[Badss540]

Hi guys, been here before but newly registered and hope you can help. I'm in need of finding radius rod bushings for my 67 firebird 400, it has both rods on it and it seems I can't find the factory style bushings for it,does anyone know where to get these or am I going to have to use polygraphite?? Thanks.

[69lm69gp]

Never heard of radius rod on a Firebird. I think you need to figure out the proper term for the part you are looking for.

[Badss540]

FYI that is the proper term. Maybe you need a link to it?

[69lm69gp]

Sure you do that.

[Badss540]

Here ya Go Chief, make sure to read it down to the PONTIAC section. Your Welcome-glad I could educate you

C R G CRG Reports Exterior Engine 1967 Model ID
Numbers Decode General Info Interior Transmission 1968 Model ID
Drivetrain Decode Options Underhood Chassis 1969 Model ID


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CRG Research Report


1967 Camaro Radius Rods

© 1998-2011, Camaro Research Group

Primary Author - Rich Fields, updated by Kurt Sonen
Reviewed by the CRG
Last Edit: 13-Oct-2011
Previous Edits: 23-Jan-2010, 21-May-2004, 08-Aug-2000, 18-Aug-1999, 23-Dec-1998
Original Release: 24-Sep-1998



Index
•Summary
•Design Problem
•Radius Rod Applications
•Chronological Data
•Parts Manual Data

Introduction
In mid-1967 model year, high-performance 1967 Camaros received a passenger-side traction bar, known as a "radius rod." There were two factory designs - the first design used a round rod while the rod in the second design was rectangular with increased stiffness. Additionally, later in the year, a rectangular rod service retrofit kit was made available to dealers to address wheel-hop complaints. The service kit could be applied either early vehicles with no rod at all or to vehicles with the round rod.

First Design - Round Radius Rod





Second Design - Rectangular Radius Rod


The question of which rod was applied to what model, and when, has often been a subject of much confusion. This report defines, as clearly as possible given the known data, the applications of each rod, and also discusses specific areas where data and information is lacking or weak. We encourage all 1967 Camaro owners with installed radius rods or rod brackets to please see the CRG Forum research post to contribute information about their vehicle, that we might continue to improve this report.



Summary
The overly-simplified summary of radius rod application is that starting mid-December 1966, cars with a 12-bolt axle received the round rod. After February 1967, cars with automatic transmissions and 12-bolt axles (L48/M35 and L35/M40) continued to receive a round rod, while cars with manual transmissions and 12-bolt axles received a rectangular rod. This is overly simple because there are two caveats:

1.The rectangular rod was not introduced to all manual transmission models at the same time, therefore some manual transmission cars continued to receive the round rod after other models had changed to the second design. The start date of the rectangular rod for each model is discussed below.

2.The L48/M35 car, while fitted with round rod brackets, did not always have the rod itself actually installed at the factory. Data to date indicates that only about one-third of this model have installed rods. No specific patterns of installation have emerged.
Table 1 illustrates, in a different format, these findings to date, model by model.


Table 1: 1967 Camaro Radius Rod Conclusions To-Date Application Early Use/Type
mid-Dec to Mar-Apr Late Use/Type
Mar-Apr to End-of-Model
L30 4-speed 1, 2 round (proven) rectangular (proven)
L48 3-speed round (proven) rectangular (assumed)
L48 4-speed 2 round (proven) rectangular (proven)
L48 Powerglide 3 round (sporadic) round (sporadic)
L35 3-speed rectangular (assumed) rectangular (assumed)
L35 4-speed rectangular (proven) rectangular (proven)
L35 TH400 round (proven) round (proven)
L78 4-speed N/A rectangular (proven)
Z28 4-speed 4 round (proven) rectangular (proven)
1.Introduction of the radius rod into the L30/M20 apparently lagged behind the L48 by about a month, not appearing until January/February, when the 12-bolt axle was introduced to the L30/M20 (see the L30/M20 CRG Research Report). Note that it appears that both the 10- and 12-bolt axles were used in L30/M20's in January.

