CRG Discussion Forum
Camaro Research Group Discussion => General Discussion => Topic started by: SMS on February 07, 2018, 01:19:57 PM
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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
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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.
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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.
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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.
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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.
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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. ??
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I clearly remember the Car and Driver article. Doubt if I still have it though.
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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
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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.. :)
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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.
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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.
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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!
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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.
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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.
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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.
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This just keeps getting more interesting.
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(https://farm5.staticflickr.com/4670/26293194588_c271ffc7bb_z.jpg)
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That’s an early 68 Z28, note the 302 emblem on the fender.
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That article isn’t fully accurate.
There was never a factory produced dual quad 302. And four wheel disc brakes were not a factory production option in the 68 model year.
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If anyone has EVER seen an auto magazine article that was 'fully accurate', let him please inform us all now... :)
I don't recall reading in that article that those parts were 'factory installed'... but the article implied that the parts were available for retrofit, BUT in the case of the disk brake rear end I'm not aware of the '69 JL8 rear being available OTC during the '68 model year (not even at the end of it which is when this article was written)... The dual quad setup (carburetor package) WAS available OTC as I understand it...
The OP in this thread was asking about 'details' about the disk brake rear available during the '68 model year, and the ONLY one that was available to my knowledge was the SD rear, and that one was NOT very well known or publicized, as it was basically information/parts passed along to known racers/race teams. I'm not sure when the SD rear was available OTC, but I believe by summer of '68 it was available (if one knew someone). If someone has more/better information on the Service Duty rear either details or when it was available to race teams like the Donahue/Penske team, I'd sure like to know, whether this was what the OP was asking or not.. :)
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Does anyone know how much shorter the disc brake housing was then normal?
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It was shorter than the B body (Impala, Bel Air, etc.) but probably the same as standard Camaro width.
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Does anyone know how much shorter the disc brake housing was then normal?
WHICH disk brake housing are you asking about? JL8 width is same as regular 12 bolt Camaro housing AFAIK... and the SD housing is the same or very close... ( I have one I can measure if necessary)...
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Of course the dual quad setup WAS available during 'the 68 model year for the Camaro Z28.
Actually, no it was not. It was available over the counter and could be put on ANY small block Chevy engine.
You may say "semantics" or "taken out of context", and you may be right. But I am just tired of hearing about factory installed dual quads on Z28s. It NEVER HAPPENED! Just like the three deuce setup never happened on Camaros.
Yes, magazine publishers have always been more concerned about selling magazines than making sure the facts are 100 percent accurate. That is why it can be dangerous to use magazine articles to document things without corroboration.
Gary - I do agree that the article was probably on a test vehicle, possibly for JL8 but that did not actually become a production option until about Feb to May of 1969. Don't quote me on that timeframe because I am going by memory on that. It is obviously a "mule" and probably was testing other things too.
I also agree that 4 wheel disc brakes (even over the counter stuff) were not widely known to the general public and also not known very well by a lot of regular dealerships. Performance dealerships with guys that were into racing knew, but not regular dealers.
See attached clip from the article, which is not correct.
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OK, I reread the first page. Is it true the SD was a shortened full size car housing down to Camaro width?
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It may be many variations out there. Since serious racers used Traco engines, had several third members and gearboxes I wonder why they would even use a real Z28 since they did not need anything but the body. I would bet guys like Penske made their own out of whatever 12 bolt was easy to get. With only what? 216 factory JL8,s we may never have a actual this is what they ran.
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.......
The OP in this thread was asking about 'details' about the disk brake rear available during the '68 model year, and the ONLY one that was available to my knowledge was the SD rear, and that one was NOT very well known or publicized, as it was basically information/parts passed along to known racers/race teams. I'm not sure when the SD rear was available OTC, but I believe by summer of '68 it was available (if one knew someone). If someone has more/better information on the Service Duty rear either details or when it was available to race teams like the Donahue/Penske team, I'd sure like to know, whether this was what the OP was asking or not.. :)
Part of this thread is just to be well informed, and part of it is just wondering if I could replicate the 1968 OTC SD rear disc package on my 68 Z28 to be different, and at least be able to have it a period correct kind of thing, and something you'd never see at a show or cruise in. "Yeah, you could pick that up in the parts department after you bought the car."
