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G: Gearbox (Twin) G4 Final drive shaft mod

vibrac

Well Known and Active Forum Website User
VOC Member
This is the hollow shaft that runs on the main shaft. On preparing our racer twin for next season we found the clutch end had experienced some heating and the bush G17 slipped in and out with finger pressure. Good authorities tell me that there is a modification written somewhere detailing extra holes in the body of G4 and scalloping of the that end to increase lubrication which is restricted by the close association G12 and the washer G20/2 against the bushed clutch side end. I have had a good search for any info and drawn a blank can any one guide me to it?
 

Peter Holmes

Well Known and Active Forum Website User
VOC Member
Speak to Graham Maughan or Steve Hayward at Maughan & Sons, I think it is a well known problem.
 
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vibrac

Well Known and Active Forum Website User
VOC Member
Yes well known but that article about it seems very elusive I dont think its in 40 years on but there is a chance, I will have a search (for the book!) its times like these that a full index of MPH would help
 

passenger0_0

Well Known and Active Forum Website User
VOC Member
As an alternative suggestion, on the Fast Lady I simply ran the gearbox oil level at the top mark level, rather than the lower, and never had an issue with this bush or shaft.
I didn't do the 'drill the oil hole mod' as oil doesn't flow against centrifugal force.
 

Bill Thomas

Well Known and Active Forum Website User
VOC Member
I cut a pair of small V s in the end, I am sure I didn't think of it myself,
Maybe Trev or the late John.

Also loaded the bush with Copperslip, Something we were told to do ,
With the Mini Car Primary Gear, Acts as a lube plus a sealer ?.
 

Peter Holmes

Well Known and Active Forum Website User
VOC Member
I seem to remember a few years back Graham Maughan came to the Hever rally with a newly manufactured complete set of gearbox internals, all fully operational set up in jig, I am fairly sure he mentioned that replacing the G17 bush with a needle roller bearing was possible and they were able to supply this, does the Surtees 5 speed gear cluster not have needle rollers instead of bushes?
 

Robert Watson

Well Known and Active Forum Website User
VOC Member
My main Vincent (the Woolly Mammoth) had needle rollers both ends of the G4 in the 4 speed until I put the Surtees 5 speed in it. My Black B Rapide had a needle roller on the inboard end with a bushing on the outer end, pushed in slightly and a seal fitted.
 

john998

Well Known and Active Forum Website User
VOC Member
Hello, I had a G16 Bush collapse some years ago, so I drilled a couple of 1mm holes in the tapered end of G4. Do not use phosphor bronze for the G16, G17 Bush.
John.
 

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