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Mark Rosenbaum Member 
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Background. Some years ago I discovered that one side of the rear of my car was about 3/4" lower than the other. A visual exam of my rear suspension failed to disclose anything atrocious, so I decided not to replace the bushings. But time passed, and eventually it developed that the lower arm bushings would permit insert-to-arm contact far too often, though the upper arm bushings were still in excellent shape. At about the same time, Superpro suspension bushings became readily available through the JHPS. Superpro has a very good reputation, and unlike the rear suspension bushings currently available from Delta Motorsports, accept the original pivot bolts. (I'll note here that except for this one issue, the reports I've read about Delta's bushings have all been favorable.) In any event, I decided to replace my car's lower arm bushings with the Superpro product, and ordered a set of four from the JHPS. They arrived in due course. Preparation. Many owners have reported difficulties when removing the original bushings. I didn't want my JH to be out of service for a prolonged period, so I bought a set of well-used rear suspension arms and rear springs via eBay, intending to rebuild these and install them in my car. After some experimentation, I decided that the easiest way to remove the original Metalastik bushings was to excise as much of the rubber as possible with a drill, allow the metal insert to fall free, then scrape out any residue with a knife. What I did not realize was that this left the bushings' outer shells in place in the suspension arms. The shop manual somewhat indirectly implies that these shells may be present, but I don't recall ever coming across any other mention of them -- and based on appearances, it certainly seemed that the shells were part of the suspension arms themselves. I disassembled the springs, ensured that their unloaded lengths were the same, cleaned them up, painted them an aluminum color, then reassembled things using new hollow rivets also purchased through the JHPS. After cleaning up the lower arms, I painted them a medium grey. (IMHO there's a bit too much black on the underside of a JH, and I felt these colors would be attractive without being gaudy.) The upper arms were put aside. Bushing Installation. Over the course of the next few weeks, I proved conclusively that it is effectively impossible to install a Superpro bushing in a rear arm when the old bushing shell is present. Even when a bushing was squashed flat in a press, it still refused to enter the hole in the arm end. When after considerable extreme abuse the bushing finally expired, I found it necessary to buy an additional pair of bushings from the JHPS so that I'd have four good ones for my suspension arms. Consultation with a couple of JH owners who had successfully installed Superpro bushings in their own cars resulted in many helpful suggestions. Unfortunately, due to the presence of the old bushing shells, none of these worked for me. But after repeatedly pondering the text in the shop manual, it finally occurred to me that the old bushing shells might not have been part of the suspension arms. Experimenting with one of the upper arms proved this to be the case, though at the cost of expending the arm. I then used a powered saw to slit each of the shells -- two cuts about 90^ apart -- and knocked them out with a chisel. A bit of work with a wire brush removed the residual rust, and some paint was applied to touch up the cosmetic damage done by the failed installation attempts. Once all that was done, installation of the Superpro bushings was fairly anticlimactic. One slathers a generous amount of the provided white lubricant in the hole in the arm, and over all but the outer face of the bushing (where the insertion force is to be applied), then squeezes the bushing into the hole. This could be done with a vise, a light press, a giant C-clamp, or a threaded rod with two nuts and a couple of body washers. Conceivably one could even place a metal plate over the bushing, lean on it heavily, and force the bushing into place that way. The bushing will rarely enter the hole squarely, and may occasionally pop out if it's badly misaligned. Usually, though, if the inserting force is slowly increased, the bushing will eventually bend, flex, twist, and squirm all the way through the arm, and its rim will pop out on the far side if you remember to provide room for that to occur. The metal inserts can then be lubricated and inserted so that their ends are flush with the bushing faces. Under the Car. Removing the old lower arms and springs, and installing the new ones, is quite easy and took me only a few hours. I started by putting chocks at the front wheels, then loosened the lug nuts for the rear wheels. Next, I jacked up the rear of the car and put jack stands under the chassis, just forward of the front pivot points for the lower arms. After satisfying myself that these would support the weight of the car without