68 Rear Disc Brake Package

[SMS]

Probably here somewhere but my searches didn’t quite resolve my question.

Being as the 1968 rear disc brake option was an over the counter only option, what all came with that?  I did read that the housing was narrower on the disc optioned cars but does that mean for 69 only when it was a factory option?  It’s hard to imagine that a rear brake kit from the parts department included a housing and axles as well......  but I’m curious how this was all handled.

Thanks,

Bill

[69Z28-RS]

The Service Duty Rear End was not an option; it was just a little known available part Over the Counter.   One couldn't buy that part unless one KNEW about it, and predominantly only people involved in road racing knew about (Trans Am etc), Vince Piggins was involved in it's development; my friend who obtained one got it more quickly by working with Vince directly.

The part was ~ $700 (jobber price) and was a complete rear end from 'brake to brake'.   It was 'developed' as a shortened FULL SIZE differential (in order to fit the Camaro platform).  The Full Size was used as a base because of it's larger diameter axles and larger axle bearings.  The SD differential included a higher number of plates and significantly heavier springs in the posi unit, and of course the Corvette based disk brake units were used on it. 

[william]

Little known?

The cross-ram & 4 wheel disc brake retrofit kits received coverage in many of the magazines back in the day. You could buy the entire rear axle but the kit included parts to adapt Corvette discs brakes to the production rear axle. Did not include a parking brake and wasn't street-legal.

[69Z28-RS]

William,

I think you are referring to the 1969 model year, when JL8 WAS an option on the Camaro, and of course ALL the magazines reported on the 'available' crossram and disk brake equipment.

The OP was asking about the SERVICE duty rear - during the '68 model year, and which was available OTC from sometime during the '68 model year if you knew about it (summer maybe?).   The Service Duty Rear was *totally different* than the JL8 equipment.  A friend of mine, who bought a '69 Z28 in Dec '68 (69 model year) and converted it to an SCCA racer immediately, had to go thru Vince to get his SD rear; Vince had it shipped to him directly~   

PS.  if you are aware of a magazine article on the Service Duty rear during the '68 model year, then I'd really like to try to find the article, because information on the SD rear is almost non-existent even today.

[william]

No I was referring to the May 1968 Hot Rod feature: "Just For Fun: 68 1/2 Chevys" featuring a cross-ram/4 wheel disc '68 Z/28. Then, there is the July 1968 Car and Driver feature "Z/28 Camaro vs. Tunnel Port Mustang. The Z/28 had a cross-ram with the plenum breather and 4 wheel discs. None of this was RPO; retrofitted to production cars.

Point is, 4-wheel discs were fairly well publicized at the time.

[69Z28-RS]

I'd like to read that article if anyone has it possible in digital form? 

William:  Was the disk brake rear an actual full OTC Service Duty (as would have been on the TransAm cars of the time), or was it a std 12 bolt Camaro rear, with the Corvette caliper brackets and calipers??  I do know it was possible to do that 'retrofit' at the time, but what would be NEW to me is if a magazine actually reported on the Service Duty rears in mid '68?   I *think* that was around the time Chevy began unofficially supplying them to racers... Donahue etc.  ??

[maroman]

I clearly remember the Car and Driver article. Doubt if I still have it though.

[SMS]

https://www.caranddriver.com/photo-gallery/1968-tunnel-port-ford-mustang-vs-chevrolet-camaro-z-28-gallery#57

The main article. https://www.caranddriver.com/comparisons/1968-tunnel-port-ford-mustang-vs-chevrolet-camaro-z-28-archived-comparison

[69Z28-RS]

Interesting article in the C&D, but nothing about the brakes (other than having rear disk brakes)!  Sam Posey's comments made that article...  it was also interesting that Ford showed up with the F60 15 Polyglas tires in july '68 ( a bit more than a year before Goodyear introduced them in a couple of new cars!)...

I don't remember reading either article, but I wasn't much of a C&D fan as they leaned too heavily towards foreign cars in their mag, and I likely missed both article since I was in basic at the time... (at that time we didn't get any 'extras' in basic! ...   

.. or maybe my memory is failing me, but if someone has that HRM article.. maybe it would wake up some memory cells..

[maroman]

If I were to read the articles now I would have dropped my subscriptions back then. They both have admitted lying and cheating to make the cars faster. Like the GTO article in '64 they faked stuff. The red '67 SS Camaro they tested for months was nothing but a big lie. Meanwhile we all drank the koolaid and here we are.

[69Z28-RS]

Not only is my memory questionable from 50 yrs ago, it's not 'perfect' even for a few months!     

I was looking online, ebay, etc to possibly buy an old copy of that May'68 HRM magazine and in looking, it of course showed a photo of the cover...  The more I looked at the photo, I came to realize... I probably HAD that magazine.  THEN i recalled that a few months ago, I'd brought over a box of 'old car magazines', thinking of perhaps selling them one at a time via ebay (as others are doing)... so I spun my chair around to find that box (messy office), and right behind me, on the floor, 3 feet from my chair was the box.. and right on top was that May'68 magazine!~   ( I need to hire a secretary to keep me straight at home!)..

