Options for replacing rear struts needed.

[DPS.01]

On 4/18/2022 at 4:17 PM, Ronnie said:

… someone with and old one needs to cut it apart and see what's inside. Probably a pipe cutter would do the best job of keeping everything intact as much as possible.

FWIW:

I used a portable band saw attached to a base plate. Worked really well. 

Edited March 5, 2023 by DPS.01

[Ronnie]

2 hours ago, alchemist said:

Will also need a ring to pot the base of the insert and to keep it secure within the diameter of the original housing.  Definitely do not want it rattling around inside the housing.

That answers a question I was wondering about. Without something to hold it in place on the bottom end, not only would it rattle, the alignment of the knuckle would change as it moved around.

[alchemist]

1 hour ago, DPS.01 said:

Originally thought of using a rubber bushing (think upper mount strut tower) compressed between the gland nut and the strut insert, and then drill  4 holes midway down the strut body opposite each other and use set screws to hold the insert centered to accomplish the same thing.

 

A combination of figure “a” bushing and figure “b” gland nut below. 
 

 

 

The strut wall should be strong enough and the set screws can keep the insert centered. 

I do like the ring idea, but tolerances may be a variable depending upon the insert cartridge used (OD) and the donor strut used (ID). There may  also be differences in the OEM hydraulic strut body and the aftermarket gas strut body. 

The bending moment cause by the reaction of the lower control arm will necessitate a large bearing area on the inside diameter of the original strut tube.  Simple set screws would lose the battle as there is not much thread engagement to carry the load.

 

Your pictures and investigation have been highly beneficial and I feel a reasonable solution is right around the corner.  Just need some information about the old strut housing to finalize a design.  Would need OD, ID, Overall housing inside depth (from the cut line in both directions).  The tubing used by GM on the original strut and that used by KYB is probably DOM (Drawn Over Mandrel) material so the tolerances should be quite good.  I measured the Monroe 73305 cartridge I have for prototyping, and the OD is a very cosnsitent 1.756" with the exception of at the top of the strut where the gland is press fit into place.

 

The overall length of the insert is 22" which matches the original equipment unit.  The only question is the thread length on the rod being 1.25".  How does this compare to the OEM and what is the diameter of the OEM rod thread?

Edited March 5, 2023 by alchemist

[DPS.01]

Point well taken on lateral forces applied to the strut assembly. 

Looking @ the internals of the original strut, there are other pieces that can be reused with the drop in cartridge, mainly the “upper retainer”. 
 

Top view of strut at cut line:

The body wall is machined to accept an upper retainer. 
 

Wall thickness:

Machined Portion:  1.56 mm

Remainder of body:  3.06 mm

 

OEM Upper Retainer Side View:

Diameter Top:  51.2 mm

Diameter Bottom:  41.78 mm

 

Upper Retainer; Top View:

The bandsaw cut lines ar visible on the upper retainer in photo above. 
 

Upper Retainer; Bottom View:

Upper Retainer on strut cartridge:

Strut cartridge and upper retainer inserted into strut body. 

(At the moment, the upper retainer does not go into the strut body fully as it contacts the top of the strut cartridge.  Modification to the upper retainer would solve this)

The strut was cut just below the curvature at the top of the strut to maximize the usable length of the strut body. 

 

Using the OEM upper retainer holds the strut cartridge firmly in place. The bottom of the cartridge is forced into the concave bottom of the OEM base (similar to the OEM hydraulic components) and is held in place by compression of the top gland nut. 
 

The top assembly may need to be redesigned to thread on the outside of the OEM strut body vs. the inside due to overall body length increase that would be required to use KYB top gland nut  (below). 

 

The threaded portion of the OEM strut is longer than the strut cartridge:

OEM:  68.82 mm

Strut Cartridge:  35 mm

 

diameter measurements at each step are similar:

 

threads:

OEM:  15.75 mm

Insert:  15.75 mm

 

sleeve portion:

OEM:  16.9 mm

Insert:  16.84 mm

 

piston:

OEM:  24.8 mm

Insert:  24.75 mm

If the length of the threaded portion is an issue for mounting in the upper strut tower, it can be solved in a similar fashion as the Cardone Allante strut modification discussed earlier in this thread. 
 

overall length from cut line:

outer:  13.75”

inner:  13.5”

 

OEM strut body:

OD:  54 mm

ID:    47.66 mm (body)

ID:     50.95 mm (machined upper portion)

 

OEM inner piston sleeve:

this piece accepts the piston and fits into the strut body

OD:  38 mm

 

 

KYB Cartridge:

OD:   46 mm (body)

OD:   42.63 mm (bottom taper)

OD:   32.5 mm (bottom foot weldment)

 

Let me know if additional measurements are needed. 
 

All measurements are as accurate as could be taken with available instruments. 

