Installing Rancho RS-99251 F-250 shocks on the Buick Riviera (version 2.0)
(thanks to Camlifter for this mod)
Rancho F-250 shocks are a great mod for improving the handling of the Riviera while getting rid of the air ride, which can be an expensive repair. Ride height is unaffected, and the ride remains smooth.
Changing stock shocks on the Riv is super easy - the F-250 mod is more involved. Challenges include transferring the cross pins from the old Riv air shocks to the new Rancho shocks, and modding/replacing the shock mounts.
The mod should take between 6-10 hours, depending on your fabrication skills. If you've got the time and the extra $$, here's how to do it.Tools -
millimeter and English socket sets
big grinding wheel (optional)
dremel with various grinding wheels
penetrating oil (wd-40 or the like)
breathing maskParts Needed:
Pair Rancho RS-99251 shocks
Pair S.A.E. nuts to fit the Rancho shocks (the nuts on the Riv's air shocks are metric and will not work!)
Pair 95 Riviera shock mountsThe Process
First, a comparison of the 95 (and 96?) and 97 (and up?) shock mounts.
(note that I've begun modifying the top of the bushing pin and the rubber projections on the 95)
GM made several changes between the 95 and 97 model year shock mounts. Most notable for the purpose of this mod is the lengthening of the bushing pin. The bottom of the 95 pin is shorter, and the overall length of the 95 pin is shorter. The inner and outer diameter of the 95 pin is smaller than the 97 pin. These factors make the 95 shock mount more desirable for the F-250 shock mod, as the bushing pin must be modified. The threaded portion at the top of the Rancho shock is shorter than the threaded portion of the stock air shock, and the shock mount has to be modified to accomodate it. To modify a 97 pin would mean grinding through more material on the top of the pin, and grinding the pin on the bottom as well. IMO modifying the bottom of the 97 pin can not be done with hand tools. Because the bottom of the pin is a contact surface (the top is not), it's my opinion that it has to have the same perfect machined surface as stock, or a failure in the shock or the pin could be induced. Do yourself a favor and don't even consider modifying a 97-up shock mount unless you're a machinist or can have one do it for you. Modding the Shock Mounts
This is going to take time, and a little trial and error. Don't rush it and take too much material off at a time.
It's necessary to grind down both the rubber projections on the top of the shock mount, and the bushing pin.
Put on your safety equipment, and work with good ventilation.
I used a wide grinding wheel on the rubber projections and the bushing pin, and a narrow one to cut down the parts between the rubber projections. You might want to have two of the wide grinding wheels on hand. When I was done, my grinding wheel was rounded off like this:
It doesn't do such a good job in this condition : )
Start with the rubber projections. Grind them down so there's a slope pointing towards the top of the bushing pin (grind on left, unmolested mount on right). By going across the projection instead of along it, a great deal of control can be achieved.
Grind down the top of the bushing 1/8" by first beveling the inside, and then grinding down the rim. You will have to repeat this process, grinding down the rubber projections, and then the bushing, 1-2 more times.
Pop a washer onto the top of your modded mount and use a dowel or whatever's handy to mark your progress. Shoot for a height of 2 3/16" - 2 1/4"
. At 2 1/8" I took a little more off mine than was necessary - you might as well leave on all the rubber you can to absorb the shock rebound.
Note that I'm pressing my dowel all the way down to the bottom of the shock, not the bottom of the dowel pin.
Finally, shoot for an 1/8" clearance between the washer and the top of the bushing pin when grinding the bushing pin down. Removing the Old Shocks
When you're done modding the shock mounts, it's time to remove the old shocks.
While your Riv's on the ground, pop the trunk and loosen the carpet around the top of the shocks. You need to remove one of the ties for the cargo net, on each side, and two plastic rivets.
Pull the carpet over, here's the top of the shock -
Go ahead and take that nut off.
Break out your jack and remove the rear wheel.
First, unclip and remove the air line.
Push it back into the fender and it will be stored neatly away. In case you ever want to use the air ride system again, cover the openings in the line so the tire doesn't throw debris up into it.
Now there are only two bolts to remove.
Nothing to it. Squirt some penetrating oil on them, and unbolt the bolts. Grab the clips that slide off the cross pin, you'll need to put them on the Rancho later.
Rotate the shock 90 degrees, and lower it downward through the slot in the A-arm. It may be stuck at the top, tug it free. When the top's clear, pull the shock up and out of the fenderwell. Swapping Shock Mounts
Sit the old air shock aside - you'll need it again later. If you've got a 97-up car, grab the washer that came off the top of the shock. It's different from the 95 washer, and supposedly better (it appears to form a sound chamber with the rubber wall around the bottom of the shock mount, surrounding the shock/shock mount bushing interface).
The shock mounts are easy to replace. They're held on with two nuts. Remove the two nuts and the metal plate and set them aside. The old mount drops free. Install the modded mount. Don't forget to put the metal plate back on.
