410 Gearboxes, differences and 4 to 5 speed conversions etc.
Posted: Thu Nov 10, 2011 12:27 pm
After a few people being interested in converting their 4 speed 410s to 5 speed I thought I'd do a bit of research into your options, this is a work in progress so until I have done more research I cannot Guarantee that all info is 100% correct but hopefully we can build up a good bit of info for anyone who wants to convert their 410 to a 5 speed. If you have any additional input, good photos of SJ gearboxes for comparison etc. then post them up so we can work out all the differences and see what is compatible.
Pre November 1984 sj410 gearboxes had a shorter tail section and longer input shaft, with these they locate into a bearing in the end of the crankshaft not into a bearing in the flywheel.
In November 84 that they swapped to the later 410 gearbox, essentially a hybrid 410/413 gearbox that uses a 410 bellhousing section and sj413 gears and tail section as well as a shorter input shaft, the shorter input shaft is located in a bearing in the flywheel (not in the crank like pre 11/84) with this they also changed the gearbox crossmember and the gear lever position ends up further back.
You can convert a 4 speed to 5 speed if you have a later 4 speed (Series 3/4/5 11/84 onwards) gearbox and a 1.3 5 speed gearbox. Take the case assembly, the upper and the lower, the input shaft and the input shaft bearing retainer of the SJ 410 and install the case extension, the forks and the rest of the gears from the Samurai gearbox. The hole in the floor needs extending about 1" and the crossmember mounting will also need attention as the Sammi gearbox is longer than the 1.0. Also the rear of the case needs some machining for a bearing for the 5th gear
Also bear in mind that post 88 samurai 5 speed boxes have a lower 5th gear.
I will take a pic of a 410 4 speed later when i'm in the workshop but here's a few pics to try and identify differences.
410 5speed with short input shaft (94)Samurai 5speed (you can see that the lever position is about 1" further back)
Pre November 1984 sj410 gearboxes had a shorter tail section and longer input shaft, with these they locate into a bearing in the end of the crankshaft not into a bearing in the flywheel.
In November 84 that they swapped to the later 410 gearbox, essentially a hybrid 410/413 gearbox that uses a 410 bellhousing section and sj413 gears and tail section as well as a shorter input shaft, the shorter input shaft is located in a bearing in the flywheel (not in the crank like pre 11/84) with this they also changed the gearbox crossmember and the gear lever position ends up further back.
You can convert a 4 speed to 5 speed if you have a later 4 speed (Series 3/4/5 11/84 onwards) gearbox and a 1.3 5 speed gearbox. Take the case assembly, the upper and the lower, the input shaft and the input shaft bearing retainer of the SJ 410 and install the case extension, the forks and the rest of the gears from the Samurai gearbox. The hole in the floor needs extending about 1" and the crossmember mounting will also need attention as the Sammi gearbox is longer than the 1.0. Also the rear of the case needs some machining for a bearing for the 5th gear
Also bear in mind that post 88 samurai 5 speed boxes have a lower 5th gear.
I will take a pic of a 410 4 speed later when i'm in the workshop but here's a few pics to try and identify differences.
410 5speed with short input shaft (94)Samurai 5speed (you can see that the lever position is about 1" further back)