
Harv

[FireKraka]

That's great info Greg something I have also been having an issue with, not feeling as if the booster is working I will look into my own issue a bit better now.

[EK283]

So its diff time kiddies,

Around the nationals and the after party I clocked up approx 1500 kms mostly open road running. It was established pretty early that the gears in my diff were too tall, 2.75 ratio with 25.6inch old school (215x60x15) tyres new school.This combo with the turbo 700 and overdrive was bogging the motor down around 1800-1900 RPM at 100 km/h. Noemally these revs would be ideal but the cam i have wont sart working till just over 2000 rpm so I was getting a slugish and doughy feel to the engine if i accelerated, once past 2000rpm no issue. The decision was made to swap out the ratio for a bit better "get up and go".
Now you would think swapping a ratio would be an easy thing in a 9 inch but there is lots to think about. My intention was to run 3.5 around the hood and have a complete centre with 3.0 gears for the long trips if i so desired.
No issue i have another diff stashed so i will swap the ratio in that one and swap the centres out. No such luck im afraid !
My stashed diff is a LSD but it is a single ribbed centre and is 28 spline, so my 31 spline axles don't fit obviously.
I also have a N case (Nodular iron) 2 ribbed case, much stronger, that was in the car so out it come.

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I then decided a truetrac was the go as my LSD in the car was very tight and noisy around corners, so i bought an eaton 31 spline unit. Because its aftermarket the carrier bearings are larger than the original &*#@ ones, GRRRR. I hate destroying new parts so a new case is on order now to suit the larger carrier bearings. The other considerations are the yolk lengths and pinion supports, different types and lengths as well !!!
To avoid cutting my tailshaft down i have decided on using the original pinion support so i dont lose or gain any length on the yolk.
Updates as soon as my new bits come in, i will document the diff build and ad it here for reference should anyone be interested.

Greg

[Harv]

Ouch. Sounds like every time I pull something apart... what should be a simple task ends up like There's a Hole in the Bucket, Dear Liza.

Cheers,
Harv

[Blacky]

Sounds about right - change one thing , change 3 others to account for it

[Errol62]

I remember the clutches in your diff were very tight, Greg. I'm pretty interested in the truetrac option. I would consider putting one in the Borg Warner I have, and possibly the LJ bango currently in the ute.

Sent from my SM-G781B using Tapatalk

[Harv]

I’ve got a trutrac in the wagon, one in the young blokes VL, and another one going into the daughter’s VL tomorrow. All BW78s, all 31 spline. They get the snot beat out of them, and have not missed a beat. Like any slippery diff they can break traction mid corner in the wet, but it is manageable provided you back off.

Cheers,
Harv

[60Special]

Glad you got the brakes sorted Greg. A trap to be aware of.

[FireKraka]

Greg I really need to look at my brakes as well I have been wondering if I might have a similar issue to you, my pedal if a bit firm and the vacuum pump seems to be always running even when just driving down the road, your thoughts would be appreciated.

[Brett027]

For those using unmatched boosters and master cylinders, this tool is very handy to work out the length required to set the adjuster/ rod length. Worked a treat on my setup with bignut master and knock-off booster. Lots of videos on You Tube showing how to use it. $20 or so bucks well spent to avoid a lot of guess work.

[EK283]

Thanks Brett,
I have a measuring device like that and they are great. My issue was the preload on the master being a Fraud unit i got wrong.
Majority of masters will have a circlip so you need to have some play between the pushrod and piston, 20 thou normally.

Neil,
Im going to guess it could be your problem that you have no play on the master from the booster. Not sure what your combination is but if the master has a circlip then it needs a gap between the booster pushrod and master piston.

Greg

[FireKraka]

Cheers Greg I think you are spot on, the booster and master are off Evilbay chrome ones I did adjust the booster push rod thinking it wasn’t making enough contact I probably should have left it where it was originally where an I get one of those tools

[Brett027]

You can borrow mine