Miller Garage

Driveshaft and U-joints

Tom Sotomayor February 2003

The universal joint (or U-joint – originally known as a Hooke’s joint) has been with us for quite a while. As you know, they are used to connect two or more shafts together that otherwise don’t line up, but intersect at a point. The typical configuration has two “U”s, or “yokes” connected with a “cross”, or “spider”. A driveshaft uses a U-joint assembly at either end, with an intermediate shaft in between, to connect the transmission with the rear axle..

If a car had a rigidly mounted engine, transmission and rear axle perfectly in line, the driveshaft would not need any U-joints. However, engines and transmissions are rubber mounted to keep annoying vibrations from being transmitted to the vehicle occupants. Since the rear axle is normally part of the suspension, it has to move to deal with varying loads and road conditions. All of this movement means the driveshaft needs to work with components that are constantly changing position.

The problem is a single U-joint has a “dirty little secret”. As you increase the angle between the shafts, the angular velocity of the two halves is not constant.

So, what does this mean? If an input shaft runs at a constant speed, an output shaft connected to it through a single U-joint will run at the same constant speed only if the output shaft is directly in line with the input shaft. As the chart below indicates, as the angle between the two shafts change, the output shaft will speed up for one quarter of a full revolution, and then slow down the following quarter revolution. In other words, it will speed up and then slow down twice for every full revolution of the driveshaft.

There would be a real problem with component longevity if only one U-joint was used. The speed variations would be felt as vibration. The U-joints, bearings, clutch, gears, etc. would be getting constant, reversing impact loads. As the angle of the driveshaft increases, so do the speed variation and the impact load.

To solve this dilemma, two U-joints are put into the driveshaft in series, one at either end of the shaft. As one U-joint increases speed, the other decreases speed. The net effect is constant speed in, constant speed out.

Looking at the diagram above, “C” is connected to the transmission and “D” is connected to the rear axle.

The main purpose of the U-joints is to allow the rear axle to move up and down while still getting power. This doesn’t come for free though. As the axle moves vertically (up) and the driveshaft angle lessens, the driveshaft needs to get shorter. The vast majority of British cars including MG, Austin Healey and Triumph use a sliding splined joint between the U-joints on the shaft itself. One of the exceptions is the Sprite / Midget. It uses a sliding spline on the end of the driveshaft where it slides into the gearbox.

To work properly the U-joints must be in proper “phase” with one another. Unfortunately, Murphy’s Law rears its ugly head. Occasionally some enterprising person will disconnect the driveshaft at the splined joint to save unbolting the four driveshaft flange bolts during a clutch job. When it gets reassembled no attention is paid to the “phasing”. If they are not in phase the speed change effect will be cumulative, making the situation much worse. It can get twice as bad as a one U-joint system!

To make matters more confusing, many repair manuals show the phasing incorrectly. Referring to the sketch above, the “fixed” yokes (A and B) must always be parallel. Roughly ¾ of the cars I’ve worked on with driveshaft segments, have them out of phase. Check your own car out, you’ll be glad you did!

This monograph may be reproduced only for non-commercial use without other permission of the author. Reproduction for commercial use only by written permission.

2008 February/March - Gearbox and Driveshaft

An overdrive gearbox is not being installed in the GHN3L131923 project. After all the time and effort to locate an overdrive gearbox, correct speedometer, and vacuum switch, one small detail was overlooked. If a D type overdrive gearbox is rare in the US the one that would be correct for a 1967 B with reverse lights would be even harder to find. Why, you ask? The gearbox control tower on a D type Gearbox was modified to mount a reverse light switch. The earlier D type OD gearbox control towers do not have the capablility of simply installing a reverse light switch. The British Leyland parts book shows additional parts no longer available that install in the control tower. The earlier version of the control tower is not machined to allow the additional parts required to activate the reverse switch. No, the D type OD and parts are not for sale, they will fit perfectly in the 1966 B GHN3L106098 project.

The original four speed three syncronized type D non overdrive gearbox in the car is in good condition and will be refreshed for the project. New front and rear seals installed. The oil is drained and replaced with Castrol 20W/50 to specifications. The clutch fork bolt and bushing is replaced with new parts and have a firm movement. The gearbox outer casing is cleaned an wire brushed.

