64 rear end mystery part

[SnikPlosskin]

I’m rebuilding the rear end in my quest to get the 64 back on the road after sitting for six years. Lots of upgrades and refinement including the biggest Mickey Thompsons that will fit.

However I removed the spring and found what appears to be a DIY spacer between the strut rod bracket and the differential (which is getting rebuilt).

I assembled this 25 years ago but I didn’t make that spacer. I think it was in there and I just put it back. The AIM doesn’t show it so I think bubba was here.

Question. What purpose could that be serving? Would it raise the ride height in the rear (an issue ever since I went to composite spring.) It’s about a 1/2” thick.

I want to lower the rear about 1/2” and I’m guessing somebody put that in there to correct sagging steel springs. But I’m unclear on the geometry. It seems like adding space above the spring would raise the car.

[Torqaholic]

Might be there to give the muffler pipes clearance over the axle?

[Yadkin]

Back in the day raising the rear end was a thing. Maybe for that?

[Black94lt1]

I’m guessing to offset the spring sag as you mention.

[Don Rickles]

Originally Posted by SnikPlosskin

I’m rebuilding the rear end in my quest to get the 64 back on the road after sitting for six years. Lots of upgrades and refinement including the biggest Mickey Thompsons that will fit.

However I removed the spring and found what appears to be a DIY spacer between the strut rod bracket and the differential (which is getting rebuilt).

I assembled this 25 years ago but I didn’t make that spacer. I think it was in there and I just put it back. The AIM doesn’t show it so I think bubba was here.

Question. What purpose could that be serving? Would it raise the ride height in the rear (an issue ever since I went to composite spring.) It’s about a 1/2” thick.

I want to lower the rear about 1/2” and I’m guessing somebody put that in there to correct sagging steel springs. But I’m unclear on the geometry. It seems like adding space above the spring would raise the car.

What's the part number on it?

[SnikPlosskin]

Originally Posted by Torqaholic

Might be there to give the muffler pipes clearance over the axle?

The car did have exhaust out the back when I got it.

Originally Posted by Yadkin

Back in the day raising the rear end was a thing. Maybe for that?

It does have hogged out rear fenders so methinks somebody put big tires on the rear. But I’m not sure you’d get much lift from a block.

Originally Posted by Black94lt1

I’m guessing to offset the spring sag as you mention.

I’m thinking that too. Same principle if you lift a truck, right?

The spacers go between the body and the spring u bolts. This would place the springs center lower -pushing down on the spring ends. Assuming the car is on the ground, this pressure on the ends (like tightening the nut on the long bolts) lifts the body.

At least that’s how it works in my brain. Can anyone confirm?

The steel spring was totally clapped out.

Originally Posted by Don Rickles

What's the part number on it?

I’ll see if I can discern it. It’s punched into it and a bit scratched. I’ll get a photo and see if I can bring it out through the magic of photoshop

[GTOguy]

If the diff third member housing bolts to that spacer, it will lower the ride height. (raise the wheels upward closer to the floor of the car). Just like lowering blocks on conventional leaf sprung cars. At least that's what it looks like from what I can see.

[JRD77VET]

Originally Posted by GTOguy

If the diff third member housing bolts to that spacer, it will lower the ride height. (raise the wheels upward closer to the floor of the car). Just like lowering blocks on conventional leaf sprung cars. At least that's what it looks like from what I can see.

It would lower the ride height.

[Mike Mercury]

Originally Posted by Don Rickles

What's the part number on it?

[Rodnok1]

Took me a while Butner I knew I'd seen them in person installed.

https://www.globalwest.net/63-64-65-...rods-leaf.html

[SnikPlosskin]

I just remembered what it is. It corrects the geometry on the strut rods dropping the center mount down.

I’m not sure what the differential third member is?

This spacer goes on he top of the strut rod bracket that is bolted to the bottom of the diff.

I think you are saying that the diff is attached to the frame via crossmember. So it would lower the rear. Which is good. Maybe I should have a 1” block machined. It’s just aluminum with holes.

I’m dropping the differential too. My crossmember won’t budge. Bolts are out but it won’t drop down.

[SnikPlosskin]

Originally Posted by Don Rickles

What's the part number on it?

593-092

[SnikPlosskin]

Just ordered a 1” block of aluminum. I’ll drill the holes. It seems nobody sells the block. I already have aftermarket adjustable struts so I don’t need the whole kit. If it lowers the rear, another half inch will be perfect.

[Sea Six]

Originally Posted by SnikPlosskin

593-092

583

Not 593

[zeek]

Could also be used to adjust the pinion angle.

[GTOguy]

Originally Posted by zeek

Could also be used to adjust the pinion angle.

It will for sure change the pinion angle. Likely not for the better, if far from stock.

[SnikPlosskin]

Originally Posted by GTOguy

It will for sure change the pinion angle. Likely not for the better, if far from stock.

.

It does change the angle. One reason these cars have so much oversteer is that the camber changes as the rear trailing arm travels - a lot.

Check out the video in post 10.

They measure the camber change on an alignment rack as they raise and lower the body Putting the rear arms through their travel.

The block drops the angle down so the camber barely changes (it still changes but much less) resulting in more tire on the ground during acceleration, braking and cornering.

Now that I remember why that block is in there I remember being shocked at the oversteer of the car. Adding that block really helped.

Now I want to see if I can get the rear end down just a bit. I’m using the longest bolts that are safe and they are at the end of their adjustment.

Because the car has the infamous hogged out fender wells, even with these big tires it looks high. Although that is more from the composite spring. They seem to sit higher in my experience - probably because they weigh a fraction of the steel spring.

If I don’t like the handling, it’s easy enough to remove the block, replace with the 1/2” block or go au natural.

I want the car level. The car handles really well. But dang it, my brain says it should be level.