66-74 ? J56 front pads 5468882 vs 5470991

[Wayne M.]

I have 2 sets of the former part number (auto-load pic); yet on eBay, back around 2005, there were several people offering # 5470991 (and of course, being eBay, claiming all sorts of advantages -- ie. thicker linings, stiffer backing plates; racing Can-Am, L88 Corvettes, etc...).

The orange paint stampings on the friction material edge of the earlier # 5468883 [which shows up in my GM parts books '66 thru '70 (perhaps even later) are as follows "DELCO" (903FF) 5468883 (one digit higher than the brake lining "kit" part # on the box).

For the eBay boxes with number 5470991, the orange stamping is as shown in the thumbnail pic. The common number is the 903FF, which maybe is the formulation of the friction material.

Anyone know if these two sets are interchangeable ? Was the latter # a replacement for the earlier (say) post-1972; and were they used on the Z07 option '74s ?

[Joe L.]

Re: 66-74 ? J56 front pads 5468882 vs 5470991

I have 2 sets of the former part number (auto-load pic); yet on eBay, back around 2005, there were several people offering # 5470991 (and of course, being eBay, claiming all sorts of advantages -- ie. thicker linings, stiffer backing plates; racing Can-Am, L88 Corvettes, etc...).

The orange paint stampings on the friction material edge of the earlier # 5468883 [which shows up in my GM parts books '66 thru '70 (perhaps even later) are as follows "DELCO" (903FF) 5468883 (one digit higher than the brake lining "kit" part # on the box).

For the eBay boxes with number 5470991, the orange stamping is as shown in the thumbnail pic. The common number is the 903FF, which maybe is the formulation of the friction material.

Anyone know if these two sets are interchangeable ? Was the latter # a replacement for the earlier (say) post-1972; and were they used on the Z07 option '74s ?

Wayne-----

The GM #5468882 J-56 front pad set was a PRODUCTION and SERVICE part for 1969-75 Corvettes with J-56 brakes. It was also SERVICE for 66-68 Corvettes with J-56 brakes and originally using pad set GM #3886394 (1966), GM #5452514 (1966), and GM #5463160 (67-68).

The GM #5468882 pad set was discontinued without supercession in May, 1987.

GM #5470991 was a SERVICE only, "heavy duty" pad set for 1966-75 Corvettes equipped with J-56 brakes. How it differed from the 5468882 I do not know. I think the backing plate MAY have been thicker on the 5470991 and it MAY not have been manufactured of inconel. However, when both were available, the 5470991 was substantially less expensive than the 5468882 and that may or may not IMPLY a significant difference. The GM #5470991 was discontinued without supercession in October, 1983.

[Wayne M.]

Re: 66-74 ? J56 front pads 5468882 vs 5470991

...GM #5470991 was a SERVICE only, "heavy duty" pad set for 1966-75 Corvettes equipped with J-56 brakes. How it differed from the 5468882 I do not know. I think the backing plate MAY have been thicker on the 5470991 and it MAY not have been manufactured of inconel. .....

Joe; thanks for your research. Out of three of these "991" sets that I took down pics and /description/prices from eBay auctions, one seller mentioned that they had the inconel backing plates, and that they were non-magnetic. The plate might have been the most expensive component of the pad assembly.

The mystery deepens, especially as you say that the "882" was available in service for a 3_1/2 year longer timeframe beyond the "991".

[Richard F.]

Re: 66-74 ? J56 front pads 5468882 vs 5470991

The "882" pads had the Inconel backing plates. My understanding was that you had to turn in old pads to get new ones, because the Inconel was rare and difficult to come by like titanium used to be. I bet that the "991" pads had a different backing material, and that's why they were cheaper. I may be totally wrong on this, but maybe it will trigger a better memory than mine.

[Terry M.]

Re: 66-74 ? J56 front pads 5468882 vs 5470991

I worked in metallurgy research for a few years after leaving the military. One of our projects was forming turbine blades from Inconel. I can tell you it was (and likely still is) VERY expensive, and extremely difficult to form -- even that simple right angle bend that is in the backing plates would be a challenge and require larger equipment than the equivalent steel piece. One of its features is it holds its strength at very high temperatures, which is why it is used in this application. It is also relatively (for its strength) light weight, another advantage in this application. it is also highly corrosion resistant.

[Wayne M.]

Re: 66-74 ? J56 front pads 5468882 vs 5470991

Just a bit more info: thickness of backing plates; the J56 are 0.129" and the other two standard pads below (original # 5452513 asbestos in the middle and a (newer ?) 2621609 (organic ?) on the right have 0.120" thick plates; not a significant difference.

But the WEIGHT of the J56 pad as shown is 17.3 oz., compared to 11 oz. for the asbestos. So I'm deducing that most of the difference is in the friction material. Coded 903FF for the J56; 601FF (ink stamped on back -- note direction of disc rotation ) for the asbestos, and 107FF for the organic. Also, notice the different shape of the friction pad on the organic unit on the right -- does not extend to the edge, but is slightly fatter in width (to compensate ?).

[trivia] Both of the standard disc pads have that little delco symbol [visible by looking down the holes on the friction side] on the head of the 8 brass rivets.

[Joe L.]