damaging anything, I raised the rear axle, put jack stands under its axle tubes, and ensured that they would hold things safely in place. I then removed the rear wheels to ease access to the suspension parts. Removing the lock nuts that hold the pivot bolts in place took some effort as these are torqued to 50 ft-lb, but that's what a two-foot-long breaker bar is for. I then undid the nut holding the lower spring attachment piece in place, placed the jack under the rear of the suspension arm, and raised the arm end slightly to unload the rear pivot bolt, which could then be tapped out without trouble. Next, I released the jack, which allowed the arm and spring to separate, and tapped out the forward pivot bolt. With the lower arm out of the way, it was simple to undo the bolt holding the upper end of the spring to the chassis. A look at the upper spring seat reveals a second hole, to the rear of the threaded one, for the fixing pin at the top of the spring bushing, and this needs to be taken into consideration when the spring is reinstalled. With the spring out, access to the upper arm is easy, if one wishes to service that part. As noted above, this didn't seem to be necessary in my case. My refurbished springs went in easily, and were secured at the top with the original bolts, which must be torqued to the desired tightness at this time. Don't over-tighten -- the weld-nut into which the bolt fits is completely inaccessible, so its replacement, should that become necessary, would be a major undertaking. Once the upper end of the spring was mounted, I slipped the front end of the suspension arm into place. Even with the broad Superpro bushing in place, this takes only a bit of hand pressure. After aligning the holes I installed the forward pivot bolt and started its nut. I next secured the lower end of the spring to the suspension arm, using a jack to hold the arm in place while the nut was tightened but not yet torqued. The rear pivot bolt holes were then aligned, the bolt inserted, and its nut started. It should be noted that while the front and rear pivot bolts can be installed either way, the head of the forward one should face outward, while the head of the rear one should face the center of the car. This makes removal and installation much easier, particularly if a gentle tap might be required. The process was repeated for the other side. The wheels were then reinstalled, the jack stands removed, the car lowered to the ground, and everything torqued. Performance. After bouncing the car's back end a few times, I measured the height of each rear corner. The difference is now about 1/4", which is a considerable improvement over the 3/4" measured some years ago. Unfortunately it didn't occur to me to measure things just before the bushing installation, so this can't be considered as conclusive proof that the new bushings were the cause of the improvement. On the road, there's a very noticeable change. Previously, the rear bushings would easily and abruptly deform to their limit when disturbed, but with the Superpro bushings in place, this is much more progressive. I haven't had a chance yet to see how the car's manners will change under aggressive driving, but I'm sure there will be a considerable improvement. I don't know how long it will take for the Superpro bushings to wear out, but I'd expect their lifespan to be at least as long as the original Metalastik parts. I should comment here that the polyurethane bushings offered by Delta Motorsports should perform about as well as the Superpro ones do, and are somewhat less expensive. I suppose I could test that some day, if someone were to subsidize the expense.... ;^} Technical Information. I used copious amounts of anti-sieze compound on all the suspension hardware, which may not be necessary but which should prevent any future rust problems (not that I had any, though). It is vital to note that this counts as lubricating the hardware, and that the torque values listed in the shop manual must be reduced considerably when this is done, or the hardware could fail catastrophically in use. Using cheap Grade 2 hardware in the rear suspension would ensure such failures. Spring mounting hardware: Shop manual 32-35 ft-lb Grade 5 accepted maximums 35 ft-lb dry, 25 ft-lb lubricated. Pivot bolt hardware: Shop manual 50 ft-lb Grade 5 accepted maximums 55 ft-lb dry, 40 ft-lb lubricated. The upper spring securing bolts (Jensen part number 91401) are Grade 5, 3/8" x 24 tpi x 1+3/8" long. The threads here are 1" long and the remainder is an unthreaded pilot point. The lower spring securing bolt is part of the retainer assembly, but would be a similar bolt were it separate. The securing nut (91416) and lock washer (91417) would be Grade 5. The pivot bolts (91399) are Grade 5, 7/16" x 20 tpi x 3" long, heavily cadmium plated, with heads 5/8" across flats. These mate with Grade 5 lock nuts (91400) that are 11/16" across flats. Curiously, in my car, the front pivot bolts were secured with conventional lock nuts while a PO had replaced the rear ones with Nyloc lock nuts. Special Thanks. Dan Eiland and Erik Harkes were kind enough to provide advice, suggestions, and moral support during many of the more frustrating events related here. Quite probably I would not have been able to complete the bushing installation without their assistance. Photos. I've posted some related photos on the JHP Photo Gallery. See: http://shorpac.com/v-web/gallery/album93 Last edited on 08-10-2005 07:46 pm by Mark Rosenbaum |
