Dibble rear chassis repair

"The Return of Dibble part1, rear chassis repair"

I've been requested by Nick, a member or the national Morris Minor message board to put up an "idiots guide" as to how to replace Morris Minor rear chassis leg (spring hanger). DISCLAIMER! This is how I did the job, with Nick watching much of it. You may follow this guide at your own risk and use common sense with regard to safety. Now I'm sure none of you reading this are idiots, as having an interest in Morris Minors clearly shows great taste and intelligence!

Strip Down

Securely chock the front wheels. Jack the car up using your workshop trolley jack under the axle and support the body of the car using axle stands. If you didn't chock the front wheels the car may now be rolling. We will be removing the axle so the body of the car cannot be supported by the axle. I used large balks of wood- (part on an old garage door frame in my case, or thick fence posts etc could be used)- between the stands and the body of the car. Be VERY careful that the car is supported securely and safely as you will be working under it for many hours. I place the blocks of wood to spread the weight, fairly close to the position of the cars spring mounting points. Remove the hubcaps, and unbolt and remove the rear wheels. Leave the handbrake off.
First of all, you need access to the rear spring hanger/chassis leg area and ideally this means removing the rear axle, and preferably for safety the petrol tank as well.. I have, in the past done this job with only one side of the rear axle dropped. However, it makes for so much better for access if the axle and petrol tank are removed. The axle is removed by these steps (in brief, this is covered in detail in the Morris Minor club technical manual).

A few days before you start, its a good idea to soak all the nuts and bolts in the rear spring area with plus- gas or some other penetrating oil/spray.

Axle removal
1. Disconnect the flexible brake hose from the union above the axle - I have found brake union spanners invaluable for this, together with a Whitworth spanner to prevent the union on the body side from turning. I also use a brake pipe clamp on the flexible hose to prevent brake fluid from spilling on the floor.

2. Disconnect rear flange of propshaft from the diff flange. This is done by undoing the four nuts and bolts. These are 1/4" Whitworth / 5/16 BSF (they were on this car!), your Whitworth spanners and sockets are needed here. Once the nuts and bolts are off, support the propshaft in one hand and gently tap the flange with a hammer. If the prop did not already fall away from the diff, it should now. Before going any further bag up and label the nuts and bolts for ease of finding the right fixing during future re-assembly.

3. Handbrake cable removal. The handbrake cable is removed by with drawing the split pin that holds the handbrake cable to the rear cylinder actuating lever via a thick pin. This may be rusted solid, so you might need to drill the split pin out. Then undo the nut that holds the handbrake cable to the axle and withdraw the handbrake cable. Keep the split pin in the hole in the big pin and re-attach the nut onto the thread so you don't lose it.

4. Support the bottom of the axle (drain plug area) with a workshop trolley jack. Undo the nuts and bolts that hold the shackles to the body of the car at the rear of the springs. (Shackles are the small thick plates that connect the rear of the spring to the car bodywork)
rear left spring hanger

5. Unbolt the rear lever arm dampers (shock absorbers) link arm from the chassis legs- again using BSF/Whitworth tools.

6. Now for the tricky bit! The only fixing holding the spring to car body should now be the front spring hangers. This consists of a bolt connected to a plate with two small nuts and bots securing this plate to the hanger. The large nut on the bolt on the outside of the car should undo easily enough, but the two little nuts and bolts that hold the plate to the hanger may have seized and require grinding off. Try not to damage the plate as it may be re-usable. Now screw the large nut on the front hanger bolt again so the face of the nut is flush with the end of the bolt thread. Carefully tap the bolt/plate out (towards the inside of the car) using a hammer and drift.