Driveshaft and Hardy Spicer ujoints. Have you ever seen the John Twist, of University Motors 5 minute ujoint video? A five minute ujoint will never happen in my garage. It seems every driveshaft I needed to replace ujoints had them welded in place with rust. My ujoint video would be an hour long with many minutes of five pound hammer beating entertainment. First, at least one circlip will break. Time will be spent chasing the broken circlip around the joint with a hammer and punch until it is pryed loose. A 5/8 inch socket will be destroyed beating out the old ujoint caps. Then the new ujoint install will go smoothly until the last cap has the needle bearings stack and jam. But in the end, the satisfaction of doing it yourself is priceless.

2007 November - Windscreen

Windscreen glass replacement, glass polishing and frame polishing.

A windscreen was purchased on a popular internet auction. The frame and glass was removed from a 1966 B and the glass was original Triplex. The purchase was originally for the frame which was described in very good condition. The complete windscreen was shipped in a cardboard box without any packing and received in one piece. Upon inspection of the glass it was original Triplex clear and had wiper scratches. After reading and hearing stories of poor replacement glass fit, it was decided to try polishing the glass. A glass polishing kit was ordered from Eastwood Restoration Supplies. This kit contained a thick felt wheel and a powder polishing compound. The directions instructed to mix the compound with water and soak the felt wheel in water. The felt wheel was mounted to the electric buffer. The windscreen was positioned on the workbench with the outside glass facing up. The polishing process started by dipping the felt wheel into the polishing compound paste. The paste was smeared across the glass with the felt pad spinning about 3000 rpm in a east to west motion. A spray bottle of water was kept near to apply additional water when the paste started to dry. The felt pad was moved evenly in an east-west, west-east motion over a one square foot area of the glass. The same was repeated in an north-south, south-north motion. This method was used with over lapping the one square foot of polishing area until the entire windscreen glass was polished. The process was repeated several times until the scratches faded from the glass. After 120 minutes of polishing the results were positive. The wiper scratches were removed from the glass. One last comment, some distortion was noticable in one area of glass at the outside edge of the wiper sweep. The wiper scratches wore a groove in the windsrcreen. Overall the product worked as described.

Polishing the frame. The best frame of the three in the garage was selected for refinishing. The early chrome bumper cars had a windscreen frame plated with chrome on the top and bottom rails with the side pillars anodized aluminum. The budget did not allow for re-chroming so the windscreen frame was polished and painted. The top and bottom rails are made from extruded aluminum and can be polished to look like chrome. The top and bottom rails were wet sanded with 800, 1000, and 2000 grit sandpaper. When sanding, move the sandpaper in one direction back and forth. Do not use a circular motion. The next step was polishing with a 6 or 8 inch loose flap polishing wheel mounted to a drill press or benchgrinder that can produce 3000 rpms. A white rouge polishing compound was used on the wheel. Polish with the wheel across the wet sanding for the best results. The top and bottom were polished to a brillant shine and maintained with occasional wipe of aluminum polish. The side pillars were wet sanded with 400 grit and painted. The silver paint selected and applied gave the appearance of the original anodized finish. Powder coating or polishing are other options for the side pillar finish.

Installing the glass. The most difficult task on an MGB was squeazing the glass into the aluminum frame followed by mounting the frame with a new frame to car seal. Plenty of lubrication was required on the glass and internally to slide the glass into the frame. Extra hands are needed to help, more than two are required unless ratcheting straps are used in the procedure. In this case, help was not available and four ratcheting straps were used. First, the workbench is cleared and the work area was prepared to accomodate the size of the windscreen and frame. Cover the bench to prevent scratching the glass. The glass was placed on the bench with the ends of the glass on the bench and the curved outside up. Dish detergent and water was applied to the seals and glass. The procedure was started with sliding the bottom rail to car seal into position with extra rubber at each end. Compress the seal toward the center on each end eliminating the chance of shrinking and not fitting to the side pillars. This much more difficult to do later with the side pillars mounted to the top and bottom rails. Next, find and mark the center of the width of the glass and rails. Install the seal around the glass and use plenty of soapy lubrication. The seal will partial side off the top and bottom of the glass. Take the four rachet straps and position the equally along the width of the glass leaving room for the top and bottom rails. Pad the buckles to protect the glass from scratching. Position the top and bottom rails on the seal using the center line guide. Use the ratchet straps to pull the assembly together, note, not much pressure is required and keep the pressure equal across the rails. This may take several attempts given the slippery nature of the glass, seal and rails. Check the rail to glass seal fit and flip the glass over to the center down on the bench and the ends in the air. Carefully remove two of the four straps. The two remaining straps will hold the top and bottom rail to the glass as the side pillars are installed. Place a side pillar to the top and bottom rails and slide the brackets into the rails. Adjust the tension on the straps holding the top and bottom rails if the brackets are not aligned to the rails. Check the bottom rail to body seal and cut to fit tight against the side pillar extension. Add soapy lubrication to the side pillar and start the brackets in the top and bottom rails. Tap the pillar with a large rubber mallot to drive the brackets into the rails. Repeat this step on the other side pillar. Place the two ratchet straps around the windscreen frame from pillar to pillar. One strap at the top and the other at the base of the pillars. Use the straps to draw in the side pillars with sight pressure. Remember to protect the glass from the buckles and clips. The ratchet straps are there as extra hands, some force can be exerted with the straps to assist the pillars into position but the straps will pull or twist the pillars inward. Use the rubber mallot to drive the side pillars into position. The straps will hold the side pillars until the screws can be inserted through the top and bottom rails into the brackets. It is important to use the correct length screws or the glass will break.