You need to do a little test fitting with the Rancho shock now to make sure you've cut down the modded mount enough. Don't worry that the wrong cross pin is still in the Rancho, you aren't going to mount it at the bottom yet. Pull on the round plate at the top of the shock (the Rancho ships in a retracted configuration) and a chrome rod will extend. Stick a washer on the top of the Rancho and push the threaded part up into the shock mount. Try to put a washer and nut on at the top. The Rancho threads are not metric like the stock air shock threads. You can not reuse the nut from the Riv shock!
This is what you're shooting for - both washers on, and the nut fully on the threads. Again, I took a little too much material off and ended up with a couple threads sticking out at the top. Try to do better than I did, and leave a little more material on.
It would be wise to take a metal brush and clean the paint off the Rancho's threads before installing. Otherwise the nut is likely to stick and start turning the chrome rod inside the shock, and you'll have to pull out a pair of vise grips and tighten the top nut up this way:
When you're satisfied that your new shocks will install in the modded mounts properly, set them aside. We're going to work with the old air shocks next. Modify the Air Shock Cross Pin
The next step is to grind down one side of the air shock cross pin, for easy insertion into the red rubber of the Rancho shock later.
Here's the problem - those square corners need to be rounded off (one side only) before you can put this into the Rancho.
Here's what I used to round the corners off.
When I was done with the big grinder, I used a little grinder on a dremel to smooth the edge burs left by the big grinder down. Removing the Air Shock Cross Pin
Get ready for the most (or second most) fun part of the entire mod - pulling the cross pin and prepping it for the Rancho. The sticky black rubber Buick used is a heck of a material. You'll be cutting it with a pocket knife, but be warned - it doesn't cut easy. It's better to go slow with the blade and "worry" at it then to try for one quick smooth forceful stroke. This stuff absorbs impact energy very, very well, but a continuous pressure will get it.
Cut the rubber flush on one side of the shock.
Stick the cross pin in your vise. Note that I have it clamped in sideways - if you do it the other way, it will bend. That will both keep you from getting the cross pin out, and maybe-possibly damage the pin. I'm not an expert on metal fatigue, but seeing an important part like this bend scares me.
When you've got the pin clamped in, lever the shock around until you get the pin and it's accompanying plug of rubber out of the eyehole.
Almost there. You've got to shave that rubber plug off the cross pin. It's thoroughly and completely glued on to the pin - you can't pull the pin out, you have to cut the rubber off in chunks.
It'd be a good idea to leave a 1/16" thickness of rubber on the cross pin, as it is slightly loose in the Rancho otherwise. Removing the Rancho Cross Pin
Onto the last "fun" part of the mod - again, removing a crosspin. This time it's the relatively easy crosspin of the Rancho's, so break one out.
Here's what you need to remove.
Here's how to do it. There's three steps. First, stick a deep socket on one end, and then pop the shock into your vise. Use the vise to press one side of the cross pin flush with the eye socket of the shock (thanks to Camlifter for this technique).
Second, take a socket of the same diameter as the cross pin, and use it to press the cross pin about halfway down into the eyesocket. Don't go too far or you'll have trouble getting the socket out.
Does this look familiar? Leverage the shock free of the cross pin, and then flip it over and get the socket out, if you can't do it with your hands.
It's all downhill from here. Preparing the Rancho for Install
Stick the old cross pin in the new shock. It goes in easy enough, I did it by hand.
Next, grab the disk thing on the other end of the shock and puuuull the chrome rod part out. Measure the length of it against the old shock - open the Rancho out four inches less than that.
Slide the red rubber dust boot on. If you haven't seen one of these before, the ends are different. There's a wide opening, that's the bottom, for the body of the shock. And there's a smaller opeing, which is the top. Inspect the top opening so you can see how it fits onto the disk type structure at the top of the Rancho. There are two lips, the disk goes inbetween them, sealing in the chrome part of the shock.
There's a trick to installing the Rancho so that the dust boot doesn't a) fold up over itself and look stupid when you lower the car and b) doesn't pop off at the top when you extend it out far enough to reach into the trunk (this is why you pulled the chrome rod out 4" shorter than the air shock).
Install the dust boot so it looks like this. Put the washer you set aside from the old shock onto the top of the Rancho. Stick the Rancho in the wheel well, put the clips back on the cross pin, and bolt up the bottom. The threaded part at the top of the shock should just barely reach into your shock mount.
Check the setting - the red knob at the bottom of the shock. I have mine set with "3" in the 12 o'clock position. I've yet to learn if this actually indicates a setting of 3, but it does ride and handle well.
Remount your wheel and lower the car. The threaded part of the Rancho will slide up into the shock mount as the shock compresses. When the car is down, install your washer and nut at the top of the shock mount.
That's it for this side. Do the other and go for a ride!
Edit - Read the comments in the original RegalGS.org thread too - Link