Re: 66-74 ? J56 front pads 5468882 vs 5470991

The "882" pads had the Inconel backing plates. My understanding was that you had to turn in old pads to get new ones, because the Inconel was rare and difficult to come by like titanium used to be. I bet that the "991" pads had a different backing material, and that's why they were cheaper. I may be totally wrong on this, but maybe it will trigger a better memory than mine.

Richard-----


There was never any sort of "exchange requirement" that I'm aware of for the inconel J-56 pads. There was no "core charge", either. In fact, I have a large number of these pads [none for sale] with worn out lining. When I find someone that can rebuild them with new lining, I might just get them done.

There is a big difference between titanium and inconel. First of all, titanium is a METALLIC ELEMENT. Most alloys of it (as used in the aerospace industry) are mostly titanium combined with smaller amounts of other metals. Titanium is not a particularly rare element, at all. It's just a very difficult metal to machine and work with.

Inconel is an ALLOY; it is not an element. Inconel alloy is mostly chromium and nickel with a smaller amount of iron and other elements. There are quite a few different inconel alloys with varying amounts of chromium and nickel. The basic elements which comprise inconel alloys, chromium and nickel, are not particularly rare elements.

[Richard F.]

Re: 66-74 ? J56 front pads 5468882 vs 5470991

Joe--
You may well be right that there was no exchange program, but I think we need to hear from somebody who walked up to the parts counter in 1969 and ordered a set. I have two sets myself, one new and one I had relined.

Maybe rare was not the right word for me to use, but rare certainly doesn't imply that it must come out of the ground in very small quantities. ZL1's are rare. Back in 1968 titanium was rare in this country because it mostly came from the USSR. Our government was making nuclear subs and fighters out of it, so they got first dibs. Maybe they were also glomming onto most of the inconel that could be produced.

I notice in my 1976 price book that you could get pads for all four corners for $30, but that "882" just for the front were $211. Can this be mostly attributed to the cost of machining the inconel?

[Joe L.]

Re: 66-74 ? J56 front pads 5468882 vs 5470991

Joe--
You may well be right that there was no exchange program, but I think we need to hear from somebody who walked up to the parts counter in 1969 and ordered a set. I have two sets myself, one new and one I had relined.

Maybe rare was not the right word for me to use, but rare certainly doesn't imply that it must come out of the ground in very small quantities. ZL1's are rare. Back in 1968 titanium was rare in this country because it mostly came from the USSR. Our government was making nuclear subs and fighters out of it, so they got first dibs. Maybe they were also glomming onto most of the inconel that could be produced.

I notice in my 1976 price book that you could get pads for all four corners for $30, but that "882" just for the front were $211. Can this be mostly attributed to the cost of machining the inconel?

Richard-----

I don't think we need to hear from someone who tried to buy the J-56 pads in the 1966-1975 period. Exchange charges (or, presumably, an exchange requirement although I've never seen such a requirement from GM) are shown in the price book and, sometimes, the P&A Catalog. I have all the catalogs going back to 1953 and price books dating from 1967. If it wasn't in there, the dealer would have no way of knowing about the charge or requirement. Nowhere in any does it specify any sort of exchange charge or requirement for these pads.

I expect that the much higher cost of the pads related to the cost of the inconel backing plates and the very low production volume. At some point, if not from the beginning, I think these pads were manufactured by Raybestos. I realize they had Delco edge coding on the friction material but I don't know that means they were actually manufactured by Delco. In general, GM internal manufacturing operations in days-of-old concentrated only on high volume type parts. Low volume parts were out-sourced to other manufacturers, sometimes by "coercive" tactics since they didn't really want to make these type of parts, either.

[Wayne M.]

Re: 66-74 ? J56 front pads 5468882 vs 5470991

.... Exchange charges (or, presumably, an exchange requirement although I've never seen such a requirement from GM) are shown in the price book and, sometimes, the P&A Catalog. I have all the catalogs going back to 1953 and price books dating from 1967. ........ Nowhere in any does it specify any sort of exchange charge or requirement for these pads.

Joe -- a question about price books; I have only one, a 1980 Master price list D85, from GM Canada, May 1980, 1394 pages. Even though prices were in Canuck bucks (the exchange rate was not that different back then), I notice that the 5470991 J56 pads were $148.00 list. But there's a 4th price column (after trade and dealer prices) that's headed W.C., with $13.32. If your price books have a similar format, what is that last column ? I guessed at "with core", but does that add or subtract from the list price ?

Agree that nothing in Gr 5.017 (brake linings) indicates a core charge, but there are several areas in the P&A's that do, especially electrical. One of my favorites is Gr 2.500 voltage regulators. For example, the transistorized V.R. # 1116378 has a note: (Exchange item -- Note 1).

Then below is Note 1's description: "List price shown does not include exchange charge. Refer to Dealer Parts Price Schedule for exchange price".

So in my 1980 price book, list for 1116378 is $85.65, and the W.C. column is $15.25. In your opinion, is this the core charge or credit, and how does this figure back into the W.C of $13.32 for the brake pads ?

[Bob J.]

Re: 66-74 ? J56 front pads 5468882 vs 5470991

Wayne, the WC in the last column refers to wholesale compensation which added an extra discount to the dealers price.

I bought J56 pads in the seventies and there was no request at the parts counter for cores (and no core charge) Bob

[Richard F.]

Re: 66-74 ? J56 front pads 5468882 vs 5470991

Bob---

Thanks for jumping in. Your theory makes perfect sense. I'm glad I raised the question. Best wishes.