Both jacks are doing their job. One can carry a complete housing (suchas this one from Quick Performance) with the third-member, while theother holds a third-member up in place for installation. Both can bevery handy when working alone.
The basis of this article is the inexpensive 2-ton jack available atmany auto parts stores. I think they are made in different factories inChina, but they are all copies of one another and have only slightdifferences. However, if the box says they will go up to about 151/2inches, they will work for our purpose.
I have used and modified jacks of this type for years. In some I havecut off the wheels, added a plate, and made some changes to the handle.This jack works fine in a dirt pit area.
Now, I have modified these jacks again to do a specific job. The firsthas looks reminiscent of a helicopter. Sadly, it won't fly, but it willlift a rear-end housing.
More than once I have had to install a rear end by myself. Trying tohold and balance the housing on my regular floor jack while rolling andturning it under the car has proved to be quite a chore. On aleaf-spring car this might not be too bad, but hooking up three or foursuspension links is a different matter. This seems especially true onthe GM metric cars. In these cars, the bolts go in at odd angles andmake correct alignment difficult. I appreciate anything that makes thisjob easier.
BUILDING THE HOUSING JACK
Topview of Housing Jack
The first thing to do is make the wide front legs with the outriggerwheels. This is necessary to keep the housing from overturning the jack.Split the front axle of the jack. Install each half in the outrigger tosupport the wheels. I have found the size and shape of the arms workwith the 9-inch Ford and 10-bolt Chevy rears that I have. There are manyvariations of brackets and castings, so measure yours and adapt theplans accordingly.
As designed, the jack holds a 9-inch Ford housing, with or without thethird-member being installed, as well as the 10-bolt Chevy. All the armsare made from 1x0.095-inch square tubing.
Sideview of Housing Jack
The yokes and the half-circle bracket are made from 1 x 3/16-inch flatsteel. Use whatever materials you happen to have in your shop and makesure that they are at least as strong as what I have used here. There isone change from the pictures on the arms. Instead of the arms angling uptoward the yokes, use a straight tube with vertical tubes up to theyokes. This simplifies construction. It is shown on the plans this way.
The half-circle yoke is attached to a threaded rod so that it canrotate. The rod can be adjusted vertically to fit and level the nose ofthe rear used. This rod goes through a long coupler nut welded to a tubecoming from the center of the arm.
Outrigger placement of the front wheels of the jack helps avoidoverturning when the housing is in place in the yokes. Cut the frontaxle in half and use the parts to attach wheels to the outriggers.
This unit is now welded to the cup on the top of the jack. To do this,pull out the clip under the cup and remove the cup. Weld the cup to thearm. Do not reinstall the cup using the clip. Weld a washer in itsplace. The clip is too weak to handle the side-loads the housing can puton it. When finished, there will be enough rock in the arms to allowline-up if your car is reasonably level with the floor.
I found the jack handle to be in need of modification too. It needs tobe shortened and welded at an angle. This greatly assists in giving youmaneuvering room under the car. The handle is then welded to its socket.Be sure to pull the clips and remove the socket before welding. Thiskeeps the welding current from going through parts of the pump and jackcylinder.
On the housing jack, the handle is shortened and welded back at anangle. This gives more room around the jack when you are under the car.When welding the handle, take it loose from the jack to keep the weldingcurrent from damaging the internal parts.
The jack's valve has only a stem sticking out. Weld an extension to itabout 11/2 inches long with a washer on the end to make it easy tooperate. When you are under the car with it, the valve will be withineasy reach. Before removing the valve stem, stand the jack vertically onits front wheels so fluid won't run out. Remove any O-rings or washersfrom the stem and wrap the threads with tape. This will protect thethreads from debris when welding. Now, weld on your extension, and youshould be finished with your first jack.
This shows the rotating cup from the jack with the clip beside it. Inthis case, the riser for the third-member jack has been welded to it. | 
When the rotating cup is replaced, do not use the clip. Weld a washer tothe stud. I judge the clip to be too weak for any real side loads. | 
Standing the jack on its front end allows you to remove the valve stemwithout losing fluid. With the stem out, weld an extension and a washeron it for a handle. |
BUILDING THE 3rd-Member JACK
Top View of Third Member Jack
I thought of building this jack once when I found myself under the carwith a 9-inch third-member lying on my chest. This jack is sometimes amate to the housing jack. Changing an iron third-member using this jackmakes the job almost a pleasure.
The jack used is the same inexpensive parts store jack as used for thehousing jack. The first thing I did was reverse the handle. It is weldedon top of its socket in the opposite direction. A kink that can be abend or a cut-and-weld keeps the handle close to the jack body. I foundthis position worked well under the car. The valve should be modifiedthe same way as the one on the housing jack.
I found reversing the handle on the third-member jack to my liking.Putting a bend in it keeps it close to the jack for storage and providesmaneuverability under the car. It does feel a bit strange to push thehandle up to pump the jack.
Rather than go to the trouble of making a wider front track, I made somewings from 3/8-inch steel rod. These stick out about 8 inches and clearthe floor by 3/16 inch. This is enough stability that I didn't have aproblem with the weight of the third-member turning the jack over duringthe installation process.
The holder for the third-member is made from a piece of 3/4-inch pipe(about 1 inch diameter) that clamps in the U-joint socket with theU-joint bolts. The pipe is then welded to a square tube that has3/8-inch round rods welded to it in a "V" formation. This "V" forms aplace for the casting to nestle during installation. Again, there arevariations in the 9-inch castings, so your dimensions may vary from theplans. To reach the proper height, a piece of the same 3/4-inch pipe isused as a riser. One end welds to the square tube holding thethird-member while the other welds to the cup on top of the jack. Asbefore, remove the cup to weld. Weld a washer in place of the clip tomake sure that the tiny clip doesn't shear with the side-loads.
Adapter for Third Member Jack | 
This photo gives a good view of the third-member carrying attachment asthe jack lies on its side. A yoke fits under the third-member whileU-bolts secure it to the attachment. | 
Wings made of 3/8-inch steel rod are welded to the sides of thethird-member jack. This reduces any tendency to topple over. Groundclearance at the wing's tip is 3/16 inch. Only one wing is shown in thephoto, but one on each side is required. |
CONCLUSION
The third-member jack is handling its load. Move the jack close toposition before raising the third-member.
The changes to these jacks can be accomplished with a welder, a torch,and a drill. I had originally planned to use the same jack and changethe cup. After seeing the small size of the clip holding the cup inplace, I decided to weld a washer on the bottom of the cup stud. Thejacks are so cheap that I made a dedicated unit for each purpose.
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