Quote:
Originally Posted by Derek UK
The 2 seals are an O ring and what is know as the top hat seal. If you do have an 1800 box it has the fine toothed gear and black gear. There are no other gears that can be used with this fine toothed gear. 1800 used Smiths instruments whereas the Amazon used VDO.
Talk to OD Spares in Rugby to see if they can swap over an Amazon gear. That will at least give you a choice of the Amazon gears. They will probably say that D type gears are hard to find. Certainly some are easier than others. They might be able to do it while you wait if you take the box to them. Not too far away. I think you just have to take the flange off and then remove the tail casting. The gear then just slides off. I'm interested in this as I have an 1800 OD box in the garage. I can check in the parts book but I want to know if the same gear is used in both the M40 and M41.
http://www.odspares.com/
01788 540666
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Thank you for that, it is really helpful to know that no other pinions will fit. Having researched this issue a bit it would appear that the M40 and Type D O/D speedometer drive gears are not the same, but the metal M40 one may be machined down to fit. I don't have a M40 gearbox to borrow the speedometer gear from, so this is a bit of an academic issue.
This has been a useful discussion in the posts above, but I have concluded it is a problem that just isn't worth trying to fix. I'm happy just knowing the speedometer is a bit out and mentally correcting for that, or using the GPS app on my cell phone (that I already use for internet radio reception and SATNAV) if I ever need greater accuracy. I like the advantages of the type D overdrive unit, it is a pity Mr Volvo never intended it for a 4.10:1 rear axle - otherwise there would be a 16t pinion that would fit, but never mind.
As is so often the case, this forum is so useful in getting to the bottom of issues. Many thanks to all those that contributed to this one.
:-)
Alan
PS. Another way of skinning this cat would be to have the VDO speedometer re-calibrated. This company would seem to provide that service, but I doubt it is cheap (or easy):
https://speedycables.com/speedometer-calibration/