MT75 4×4 Gearbox

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The MT75 is available in 2wd and 4wd formats. The MT75 4×4 is used in the Sierra Xr4x4 and in hybrid form it appears in the Ford Ranger/Mazda B Series pickup. Although the pickup uses the Duratec, the box is longer and fitted with a second separate low ratio selector.

The MT75 4×4 was found in the following models:

  • 2.0lt DOHC 4×4 Sierra Saloon and Estate (1982-1993)
  • 2.9V6 4×4 Sierra Saloon and Estate
  • Sierra Sapphire xr4x4
  • Cosworth Sierra 4×4
  • Cosworth Escort YB 4×4
  • Granada Scorpio 4×4 (1985-1991)

There are 3 different bellhousing patterns. The V6 has a different bellhousing to the 2.0lt DOHC, the 2.0lt Cosworth and the 2.8 v6 and 2.9 v6 version have different input shaft lengths.

It maybe that a Ranger / Sierra hybrid bolts directly to the Duratec v6 without an adaptor plate, but without purchasing loads of gearboxes it’s hard to tell.

A good article on the MT75 2wd gearbox is located here.

Originally, the intention, with this design, was to use a Jaguar AJ30 Duratec 3.0 V6. The X-type has a MTX-75 gearbox with attached transaxle. The S−Type has longitudinal Getrag gearbox. To mount the engine length ways and use a Sierra MT75 4×4 gearbox an adaptor plate would have be needed.

However, since the purchase of a Jaguar AJ-V8, the gearbox may well be a Nissan Skyline RB26DETT.

MT75 Cosworth Gearbox CAD

The above shots show the gearbox complete with the rear balancer. It is important that this is used. I have seen some vehicles that don’t have one. The balancer is there for a good reason – it’s needed!

It is not simply a lump of metal and rubber, it’s a small flywheel. It is there to take the initial strain out of gear changes. Without this damper there would be greater strain on the output shaft bearings and gearbox internals. Vehicles without one, would first make a whine noise, then simply shear their output shaft – that’s if the chain to the front prop doesn’t snap first.

MT75 Cosworth 4x4 Gearbox CAD

The above is pretty accurate to the box I have, but if you compare it with the box below you will see that some of the lumps and bumps are slightly different, suggesting that there were several variations available.

image: MT75

The gear ratios of the MT75-4×4 gearbox are :

  • 1st Gear – 3.89
  • 2nd Gear – 2.08
  • 3rd Gear – 1.34
  • 4th Gear – 1
  • 5th Gear – 0.82

The ultra rare Transit Countryman was also 4×4 but this gearbox was very different. The front propshaft is on the other side and the whole thing is much longer.

Transit Countryman 4x4 gearbox

The Ford Ranger / Mazda B2500 was also fitted with a 4×4 gearbox but had the central addition of a low ratio selection lever. I believe some of these were MT75 derived.

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