Edited March 5, 2023 by DPS.01

[alchemist]

Based on the initial measurements by DPS.01, here is the concept adapter shown in blue highlight, assembled onto an existing OEM shock housing.  Would need to be welded in place.  The pitch and diameter of the gland nut thread are not perfect yet, but easily modified.  The OD of the adapter may need to grow slightly for stability during manufacture.  Going to have a budgetary quote done by one of our machine shops.  Also need to develop the proper spacer to hold the insert coaxial to the original housing (this is pretty straightforward).

 

 

Edited March 6, 2023 by alchemist

[Ronnie]

Looks like the adapter is going to work. Thanks to everyone for all the work that is being done on this. 

[sarookha]

Can't wait!  I have a pair ready to modify.

[alchemist]

31 minutes ago, sarookha said:

Can't wait!  I have a pair ready to modify.

Stay tuned here for updates.  The adapter is out for quote now.  Is the pair of struts you have currently in the car, or out?

[DPS.01]

@alchemist:

 

I am sure that there will be a lot of interest in how your modeled adapter turns out… myself included. 

 

The adapter is the last step…

I have a set off the car… last component needed is your adapter. 
 

Thanks for your (and everyone else’s) insight and work on this project. 
 

[sarookha]

15 hours ago, alchemist said:

Stay tuned here for updates.  The adapter is out for quote now.  Is the pair of struts you have currently in the car, or out?

They are already out of the car, awaiting renewal.

[alchemist]

23 hours ago, DPS.01 said:

@alchemist:

 

I am sure that there will be a lot of interest in how your modeled adapter turns out… myself included. 

 

The adapter is the last step…

I have a set off the car… last component needed is your adapter. 
 

Thanks for your (and everyone else’s) insight and work on this project. 
 

P.M. me your mailing address.  I am going to have one of my colleagues 3D print a plastic version of the adapter and I would like to send it to you for fitment and proof of concept.

[DPS.01]

23 minutes ago, alchemist said:

P.M. me your mailing address. 

Done ✅. 

[sarookha]

And then what is this?  Claims to have a lifetime warranty, appears to be in stock.  Not cheap.

 

https://www.universalairride.com/product/1988-1991-buick-reatta-rear-electronic-to-passive-suspension-air-shocks-conversion-kit/

 

????

Edited March 8, 2023 by sarookha
added information about warranty

[alchemist]

6 minutes ago, sarookha said:

And then what is this?

 

https://www.universalairride.com/product/1988-1991-buick-reatta-rear-electronic-to-passive-suspension-air-shocks-conversion-kit/

 

????

Those are the same air assist struts as used on the Riviera.  I have a new set of those in the garage, Monroe 71801 is the part number.  If they have them in stock, may want to buy.  I picked up the last set on Rock Auto for $41 per strut.  They will work but may need to do something to lightly pressurize the air bladder when in use, or cut it off.

 

The Reatta never used an air assisted strut, straight damper strut only.

Edited March 8, 2023 by alchemist

[DPS.01]

3 minutes ago, sarookha said:

 

And then what is this?

 

…interesting, and expensive. 
wonder if it is a genuinely available part?

 

many on the various forums have been down that road, that ends with no availablity…

 

who wants to bite off on it?

[2seater]

I don't want to interfere with the great looking progress so far, but perhaps a machinist could invent something for the upper attachment issue? Adding the threaded extension will add substantial length to a pretty well-matched strut cartridge, possibly reducing available travel. Perhaps a top flanged nut with the lower female threaded sleeve to extend from the top down through the rubber bushings and engage the threaded portion of the new strut cartridge?? 

[alchemist]

2 minutes ago, 2seater said:

I don't want to interfere with the great looking progress so far, but perhaps a machinist could invent something for the upper attachment issue? Adding the threaded extension will add substantial length to a pretty well-matched strut cartridge, possibly reducing available travel. Perhaps a top flanged nut with the lower female threaded sleeve to extend from the top down through the rubber bushings and engage the threaded portion of the new strut cartridge?? 

Or just thinner bushings...  Or no bushings.  The stroke of the insert strut cartridge is 0.25" longer than the OE strut so we might be good there.

 

Appreciate the questions and comments.  We all need to work together to keep these classics on the road.

Edited March 8, 2023 by alchemist

[sarookha]

2 minutes ago, DPS.01 said:

…interesting, and expensive. 
wonder if it is a genuinely available part?

 

many on the various forums have been down that road, that ends with no availablity…

 

who wants to bite off on it?

I'll probably give it a try.  Since it's not a parts distributer claiming to have Monroe Reatta struts in stock, I'm hopeful.  It appears that Universal Air Ride develops their own parts for the "lifted" and AIr Ride community.

[sarookha]

And isn't a lifted Reatta what we've all been dreaming of 🤣🤣🤣

[alchemist]

2 minutes ago, sarookha said:

I'll probably give it a try.  Since it's not a parts distributer claiming to have Monroe Reatta struts in stock, I'm hopeful.  It appears that Universal Air Ride develops their own parts for the "lifted" and AIr Ride community.

Jump in an give it a try.  Those pictures are exactly the Monroe 71801.  If things do not work, I am continuing down the path of the weldable adapter.