[wmurrell]

There was an NOS idler arm P/N 5678345 sold yesterday on eBay.

https://www.ebay.com/itm/13400028269...p2047675.l2557

When I compare it to my idler arm (same P/N 5678345) for my ’65…I noticed my casting number is 5678347 versus his 5693755. Also, it looks like my center link hole is smaller.

Is it possible to have the same part number and yet have different casting numbers/configuration?

[John V.]

Bill, I'll take a stab at this, don't have any specific info related to this part, so just my thoughts.

First, the seller mentions a 1st and 2nd design for the Assembly p/n 5678345 with the 2nd design being identical to the first except for the 2nd having a larger center link hole.

I have to believe that he has seen this Note in a later model MPC.

My MPC is 1966, it lists the 5678345 as the Service Part for '64-'66 and there is no indication of a 1st and 2nd design.

The casting was not a Serviced Part so you won't find the casting p/n in the MPC. You would need to have the original engineering drawings for both the casting and the Assembly. My guess is that the original Assembly Drawing will show the inclusion of the 5678347 casting, the one you find on your '65.

And most likely, the Assembly Drawing was revised, perhaps for the '68 Model Year to include the 5693755 casting. By p/n alone, pretty obvious that the 5693755 came along a good bit later than the 5678347 casting.

Perhaps the casting was revised so that a larger center link hole could be accommodated.

What would be unusual is that the Assembly p/n wasn't revised at the same time.

What this suggests to me is that the original small center link hole arm was no longer to be Serviced.

If that meant that the center link itself or perhaps a bushing had to be serviced for the earlier Model Years whenever the Idler Arm was to be replaced, the MPC likely would explain that.

A newer casting p/n certainly could be used to supersede the older casting if it could be machined to suit the earlier application so the only surprise to me is that they chose not to Service the 1st (small center link hole) design separately from the 2nd design with unique Assembly p/ns for each.

The advantage was so that they wouldn't need to inventory both designs. The disadvantage was that any old inventory of Service p/n 5678345 at the Parts Warehouses or at the Dealerships would probably need to be scrapped to avoid having somebody attempting to use a part that was "correct" by p/n but didn't fit (assuming the 2nd design didn't directly fit the early applications and the 1st design didn't directly fit the later applications).

It is conceivable that the 1st and 2nd design Assembly parts were interchangeable despite the hole size change in which case it wouldn't matter whether you got the 1st or 2nd design when Servicing the part.

Take a look at a '72 MPC and it might become more obvious.

[johnta1]

Here's a bulletin from Pontiac:

Steering Linkages

Not sure if it helps?

[Pontiac Marv]

The arm offered on eBay was either mislabeled originally, or it got moved to that box later on. That arm is actually service part #5693754.

It is the original design arm for SOME 1964-65 Oldsmobile A-Body cars, SOME 1964 Buick A-Body cars, and ALL 1965-66 Buick A-Body cars. This arm was used with the corresponding center link that had “larger” diameter ball studs.

SOME 1964-65 Oldsmobile A-Body cars, and SOME 1964 Buick A-Body cars used the service part #5678345 arm. This was the same arm that ALL 1964-67 Pontiac A-Body cars used. This arm was used the the corresponding center link that had “smaller” diameter ball studs.

1964-67 Chevrolet A-Body cars used similar style arms with “smaller” and “larger” diameter ball stud holes, however they had different parts numbers as they were not made by Saginaw like the BOP arms.

Later on these original design arms were replaced with the newer 1967-68 (depending on division) design arms that incorporated a grease fitting as service parts.

BTW - All 1968-72 GM A-Body cars used idler arms with a “smaller” diameter ball stud hole.

[wmurrell]

Thanks for the great info!!

I was going to purchase the arm, until I noticed that the casting number was different and realized that it had the larger hole. I told the seller that I thought it probably was not the original box and was actually a different part number. He got nasty about it, so I just moved on.

[John V.]

Pontiac Marv, awesome detailed explanation!

I assume you could switch to the 5693754 if you also swapped to the larger dia. ball stud center link? Any reason to believe that the larger ball studs on the center link would be an upgrade for the '64/'65 Pontiac A bodies?

Kinda thinking not an upgrade if GM went exclusively to the smaller dia. ball stud center link for '68-'72. Then again, maybe the larger dia. ball studs were superior but GM opted for the smaller dia. as "good enough" at a lower cost?

[Aluminum Chief]

Box part # 7801909
Cast #7801910
Easy to recognize with the large silver nut on the bottom, most originals had this nut even early 60`s big car.
Fits 64-72 A Body as far as I know.

[6d7gto]

Originally Posted by Aluminum Chief

Box part # 7801909
Cast #7801910
Easy to recognize with the large silver nut on the bottom, most originals had this nut even early 60`s big car.
Fits 64-72 A Body as far as I know.

