[Tom Vaught]

They are two different lengths for the uppers

S280 for the 64-67 A-Body vehicles and S282 for the 68-72 A-Body vehicles.

If they do not fit the 68 chassis then they are for the 64-67 vehicles. Hard to argue when they do not fit.

Tom V.

[AG]

What's the difference in length between the 64-67 and 68-72?

[Tom Vaught]

Originally Posted by bulletpruf

No, I'm pretty sure I pulled them off a 68-70 parts car years ago.

Thanks

OK, I went thru some of my suspension stuff tonight and located my spare set of 64-67 upper rear cross-member braces.

The dimensions are for a 64-67 chassis:

The measurement was using a flexible tape measure.
Should be accurate with-in .050" on the length of the braces.
You were talking a inch too short in your posts.

The Brace has a Fat end and a Skinny end.

Measuring from the Skinny end hole centerline to the Fat end hole centerline
on the "closed" side of the brace. Do not measure across the open side of the brace so we are both measuring the same. Also really easy to do the closed side measurement.

Center of the "small end" hole to the center of the "large end" hole is exactly 13.5" for the 64-67 chassis. SO WHAT IS YOUR DIMENSION? BULLETPRUF? The 68-72 reinforcements are 1" shorter in length roughly. Maybe 12.5 inches doing the same measurement.

Since you could not install them and assume they are on a bench or storage race somewhere, easy to see if they match the 64-67 length.

Tom V.

[Singleton]

The 68-72 braces would be approximately 1” LONGER, than the 64-67 braces wouldn’t they?

68-72 upper control arms are shorter than 64-67, but lower control arms are same length 64-72, so that would mean the upper crossmember is further rearward on 68-72 than 64-67, requiring a longer brace between upper and lower arm attaching points.

[bulletpruf]

Fellas -

Measured and mine are 15.5" - measured from center bolt hole to center bolt hole on the inside.

Does anyone have any 68-72 braces that they could check length on?

Thanks

Scott

[Tom Vaught]

The measurement was using a flexible tape measure.
Should be accurate with-in .050" on the length of the braces.
You were talking a inch too short in your posts, I believe
Bottom line from above.

That would make them 64-67 braces where he said that they were 68 braces but did not fit (he says he took them off a 68 vehicle). I say it was some sort of 64-67 vehicle part that he has.

We are both saying the same thing.

Measure on the outside please.

Tom V.

['ol Pinion head]

Originally Posted by bulletpruf

Fellas -

Measured and mine are 15.5" - measured from center bolt hole to center bolt hole on the inside.

Does anyone have any 68-72 braces that they could check length on?

Thanks

Scott

Will ck, have several pairs.

['ol Pinion head]

Same dimension, aprox 15.5" from center of round hole to center of the long oval hole.
laying flat on steel rule with round hole end down, overall total length appears to be 16 3/4"

FWIW, the very late '65-67 style of braces were much harder to find used.

[bulletpruf]

Originally Posted by 'ol Pinion head

Same dimension, aprox 15.5" from center of round hole to center of the long oval hole.
laying flat on steel rule with round hole end down, overall total length appears to be 16 3/4"

FWIW, the very late '65-67 style of braces were much harder to find used.

Thanks, Roger!

[Tom Vaught]

Some additional info on the 65-67 parts:

PONTIAC SERVICE NEWS FLASH Date 6-24-65
File Ref:1A
No: 65-108

SUBJECT: Tempest GTO Rear Crossmember Reinforcement Brackets


Two reinforcement brackets,#3869875 (F) left side,and 3869876 (F) right side have been released for all GTO Tempests with manual transmissions.These reinforcement brackets are designed to provide extra rigidity and improved load distribution in the frame rear cross-member and lower control arm area.

It is recommended that (not exact wording) the brackets be installed on any GTO brought in for repair of this area.
(At the owner's expense).
The brackets attach between the frame rear x-member and lower control arm bracket on each side, (utilizing the forward upper and lower control arm attachments).

CAUTION:CHECK FOR PROPER BRAKE LINE CLEARANCE BEFORE INSTALLATION

Installation of reinforcement brackets on cars in SEVERE SERVICE (underlined on memo, my copy) should be handled as owners responsibility and expense.

THEY ARE BOLTED ON_NO WELDING !!!!!!!!!

Tom V.

[OG68]

oh, this one...

[Tom Vaught]

Thanks for the actual document Ed, Yep! That is the one.

Tom V.

[Skip Fix]

I had a guy I knew who ran the speed shop I bought parts at in Dallas that raced a M/P 65 Chevelle with a big block Eddy crossram big slicks "spin" and break the mounts as he did not have those.

[Tom Vaught]

Same deal Skip, 64 GTO Race Car Guy in college (with a 396/375 engine) tore out the upper rear portion of the frame on the passenger side.

Tom V.

[amcmike]

Run the larger front sway bar and a rear bar. Upgrade the shocks with double adjustable Vikings. Make sure to mount the shocks so it's easiest to reach the adjustment dials. At the strip, start with dialing in the fronts stiff compression/soft rebound' the rears opposite. Then fine tune for best launch. Here's some additional information: https://www.onallcylinders.com/2013/...g-race-shocks/

For the street, redial them more evenly for compression/rebound based setting the front versus rear based on your individual tastes for combination of handling and ride. Here's some information on dialing in settings more related to handling : https://www.turnology.com/tech-stori...our-lap-times/

[TCSGTO]

Looking at these braces and how they are mounted and oriented, would the aftermarket tubular versions really offer any more support than the stamped steel factory ones?

[Tom Vaught]

Only advantage of the adjustable ones is that you can install the parts on a vehicle that already has some twist on the rear cross member and bring the rear axle/driveline somewhat back to the factory position. Or not let it get any worse.

Think that is what the factory stuff basically did, keep the M/T cars from failing the frame cross-member.

Tom V.

[tjs72lemans]

Due to the shock loads of manuals, I assume this is not relevant for an auto tranny ?

[AG]

Originally Posted by TCSGTO

Looking at these braces and how they are mounted and oriented, would the aftermarket tubular versions really offer any more support than the stamped steel factory ones?

I think so since the tubular aftermarket braces on my '65 are a lot more robust than the factory stamped versions.

[OG68]

Originally Posted by tjs72lemans

Due to the shock loads of manuals, I assume this is not relevant for an auto tranny ?

It started out that way. High HP manual transmission cars were the first to have the braces. Then over the years automatics, El Caminos, anything with a larger than stock V8, had them. Guess GM figured it was cheap insurance to prevent frame damage.