2.The L30/M20 and L48/M20 transition to the rectangular rod appears to vary by plant. Norwood transtioned to the rectangular rods about 04A. There isn't enough data on Los Angeles cars to be certain, but it appears that the transition occurred later in April.

3.About one-third of L48/M35 cars have been noted with the round radius rod installed, while the remainder have the rod brackets but are absent the rod. No definite installation pattern has emerged.

4.Z28s used the rectangular bar starting in early March.




Design Problem
High-performance 1967 Camaros under heavy initial acceleration experienced a rear suspension problem called "wheel-hop" (or "wind-up"). This problem was accentuated by a combination of insufficient suspension stiffness about the axle centerline and insufficient suspension damping in the monoleaf spring/vertical shock system. High engine torque applied to the differential rotated the entire differential assembly about the axle transverse centerline toward the front of the vehicle and twisted the monoleaf springs into an "S" shape, until the torque broke the tires loose. With the tires off the ground the engine torque no longer applied a load to the deformed springs - with the result that the springs violently rebounded and forced the tires back on the ground, starting the cycle over again. This shuddering, traction-losing, U-joint-breaking, behavior repeated at high frequency until the driver backed-off the accelerator.
The temporary fix implemented by Chevrolet engineering during the middle of the 1967 model year (until the 1968 model year suspension changes were implemented) was a form of traction bar, known as a "radius rod." The radius rod was a single, end-hinged, rigid link between the passenger side of the rear axle and the chassis.





Floor mount, under the rear seat
The theory was that such a rod would allow an acceptable amount of vertical translation in the rear suspension, but resist rotation of the suspension about the axle centerline such as occurs when a large torque is applied to the driveshaft during a hard start. In practice the Chevrolet factory rod reduced, but did not eliminate, wheel hop, and therefore neither of the two Camaro versions of the radius rod were fully successful.
Both of the Camaro radius rod designs used a rigid steel rod with one end thru-bolted (hinged) to an axle bracket and the other end attached to a bracket bolted to the body (under the passenger-side rear seat). The first design was a round steel rod with a bushing at each end, part number 3914808. The second design improved upon the first and was a stiffer 1-inch by 1.25-inch rectangular rod, part number 3920234, with a modified axle bracket interface.

In the 1967 Camaro Assembly Manual, sheet B3 for RPO L48, dated 08-Nov-66, describes the first design version used with the round rod. The 07-Apr-67 revised sheet A8 for RPO L78 describes the second design version. The bracket welded to the rear axle was slightly modified for the 2nd design - it was wider with an extra hole added and the foward edge of the bracket was stepped. It is believed that all axle brackets were changed to the second design about the time the rectangular rod was introduced. A supplemental "stop" bracket that included a new rubber bumper was bolted to the bottom of the ears in the second design. For both designs, the body bracket was identical: part number 3914806. The body bracket was bolted to the rear frame rail and to the two studs that protuded through the floor.



First design axle bracket Second design axle bracket Sketch of second design axle bracket



Stop bracket for second design rod Stop bracket - installed

In contrast, the 1967 Pontiac Firebird included radius rods for both left and right sides of the axle on their higher performance models. The Firebird rod had an I-beam cross-section design (compare to the round or rectangular bars used on the Camaro). See Firebird rod - view 1 and Firebird rod - view 2 for pictures of the Pontiac-designed radius rod.

Radius Rod Applications
The first rod design was applied in mid-December 1966 to all models with a 12-bolt axle. This was expanded to the L30 275HP/4-speed model, when the 12-bolt axle was included in the L30/M20 in January / February. The second design rectangular rod was introduced in early February for the L35 big-block manual transmission applications, and was also applied to the L78/M21 from the start of that model in late March.
The replacement of the round rod with the rectangular rod on the Z28 appears to have occurred in March. The L48/M20 and L30/M20 cars transtioned to the rectangular rods about 04A at Norwood and later in April at Los Angeles (though the data on the Los Angeles cars is not definitive). Despite an assembly manual cancellation notice, the round rod remained in use for the rest of the year on L35/M40, as well as (sporadically) on L48/M35. GM documentation was used to derive these applications and actual vehicle data supports that information.

