Rear Chassis Kick-up

©By: Bob Adair
dot_clear Boise, Idaho       (208) 343-3846

Originally written: 1999

Last update: June 16, 2009 - Reformatted page

If you have an older Morgan which you drive (not a garage queen) there is a good chance it has kick-up on each side of the chassis under the rear axle. This is caused, over time, by flexing of the chassis and bottoming out of the axle housing on the chassis. The side of the chassis where the axle housing crosses over (hereafter referred to as the arch) will also cave inwards. The kick-up and cave-in will reach a point where the lobes of the lower steel plate which the axle-to-spring outer U-bolts pass through will rub and wear on the inside of the chassis. You will notice the doors and hood do not fit properly

To determine the extent of kick-up and cave in lay a straight edge under the chassis from just in front of the arch to the rear, on my 1959 DHC was up over 1/2 inch. Next run your hand across the side of the chassis under the arch area. If you have kick–up you will have cave-in here. My DHC has 120,000 miles on it, but, I've seen serious kick-up and cave-in on Morgan chassis with less than half that mileage. Newer chassis have the outer edge of the top lip turned down in the arch area, but I believe are still vulnerable to kick-up

You do not need to buy a new chassis. You do not need to take the body off the chassis, and the rear axle unit can remain in the car. I'll attempt to explain how I healed this malady in my garage using a 2 ton floor jack, some pieces of timber, an adjustable steel basement post, hand tools, and a 74 year old friend who has welded most of his life.

The method is to hold down one side of the rear of the chassis while you jack up on the underside of the chassis in the arch area. As you gradually jack upwards, you C–Clamp the sides (explained later) and hammer and dolly the sides of the chassis. Using the right materials and welding techniques, the finished product will be strong and look very nice.

First, determine how you can hold the rear of the chassis down. If you have tie downs in your garage floor (most do not) you could chain it to the floor. You could put a timber under the length of the chassis with blocks of timber fore an aft, chain the timber to the chassis, then jack between the timber and the chassis. I have a large timber running the length of the ceiling in my garage. I placed an adjustable steel post between the timber and the rear cross member of the chassis. If you do not have a timber in the ceiling you could nail a 2 X 4 or 4 X 4 underneath 2 or 3 ceiling joists to spread the load, then place a post under it.

Position the rear of the car under or over the area where you will hold it down. Support the rear of the car by blocking under the chassis cross member which is just in front of the rear axle. Remove the rear wheels, spare tire, rear shocks and springs. Lift the axle housing off of the chassis on the side you chose to straighten first and support it on a jack stand. You now have the caved in arch area of the chassis clear for healing. Place the post between the ceiling and rear cross member making sure the top of the post is temporarily attached to the ceiling timber. It will loosen as you straighten the chassis! Pull tight and fasten a string underneath the chassis from front to rear.

Place a jack under the arch area using a 5 to 8 inch long 2 X 4 between the jack and chassis to spread the pressure. Slowly jack up the chassis, the front of the car will not lift off the floor. Release the jack and sight along the taut string to see how much the chassis has straightened. You will eventually have to jack up the arch area beyond straight, as it will spring back a bit. As you repeat the jacking process and have tension the chassis, position a 1/4 inch thick steel plate about 10 inches long shaped to fit under the arch on each side of the chassis, and alternating with 2 large C clamps, tighten the clamps as tightly as possible on the plates throughout the caved in area. In other words, you are compressing the caved in area back into shape using the clamps. This will remove most of the cave in and help straighten the chassis. Hammer and dolly to finish the job. Once you have the chassis straight, with the jack removed, you can do the same to the other side. Now you can make the reinforcing pieces kickup , without these reinforcing pieces the chassis will eventually kick up again.

Make a template out of heavy paper of the arch area including about 2 inches on each side. Make it so it fits right up under the arch. It will be about 7 inches wide by 18 inches long. The 7 inches includes enough material to bend 90o under and cover the lower lip of the chassis. The 18 inch length includes about 2 inches in front and behind the arch area. You will notice that the 2 rear shock mounting plate bolts are covered. Not to worry! Using the template, mark around it on 1/8 inch thick mild steel stock. It need not be thicker. I would not use thinner. I used a friends metal cutting band saw to cut the two reinforcing pieces. You'll need a power brake to bend the 1/8 inch thick steel.

Mark and drill for the 2 shock mounting plate bolt holes. Lay out and drill 5, 1/2 inch diameter holes about equal distance and centered along the side and bottom lip of both pieces. Fasten the reinforcing piece to the chassis using a C clamp at the rear and the 2 shock mounting plate bolts in the front. Plug weld the holes and strip weld 1 inch welds about 1 inch apart along the top of the reinforcing piece and along the edge of the chassis lip. My friend who has welded over 40 years as a profession did the welding for me using a Mig welder. He said it is a no-no to weld vertically on the side of the chassis, so the ends of the reinforcing pieces are not welded.

Grind and sand the plug welds smooth. Seal the open edges with 3M Seam sealer which is paintable and really seals. Metal etch, prime and paint to match the chassis paint.

Take time to spiff up the insides of the chassis while the springs are out and the rear axle unit is movable. Do you need new U-bolts, lower plates, bushes, links and shackles for your springs and shocks? Good time to do it. Notice those groves on the top of the axle housing caused by the U-bolts. A good fix is to cut 2, 3 X 3 inch pieces of 16 gauge mild steel, roll them in a slip roll to the radius of the axle housing, paint them and insert under each set of U-bolts. I have done this to several Morgan over the years and it seems to keep the U–bolts tight and there is no more wear in the top of the axle housings.

Reassemble springs to chassis, spring to axle, shock to mounting plates and U-bolts, put the wheels back on and you and your Morgan will be anxious to go for a ride!

P.S. This malady is not restricted to older Plus 4's I have seen the same on 4/4's early Plus 8's two seat roadsters as well as four seaters.

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