I have been researching this topic and am more mixed up now than ever. I have a 'Parts Wanted' thread: https://forums.maxperformanceinc.com...d.php?t=856109

The idler arm with the giant nut is not what I am finding on original 64-67 GTO'Tempests even though my parts book lists that number (GM# 7801909) as correct for 64-67.. The ones that were factory installed didn't have the grease fitting. I'm betting the original 65 did not come with that type idler arm. Needs more research.

[wmurrell]

I believe this is the correct idler arm for '65 & '66; not sure what other years it fits.

[6d7gto]

Originally Posted by wmurrell

I believe this is the correct idler arm for '65 & '66; not sure what other years it fits.

That's the one I believe to be the correct factory idler arm. Do you want to sell it? I will pay crazy money for it!

[Pontiac Marv]

The arm shown in post #7 is the original style 1968-72 Pontiac A-Body one.

The arm shown in post #9 is the original style 1964-67 Pontiac A-Body one.

The 1964-67 arm was discontinued by GM Parts in April 1968. The 1968-72 arm was then offered as a service replacement for the 1964-67 arm thereafter.

Although the arm designs are different, the two arms are completely interchangeable.

If one wanted to use a larger ball stud hole Chevrolet/Buick/Oldsmobile idler arm, a larger ball stud center link, and a larger ball stud hole steering box pitman arm would have to be used too. This would be only possible for a 1964-67 A-Body applications as there was no larger ball stud center link for the 1968-72 GM A-Body cars.

[wmurrell]

Originally Posted by 6d7gto

That's the one I believe to be the correct factory idler arm. Do you want to sell it? I will pay crazy money for it!

Already paid crazy money for it and do not want to sell it. I thought originally I was going to get another one for $150 and then realized it was incorrect.

[6d7gto]

Originally Posted by Pontiac Marv

The arm offered on eBay was either mislabeled originally, or it got moved to that box later on. That arm is actually service part #5693754.

It is the original design arm for SOME 1964-65 Oldsmobile A-Body cars, SOME 1964 Buick A-Body cars, and ALL 1965-66 Buick A-Body cars. This arm was used with the corresponding center link that had “larger” diameter ball studs.

SOME 1964-65 Oldsmobile A-Body cars, and SOME 1964 Buick A-Body cars used the service part #5678345 arm. This was the same arm that ALL 1964-67 Pontiac A-Body cars used. This arm was used the the corresponding center link that had “smaller” diameter ball studs.

1964-67 Chevrolet A-Body cars used similar style arms with “smaller” and “larger” diameter ball stud holes, however they had different parts numbers as they were not made by Saginaw like the BOP arms.

Later on these original design arms were replaced with the newer 1967-68 (depending on division) design arms that incorporated a grease fitting as service parts.

BTW - All 1968-72 GM A-Body cars used idler arms with a “smaller” diameter ball stud hole.

Researching using Ebay's advanced search with 5678345, I came up with at least two recently sold NOS Saginaw idler arms with that number:

https://www.ebay.com/itm/11508417354...p2047675.l2557

So I doubt both sellers mislabeled the boxes or moved them to those boxes later on. Odd thing is, I can't find that Saginaw part number (5678345) in my Pontiac parts book. Nor can I find the number you gave (5693754). The only numbers for 64-72 A bodies are 7801909 (which look totally different than the factory installed originals) which is for ALL 64-72 A bodies and part number 7801911 (68-72 All A bodies less support and bushing).

Very confusing. The NOS arms with the larger ball joint holes with same part numbers as the ones with the smaller holes (both Saginaw 5678345) are also totally different from each other. The arms themselves (smaller diameter arms with thlarger holes) and casting numbers are also different. Even though they will work as long as you use corresponding sized ball joint ends on the center link and Pitman arm.

[6d7gto]

Try this link:

https://www.ebay.com/sch/i.html?_nkw...ete=1&_fosrp=1

[gto4ben]

Found a 5678345 mentioned in 64-76 Olds MPC.

[6d7gto]

Originally Posted by gto4ben

Found a 5678345 mentioned in 64-76 Olds MPC.

Interesting. Notice the part #7801909 in your book infers that the support is part #5678345. I thought the support is the part that attaches to the vehicle frame. The ones that sold on Ebay are complete with joint, bushing and support included. Can these idler arm assemblies be dismantled and put back together with interchangeable components?

[gto4ben]

If you are referring to the acronym "SUP", I believe it is short for "supercedes".

[6d7gto]

Originally Posted by gto4ben

If you are referring to the acronym "SUP", I believe it is short for "supercedes".

My mistake. In my parts book it uses "less supt. and bushing". In closer look, yours says "sup" which now I realize means supercedes. That makes more sense! Thanks for the heads up!