70 front shock top hole diameter and repair

[Bill L.]

What is the correct diameter of the hole in the front shock tower?

Did the holes have any type of pressed in washer? Both sides appear to have a steel insert pressed in from the bottom. (Alan pointed out the steel insert today)

How closely did the top rubber bushing bottom diameter match the hole in the tower?

I need to repair the damaged hole on the passenger side too.

Thanks,


Bill

PS Upper Shock Hole 2.jpg

[Paul O.]

Re: 70 front shock top hole diameter and repair

Bill

The original bushing called a grommet was P/N 3790341 there were discussions on this part before. Type the part # in the search box at the top right of this page and you will get more answers. That bushing/grommet was much larger then the replacements that came with new shocks. The bottom bushing/grommet P/N 3708378 was of the standard size of replacement shock bushings and also was used on the sway/anti-roll bar. As far as the hole opening size I do not have an answer.

[Bill L.]

Re: 70 front shock top hole diameter and repair

Bill

The original bushing called a grommet was P/N 3790341 there were discussions on this part before. Type the part # in the search box at the top right of this page and you will get more answers. That bushing/grommet was much larger then the replacements that came with new shocks. The bottom bushing/grommet P/N 3708378 was of the standard size of replacement shock bushings and also was used on the sway/anti-roll bar. As far as the hole opening size I do not have an answer.

Thanks Paul.

I have the correct larger grommet for the top. I am really curious about the steel insert and hole diameter and how that larger bushing fit in the correct hole.

Bill

[Paul O.]

Re: 70 front shock top hole diameter and repair

Bill

A good guess on the holes diameter maybe by measuring the bushing/grommets rubber alignment ring would be slightly smaller the the hole.

[Bill L.]

Re: 70 front shock top hole diameter and repair

Bill

A good guess on the holes diameter maybe by measuring the bushing/grommets rubber alignment ring would be slightly smaller the the hole.

I kinda thought the same thing yet the grommet is pretty loose in the good hole on the driver's side.

Did the factory use a steel insert in the holes?

Thanks,


Bill

[Paul O.]

Re: 70 front shock top hole diameter and repair

Bill

It has been a few years since I restored a frame but I do recall that a separate steel sleeve was pressed or somehow attached at the shock mount.

[Alan S.]

Re: 70 front shock top hole diameter and repair

Hi Bill,
The shock seats in my 71 frame are tight on both right and left sides.
I can only estimate the size of the hole in the frame… 13/16".
If you order the new seat you'll need, won't you know for sure the size of the hole required (and the amount of repair you'll need to do) when the new seat is in hand?
You can see in the third pic the underside of the seat is very much cup shaped.
Regards,
Alan

[Bill L.]

Re: 70 front shock top hole diameter and repair

Perfect! Thank you Alan.

I have since found out that somewhere around 1965, the seat was installed from the top.

Now I need to try and figure out how to crimp the seat in place. I ordered today based on the source you suggested

How tight does top grommet fit in the seat? I am guessing when tightened down the grommet expands quite a bit.


Bill

[Alan S.]

Re: 70 front shock top hole diameter and repair

Hi Bill.
I don't see any way the seats in my 71 frame could have been installed from the top.
The outer diameter of the 'cup' is between 1-1/8" and 1-3/16", so won't fit through the hole in the frame. I can't tell the size for sure because I can't get enough fingers in there to measure it accurately.
Yes, when you tighten the upper shock mounting nut the upper and lower bushings expand quite a bit. The upper bushing does fit snuggly in the seat, but it only takes slight pressure to push it in place.
Just a minor detour for you!!!!
Regards,
Alan

[Bill L.]

Re: 70 front shock top hole diameter and repair

Hi Bill.
I don't see any way the seats in my 71 frame could have been installed from the top.
The outer diameter of the 'cup' is between 1-1/8" and 1-3/16", so won't fit through the hole in the frame. I can't tell the size for sure because I can't get enough fingers in there to measure it accurately.
Yes, when you tighten the upper shock mounting nut the upper and lower bushings expand quite a bit. The upper bushing does fit snuggly in the seat, but it only takes slight pressure to push it in place.
Just a minor detour for you!!!!
Regards,
Alan

By chance is this the original bushing on top? I am wondering if it had already expanded from having been installed. The bushing I have moves around in the seat. Mine is not a GM bushing.

Thanks, Bill

[Joe L.]