Installing the windscreen to the body. Six bolts hold the windscreen frame to the body, two bolts in the center of the bottom rail to the cowl, and four bolts into the side pillars. Two of those bolts in the side pillars are extremely difficult to access if the dash is in the car. The install prcedure starts with placing the side pillar seals on the posts. Set the windscreen on the cowl placing the to side pillar posts into the wings. Tilt the windscreen forward and start the two center bolts through th bottom rail into the cowl. This is the time for a rope trick. The windscreen to body seal will be curled under, to pull it out a rope can be placed under the seal an pulled toward the front of the car. This uncurls the seal and puts it into the correct position. Place the ends of the windscreen to body seal over the side pillar seals for the correct factory appearance. Apply some windshield sealant under the side pillar seals where they contact the windscreen to body seal. Place a paint mixing stick between the vent windows and the side pillars. This will provide space to prevent the rear of the vent window from stressing the door skin. Push, pull, or whatever it takes to get the windscreen to position to start the bolts into the side pillar posts. Install the top bolts in each side then keeping the loose. Position the windscreen to the vent windows and install the bottom bolt in each side pillar. Tighten all six bolts and the windscreen install is complete.

DIY Quarter Panel (Wing - Rear) Lower Half Repair

During a restoration of the car, the front wings and a portion of the rear wings were removed to repair the sills. The dogleg section, the area behind the door, below the trim strip, and forward of the wheel was cut out to install the sills. The material removed for the sill replacement will determine the method used to install the wing repair panel in that dogleg area. The best option was to leave a least 3/4 inch of metal below and behind the door opening.

Tools and equipment used to complete the work were a air body saw, air chisel, angle grinder with 36 and 50 grit disks, rotary tool with carbide cutting tip (Dremel), air hole punch/flanger, big hammer, tape measure, vise grips, c clamps, clecko, MiG welder, auto darkening helmet, safety glasses, gloves, ear protection, and dusk mask.

Before cutting any metal, take a pen, paper, and measuring tape, and record measurments. Take measurements of the door opening, the distance of the edge of the wheel well to the trimline edge, the depth of the wheel well, and other points that will be benefical for reference when fitting and welding.

The repair was started by deciding how much of the lower half of the wing was to be replaced. In many cases, the area behind the wheel to the tail lamp is not rusted and does not need replaced. A bit of work can be saved by not replacing the complete lower half. As they say across the pond, offer the repair panel up to the wing to observe the panel's fit. Use a marker and draw the rough cut lines on the car's wing. Drawn a line across the wing using the bottom of the trim as a guide or if the trim piece is removed estimate the bottom edge. Mark a line 3/4 inch behind and below the door following the contour of the door opening. If the rear of wing is in good condition, mark the wing where the repair panel will end.

Removing the old lower wing. When replacing the entire lower half wing locate the wing valance seam and drill out the spot welds, below the trim line grind the edges tail lamp, clean up with hammer and chisel, and cut the seam below the tail lamp. Drill the spot welds in the wheel well and wing edge. Using a air body saw or angle grinder with a cutoff wheel, cut the wing along the marker lines.

