5 Speed Nissan Gearbox Commented

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FITTING A NISSAN BLUEBIRD 5 SPEED GEARBOX TO AN MGB Eric Banks has written this detailed description of fitting a Nissan Bluebird Mk II 5 speed manual gearbox to his Mk I MGB roadster. Eric’s car was built in October 1964 and has one of the first 5 bearing engines. Herb Adler followed Eric’s description and has added comments, in italics, about issues and traps he found when fitting his ‘box. Brands and suppliers referred to are Australian. First you will need a new clutch plate, mine from Repco part number R7926W. Starting with the old gearbox separated from the engine and the old clutch pressure plate removed:- Actually, first you will need a Nissan Bluebird gearbox. Make sure that you also get the matching tailshaft, when you buy the ‘box. 1.Fit the new spigot bearing. 2.Setting the gearbox onto the engine. 3.Aligning and securing the 2 units together. 4.The rear gearbox mount. 5.Creating an adaptor plate for the Holden HQ (a GM part) rear gearbox mount. 6.New Speedo cable. 7.Creating a new gear lever. 8.Visit Peter Smith, "Al Balancing", in Douro Street Nth Geelong to get him to make you a new tail shaft. Any reputable driveshaft shop can do this. 1. 1. As the spigot on the Nissan box is 0.625" dia (5/8) and it is necessary to replace the spigot bush in the end of the engine crankshaft which is 0.875" the choice has to be made either to have a bush turned at 1.125" OD by 0.625" ID which is not self lubricating, or try a sintered bearing. I chose sintered bearings as they retain the oil for lubrication, using hypoid 70/80 to lessen the loss of oil by centrifugal force. From Hamilton Bearings I purchased 2 1.5" long bushes, one 1.125” OD by 0.875" ID, the second 0.875" OD by 0.625" ID. For the fussy engineers, don’t panic. After soaking the bushes in oil for 2 days, press one into the other and, to secure them together, drill and tap a hole in one end between the two matching diameters and fit a 1/8th metal thread. The bush is then inserted into the crankshaft with the screw innermost causing the faces to be flush with the end of the shaft. DO NOT HAMMER them in they crush easily, get a 5/8" bar with a sleeve and with a true face, to contact the bushes over the entire face. They will go in relatively easily and when measured mine was 0.628"diameter, a quite acceptable fit. I chose to leave the existing bush in place and insert the smaller 0.875 X 0.625 bush into it. Unfortunately this crushed the new bush by a few thou, and the input shaft no longer went in. Luckily I found a 5/8” drill, which I used to open the bush up some. The shaft now fits. Maybe I should have done as Eric did and replace the original one too. 2. Stand the engine on the front end, using large wooden blocks to keep the crankshaft up off the floor. Using a block and tackle or an engine crane, remove the clutch fork from the bell housing. Remove the original dowels if locked in the original engine backplane. I made up a stand from Unistrut to support the engine front down. Place a sheet of thin butcher’s paper large enough to cover the backing plate generously, and with 6" diameter hole cut in the centre, this will enable you to watch that the spigot goes in correctly and when the gearbox is put in place to align it. NOTE .... The drive shaft of the gearbox must turn freely with the box in gear.

Transcript of 5 Speed Nissan Gearbox Commented

Page 1: 5 Speed Nissan Gearbox Commented

FITTING A NISSAN BLUEBIRD 5 SPEED GEARBOX TO AN MGB Eric Banks has written this detailed description of fitting a Nissan Bluebird Mk II 5 speed manual gearbox to his Mk I MGB roadster. Eric’s car was built in October 1964 and has one of the first 5 bearing engines. Herb Adler followed Eric’s description and has added comments, in italics, about issues and traps he found when fitting his ‘box. Brands and suppliers referred to are Australian. First you will need a new clutch plate, mine from Repco part number R7926W. Starting with the old gearbox separated from the engine and the old clutch pressure plate removed:- Actually, first you will need a Nissan Bluebird gearbox. Make sure that you also get the matching tailshaft, when you buy the ‘box. 1.Fit the new spigot bearing. 2.Setting the gearbox onto the engine. 3.Aligning and securing the 2 units together. 4.The rear gearbox mount. 5.Creating an adaptor plate for the Holden HQ (a GM part) rear gearbox mount. 6.New Speedo cable. 7.Creating a new gear lever. 8.Visit Peter Smith, "Al Balancing", in Douro Street Nth Geelong to get him to make you a new tail shaft. Any reputable driveshaft shop can do this.