Anyway, I read the article, then decided to scan it and post it here for you guys that maybe haven't seen it, but I have to say after reading the article there is VERY little on the rear disk brakes; it did give a pn for the complete axle unit and stated it had to be swapped out complete!   It also implied that it might be available before '68 yr end, but we all know that wasn't the case (except for the Service Duty units for racers), and since they discussed the emergency brake equipment for this one it implies it's the JL8 unit that they were *testing* in the '68 model Camaro. 
Of course the dual quad setup WAS available during 'the 68 model year for the Camaro Z28.  Anyway, I still contend that VERY LITTLE has ever been written (that I've found) on the HD Service Duty disk brake rear axle with all it's many differences from the JL8. 

[69Z28-RS]

Page 70 (3rd and last page) of the May68 HRM article on the '68-1/2 Chevys'

PS.  one of the most interesting aspects of that article was discussion of the 327/325hp engine availability in the '68 Nova.  I don't know if any one of you have driven a car with that engine, but when I was in the USAF one of my best friends owned a '68 Chevelle with that engine and 4 speed of course.  It was VERY strong, in fact stronger than any of the Chevelle SS396 cars we ever raced (and we did race a few!).. probably not including a 375 version though?

I'd love to have a Nova with that engine and a 4 speed; it would be a very good runner!

[Kelley W King]

I also had a friend with a chevelle  327 325HP. It was strong. Same engine as the 350HP. I tried to copy that engine in the 70,s. Pistons,cam,intake,ect. but found that until I went with the 2.02 valves I was wasting time. Same thing with the big blocks, add everything but until you go with the L78 size valves not much of a prize. They say big block oval port heads are best for the street and they are, as long as they have the large valves.

[SMS]

Not only is my memory questionable from 50 yrs ago, it's not 'perfect' even for a few months!     

I was looking online, ebay, etc to possibly buy an old copy of that May'68 HRM magazine and in looking, it of course showed a photo of the cover...  The more I looked at the photo, I came to realize... I probably HAD that magazine.  THEN i recalled that a few months ago, I'd brought over a box of 'old car magazines', thinking of perhaps selling them one at a time via ebay (as others are doing)... so I spun my chair around to find that box (messy office), and right behind me, on the floor, 3 feet from my chair was the box.. and right on top was that May'68 magazine!~   ( I need to hire a secretary to keep me straight at home!)..

Anyway, I read the article, then decided to scan it and post it here for you guys that maybe haven't seen it, but I have to say after reading the article there is VERY little on the rear disk brakes; it did give a pn for the complete axle unit and stated it had to be swapped out complete!   It also implied that it might be available before '68 yr end, but we all know that wasn't the case (except for the Service Duty units for racers), and since they discussed the emergency brake equipment for this one it implies it's the JL8 unit that they were *testing* in the '68 model Camaro. 
Of course the dual quad setup WAS available during 'the 68 model year for the Camaro Z28.  Anyway, I still contend that VERY LITTLE has ever been written (that I've found) on the HD Service Duty disk brake rear axle with all it's many differences from the JL8.

Thanks for that!   The caption beside the photo does indeed seem to answer my question.  You had to get the whole rear axle as the service unit. 

[69Z28-RS]

Not only is my memory questionable from 50 yrs ago, it's not 'perfect' even for a few months!     

I was looking online, ebay, etc to possibly buy an old copy of that May'68 HRM magazine and in looking, it of course showed a photo of the cover...  The more I looked at the photo, I came to realize... I probably HAD that magazine.  THEN i recalled that a few months ago, I'd brought over a box of 'old car magazines', thinking of perhaps selling them one at a time via ebay (as others are doing)... so I spun my chair around to find that box (messy office), and right behind me, on the floor, 3 feet from my chair was the box.. and right on top was that May'68 magazine!~   ( I need to hire a secretary to keep me straight at home!)..

Anyway, I read the article, then decided to scan it and post it here for you guys that maybe haven't seen it, but I have to say after reading the article there is VERY little on the rear disk brakes; it did give a pn for the complete axle unit and stated it had to be swapped out complete!   It also implied that it might be available before '68 yr end, but we all know that wasn't the case (except for the Service Duty units for racers), and since they discussed the emergency brake equipment for this one it implies it's the JL8 unit that they were *testing* in the '68 model Camaro. 
Of course the dual quad setup WAS available during 'the 68 model year for the Camaro Z28.  Anyway, I still contend that VERY LITTLE has ever been written (that I've found) on the HD Service Duty disk brake rear axle with all it's many differences from the JL8.

Thanks for that!   The caption beside the photo does indeed seem to answer my question.  You had to get the whole rear axle as the service unit. 

Yes, the article stated that, BUT..  it wasn't stated which rear they were referring to, OR which rear was installed in the '68 Test Camaro, although the one they pictured (with emergency brake) was apparently a '69 JL8 prototype unit (ie. an early street disk brake rear).   They did provide some PN's for those 'complete' rear units and I haven't checked to see if I can find out WHICH rear ends those PNs refer to (The two PNs were 3941917 and ...18 for the 3.25:1 and 3.42:1 ratios, respectively)...
I checked some old P&S manuals and also found a 3945131 axle (for a 3.73:1 ratio) but again it wasn't clear if that was for the street JL8 or the service duty rear.
(It *may* be that the 'Service Duty Rears' were built from full-size differentials -per order, in special GM shops!) ..

But it seems pretty clear to me that the rear end referenced/photographed in the article as installed in the '68 Camaro (in My-July '68) WAS an early '69 JL8 unit, NOT a service duty unit.