76 -- J10 Master cylinder questions?

[Amphi]

I just bought a 76 J10 and the brakes don't work very well. It has all new brakes, drums, and master cylinder. It is a six-lug open knuckles axle with drums. I've been told this may not be stock.

The Master cylinder has two reservoirs with the large one forward. Two different sized lines running to proportioning valve on the frame. The smaller line is plumbed to the larger reservoir and the larger line to the smaller reservoir.

My questions: Is the master cylinder plumbed properly? Are the lines crossed?

Thanks for any reply!!

[ob1jeeper]

Hmmm... From your description of hte front axle, it's pretty likely that it's original, or at least it could be the original axle... But these things are SO subject to modifications and parts swapping, that it's hard to say from your description... Crawl under and get the numbers of the tag on the axle cover (if it's still there)... Being a '76, the axle number should start with a 535 or 536 followed by XXXX other numbers... May also have Dana identifier and ratio numbers on it...

Lines to the M/cyl can't be crossed (at least without damaging them)... The fittings have different threads... (and flare seat angles) Was done to keep mis-installs from occurring on the assembly line...

It doesn't look as if it does, but it's hard to see in your pic... Does it have a power booster? If so, is it getting vacuum? Is it leaking vacuum?

You said all brake parts are new, but that M/cyl sure don't look all that new in the photo...

Need more info to diagnose... AND since brakes are critical to your safety, it's really best to have a p;rofessional someone who is able to look at your parts, and is knowledgeable about them to help you diagnose your issues... Diagnosing by proxy is a crap shoot at best...

Good Luck...

[Crazy_Jeepman]

If you have Drums on the front for some strange reason..............the M/C is wrong as would be the Proportioning valve. Drum Brake M/C both the resivoires are the same size and am told is valved differently, and the Prop. Valve would also be ballanced for Disc/ drums, and not drums on both ends.

[Amphi]

oby1jeeper:

Thanks so much for the reply!! I'll look for a tag. No power booster (yet). Good info on the threads ? I was going to try and swap them (probably would have bunged-up the threads). M/Cyl was said to be new about a year ago but driven less than 100 miles since. Not sure but could have rusted being an unpainted casting. I'll look inside. I'll also pull the wheels and drums and take a peek. I locked them up on gravel and found three skidded but one didn't (left rear) so I really need to check adjustment, bleed them properly and all the other good stuff.

Thanks again for the great info on the lines and fittings.

Crazy_jeepman:

That would explain why it doesn't want to stop. Somebody swapped the front axle.

Thanks Guys

[Crazy_Jeepman]

Are you sure your truck is a 76, I find it very odd that you do not have Vac Booster in it. Check your vin against the info here:

http://www.ifsja.org/tech/figures/index.html

Something is Odd thats for sure

[Amphi]

Just checked the VIN and everything matches year, engine, tranny etc. Also matches the number on the door tag.

I did get a box of spare parts and there is a booster in the box --- need to see if it will bolt on. I think I'll need some sort of rod.

[Amphi]

See the first post in the following thread. It has pictures and describes what I brought home.

http://m715zone.proboards102.com/index.cgi?board=open&action=display&thread=1166902068&page=1