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Gearbox Nose

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mylesw

Jedi Hopeful
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Hello

I have changed the clutch on my TR4 to a TR4A type. I also have an TR4 overdrive gearbox ready to install. The Moss catlogue says something about making sure the Front Cover is the correct one otherwise it interferes with the clutch diaphragm. How do I check if the front cover on my O/D gearbox is the correct one or not? If it's not correct do I need to buy a new one or can I machine the one I have?

Thanks for your help.

Myles
 
I assume that you are talking about the front cover that the throw-out bearing rides on. They give the lengths at the Moss site. The early one is 2 3/8", the later TR4A type is 1 31/32". Measure it. If you have to cut it down, it's an easy enough job for a machine shop. Or, you probably could do it yourself with a hacksaw and then true it up with a file. I would imagine that the dimesions Moss gives is just for the sleeve section of the front cover.
 
/bcforum/images/%%GRAEMLIN_URL%%/iagree.gif The measurement is taken from the 'step' at the end of the machined area to the tip of the front cover. 2" is short enough, IMO.

Although reportedly some 4A pressure plates won't hit the longer front cover, careful measurements convinced me that mine would. It looks fine until the PP is compressed, then the fingers move inwards and grab the nose.

I trimmed mine with one of those cheap angle grinders from HF and a cutoff blade. Didn't seem worth setting it up on the lathe. Hacksaw would also work. However, I would recommend removing the front cover from the gearbox for cutting, both for better access and so you can clean away the swarf. No sense leaving it in there to potentially get into the seal and ruin it (or get in the clutch and tear it up).

Be sure to carefully deburr the outside edge afterwards; a small radius is a good idea IMO. Also check that the sleeve slides easily before putting it all back together.

Don't forget that the bolt heads for the front cover need to seal against gear oil. Early boxes used lead washers that need to be replaced every time, but I used copper washers (from HF) smeared with Hylomar and they seemed to seal fine. I've also used RTV in the past with success, but I don't recommend it.
 
Thanks for the advice. Just took the front cover off my old gearbox and cut it down using a hacksaw. Deburred it and it looks good. Removed the clutch cross shaft pin on the old box to remove the cover and of course only half came out so got that to deal with now... However learnt my lesson and on the new box just slid the shaft over to get access to the front cover. Replaced it with my newly shortened one. Had to reuse the gasket and used the old copper washers from the bolts. Both looked in good condition so have to cross my fingers and hope...

Myles
 
mylesw said:
Removed the clutch cross shaft pin on the old box to remove the cover and of course only half came out so got that to deal with now... However learnt my lesson and on the new box just slid the shaft over to get access to the front cover.
Click to expand...
Bad idea, IMO ... you want to be certain that pin is in good shape! By all means take it out; if only half comes out then it was broken and the clutch would not work properly when you put it all back together.

After having to pull a gearbox myself because that #@! pin broke, I'll never install another without
a) Checking the pin
b) Adding a cross bolt to reinforce the pin

IMO it's also a false economy not to remove the shaft and inspect the shaft/bushings, as long as you have it out of the car. They do wear, and mine have usually needed to be replaced.
 
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