Preparing the repair panel. You just cut a big hole in the side of your car, now you are committed to finishing the job. This is when fitting and measuring will be repeated until the repair panel is trimmed and flanged to match the body. On a 67B the front end of the panel where it meets the sill is folded flat. The repair panel will have this edge folded at 90 degree angle. The end will need to be folded over or trimmed for the leading edge of the panel to lay flat with the sill. Offer the panel to the car and clamp the wheel well edge to the outer wheel arch and along the sill bottom. The front lower portion that covers the sill should have a gap between the sill and the end of the dogleg. Check the fit at the tail lamp if replacing entire lower half. Adjust the repair panel for best all around fit. The repair panel will need to be trimmed to fit at the top and door. Mark the repair panel for cutting leaving 1/2 - 3/4 extra metal on the edges for fitting and flanges. Remember how much you paid for this piece. Measure 3 or 4 times and if needed cutting twice is much better that cutting it to short. Cut the repair panel with a air body saw or angle grinder with cutoff disk. Offer the panel for fitting again. Be careful not to fold or bend because the supporting panel edges have been removed. Trim again if required. Using a hand tool or an air punch/flanger, a flange is made in the repair panel. The flange will fit under the wing along the top and at the door!!!!! Again, offer the panel for fit. The flange will allow the repair panel and wing to set even to the other. Set the panel for welding with cleckos or screws. Note: welding will shrink the metal.

more to be added

2007 October - Wire Wheels, Tires, and Windscreen

Sand blasted, primed, and painted the wire wheels with Eastwood Detail Silver finished with Dupli-color Clear wheel paint. Purchased and mounted Vredstein Sprints 165SR from Universal Vintage Tire near Hershey PA. One wheel wobbled on the balancing machine so that one will be replaced with another from the extras stored in the garage. When weather permits another wheel will be sandblasted and painted. Four steps forward and one step back.

Wind screen and frame work in progress. A new clear windscreen ordered from The Roadster Factory arrived in one piece. During the 4 week wait another windscreen frame with Triplex glass was won on eBay. The glass has some wiper marks so a polishing kit was purchased from Eastwood. A search is underway for anodizing the windscreen frame side pillars. The aluminum pillars on the three frames in the garage have wear and corrosion on the anodized finish. The top and bottom pieces will be sanded and polished. Then the fun begins to get the glass into the frame.

It's time to start thinking about rebuilding the engine, which parts and where to buy them.

2007 April - Interior

Carpet from BHive. Moss Motors panel kit. Original rubber floor mats eBay. Dash repainted with black wrinkle. New dash pad mounted to the dash. Door caps recovered with black vinyl supplied with the Moss kit. Seats with new foam and diaphrams recovered with leather kits from MG Centre UK restored earlier during the project bolt to the floor. The Les Leston steering wheel is restored. The wooden rim is reglued, coated with polyurethane, and the center spokes polished. The LL steering wheel will be inchanged with a original banjo steering if the car is presented for judging.

2007 March - Wiring

Wiring. The car was stripped to the bare shell for painting and all the wiring was removed. Pictures were taken of the wiring in the area of the engine compartment and under the dash before it was removed. A good wiring diagram was copied from the Bentley book and enlarged for easy reading. A new wiring loom was purchased from British Wiring. Before the wiring loom was installed it was was sprayed with Sunbrella 303 fabric protection to keep it looking new. A battery charger was connected to the wiring to check the wiring an lights. New wire, clean connections, dielectric grease will keep the Lucas curse at bay. Wiring

2006 November - Suspension Front

Front suspension. The front suspension was removed from the car 11/2004 as a complete unit. The first challenge is to remove the springs. A cheap spring compressor was located and modified to fit inside the spring. Every nut and bolt was rusted solid and needed several applications of penetrating oil and heat to break them loose. The springs were compressed and the upper trunion bolt was hammered out. Once the springs were removed, the crossmember was striped bare and all the parts were cleaned, primed and painted black. The spindles required rebuilding with new kingpins and bushings. The crossmember was mounted to the frame rails the suspension was assembled. Deteriorated rubber was replaced with new black polyurethane bushings and crossmember pads. Suspension front

2006 October - Suspension Rear

Rear suspension. The springs were removed and the rear axle was cleaned and painted black. New polyurethane pads were used along with new u-bolts and bushings attaching the axle to the car. New brake shoes, cylinders, and brake lines were installed. The differential and axles did not appear to be leaking so they were not disturbed. Suspension rear

2006 June - Assembly Begins

The assembly process begins. The first part to go back on the car is the fresh air vent drain tube. The heater is the next. Now an awareness and caution overcomes the enthusiasum, BE CAREFULL, don't scratch the paint. Parts are going back on the car much slower than when they were removed. One tip I learned from Carl Heideman, Eclectic Motorworks, at a Tech Seminar held during the Carlisle Import Show, was to have all the parts refurbished, cleaned, and ready to install with required hardware and gaskets. His main point was to do this as the parts are removed from the car so everything can be boxed, labeled, and stored. Well that tip was too late for me, the car was already stripped, but over the years of the project during the winter months many of the parts were rebuilt, painted, and cleaned.