Rebuilding a pre unit 4 speed gearbox may not be too hard, but getting all the correct wear parts together sometimes is . After rebuilding these gearboxes for years, I finally put together a kit of all the commonly replaced parts. This kit has most everything you need to get your Triumph pre unit four speed gearbox back into shape.
This is for gearboxes from 1950-1960, which have bronze bushings to support the layshaft. If your pre unit gearbox has needle bearings on the layshaft order the 650/750 4 speed kit here.
This kit is not for pre war or earlier style 1946-1949 transmissions.
The high gear bushing is a two piece design which is easier to install than the originals, but it must be honed or reamed to size after installation. The low gear bushing also needs to be sized after installation- this allows you to custom fit your bushings for an exact fit.
Instructions and tips are included in a 28 page booklet.
Tab washers and oil seals are included, and this convenient and complete kit will also save you money as these components purchased separately would cost over $300 at most online shops.
This 20 piece kit includes:
57-0448 HIGH GEAR BEARING x1
60-3552 (S35-7) MAINSHAFT BEARING x1
57-1367 LAYSHAFT BUSHING x2
57-0412 GEARCHANGE SPINDLE BUSHING x1
57-0946 OIL SEAL 4 SPEED SPROCKET x1
57-2240 (T732) MAINSHAFT LOCKING WASHER x1
57-3988 (PT108B) CLUTCH PUSHROD BUSHING x1
57-1370* (2 pc) HIGH GEAR BUSHING KPMI x1
* MUST BE SIZED AFTER INSTALLATION
57-0928* LOW GEAR BUSHING x1
* MUST BE SIZED AFTER INSTALLATION
57-0057 GEARCHANGE SPINDLE BUSHING x1
57-0023 KICKSTARTER SPINDLE BUSHING x1
70-3309 SHIFTER O RING (if needed) x1
57-0404 QUADRANT RETURN SPRING x2
57-0405 SHIFT PLUNGER SPRING x2
PT104B DRAIN PLUG FIBER WASHER x1
QUADRANT SPINDLE SPLIT PIN x2
Don't waste all your time looking in parts books, spend it putting your transmission together with all new quality parts.
This kit is also great if putting a later Unit construction 4 speed gear cluster into a pre unit gearbox. The needle bearings will replace the bushings with no modification.
