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MG Car Repair/MG-TD Gearbox Rebuild


3rd/4th slider gears
3rd/4th slider gears  

3rd/4th slider and synchromesh hub
3rd/4th slider and syn  
I purchased a new 3rd/4th gear slider to eliminate excess wear on the grove that the selector fork rides in, but suspect the new slider is improperly machined. It will not slide onto the synchromesh hub by any amount of thumb force, but must be persuaded with a firm rubber mallet to get into position. The original can be pushed on by firm thumb pressure alone. This new slider gear has the correct sized grove, but are the teeth not machined correctly when I have to hammer it in place with a mallet? The part is listed as "Made in England". Should I return it to the vendor as a defective part?

Hi Kenneth.  The first photo shows two sliders.  We call them Striking Dogs.  The Sliding Dog should slide easily onto the Sliding Hub, only the locating balls giving any resistance.  The need for a mallet sounds excessive.    

I would examine the splines of your old Sliding Hub very carefully. Is there a high spot?  The splines may have developed a raised edge that the new Sliding Dog is sticking on.  It might just need a little work with a needle file.  

Failing that, you would appear to have a defective new component.  

You could get your old selector forks built up to fit the old dog.  It is usually the forks that wear, not the dogs.  A good machine shop should be able to do that for you.  

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Barrie Jones


MG Sports Cars from 1949 to 1980 - Including MGB, MGBGT V8, TF1500, TF, TD and modern Midgets. I also specialise in SU carburettors, Lucas wiring, suspension, steering & brakes.


I have owned my 1955 TF1500 since 1966. Technical specialist for the TD and TF with the MG Car Club T Register. Also owned 20 MGBs and currently own an MGBGT V8. Written 3 books on MGs and produced a DVD on how to strip and rebuild the TD/TF gearbox.

MG Car Club.

Barrie's Notes on the 1953-55 MG TF (author). /=====/ Barrie's Notes on the MGB (author). /=====/ Barrie's Notes on the MGB GT V8 (author). /=====/ The Essential Buyer's Guide to the MG TD, TF and TF1500. (author)

M Phil, C Eng, BSc (Eng).

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