The one area of ambiguity is the L48/M35 model, which has sporadic radius rod application. There is no indication in the assembly manual that the traction bar was not applied to all SS-350 models, but other Chevrolet documentation indicate that it was not applied to the L48/M35 SS350/Powerglide combination. The CRG vehicle database provides insight in the actual usages. Of the approximately 100 L48/M35 cars built 012A or later for which we have rod-related data, 35% are reported with the round rod, and 5% with a rectangular (presumably) service retrofit. The remainder (60%) do not have a rod, but have one or more of the mounting brackets There is no obvious pattern of application. Even cars with optional performance axle ratios do not have the rod.

The rectangular rod documentation in the 1967 Assembly Manual was revised after initial release; CRG has only the revised version of this sheet and does not know what the initial release looked like. The 1967 Assembly Manual UPC L78 Sheet A2 table of contents lists the radius rod sheet in the initial release as for "RADIUS RODS" (note the plural). CRG speculation is that the initial release of this sheet included both round and rectangular rod configurations, and that the April revision to the sheet was for the purpose of eliminating the round rod configuration from this sheet.

Chevrolet Dealer Service Technical Bulletin 67-T-30, dated 12-May-67 (pdf file), indicates the round radius rod was actually implemented in production on 15-Dec-66. This same bulletin indicates that the second design went into production on 27-Mar-67. However, use in the L35/M20 pre-dates the production introduction date in the bulletin, since we have several L35/M20 datapoints from 02A to 03A, all of which have the rectangular rod.

It would appear that the 27-Mar-67 introduction date only applies to the L30 and L48 vehicles, which does match with vehicle data. The scope of Bulletin 67-T-30 is to specify retrofit instructions for the rectangular radius rod for L30 and L48 4-speed complaint vehicles, and therefore it makes sense that the information in the bulletin literally applies only to these vehicles.

Note also that Bulletin 67-T-30 includes a reference to "... vehicles built after December 15, 1966, with provisions for a radius rod." Note that this quote doesn't say "with a radius rod," but says with "provisions" for one - indicating that some vehicles had the brackets installed at the factory (the provisions) but without the rod in place.

A significant complication to the analysis of the radius rod applications is the rectangular radius rod service retrofit kit. This makes it a bit more difficult for us to be sure if a rectangular bar was factory installed or dealer installed. However, by comparison of the service replacement instructions with the original factory assembly instructions, it appears that there are three clues that should distinguish a service replacement rectangular bar from its factory brother:


1.When the service kit was applied to a car with no previous bar, the body bracket was welded to the body, rather than bolted-on as was done at the factory.

2.If the axle bracket didn't have holes to mount the stop bracket, the service kit required the bumper stop bracket to be welded to the axle bracket, rather than bolted-on as was done at the factory.

3.When the service kit was applied to a car with a pre-existing round bar, the round bar axle brackets were not replaced with the new brackets but remained on the axle and were used as-is. The two bracket types have distincly different shapes.

Supporting Data
Chronological Data
In chronological order, here is what is recorded in the 1967 Camaro Assembly Manual, 3891775, combined with information from Bulletin 67-T-30, and key datapoints from the CRG database:

Table 2: Chronological Documentation of Radius Rods Document
RPO Reference Status Date Notes
--- ---------- ------- ------- -----------------------------------

M40 67 AIM new dwg 26Aug66 M40 docs released include drawing with
M40 all radius rod ears on the axle indicating
that this change was contemplated even
at the beginning of production.

L48 67 AIM new dwg 08Nov66 L48 docs released for round rod
L48 B3 (1st design).

Z28 67 AIM new dwg 09Nov66 Z28 docs released referring to L48 for
Z28 A2 round radius rod.

