Race failure is a chronic problem with TH350 transmissions. High torque loads cause the race to fracture at two stress points: the radial lube holes that contact the rollers and the sharp inside corners at the base of the outer splines. Despite many attempts to create improved versions, most aftermarket races were never significantly tougher than used OE parts.

Sonnax looked at all the issues to develop an upgraded outer race proven to eliminate every weak point. Lube holes are offset so rollers never travel directly over the holes. They’re also spaced so only one roller is ever positioned near a hole. Both features radically reduce risk of fracture. Design improvements to the splines, plus upgraded material and a custom manufacturing process, further improve durability to make this heavy duty race the best option available for the TH350 and TH350C.

• Double the torque capacity of OE or other aftermarket races
• Improved design significantly reduces risk of fracture at lube holes and splines
• Case-hardened steel alloy outperforms brittle, hardened aftermarket races
• Direct replacement race reduces need for expensive sprag conversions