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People often ponder if they can ‘upgrade’ their MQ diffs with units from another vehicle with the most popular candidate being GQ units.
No diff from any other vehicle will bolt into an MQ without major modifications!
The intent of this page is to describe the hurdles you may face when using diffs from different vehicles (knowledge is power!). It is an ‘overall’ document, and would apply to any diff such as GQ, Dana or even Unimog. It is not a how-to.
Things to Consider
Diff Pumpkin Location
MQ’s have a RH droop transfer case, ie the front and rear outputs of the transfer are both on the RH side (Australian drivers side). Both the front and rear diff ‘pumpkins’ are offset the same, so that the drive shafts are straight. Newer vehicles, such as the GQ, have direct-drive rear outputs on the transfer cases, which come out of the center. This means the rear diffs also have central diff pumpkins, and the front are still offset (to the RH side on GQ). Some American made vehicles, such as Jeeps with Dana diffs, may have the diff pumpkin offset to the LH side.
Having an offset transfer output and central diff pumpkin on the rear puts the drive shaft on an angle (when looking from above/below the vehicle). This can cause bad vibrations and lead to premature failure of the uni-joints. Further exaggerating the problem, vehicles with suspension lifts already have an increased drive shaft angle when looking from the side. However, there have been numerous people that have run 4wds with offset transfer + centre diff pumpkin (such as RMP&O on Patrol4x4.com forum) and they have not experienced any problems.
If you only upgrade 1 diff, and it is a different stud pattern to the original, you would need to carry 2 spare tyres. This would be quite inconvenient.
Some diffs may have different chassis-to-diff hoses/setup/locations. On Australian MQ’s;
The master cylinder is on the RH side of the vehicle.
The front steel brake line passes across the firewall (above the engine), along the top of the LH chassis rail and stops just above the diff. A rubber hose connects the chassis steel hose to a steel hose that runs along the diff. At the ends of the diff mounted steel hose, a rubber hose connects to the brake calipers.
The rear steel brake line travels along the RH chassis rail. Near the fuel tank, a rubber hose joins to the steel brake line on the diff.
The rear diff you upgrade too will likely have brakes better than the MQ drums, or at least equivalent. Be mindful of pressure requirements (ie that your master cylinder is of sufficient size).
Some newer vehicles also feature the handbrake within the rear disc (basically a mini drum brake inside the disc rotor). You may prefer this over the MQ’s transfer mounted drum brake.
Many diffs that are desirable upgrades for the MQ are wider than the stock MQ counterparts. Ensure the final location of your wheels is acceptable in relation to your guards.
No matter what diff you are putting into your MQ, you will need to fabricate all new suspension connections to suit your desired setup, which could be leaf sprung under (like stock), leaf sprung over, or coils. Whilst planning such mods, be mindful of the diff pumpkin location, as it may interfere with your pick-up points. Similarly, if you are using diffs from a coil-sprung vehicle and plan to use the mounts it already has, check how these line up suitably with the chassis.
Other diffs will likely have different ball joint sizes and tie-rod location than the C200 in the MQ’s. Consider how you will connect these dissimilar components.
Other diffs may have the pinion flanges at a different distance from the axle centreline. This may require your drive shafts to be shortened/lengthened to suit. The flange may also have different bolt centres or count (for example, GQ rear have a larger bolt pattern). Some vehicles may also run a completely different drive shaft to pinion connection, which needs to be considered.
GQ leaf sprung diffs
Jelmer160 from Patrol4x4 has done the conversion. See his thread here: http://www.patrol4x4.com/forum/nissan-patrol-mq-mk-12/jelmers-patrol-160-holland-314225