I have a 11/70 car that I redid all the bushings, power coated the suspension, added Eibach lowering springs, and Koni yellow shocks. Now the rear wheels sound like absolute grinding hell when I try to move the car, and the E-brake no longer holds (I tried to adjust it). I don't know, but suspect the original style cylinders might not be working properly. Is changing to the 73 and up style a good 'upgrade' or should I try something else first?  Thanks!

The original wheel cylinders may be leaking and the newer style is a good compromise but a leaking wheel cyl wouldn't cause the grinding sound you describe.  jack it up, remove the wheels and and spin the hubs, could just be the drums rubbing against the backing plate.

31 minutes ago, loudoun said:

 Is changing to the 73 and up style a good 'upgrade' or should I try something else first?

I'm not totally sure I understand the question, so I'm just gonna shotgun a little:

It's not 73 and up. It's actually 73 to 76.
In 77, they changed the wheel cylinders dramatically.

So... If your question is "Should I change to the 73-76 cylinders?", then my answer is "No. There is no "upgrade" to making that change at all." So unless there is something wrong with your current cylinders, there is nothing to be gained by changing to the 73-76 style.

And if your question is "Should I change to the 77-78 style cylinders?", then my answer is "The 77-78 style cylinders are way better than any of the previous years, but changing over to them is not an easy conversion."

Okay, you did the bushings, springs, and struts plus some powder coat - but what did you do to the rear braking system? Shoes, springs, retainers, cylinders? You left the rear axles and bearings intact? 

38 minutes ago, Captain Obvious said:

So... If your question is "Should I change to the 73-76 cylinders?", then my answer is "No. There is no "upgrade" to making that change at all." So unless there is something wrong with your current cylinders, there is nothing to be gained by changing to the 73-76 style.

But wait, I did this conversion back in 2017 and documented here;

 

cgsheen1, excellent question. I pulled the suspension off of a 2/71 car, cleaned it up, powdercoated, and swapped it on the 11/70 car. New bushings, and in most cases, bolts went in. Not that this matters for the rear, but a new steering rack and ball joints up front, and rebuilt half shafts with U-joints in the rear. For the rear, the original brake cylinders and e-brake cable stayed. I did replace the rear drums with the available cast iron drums and put new pads on. The first set of shoes actually adhered to the rear drums after a bit, and the rear edge broke off as I extracted the drum. I have new shoes on now, but still the same grinding. I have it on a four post lift now and do not see any grinding marks on the half shafts.

10 hours ago, Captain Obvious said:

I'm not totally sure I understand the question, so I'm just gonna shotgun a little:

It's not 73 and up. It's actually 73 to 76.
In 77, they changed the wheel cylinders dramatically.

So... If your question is "Should I change to the 73-76 cylinders?", then my answer is "No. There is no "upgrade" to making that change at all." So unless there is something wrong with your current cylinders, there is nothing to be gained by changing to the 73-76 style.

No, not an upgrade, but the if the originals are leaking then replacing them with the early style will cost hundreds of dollars more than going with the 73-76 wheel cylinders.

And if your question is "Should I change to the 77-78 style cylinders?", then my answer is "The 77-78 style cylinders are way better than any of the previous years, but changing over to them is not an easy conversion."

 

9 hours ago, loudoun said:

 I have new shoes on now, but still the same grinding. I have it on a four post lift now and do not see any grinding marks on the half shafts.

Do you hear the same grinding when you spin the hubs with the drums removed?  If the backing plates aren't interfering with the drums then the grinding could be a bad wheel bearing in the hub.  

10 hours ago, w3wilkes said:

But wait, I did this conversion back in 2017 and documented here;

Understood. But it's a matter of AVAILABILITY, not performance. There is no performance change at all. It's more of an "unfortunate necessary substitution driven by inability to get the better fitting part".

The OP asked if the 73-76 cylinders were a good upgrade, and I believe the answer is "no".

  I'm not trying to cause any trouble here.  

14 hours ago, loudoun said:

cgsheen1, excellent question. I pulled the suspension off of a 2/71 car, cleaned it up, powdercoated, and swapped it on the 11/70 car. New bushings, and in most cases, bolts went in. Not that this matters for the rear, but a new steering rack and ball joints up front, and rebuilt half shafts with U-joints in the rear. For the rear, the original brake cylinders and e-brake cable stayed. I did replace the rear drums with the available cast iron drums and put new pads on. The first set of shoes actually adhered to the rear drums after a bit, and the rear edge broke off as I extracted the drum. I have new shoes on now, but still the same grinding. I have it on a four post lift now and do not see any grinding marks on the half shafts.

What granny said and pull the drums and look for scoring, scratch, rubbing - not so much on the area where the shoe (friction) meets, everywhere else. Put up a pic of your shoes and springs and cylinder.

Edited July 10, 2024Jul 10 by cgsheen1

16 hours ago, loudoun said:

rear wheels sound like absolute grinding hell when I try to move the car,

 the E-brake no longer holds (I tried to adjust it).

I think that you're going to find a shoe retaining part, or a broken/loose spring inside a drum.  The parking (not "E) brake "no longer" works, meaning that it did for a while.  Something broke or came loose.

The fsm says pulling the e-brake up a few times is the adjustment after changing shoes. Mine went from almost straight up to about half way. Kinda like ED as I got older. 

 

22 hours ago, cgsheen1 said:

Okay, you did the bushings, springs, and struts plus some powder coat - but what did you do to the rear braking system? Shoes, springs, retainers, cylinders? You left the rear axles and bearings intact? 

I rebuilt the half shafts and all new bearings