The brakes on my car frankly have sucked since the day I picked it up. 86 T/A with drum brakes and stock front brakes.

New calipers, rotors, pads, shoes, drums and they were still junk. Booster is holding vacuum. Check valve is check valve-ing. I can’t push through the master.

I watched a third gen guy video on YouTube, indicating that 4th gen master & booster will add significant improvement, however one cannot use a 4th gen booster on a third gen master.

Fair enough, I, being the Great Idiot I am, grabbed a booster and master from a rear ended low mileage drum brake 97 RS from the local pick n pull. After the struggle of removing 4 pinch nuts with grab bag tools you’d think I’d have re watched the video more closely (Particularly the clearly identified part numbers), but no.

The 4 pinch nut bolts on the third gen booster are *much* more difficult to access (15mm vs 13mm), I had every variation of 15mm socket out on the floor of the car that I own and the top right nut still nearly beat me (disconnect the push rod on master for more swing room, back off cruise & brake switches helps too - more to follow on this).

After making the booster swap - that’s when it sank in. Both 4th master cylinder lines are the same, the third gen forward brake line & fitting are larger diameter. You’ve just wasted 2 hours of your life you lunkhead, and your car now has no brakes, Idiot.

Unless…third gen guy is talking about disc brake cars…

Yes, the diameter of the M/C are the same ID at the booster (3rd gen drum & 4th gen drum), the depth of the piston in the bore is the same and the height of the actuating pin is the same…






Make it so. Maybe at least I can park it in the garage.

The pushrod on the 4th gen booster must be a bit longer because I didn’t have to adjust the brake switches to attach the pushrod to the pedal. The pedal is a little closer to me.

Test drive

The car has the best brakes it has ever had in my ownership. I don’t say it stops with race car authority, but it is no different than my wife’s 4 wheel disc car econobox.

If you’re a 3rd gen drum brake guy with dull high effort brakes, you might consider an early 4th gen drum booster. Use the 3rd gen check valve. Get all the 4th gen booster hardware, don’t worry about the wavy washer on the pushrod, it won’t fit on the 3rd gen pedal anyway.

 

What is your measurement of preload clearance between booster pin and master cylinder plunger?

 

I didn’t take that measurement because the mounting depth of the two m/c was the same, the depth of the contact area of the piston/plunger to the front of the bore were similar. I should have documented it and I didn’t / was done in a rush. Having said that, for the benefit of the group and validity of my post, I will measure and post it here.

 

No, please don't pull your stuff apart again. LOL! No big deal, I was just curious in case you already had it.

 

It is a critical measurement, I knew I should’ve written it down but I was hustling to be done before my family returned from back to school shopping.

If I do go back in I’ll be sure to measure and document. I’m curious if others didn’t back off the switch adjustment in the past and had sacrificed that clearance in doing so.

Being in the heavy equipment world it’s second nature to check this when swapping a master (a new rod and adjustable clevis supplied with each new m/c, even with white box aftermarket replacement parts smh)

For now I’ll monitor.