Re: 70 front shock top hole diameter and repair

By chance is this the original bushing on top? I am wondering if it had already expanded from having been installed. The bushing I have moves around in the seat. Mine is not a GM bushing.

Thanks, Bill

Bill------

I'm having a difficult time here with terms. The GROMMET is the rubber part which goes on top of the shock absorber and which lower end has the extension which fits into the hole in the frame bracket (pictured in your original post).

The WASHER or RETAINER is the convex shaped part which installs on top of the GROMMET and is retained by a nut which threads onto the shock shaft.

The part which installs into shock rod hole in the frame bracket I would describe as an INSERT. That may or may not be the term which GM uses to describe the part. I can't determine what term GM uses because I cannot find that this part was ever available from GM in SERVICE. In fact, I do not know of a source for it. However, if one could obtain one I think it could be installed with a flaring tool, perhaps modified for the application. A cheap flaring tool should work fine.

The GROMMET, as-installed, does not fit tightly into the frame bracket hole but upon compression of the WASHER I'm sure it expands to fill the hole. That would not require much expansion, at all.

[Bill L.]

Re: 70 front shock top hole diameter and repair

Bill------

I'm having a difficult time here with terms. The GROMMET is the rubber part which goes on top of the shock absorber and which lower end has the extension which fits into the hole in the frame bracket (pictured in your original post).

The WASHER or RETAINER is the convex shaped part which installs on top of the GROMMET and is retained by a nut which threads onto the shock shaft.

The part which installs into shock rod hole in the frame bracket I would describe as an INSERT. That may or may not be the term which GM uses to describe the part. I can't determine what term GM uses because I cannot find that this part was ever available from GM in SERVICE. In fact, I do not know of a source for it. However, if one could obtain one I think it could be installed with a flaring tool, perhaps modified for the application. A cheap flaring tool should work fine.

The GROMMET, as-installed, does not fit tightly into the frame bracket hole but upon compression of the WASHER I'm sure it expands to fill the hole. That would not require much expansion, at all.

Hi Joe,

I think I may be the cause of the confusion. My terminology was not clear.

There is a steel insert that is crimped in place. Alan found one at a vendor and was kind enough to pass the info on to me. It looks to install from the bottom. I will try and use a dremel and make a series of small cuts so the crimp can be bent up to remove damaged insert. Then I will look at how much metal has been removed/damaged from the shock tower to see if it is worth welding in replacement metal. It makes me REALLY nervous to weld in that spot with the body on and the engine compartment intact.

The grommet is the rubber piece that fits in the hole and has the oversized washer on top to compress the grommet when tightened. I have a grommet and it appears to closely match the factory grommet. It does fit loosely as you say. The grommet is listed in the AMK catalog under the correct GM # 3790341.

Kindest Regards,


Bill

[Alan S.]

Re: 70 front shock top hole diameter and repair

Hi Bill,
Here are the original front shock grommets from my 71. I'm still using them.
You can see the upper (larger) grommet has a lip on it that fits quite a distance down into the seat.
The lower grommet is really positioned by the shock's rod and the 'cup' of the seat because it shows much less 'lip'.
Hope these help.
Regards,
Alan

Large grommet is 1-1/2" and small grommet is 1-1/8". I'd think these have 'expanded' and 'flattened' some from use.
First pictures shows them as installed.
Third picture shows the side of each grommet that was against the seat when installed.
Second picture shows the lip of each grommet that slipped into the seat.

[Bill L.]

Re: 70 front shock top hole diameter and repair

Hi Bill,
Here are the original front shock grommets from my 71. I'm still using them.
You can see the upper (larger) grommet has a lip on it that fits quite a distance down into the seat.
The lower grommet is really positioned by the shock's rod and the 'cup' of the seat because it shows much less 'lip'.
Hope these help.
Regards,
Alan


Large grommet is 1-1/2" and small grommet is 1-1/8". I'd think these have 'expanded' and 'flattened' some from use.
First pictures shows them as installed.
Third picture shows the side of each grommet that was against the seat when installed.
Second picture shows the lip of each grommet that slipped into the seat.

Thank you for the pics Alan. I am pretty confident I have a plan to execute the repair. Your help has been invaluable.

Bill

[Alan S.]

Re: 70 front shock top hole diameter and repair

Hi Bill,
It's a pleasure!
Both to see your level of devotion to detail and to contribute to your (our) insanity in a small way.
Regards,
Alan