1. 1. As the spigot on the Nissan box is 0.625" dia (5/8) and it is necessary to replace the spigot bush in the end of the engine crankshaft which is 0.875" the choice has to be made either to have a bush turned at 1.125" OD by 0.625" ID which is not self lubricating, or try a sintered bearing. I chose sintered bearings as they retain the oil for lubrication, using hypoid 70/80 to lessen the loss of oil by centrifugal force. From Hamilton Bearings I purchased 2 1.5" long bushes, one 1.125” OD by 0.875" ID, the second 0.875" OD by 0.625" ID. For the fussy engineers, don’t panic. After soaking the bushes in oil for 2 days, press one into the other and, to secure them together, drill and tap a hole in one end between the two matching diameters and fit a 1/8th metal thread. The bush is then inserted into the crankshaft with the screw innermost causing the faces to be flush

with the end of the shaft. DO NOT HAMMER them in they crush easily, get a 5/8" bar with a sleeve and with a true face, to contact the bushes over the entire face. They will go in relatively easily and when measured mine was 0.628"diameter, a quite acceptable fit. I chose to leave the existing bush in place and insert the smaller 0.875 X 0.625 bush into it. Unfortunately this crushed the new bush by a few thou, and the input shaft no longer went in. Luckily I found a 5/8” drill, which I used to open the bush up some. The shaft now fits. Maybe I should have done as Eric did and replace the original one too.

2. Stand the engine on the front end, using large wooden blocks to keep the crankshaft up off the floor. Using a block and tackle or an engine crane, remove the clutch fork from the bell housing. Remove the original dowels if locked in the original engine backplane. I made up a stand from Unistrut to support the engine front down. Place a sheet of thin butcher’s paper large enough to cover the backing plate generously, and with 6" diameter hole cut in the centre, this will enable you to watch that the spigot goes in correctly and when the gearbox is put in place to align it. NOTE .... The drive shaft of the gearbox must turn freely with the box in gear.

Page 2: 5 Speed Nissan Gearbox Commented

Now, use a black pen to trace around the backing plate and around the outside of the flange of the new bell housing after making sure that the gear box is correctly oriented. Remove the sheet of paper and place it on a window, trace over the outline of the pen mark which is on the other side of the paper, this will show you the shape of the extension pieces you will make out of a piece of 10mm steel. Find yourself an expert welder, like a pipeline welder, or make sure you can have the plate made absolutely flat, and have the pieces welded on. Have these welded on but remember the plate must be dead flat to ensure you have a seal when you assemble the plate to the engine.

View the photo's showing the shapes of the additions before welding and the completed plate. Using this method you now have a backplane that will accept both the MG box and the Nissan box. Bolt the back plate back on the engine. By adding these pieces to the backplane you have also closed off any gaps that would allow dirt into the clutch. Do not forget to fit a new seal to the crankshaft and check the cork seal where the sump fits to the engine. Select where you intend to drill the 2 dowel pins aim at having them as nearly opposite across the bell housing as possible, pre-drill these holes undersize slightly. 3. Re-mount the box on the engine, check that the shaft turns, and using at least 2 Gee clamps secure the 2 units together. Having someone keep an eye on your drill so that it is at 90 degrees to the back plate, drill pilot holes, then enlarge to the dowel size, I used 10mm dowels. Set the dowels. When I went to buy the dowel pins, Hamilton’s didn’t have any, so I used 3/8” roll pins. I actually bought both 3/8” and 10mm, in case something went wrong with drilling for 3/8” I would be able to open the holes up to 10mm, but 3/8” worked fine. Grind the excess length off. Use the original bolt holes in the bell housing as a guide, pre drill a cantering dimple into the backing plate and drill and tap the backing plate to suit. Except for the top right hand bolt, I actually drilled right through the plate and used the original gearbox mounting bolts. This top RH bolt needed to be drilled and tapped, as, otherwise, it would have interfered with the oil takeoff fitting. It would have been better to have drilled and tapped the top left hand bolt as well, because getting the nut on was very tight. Also, when Eric came with his car for me to look at, he mentioned that he had a problem with the new starter motor hitting the body and that he had to grind bits off the starter. What I did was to drill and tap new starter mounting holes, about 15mm CW from the existing ones, which moved the starter sufficiently to comfortably clear the body. NOTE that in the photo, I

had already had nuts welded in place to take the starter mounting bolts, in the original position. Don’t bother. Assemble the clutch plate and pressure plate as normal. I chose to use the Nissan clutch slave cylinder, it was easier but required a new clutch hose, one end to fit the steel clutch line on the body, the other end to fit the Nissan clutch slave, and I made up a slightly longer push rod. I replaced the clutch lever boot, P/No N30542E9000. I took the old MG line and the old Nissan hose to Clutch and Brake who made me a hose to do the job. There are two slave cylinders available, 19mm and 22mm. I chose the 19mm one but think that the 22mm would have been a better choice, as the clutch is quite heavy.