L35 67 AIM new dwg 30Nov66 L35 docs released referring to L48 for
L35 A2 round radius rod.

--- Bulletin start 15Dec66 Round rod (1st design) usage started in
67-T-30 prod production.

L30 67 AIM rev dwg 16Dec66 L30 docs revised to add radius rod
L30 A2 reference to L48. This was never revised
to delete the reference.

--- CRG database December Several mid-December-built L48 cars have a
round radius rod. Usage is not consistent.

--- CRG database 01B 01B Z28 car with round radius rod.

L35 67 AIM rev dwg 08Feb67 Reference to L78 radius rod added to
L35 A2 existing reference of L48 rod.

Z28 67 AIM rev dwg 08Feb67 Reference to L48 radius rod changed to
Z28 A2 L78.

--- CRG database 02A Several 02A L35/M20s exist with
rectangular rods.

L78 67 AIM new dwg 17Feb67 L78 docs released with reference to
L78 all "RADIUS RODS"- plural. Only sheets
A1-A6 released on this date. Remainder
released 23-Feb-67.

L78 67 AIM new dwg 23Feb67 Remainder of L78 sheets released, incl.
L78 A8 sheet A8 with initial L78 radius rod(s).
Note that L35 and Z28 have already
released docs referencing this.

M40 67 AIM rev dwg 17Feb67 M40 docs revised to change M40 axle part
M40 A3 number from 3910882 to 3920569. If this
was for the purpose of using the rect-
angular rod axle brackets, it didn't
materialize in actual cars. Done same day
as initial release of rectangular rod.

--- CRG database 03B 03B Z28 with rectangular radius rod.

--- Bulletin start 27Mar67 Rectangular rod introduced on assembly
67-T-30 prod line. Scope of this bulletin may be
limited to L30 and L48.

L34 67 AIM new dwg 30Mar67 L34 docs released referring to L48 or L78
L34 A2 for radius rods. The L34 was not released
in 1967 despite this documentation.

L35 67 AIM rev dwg 06Apr67 L35 docs reference to L48 radius rod
L35 A2 removed, leaving only the L78 reference.
Despite this, all L35/M40 used the
round rod.

L48 67 AIM cancel 06Apr67 L48 docs cancel round rod design sheet
L48 B3 dwg for L48 (and, implicitly, for L30).
However the round rod continues in
production.

L78 67 AIM rev dwg 07Apr67 L78 docs for sheet A8 on radius rod
L78 A8 "revised and redrawn". New release
shows only a rectangular rod.






Parts Manual Data
Supporting data from Master Parts Catalogue 721A, Dec 1971, Section 5.415:

•L35, L78, and Z28 M/T cars initially had the round rod of PN 3914808.

•L35, L78, and Z28 M/T cars later had the rectangular rod of PN 3920234 (but superseded by another rectangular rod service part number).

•L30 and L48 4-speed, and L34 M/T engine used a 3920234 rectangular rod (but superseded by another rectangular rod service part number).
Note that the L34 was never released in 1967. L34 is not the only unreleased RPO to be mentioned in a GM manual.


•All engines with TH400 transmission used the round rod.
Despite assembly manual cancellation of the round rod, the parts manual appears correct on this point - M40 cars did use the round bar.


•Upgrade kits were part numbers 3929559 to update from round to rectangular rod, and part numbers 3929559 and 3929299 to add the brackets and the rectangular rod.
Note the absence of an upgrade kit to add the brackets and the round rod.


•No mention is made of the round rod on L30 and L48 4-speed applications.
CRG believes that Bulletin 67-T-30, forced the issue and caused all of these to be changed to rectangular rods in the event of a need for service.


•Small-block 3-speed standard transmission references are conspicuous by their absence.

•Powerglide transmission references are conspicuous by their absence.




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[69lm69gp]

Well I don't care what that guy calls it, you are talking about the factory traction bar.

Oh and I recomend the search function at the top of the page.

