Rear cross member frame cushion

[Zeke68]

In the process or replacing my trailing arms I also am replacing the frame cushions. I have them out but the nuts up in the sombrero are bad. The previous owner tried to helicoil them and did a poor job. I was wondering if anybody had any secrets to removing the sombrero without damaging the frame gusset. It appears to be spot welded from the top and would be easy to drill out if the body were removed. The problem with drilling the spot welds from the bottom is there are no markings to show where the spot welds are and it would be hit or miss. The frame gussets are in excellent shape and I wanted to try not to damage or replace them if possible. The previous owner or owners really cobled up the rear end of this car, I think they spent more time doing the job wrong then it would have been to do it right the first time.

 

[JohnZ]

As I recall, there are 8 or 9 spot welds between the "sombrero" and the frame gusset - could be really messy trying to chisel it off. You might be better off to cut the bottom 1" or so of the "sombrero" off with a cutting wheel, remove the old nut and weld in a new one, and weld the piece back on; easier than pulling the body.

 

[slischyn]

These aren't spot welds, these are plug welds. brackets have holes in them. These are welded in from the top.

I can't imagine how you would weld the sombrero in without taking the body off. I recently did a lot of work on my frame including this area.
The way I did it was:

-with the frame upside down, install both sombreros in the differential x-member, place this assembly on the frame brackets. Align the differential x-frame with the centerline of the frame and square up the diff x-member. This insures that both sombreros on not fighting each other.

-Tack weld the somberos onto the frame brackets. Then remove the diff x-member

-Flip the frame right side up and plug weld the somberors in place.

As you can see, this would be impossible with the body on.

The frame bracket is welded on the top all around. If you cut it out your gonna have problems welding it back. You could weld it from under neath but then your putting the weld under tension. The top weld is under compression.

If you can get a sample of the frame bracket you will see where the holes are for plug welding but I thing you might find it easier just to take a grinder or whatever, and just nibble out the old sombrero and buy a new one. Be careful not to damage the frame bracket, it is just thin piece of sheetmetal. It's actually amazing that it holds up the entire rear end.

You could drill out some holes in the new sombrero for plug welding from the bottom. I don't remember how many holes there are but it is between 5-10 holes.

When installing the new sombrero, there is no alignment features. You will need to put the sombrero into the x-member, then clamp this assembly in place using the opposite sombrero for alignment. Make sure the x-member is square. Then tack weld the sombrero in place. Remove the x-member. Then plug weld the sombrero in place from the bottom. Smooth out the plug welds since the rubber rides on this surface.

I don't know if anyone has done it this way, so you should check with other members and other forums. There might be a better way of doing this. There might be some problems in doing it this way that I can't think of at the moment

Steve L
73 coupe since new

 

[Zeke68]

Thanks for the ideas guys, I think this is going to be a challenge. I'm contemplating heating the brim of the sombrero enough to be able to roll it back to the weld locations and use a small grinding wheel to separate the weld. I have several other fixes to work on while I think this one over a little more. I think the prvious owner must of had a deluxe air wrench and over torqued everything he worked on. I have found several areas with stripped threads.

 

[slischyn]

Are you concerned about originality...if not...how about just welding in a stud into the sombrero nut, then just putting a nut on after the x-member is in place.

Or

use a Dremel and cut two deep slots in an X shape at the bottom sombrero surface right thru the nut. Then peel back the metal, take out the nut pieces, put in a new nut, bend the peel back and weld the slots and new nut back. Then grind the weld flush. This might be the easiest. I would hate to destroy the sombrero to frame bracket integrity. Your sombrero and frame bracket look in excellent shape. You may only have to peel back 1 or 2 of the 4 leaves to get the old nut out and a new nut back. Again, I've never done this but it gives you more ideas.

Steve L
73 coupe since new

 

[Hib Halverson]

Or....you could try to repair the threads with a Time-Sert kit which is a much more robust repair than a helicoil.

With the Time-Sert, you drill the existing hole out. You thread it for the insert which has an I.D. threaded the same as the original hole. You install the insert using a special tool which comes with the kit. The very last part of the installation procedure locks the insert in the hole. Then you but the cross member back in place using the OE bolts which go into the new, Time-Serted hole.

 

[Bill75]

Or....you could try to repair the threads with a Time-Sert kit which is a much more robust repair than a helicoil.

With the Time-Sert, you drill the existing hole out. You thread it for the insert which has an I.D. threaded the same as the original hole. You install the insert using a special tool which comes with the kit. The very last part of the installation procedure locks the insert in the hole. Then you but the cross member back in place using the OE bolts which go into the new, Time-Serted hole.

Very interesting..never heard of Time-Sert. I did a little research and found this guys post on a fix he did. Looks real nice. Thanks for the tip on them, they look more robust than a HeliCoil.

Pics of Time sert install - ADVrider

 

[Zeke68]

Thanks Hib,
I had not heard of time sert either, my only question is will the somberero nut hold up. I assume it would have to be drilled out to have the insert put in. Also where is a good source to buy the time sert.

 

[slischyn]

Hib's idea looks the best and easiest so far.

Steve L
73 coupe since new

 

[Hib Halverson]

Thanks Hib,
I had not heard of time sert either, my only question is will the somberero nut hold up. I assume it would have to be drilled out to have the insert put in. Also where is a good source to buy the time sert.

I'm not sure where in your area you could find a Time-Sert kit but Time Fastener Co. has a web site at:www.timesert.com/

That site or their customer service phone number may be good resources with which to find retail location or distributor info. The may even sell on-line.

 

[Zeke68]

Thanks again Hib and Bill for the website, I hope this will do the trick untill I can do a frame off and replace the sombereo. I have a son and daughter in college and had to postpone my frame off for now.

 

[Bill75]

I have a son and daughter in college and had to postpone my frame off for now.

I am very familliar with that mode, it's the same as buying a new BMW every year and never seeing it.:eyerole

Good luck with the project