Rover V8 to MT75 Adaptor Plate

The goal is to mate the Rover V8 up to a Ford MT75 gearbox. Therefore I had 2 choices:

  1. Use an Rover V8 to MT75 adaptor plate
  2. Use a complete LT77 bell-housing and remove the integral MT75 bell-housing and weld on a mounting plate.

Seeing as I could not find anyone that had done Option 1. before, this option seemed less promising. Due to the Sierra Cosworth Bell-housing being a much smaller diameter than the Rover V8 LT77 5 speed, the clutch would also be a lot smaller. The output shaft of the Sierra Cosworth MT75 sticks out 4mm from the bell-housing, whereas the shat of the LT77 sticks out 13mm (9mm difference). An simple sandwich plate, would involve the use of the smaller Sierra clutch / flywheel, a flywheel spacer and an unusual starter motor position.

Option 2. would seem to be a better bet. The MT75 has an integral bell-housing, whereas the LT77 has a removable one. See drawings below. If the MT75’s integral bell-housing could be removed just aft of the hole for the clutch lever, then it would make things much simpler. Getting the jig right for the new mounting flange would be much simpler, I could use all standard ‘off the shelf’ Rover parts (apart from clutch plate) and life would be simpler…….

Unless of course the larger LT77 bell-housing fouled the front prop-shaft (see bottom picture). The lump to clear the starter motor seems OK, but the lump for the clutch lever is a real problem. For the prop-shaft to clear this there would need to be a 30° bend in the front prop-shaft and there would be no room for the clutch or brake pedals.

Step in Option 3 (Rover V8 adaptor Plate).

Remove the front 75m the MT75 bell-housing, leaving the hole for the cable clutch assembly. Make up a custom adaptor plate out of 64mm of aluminium CNC’d on a mill to reflect the front of an LT77 bell-housing minus the clutch lever relief. This plate will then be TIG welded to the front of the MT75 gearbox. The final system will use:

  • Sierra Cable clutch assembly
  • Rover V8 manual flywheel
  • Rover V8 manual clutch housing
  • Ford Clutch plate (possibly Transit)
  • Rover V8 SD1 starter motor
  • A big chunk of aluminium

I’m really starting to go off 4×4! But, if I gave up now, the chance of holding a big shiny piece of CNC machined ally would also disappear. MMMmmmm Shiny…….

LT77 gearbox bellhousing CAD

This is what an LT77 5 speed bell-housing (green) looks like super-imposed onto an MT75 4×4 gearbox.

MT75 LT77 gearbox adaptor plate

MT75 to LT77 gearbox adaptor

LT77 MT75 gearbox adaptor plate

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