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George Member
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Once again with the timely advice Mark. Thanks. I am doing the rear bushings at the same time as the brakes. I went with the ones from Delta. Man are those old ones hard to get out. I fianlly got one out with a 7/16 inch threded rod, nuts and sockets, but what a battle. On the next I am trying your suggestion of cutting thru the outer ring in two places, but the thing is still stuck in there! I can see why you thought they were part of the arm itself. Oh well, more heat, more penetrant and more force. Thanks again. |
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Mark Rosenbaum Member
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George, One thing to do is to add penetrating oil from the outside of the arm, as indicated in the attached photo. Then when cutting through the shell,you should see a line of rusty oil in the saw cut just as you breach the outer surface of the shell. Once you get the smaller shell section out, the larger section may come loose fairly easily if you reduce the shell's diameter by tapping at the edges of the cut. Or you may be as unlucky as I was, and have to apply lots of brute force.... I didn't try using heat because I'd painted the arms long before I realized that the bushing shells weren't part of the arms. Attachment: Weld and gap.jpg (Downloaded 253 times) |
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George Member
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After Action Report - I finished the rear suspension. And thought I would add a few comments. I used all Delta Motor Sports bushings and all my original bolts fit. The only problem I faced was if I tried to push a bolt thru from the side I had ground down(per the instructions). It would not go in. I had to send the bolt thru from the opposite side and tap it a few times with a hammer. The only real problem I faced was getting the old bushings out. As discussed, I ended up drilling out the rubber and then using a reciprocating saw on the outer metal. I managed to push one out with a threaded rod and washers, but if I were to do it again, I wouldn’t waste much time on this approach. If they don’t push out relatively easily, I would recommend going straight to cutting. Putting in the new ones was very easy with the threaded rod. The prothane DMS bushings are in two parts and pushed in from both sides, not sure how this compares to the Superpro ones. Once I recover mentally from the ordeal and my scraped knuckles heal, on to the front. I will soon be printing out your postings on this, Mark. Thanks to all for the advice. |
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SportsRodder Member
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Just a note regarding rear suspension arms; after replacing the bushings and reassembling the rear suspension the bolts should be left finger tight until the full weight of the car is on the rear axel. With the axel supported by jackstands the rear springs will be compressed to ride height. The bolts can then be torqued to their full specifications. Failure to do this will result in the bushings trying to act as springs and affect the performance of the rear suspension and possibly the ride height. Last edited on 09-06-2005 05:20 pm by SportsRodder |
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Harkes Member 
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Mark, glad i could return the favour for once. Your detailed notes have helped so many of us!! Your suspension arms, bushings and springs are looking great! Unfortunately i'm not back on the road, so i can not share how the car drives with the bilstein shocks, uprated Delta springs and SuperPro bushing AND the new 2.2L engine. but i can tell you for sure it will be a brand new car since my old bushings and shells had so severely rusted to the frame and suspension arms that the right front did hardly do anything. I had a classic car specialist who tried almost half a day getting my old bushings out of the front suspension/subframe!! the upper arms bushings he had to drill, heat, drill again, heat more....still didn't want to come out. Finally he managed... He said after 30 years working on classic cars he had never experienced something like this.... I recently resprayed the engine compartment (blue) and with the sides towards the tunnel in black. The floor pans i had also sanded back to bare metal and now they have been painted in POR 15 and it awaits a coating of chassic coat black (POR ). I'm now waiting for the engine to arrive... happy motoring Erik |
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