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MG MGA - Nulon in gearbox

MY 1500 A is notchy on the 1- 2 shift and is not happy 3-2 unless double clutched. The syncro works ok as it was renewed during a rebuild. All other shifts are good. I know it will never be a hot knife through butter shift. I was advised that Nulon may help.
I'm concerned ,that while it may ease shifing effort, the syncro action would be effected. Loss of friction on the cone.
Anybody tried this product in Aust.?
I remember in an other life that we used to add .with great success, bardahl, to Ford Mk 11 Zepyhers to fix
second gear baulking. All the Ford warranty mods. in the world never worked. Thanks Sean
S Sherry

The syncro hub springs get weak with age. If the baulk rings were replaced then perhaps it is weak springs. I always use Castrol GP50 oil in these boxes to make the laygear needles last longer but the heavier oil slows the syncro a bit when it is cold.
GP50 is no longer available here so now I use VMX.
Garth Bagnall

I have avoided using "anti-friction" additives etc in synchro gearboxes because, on the off chance that they really work, the synchro-mesh operation will be affected. I doubt whether the awkward gear changes are anything to do with synchro-hub springs, what I found (many years ago) was excessive end float between the individual gears. I had new thrust washers made to address this situation because the "thickest" factory replacement ones (then available from the dealers parts departments) were insufficiently thick to restore the recommended clearances (I doubt whether the factory considered the cars would cover the high mileages that they have!). With everything returned to factory specs MGA gearboxes work quite well (my 1600 coupe and roadster were restored over 20 years ago and have both done many thousands of miles).
Barry Bahnisch

Barry I should have known better. After a life time rebuilding Automatics, one key factor in ensuring proper and lasting function was carefull attention to factory clearences. [ both clutch pack and end float]
ie., to the minium specs. The more clearance the more chance the clutch drums have of not staying straight and true to the shaft. Ditto syncro hubs. I'll have to live with my carelessness, as the work to pull the box again would be ,over my dead body ! Thanks for your input Sean
S Sherry

Sean, Many thanks for your kind words. Upon reflection, the factory replacement thrust washers were probably intended to overcome variations in new gearbox assemblies rather than for gearbox overhauls. It is surprising how a few thou can make a difference to gearbox operation!
Barry Bahnisch

After reviving my A after sitting quite a few years, the gearbox was notchy and noisy. I changed all fluids exc. including the gearbox before and after driving the car. No change after a few hours of driving. A friend recommended changing to Red Line synthetic (10-40) in the gearbox, which worked very well. Much smother, less noise, and quieter immediately.
Russ Carnes

That would be smoother....
Russ Carnes

Russ, I ran the car for a two hundred mile trip with the Redline synthetic gear oil. The gears are very quiet and the shifts are much the same as with 20/50 engine oil. BUT ,,, it has turned a slightly weepy gearbox into a leaky one. I guess if it was a late model Toyoto 5 speed the synthetic would have been ok. Sean
S Sherry

This thread was discussed between 21/10/2008 and 12/11/2008

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