The propshaft transmits drive from the gearbox output to the rear axle input flange via two universal joints, which allow for the small angular changes between gearbox and axle as the rear suspension moves through its travel. Different propshaft designs were used across the Midget range, and the universal joints at each end are a service item that should be inspected for wear at every major service.
1275cc Propshaft
The early 1275cc used a propshaft with a sliding yoke at the gearbox end and a flanged yoke at the rear axle end. The sliding yoke allows the propshaft to change length slightly as the rear axle moves on its springs, without this, the propshaft would either bind or pull out of the gearbox. A later 1275cc propshaft revision introduced changes to the yoke and flange dimensions. Reconditioned propshafts are available on an exchange basis, and new universal joints can be fitted to a serviceable propshaft tube as a standalone repair if the tube and yokes are in good condition.
1500 Propshaft Design
The 1500 propshaft is a different design. It uses a flanged yoke at the gearbox output end (bolting to the gearbox output flange with four bolts and nyloc nuts), a sliding yoke and sleeve in the centre section, and a standard yoke at the rear. The 1500 propshaft also carries a grease nipple on the sliding yoke for periodic lubrication, this should be greased at every service to prevent the sliding joint from seizing, which would prevent the propshaft from accommodating rear axle movement and place excessive loads on the universal joints.
Differential Flange Connection
The propshaft bolts to the differential input flange at the rear via four bolts and nyloc nuts. Nyloc nuts must always be renewed when the propshaft is refitted, reusing nyloc nuts risks the propshaft bolts working loose, which can result in propshaft separation at speed, a potentially dangerous failure. The bolts themselves should also be inspected for thread damage and renewed if there is any sign of stretch or wear.
Universal Joint Types
Universal joints are available in both standard sealed-for-life and greaseable types. The greaseable joint has a grease nipple in each bearing cap, allowing periodic lubrication that significantly extends joint life. This is particularly beneficial on cars driven in wet conditions or stored in damp environments, where water ingress past the needle roller bearing seals is the primary cause of premature joint failure on sealed-for-life types.
Universal Joint Renewal
When renewing universal joints, the circlips securing the bearing cups in the yokes must be replaced with new items. Reusing old circlips risks a bearing cup working loose in service, which causes the propshaft to vibrate severely and, if left unchecked, can lead to yoke damage or propshaft separation. A worn universal joint typically announces itself through a clunk or vibration felt through the floor, most noticeable when taking up drive from rest or when changing between acceleration and overrun.