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Mini Gen 1 GTT Spec Supercharger ‘PTO PLUS’ Rebuild (+Options)


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NEW SPEC ‘PTO PLUS’   REBUILD…. In addition to installing new GTT Uprated PTO Gear Set, GTT Spindle, uprated bearings & seals with an oil change. (See below)… PTO Plus rebuild now also Includes Removing Snout & inspecting bearings, GTT uprated Coupler installed + Flushing out & Oil Change!….. Removing & Inspecting rotor pack condition (checking for excessive end float) + dressing out any high spots on the rotors causing rubbing to casing or each other + Cleaning of rotors and internally or rotor housing…… Repacking Rotor needle rollers grease.

BMW can now only supply recon units from Eaton at a  whopping £3450!!!!! (inc vat)  and second hand units of ‘unknown condition’ becoming both scarce and more expensive, a GTT rebuild on your own charger makes much more sense.

New 2020 Optional Extra…. The “GTT Fork Drive Pro”

This has been designed with 50% less rotational play/backlash when mated with the water pumps “fork drive”… as many will know the OEM one gets very worn from this and becomes both noisy and unserviceable. This is a Exclusive optional extra item we install with GTT PTO PLUS Rebuilds.

Note: some cases might be mandatory to replace if your OEM one has worn.

£29+vat Extra (installed only)

See images and full spec/advantages here:




If your supercharger is making a horrible rattling or clattering ‘diesel like’ sound the chances are it won’t be too long before it overheats the engine, blows the head gasket or worse!  The charger has a known week spot; namely the oil seal in the rear main casing behind the small drive gear in the PTO (Power Take off) gearbox. The PTO is a built in gearbox on the rear end of the supercharger which supply’s drive to the water pump via a drive ‘fork’ .In practice what happens is the seal fails due to a combination of age and non ideal design resulting in the already small amount of oil in its dedicated chamber being sucked out and onto the rotor assembly and inlet tract of the engine, this oil is then burnt in the combustion chambers without you even noticing. Once the oil has gone, then the real damage starts!

Firstly the gears & bearings run bone dry, overheating and literally grinding away all the teeth from both gears until, the gears have no virtually no tooth form and mesh between the two gears is lost altogether .The result?… All drive is lost to the engines water pump. At this point the engine will rapidly overheat causing potentially huge damage. The good news is the noise of the charger normally will give you warning of this impending doom first, so don’t ignore it!

Changing the supercharger oil is no bad thing but if its leaked out past the seal a first time ,the chances are it will leak out even quicker the second time . And that’s assuming you caught it before it turned all the internals into a pile of fine metal swarf!  Fortunately the M45’s front end gearbox rarely loses oil.

Repairs need to be professionally carried out at this stage to stop the noise and further damage to engine as mentioned.. Until now nobody in the UK has been able to offer a full repair solution to this scenario which is becoming more and more common as the cars get older.

The important thing to consider is that ALL the parts in the PTO gearbox will be damaged from running it dry, changing one part will only accelerate wear to the others. In particular there are two seals that need to be changed both to a higher temperature rated material and of better sealing design. Next you need a new gear set. (Never change just one of the two gears!) . The problem is these gears are not available neither from Mini or Eaton, therefore GTT have designed and made a brand new replacement set of improved design.  Specifically there is increased mesh between the two gears.

Also the needle roller bearing that supports the drive shaft, the end plate bearing and finally the driveshaft itself must all be replaced.

This little, and often over looked driveshaft supports no less than 5 items. Namely the water pump drive fork, oil seal, ball race, large gear and the needle roller. This part will be damaged when run dry and MUST be replaced. Only GTT make this and supply it with every rebuild.

To put it  into perspective ,even if you could get ALL these parts off the shelf it still takes specialist tooling and skills to get it all split down , old bearings and gears removed ( especially the needle roller bearing which is in a blind hole) ,and  then  all the new parts refitted  correctly.

Rotors, rotor bearings and snout assembly are also visually checked, with bearing radial and axial end float measured. Backlash in the front gears and rotational smoothness are all checked as a matter of course prior to reassembly.

Thank fully aside from the above mentioned issues & some light rotor contact (which isn’t really a problem unless serious) the M45 is a pretty bullet proof little unit. The only other thing worth changing whilst dismantled is the Snout Coupler. This is the round hard plastic shock absorber device that transfers drive from the pulley & ‘snout’ assembly to the rotors. Three equally spaced drive dowels entering one side of the coupler transfer the drive to a second set of driven dowels pushed in the other side of the coupler. These couplers are renowned for causing noise and although they often appear to be in good condition, changing to an upgraded GTT Coupler of superior spec material is automatically done during the rebuild, as it is easy to change whilst stripped down.

The next stage is to check & re-grease the rotor needle roller bearings, and then replace the rotor pack, snout assembly and rear end plate. At the same time carefully cleaning everything, and dressing out any minor damage to rotor shafts or casings. Sealing compound is applied to mating faces, and housing bolts re-torqued carefully. Last but not least suitable high performance fully synthetic oil is measured out and put in to both front and rear housings.


Normally a 48hr service turnaround of your own supercharger sent direct to GTT. Service is to rebuild your own supercharger (not exchange)

Remove Standard Pulley + Supply And Fit GTT Reduction Pulley Service

It is an ideal time to have your Standard  pulley removed to be replaced with a GTT -15% or -17% pulley, this is the most cost effective time to replace and the most beneficial mod for the Supercharged Mini with approx. 25-30BHP gain! . Please select option. Note: You will need to purchase a shorter drive belt with reduction pulleys.

Just £169+vat extra in conjunction with ‘PTO PLUS’ Rebuild

Spec of pulley: https://www.gtt.uk.com/product/mini-gen-1-gtt-supercharger-pulley/


The shipping charge is for us to return your item (we do not collect your charger)


£499+ vat.



Additional information

Weight 11.5 kg
Dimensions 47 × 37 × 37 cm
Rebuild Options

PTO PLUS REBUILD ALONE, Rebuild + GTT -17% Pulley, Rebuild + GTT -15% Pulley

Fork Drive

Install GTT Fork Drive (+£29), No Fork Drive