Exhaust hanger design makes no sense to me

After all my complete drivetrain build this winter in our 96 RMW, it was getting to point of running very well, reprogramming to get rid of dash lights and some shiftpoint adjustments plus all of the deletes I did were complete.  Had a bunch of trans cooler hose issues but that got straightened out.  Then all of sudden it got really loud exhaust noise as in "big leak".

I was immediately suspect of the EGR delete kit that had a gasket for the cover on the R/H exhaust manifold that looked like it could not take the heat, but I had contacted the seller and was told it was 800*F silicone/ceramic material so put it in.  Another lying ebay Asian ebay seller it appears. Tough application as it has only one bolt alongside of the cover so almost a toilet lid design with a bolt down.

Anyhow, dug out the mirror and could see the gasket was totally gone in 100 miles and cover rotated completely off the .6" diameter hole in the manifold.

In the process of removing the manifold I noticed again something that bothered me when I put it all back together again. The headpipes are supposed to be bolted solid to the transmission case.  I had left that support off because it didn't seem right to have that way.

The engineer side of me (yeah, yeah, but it is decades pounded in) knows that you don't make a rectangular box solid when one side of it is going to get very, very much hotter than the opposite side and expand more, because things break or bend.  The headpipes have the engine heat going in and then make it even hotter in the cats so they will expand plenty fore and aft.  Add this to the fact that these engines tend to have rear of the exhaust manifold leaks and bolt breakage and it sure looks like the solid mounting could cause the problems or at least make them more likely to happen or worse when they do happen.

I intend to make a new hanger system for that area that allows for some movement to take the strain off the manifold bolts, probably with rubber bushings or hangers, but maybe sliding pins in bushings.

Has anyone done such a thing or just left off the support at that area like I have it now?  In the 200+ miles I have put on it now it doesn't seem to have had any ill effects as the spherical joints haven't sagged at all. If the drawings are accurate it looks like a lot of the aftermarket cat back systems don't support there at all.

Here is the parts breakdown from the factory service manual showing how it put together, including the massive damper weights they used.

All the T56 swap cars, the owners ditched the rear support. Clear Image headers also do away with the rear support. Personally I'd rather support it there given the length of the exhaust that's now hanging on the exhaust manifold bolts, but that's me.

In all the B-bodies I've worked on, I've NEVER seen the damper on the driver's side. Ever.

The 91-93 cars had a "hook" on the back side of the muffler that slides into a rubber slot on the rear muffler support. You could get two of them from a couple of 91-93s, and mount them on the holes already there on the frame. The muffler shop I went to put a 1/4 inch rod hook on the back of the muffler to allow them to hang from the mounts.

Fred Kiehl wrote:

The 91-93 cars had a "hook" on the back side of the muffler that slides into a rubber slot on the rear muffler support. You could get two of them from a couple of 91-93s, and mount them on the holes already there on the frame. The muffler shop I went to put a 1/4 inch rod hook on the back of the muffler to allow them to hang from the mounts.

Are you talking about using them on the transmission to exhaust pipe mount that is far forward from the mufflers? That mount doesn't go to the frame of the car.

sherlock9c1 wrote:

All the T56 swap cars, the owners ditched the rear support.  Clear Image headers also do away with the rear support. Personally I'd rather support it there given the length of the exhaust that's now hanging on the exhaust manifold bolts, but that's me.

In all the B-bodies I've worked on, I've NEVER seen the damper on the driver's side. Ever.

I agree with supporting it and that is why I have the plans to make a compliant mount so the thermal expansion can't put a big load on the manifolds. My guess would be the thermal load is probably at least as high as the weight from the pipes an a small part of the muffler weight, but can't possibly know for sure. Some vehicles used to use a pipe support up close the manifold that would go to the engine someplace, typically the bell housing bolts. I haven't seen any like that in a very long time though.

booster wrote:

Fred Kiehl wrote:

The 91-93 cars had a "hook" on the back side of the muffler that slides into a rubber slot on the rear muffler support. You could get two of them from a couple of 91-93s, and mount them on the holes already there on the frame. The muffler shop I went to put a 1/4 inch rod hook on the back of the muffler to allow them to hang from the mounts.

Are  you talking about using them on the transmission to exhaust pipe mount that is far forward from the mufflers?  That mount doesn't go to the frame of the car.

The mounts are on the rear of the muffler which could be considered the back side. It would attach to the frame in front of the rear axle.

Fred Kiehl wrote:

booster wrote:

Fred Kiehl wrote:

The 91-93 cars had a "hook" on the back side of the muffler that slides into a rubber slot on the rear muffler support. You could get two of them from a couple of 91-93s, and mount them on the holes already there on the frame. The muffler shop I went to put a 1/4 inch rod hook on the back of the muffler to allow them to hang from the mounts.

Are  you talking about using them on the transmission to exhaust pipe mount that is far forward from the mufflers?  That mount doesn't go to the frame of the car.

The mounts are on the rear of the muffler which could be considered the back side. It would attach to the frame in front of the rear axle.

Thanks Fred, but the factory mount of two rubber links is working fine, I am concerned about the one on the transmission case to exhaust.

For what it's worth, I'm with you. When I reinstalled all of the stock exhaust manifolds and catalytic converters on my Impala, they were under tremendous compression between the manifold and the rear transmission brace. So I loosened all the exhaust manifold bolts and let the manifolds move to release some of the compression, but it was still in compression.

sherlock9c1 wrote:

For what it's worth, I'm with you. When I reinstalled all of the stock exhaust manifolds and catalytic converters on my Impala, they were under tremendous compression between the manifold and the rear transmission brace. So I loosened all the exhaust manifold bolts and let the manifolds move to release some of the compression, but it was still in compression.

I have that on the  driver side even with transmission hanger disconnected, so coming from further back, but at least it is rubber mounts there. On the passenger side it is in tension so just the opposite.