[Region Warrior]

Not sure what chevy called it, but Pontiac service and parts catalogs call it a radius rod.

[Badss540]

LOL, if i told you it was dark at midnight in kansas you'd disagree,lol please do yourself a favor and research before you respond.

[69lm69gp]

Originally Posted by Badss540

LOL, if i told you it was dark at midnight in kansas you'd disagree,lol please do yourself a favor and research before you respond.

Right back at ya' because I got a bunch of hits searching this board for "factory traction bar"

BTW my '67 Pontiac manual doesn't even have anything about the Firebird rear suspension at all.

And just show I am not a total A H o l e you might be able to make this Neoprene Spring Rubber work.

http://www.mcmaster.com/#rubber-hollow-rods/=n4ypqf

[Badss540]

Thanks but I ordered a set that I hope works today from a lead that Hammered had posted

[Rocky Rotella]

Badss540,

We replaced the radius rod bushings in our '67 Firebird using polyurethane units from PST. Pressing them in was more challenging that I expected, but it wasn't something that was impossible.

http://www.highperformancepontiac.co.../photo_12.html

[Region Warrior]

Originally Posted by 69lm69gp

Right back at ya' because I got a bunch of hits searching this board for "factory traction bar"

BTW my '67 Pontiac manual doesn't even have anything about the Firebird rear suspension at all.

And just show I am not a total A H o l e you might be able to make this Neoprene Spring Rubber work.

http://www.mcmaster.com/#rubber-hollow-rods/=n4ypqf

That's because there where supplemental FB body and chassis manuals.

[dlarkins]

Looks to me like BADss540 needs a RADIUS ROD ADJUSTMENT...

Look dude, whoever or whatever you are...

You come onto our forum, asking for help, and this is how you treat our family ? I say, I say boy, ya'll about as sharp as a bowling ball...

I'll go out on a limb and speak for the Membership at large, go back under your primeval ooze rock, cave, or whatever dark place you were hatched, and take your Radius Rod and stroke it...

Tools like you aren't needed here. Right out of the gate, you're downright ignorant, mean, impolite, and severely disrespectful, to good folks you've never even met ?

Go away....far far away....

Or learn to play nice with others...

[Badss540]

Originally Posted by dlarkins

Looks to me like BADss540 needs a RADIUS ROD ADJUSTMENT...

Look dude, whoever or whatever you are...

You come onto our forum, asking for help, and this is how you treat our family ? I say, I say boy, ya'll about as sharp as a bowling ball...

I'll go out on a limb and speak for the Membership at large, go back under your primeval ooze rock, cave, or whatever dark place you were hatched, and take your Radius Rod and stroke it...

Tools like you aren't needed here. Right out of the gate, you're downright ignorant, mean, impolite, and severely disrespectful, to good folks you've never even met ?

Go away....far far away....

Or learn to play nice with others...

your funny, i'd reply different if I didn't think you'd hold your breath and stomp your feet. I asked a question and got an answer that tried to correct what was already ready right by someone that was off base. As for you GFY

[Region Warrior]

dlarkins...sure your beef isn't with someone else?
Don't see anything wrong with badss540's posts.

[Region Warrior]

Originally Posted by Rocky Rotella

Badss540,

We replaced the radius rod bushings in our '67 Firebird using polyurethane units from PST. Pressing them in was more challenging that I expected, but it wasn't something that was impossible.

http://www.highperformancepontiac.co.../photo_12.html

OH NO, even HPP is wrong lol.

[Badss540]

Would like to thank Hammered for the lead to get the Radius Rod bushings from PST, they came in UPS today and I pressed them in- on to the next item.

[ANDYA]

Originally Posted by Region Warrior

dlarkins...sure your beef isn't with someone else?
Don't see anything wrong with badss540's posts.

I would agree, nothing wrong with those posts.

BTW, my friend was the original owner of a 67 Bird that I now own and back in the 70's he would refer to the factory traction bars as radius rods.