And if I did that, it would be nice to know that any old 12 bolt housing from 1968 would have potentially come in the package, because if it's true that a narrower housing came with that, I'm not cutting up a correct date and code housing for this novelty. But if it seems the OTC kit did not have a parking brake but the 69 JL8 option did, that kinda complicates my idea.
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SMS - (Would be nice if we had a name) - you would be cutting up a full size housing and there were hundreds of thousands of those from 65 to 70. Not a huge loss.
And actually I am following this thread because I may be doing this in the future. I have 3 or 4 big car 12 bolt rear ends and Corvette disc brakes. So it is just a matter of time...
Currently my car does have 4 wheel disc brakes, but the rears were added in the 90s.
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http://www.camaros.org/forum/index.php?topic=10786.0
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SMS - (Would be nice if we had a name) - you would be cutting up a full size housing and there were hundreds of thousands of those from 65 to 70. Not a huge loss.
Bill
Thanks
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The reason the OTC (
OK, I reread the first page. Is it true the SD was a shortened full size car housing down to Camaro width?
Yes, and the reason they did this (for SCCA road racing purposes) was to use the LARGER axles, and LARGER axle bearings for the severe duty application.
Shortening a full size differential is a potential route to go, BUT... you'd need the special axles with larger bearings to complete the rear end. The biggest reason cars quit using the 'Service Duty' rear was the non-availablity of the axles in the early '70's, and even before they were taken off the books, they were VERY expensive to buy.
One of my friends who ran TransAm (Robert A Christiansen) bought a new '69 Z28 and drove it from the showroom in Dec'68 to his shop and immediately began removing parts and converting it to SCCA specs. Everything I know/remember about the Service Duty rear end came from him in the 70's when I assisted a little on his cars, and he helped me rebuild the engine in my '69 Z28. I have notes from him re all the other differences in the SD rear vs the JL8 rear (and there are several). Even in Dec '68, he had to go thru Vince Piggins himself to get a Service Duty rear (I have that rear end now). Bob used the rear in his '69 Z28 racer in T/A racing, and then in IMSA GT racing until the axles became unobtainium; I have the last two sets of axles that Bob used in that car. When the '69 Z28 body became 'too old' for IMSA, he bought a '73?Camaro body and moved most of the HD parts he had to that car (and sold the '69 to some local SCCA racers in the Atlanta area - I later purchased the rear end, axles, and 2 sets of the Magnesium wheels from that car from those fellas in the late 70's, after they had sold the car to a doctor-racer in the Chattanooga area. A few years ago, I loaned one of the axles to a fella Camaro owner who had an axle mfg MAKE some duplicates of the SD axles, and he made his own SD rear by cutting down a FS differential.
PS. If you wanted to make your own 4-wheel disk brake rear (JL8 clone), you could do that from the 12-bolt std rear, and add the disk brakes and other incidentals necessary. I think all those parts are available, but you would not have a 'numbers' JL8, but it would stop/look just the same. I also have an NOS extra pair of the caliper brackets and backing plates for the JL8 if anyone is interested.
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Gary, thanks for the explanation. As a side note, this would have been the same rear end housing that Penske would bend to get camber in the rear. There was a lot of thinking going on back then. The Nascar boys still do this for the short tracks.
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Bill, what is your goal? Just better stopping? Do you want your car to look like it was an originally retrofit car with 4 wheel disc?
If you just want to stop better there are at least these options.
1. Buy a current kit from one of many vendors that sell the rear disc conversions.
2. Buy a service or possibly original JL8 from a certain vendor (HBC) but be ready to spend A LOT of money on one.
3. Take a full size housing, have it narrowed, use the existing larger drum brakes and then have custom axles made.
4. Take an full size housing, have it narrowed (using the smaller Camaro type ends - or better yet Ford type ends so you can have bolt in axles) and then figure out your brakes.
5. Buy all of the JL8 conversion parts.
Good luck.
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I'm curious about this thread as well. I've often considered building a JL8 type setup for my 68.
I seem to remember on one of the forums (TC, SYC...) some fellow(s) successfully building rear disc setups that appear "JL8-like" or "SD-like" using combinations of fabricated, aftermarket/repro, and NOS/currently available/original components and being somewhat affordable. I briefly searched but couldn't find the threads.