Mounting

Fastening components for propeller shafts ensure a secure, play-free connection between propeller shaft flanges, the gearbox output, any centre bearing supports, transfer cases and the differential input flange. MAN and Mercedes trucks, buses and vans use flange bolts, self-locking nuts, centring bolts, clamp plates and fastening kits for this purpose, among other components. These connections must withstand the full drive torque, torsional vibrations and changing angular deflections without allowing the flanges to shift. An incorrect bolt grade, insufficient preload or reuse of damaged fastening components can result in loose connections, worn flange holes and ultimately damage to the propeller shaft or differential.

Propeller shaft fastening components vary according to driveline configuration, flange type, bolt diameter, thread pitch, under-head length, strength grade and installation method. For example, there are kits for universal joint flanges with through bolts and nuts, as well as versions with bolts screwed into tapped flange holes in the gearbox, transfer case or rear axle. The fit between the flange centring spigot and the mating part is at least as important as the bolted connection: the centring fit absorbs radial forces, while the bolt preload secures the friction joint.

Always select fastening components based on the vehicle chassis number. Visual comparison, measuring the bolt size only or selection solely by model name is never sufficient. MAN and Mercedes trucks, buses and vans may have different propeller shafts, flange diameters, pitch circle diameters and bolt grades within the same vehicle series, depending on axle configuration, gearbox, engine power or transfer case drive. Also check whether the fastening component is intended for a front, intermediate or rear propeller shaft section.

Typical fault symptoms include a knocking noise during load changes, vibrations during acceleration, metallic ticking when pulling away and visible reddish-brown wear debris around the flange. This debris occurs when an insufficiently clamped connection allows micro-movements between the flange faces. Continued driving causes bolt holes to become oval, bolt shanks to wear and the centring diameter to become damaged. A detached propeller shaft may also damage lines, chassis components or the transmission housing.

First, with the vehicle safely supported and the driveline free of tension, check that all bolts are present and that no signs of movement are visible on the flanges, clamp plates or bolt heads. Then clean the connection and inspect the flange faces for pitting, burrs, cracks and fretting corrosion. Measure the bolt holes using a suitable gauge pin or internal dial gauge; an oval or worn hole means that fitting new bolts alone will not provide a lasting repair. Also inspect the centring fit and the flatness of the mating flanges using a dial gauge. Measure the radial and axial runout of the installed propeller shaft to rule out bending, incorrect installation or a damaged flange.

Always replace bolts, nuts and clamp plates as a complete set in the event of corrosion, thread damage, stretched shanks, rounded heads or signs of loosening. Use only fastening components with the specified strength grade; a lower grade may stretch plastically, while an incorrect length can cause bottoming out in a blind hole or insufficient thread engagement. Thoroughly clean threads and flange faces, remove grease or old locking compounds and check whether specified thread locking or locknuts are required.

Install the propeller shaft in its original phased position and tighten the fastening components in a crosswise pattern with a calibrated torque wrench according to the vehicle specifications. Where an angle tightening procedure is specified, this must be carried out using a degree gauge after torque tightening. After a test drive, check again for loss of tightening torque, leakage at the flange connection and new vibrations. Thanks to technical support and a wide availability of driveline components, Braem can help determine the correct fastening kit for the relevant driveline.