I fitted a new oil seal to the rear casing and cleaned up the flange where it seats. The speedo drive gear goes back in the the plain boss facing the inner bearing (towards the gearbox). Now that was sorted the annulus could go back in with the new bearings, speedo drive gear and spacer. I removed the sprag clutch by removing the circlip and brass oil thrower first-cleaned up inside and replaced all twelve rollers. It also prevents operation in reverse if the overdrive were to be engaged as it would break some components (which is not possible anyway due to the isolating switch that limits its use to 3rd and 4th gears only). If the one-way clutch wasn’t there, the cone clutch would have to take on all the driving load of the input shaft and would slip-or it would have to be much larger to accommodate it. Within the center of the annulus is a sprag clutch. This one-way clutch is used to take up some of the driving load to the output shaft when the overdrive is engaged. The speedo drive gear and spacer should just slip off. Another job for the invaluable bearing puller. The inner one came out on the shaft of the annulus when I did mine.
![laycock overdrive number laycock overdrive number](https://www.dropbox.com/s/yw8ni1zd9egy2b7/Laycock_Overdrive_J_Type_38.jpg)
The outer one can be knocked through with a brass drift. I didn’t find them too difficult to source online just from part numbers. I supported the casing between the bench and a piece of wood and carefully knocked the annulus through with a small soft mallet. I used a piece of steel I had lying around from when I did the camshaft on the Golf and used that to prevent the flange rotating while I unbolted it. Next up was to remove the annulus from the rear case. I removed the speedo drive, cleaned that up and replaced the sealing O-ring also. It’s just held in with a snap ring so easy to replace too. I replaced the sun wheel simply because it was cheap for new-old stock part at £7 and that meant a new bush also. There appeared to be plenty of material left on the cone clutch. I replaced the O-rings on the two pistons also. While I had it in bits my plan was to at least replace all the bearings and clean out the various oil filters. I removed the bearing from the cone clutch just by removing the circlip. I removed the four nuts and the bearing carrier and cone clutch could be removed. This is operated hydraulically by two pistons which push against two bridge pieces spring loaded against the bearing carrier. Next was the bearing carrier for the cone clutch. First off was to remove the rear case from the main case which pulls apart to separate the main case, brake ring and rear case. Much better for cruising.Īs I’d already stripped the gearbox down, the overdrive was removed and ready to be worked on. It basically consists of an epicyclic gear system which allows the input shaft to reduce speed by about 25% in 3rd and 4th gears.
![laycock overdrive number laycock overdrive number](https://i.ebayimg.com/images/g/cE8AAOSwTF1ghDvg/s-l300.jpg)
Mine always worked quite well so I wasn’t expecting to find anything particularly out of order. It’s a Laycock J type used on many cars of the era. Once the gearbox was complete the overdrive was next up.