1971 master cylinder

[JTRUCKSD]

A friend of mine has a 1971 J4000 that needs a new master cylinder. Was wondering if a 1973 J45 Master would work for him. (the 1973 J45 was on option thru car quest)

[tgreese]

A friend of mine has a 1971 J4000 that needs a new master cylinder. Was wondering if a 1973 J45 Master would work for him. (the 1973 J45 was on option thru car quest)

Maybe.

The GVWR of the J4000 will matter. J4000 only determines the wheelbase of the truck, not the weight rating. It could be one of three different brake systems. If you look on RockAuto.com, you will see J4500, J4600, J4700 and J4800. Look here to determine the GVWR from the VIN - www.ifsja.org/tech/figures/vin71.html - that will determine which brakes you have.

You can likely make a master cylinder from a similar application (also drum brakes) from a few years later work. However, it will not bolt in - if there is no listing for the year/model that you need, then you will need to adapt the newer master cylinder to your application in some way.

If you are a regular customer, your parts store should work with you to get something that will work. It does not cost them anything but time and effort to order the part you need, and send it back if it doesn't work - they may relax their rules for a good customer. Offer to bring in the old MC to compare it with the new, so they don't have to make a sale if it obviously won't work.

You can also send your old master cylinder to a shop and have it rebuilt. http://www.whitepost.com/brakeform.html - there are likely other places that do this too. If the bore of the cylinder is not pitted, you can hone it and install new rubber parts, if you can find the right rubber parts.

Lots of options if you are resourceful - you can buy a new universal drum brake cylinder from Summit http://www.summitracing.com/search/part ... ation/drum but there are likely dozens of OEM applications that could supply a MC that will work, but it won't be exactly the same as what you have.

[JTRUCKSD]

Thank you for the info. Defiantly shed some light into the situation.

[carnuck]

Is it single line or double line?

[JTRUCKSD]

I believe they ended up putting a '78 chevy master on it.