You should now find that the axle is no longer attached to the body of the car and can be withdrawn by lowering the jack Move the axle out of the way. Be careful! It's very heavy. You can also remove the petrol tank at this point. Drain the petrol by undoing the drain plug at the bottom- Whitworth/BSF fixing again. Undo the fuel pipe from the front of the tank, remove the wire from the sender (on top of the tank) disconnect the filler tube (one screw) and undo the cross head screws that fix the tank to the boot floor opening. The fuel tank may now be withdrawn by lifting out of the boot. (Remove hardboard boot floor first). tank removal

Now we can start cutting away the chassis leg and corresponding section of inner wing as indicated by the blue arrows. But before breaking out the grinder, break out the tape measure and measure accurately the distance from the spring and damper mounting points to various other points on the car- I use the front spring hanger on the same side of the car and the suspension mounting points on the other side as fixed reference points. Measure all the dimensions and draw a diagram. You do want the suspension to be back in the same position on the car after all this work! I measure to within 1/16" (inch) thats 1 or 2 mm. Thats close enough for a Minor. As you can see several rust holes in the leg mean its due for replacement. The car would not pass an honest MOT and is seriously weakened at a suspension mounting point and therefore dangerous to drive.

Now we can start cutting out the chassis leg and inner wing. Cut away the bulk of the leg with a grinder, I prefer the 1mm cutting disks for this kind of work. This leg has been replaced in the past and was seam welded to the boot floor. You may be lucky in having a relatively unmolested car in which case you can drill out all the spot welds using a special spot weld drill. A spot weld is visible as a small depression in the metal. Its how the cars were welded together at the factory. SAFETY NOTE- you should read, understand and follow all safety rules that come with your grinder. Angle grinders are potentially dangerous pieces of equipment. The bare minimum safety gear you must wear are safety goggles to protect your eyes from sparks and strong leather work gloves for hand protection. I also wear a dust mask, ear plugs, decent quality fire retardant overalls, steel toe safety work boots and if working under the car a cotton baseball cap to keep dirt from my head. (Its the only thing baseball caps are good for!) The chassis leg was full of rust, as was the inner wing, which having been plated in the past means replacement is the only option.

Here you can see the grinding is nearly complete. Using a combination of small chisel, grinder and pliers, I removed the remainder of the old chassis leg. You need to get down to a smooth de-rusted boot floor, try not to make the boot floor/ upper chassis leg join too thin as we will be welding the new chassis leg to this. You might also want to wire brush as much of the inside of the upper leg as you can to remove rust. I applied some jenolite which was wiped off to remove the rust and then a coat of zinc spray added to the inside of the leg for protection.

The new chassis leg (rear spring hanger) was paint stripped on the inside to remove the black transport paint, sanded (40grit) to provide a key then sprayed with weld thru zinc primer to protect the inside of the leg. The leg was hole punched every inch along the flange that joins the boot floor, then held up to the boot floor and fixed in place with self drilling sheet metal screws. At this point the damper and spring mounting point measurements (distances to other suspension mounts) we took above were checked to ensure an accurate re-fit of the chassis leg. The leg was then welded to the boot floor with a combination of plug welds through the holes punched in the flange to the boot floor and seam welds. The self drilling panel screws were then removed and plug welds made though these holes. The outside of this panel will be sanded and painted when the welding is complete in this area.
The inner wing was trimmed to give a straight line, then a section of the inner wing/ repair panel was cut to shape. A cardboard template was made of the hole in the inner wing in front of the new spring hanger chassis leg and this was used to determine the shape the repair section was cut to. The repair panel was cut with tin snips after being marked accurately with a scribe. Holes were punched in the lower part of the repair panel to enable plug welding to the new chassis leg. The rear of the panel was de-greased, keyed with sandpaper (40 grit) and sprayed with a couple of coats of zinc weld- thru primer to preserve the metal. As you can see the bottom of the repair panel was clamped to the flange of the chassis leg and the upper portion tack welded in place in preparation for a butt- seam weld. It is important to tack weld the work piece at several points to avoid distortion pulling the panel out of shape when the panel is seam welded to the inner wing.
Here the tack welding and plug welding is complete (right) and joining the tacks with seam welds can begin (lower right). The welding is finally complete in the picture below. Don't forget to weld the spring mounting point and damper mount to the inner wing repair panel as shown below. The welds have been ground smooth and all that is left to do is zinc priming, seam sealing, and a topcoat of chassis black paint. The repair will be treated to underbody wax protection both inside the newly repaired box section and on the inner wing and boot floor parts of the repair.

Dibble front hanger page