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CVRT Gearbox OIL SEAL replacement PART 1

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Many Thanks to Richard Farrant for the many message exchanges and brain picking!



List of parts

8 Slotted nut (incorrectly numbered in spares book - should be 48?)

47 Tab Washer

46 Washer

45 O ring

44  O ring

43 Output Drive Coupling

42 Oil Seal

40 Bearing Retainer and Oil Seal Holder

39 Bearing

38 Bearing Inner Spacee

37 Bearing Outer Spacer

36 Inner Lock Ring Retaining Tab Washer

35 Spacer

34 Steering Hub inner slotted lock ring

33 Steering Disc Hub

32 Oil seal

22 Gearbox Steering Hub Bearing Retainer and Oil Seal Holder

23 Bearing

24 Spacer

25 Spacer

26 Roller Bearing

27 Roller Bearing outer track retainer

13 Steering hub drive



The O rings are BS 120 and BS 131 however I believe BS 131 should be BS 133

The Outer Oil Seal AS33726237VIT42  DOUBLE  LIP - The British Spares book gives metric measurements for this seal that are nonsense, no seal can be matched to these measurements

The Inner Oil Seal 117.47 mm x 142.88 mm x 12.7 mm  (4.625 x 5.624 x .5 inch)  DOUBLE LIP if possible.  Equivalent AS56246250VIT18 (double lip) OR  - SKF CR46155(Single lip)

All seals and O rings should be Viton and all Oil seals should be double lip.

Do not waste time using Nitrile Seals. The British MOD are using PTFE seals, they are highly expensive and not needed for MV use  indeed they may lead to shaft groove wear.


The oil seals and O rings can be obtained from BarnwellManchester.


Special Tools needed:-

Motorcycle suspension castle socket 6170 – This will need to have the internal castles ground back slightly

Drive Shaft puller – it may be possible to adapt/modify a 3 leg puller

Inner Lock Ring IMPACT socket – Special Tool!  ¾” drive (contact me for info) to remove item 34

Possibly 1500Nm impact driver to remove item 34


Procedure to replace outer oil seal.

Remove gearbox out of vehicle, drain all oil, leave the brake caliper in place.

Knock back  tab washer item 47

Using the 6170 castle socket remove the slotted lock ring, to prevent the Drive coupling moving insert a suitable drift into one of its three holes and let it rotate against the brake caliper.

Remove item 47

Fit puller and pull off drive shaft  coupling against centre shaft. The washer item 46 can be recovered when the driveshaft coupling is removed.

Remove the bearing retainer item 40 lever out oil seal item 42

(Note to remove the bearing retainer remove the 6 retaining screws, using 2 x ¼” unf bolts screw into the housing in the threaded holes provided. Recover the bolts after the housing is extracted)


If there is a dust cover fitted to the bearing remove it, since it’s not needed and should not be fitted.

At this point the outer seal can be replaced and if the inner seal is not to be replaced then reassembly can begin. If the inner seal is to be replaced go to Inner seal replacement.



Examine the seal surface of the drive coupling, if it has a groove, as confirmed by a finger nail fit a speedy sleeve shaft repair (see Youtube), the shaft may have a polished ring where the seal has rubbed, this is fine as long as no groove can be felt with a thumb nail.


Use Blue Hylomar to seal the bearing housing, use blue thread locker to lock the retainer holding screws and screw in using a sutable HAMMER impact wrench to tighten.


Grease liberally the oil seal, grease liberally the drive shaft coupling, fit to the splined shaft and knock in using a soft drift, such as aluminium, brass or nylon.


Fit the two O rings, on the inner (smaller) O ring use a smear of silicon gasket maker.

Fit the washer, 46, smear grease on the lip where the outer O ring fits, smear grease on the outer face of the washer, tighten the slotted nut, and then remove it.

Fit the lock tab and grease the outer face

Refit the slotted nut and tighten – WARNING, if overtightened it may destroy the locking tab.


Knock over two of the lock tabs into the slots in the slotted nut.



Left Viton Seal, Centre Nitrile seal with gaiter spring, old nitrile seal with steel casing and spring fingers - maybe found in Belgian gearbox  get rid ASAP




Left to right:  Drive shaft coupling extractor,  drive shaft coupling lock ring retainer socket, lock ring tab washer, impact socket to remove inner slotted ring 3/4 drive.



Bearing retainer and oil seal holder removed, clearly visible is the bearing, which still has it's dust cover fitted - should have been removed!

Edited by Diana and Jackie
numerous corrections ... Jan 2020 last edit, Jan 2021 added correct metric dims and imperial dims oil seal, plus note on PTFE seals
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