LT77 Help Please!

#1
I was really pleased with myself - I've rebuilt the main part of the LT77 box with no problems, right up to now, where I try to fit the 5th gear and selector mechanism to the rear of the mainshaft. When I put all of the components together and fit them, there is insufficient room for the circlip to be fitted.

The location of the parts is decided by the position of a circlip, which is to the rear of the bearing that runs in the centre plate. This is new, and in the correct position:


On top of this there is a spacer, which I didn't photograph, but I know it's the right one as this whole assembly was cable-tied together on removal. The 5th gear then fits on top of this spacer, with needle bearings inside it:


This sits nicely on top of the spacer. Then, on top of the gear goes the parts below, in the following order:
Baulk Ring
Sychro Hub
Support Plate
Selective Washer





These parts will only fit one way and again, all slide down the shaft nicely until all are tight against each other. Unfortunately, when everything is in position, the gap isn't anywhere near large enough to fit the circlip properly in its groove:


I'm starting to think that it was never fitted properly in the first place - unfortunately I started stripping the box a good 6 weeks ago, so have forgotten exactly what everything looked like! I did take an overall picture of the that end of the box with the cover off, but I can't really make out if the circlip was fitted properly, or not. This is a zoomed in crop of that picture, but I can't make my mind up.



The smallest selective washer, if it were actually available, is 5.10mm deep, so would only give an extra 0.3mm over what's already fitted, which still isn't enough to get the circlip in the groove properly.

I guess my only option is to machine down the spacer - does anyone have any other thoughts, please?
 

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colnerov

Well-Known Member
#2
Hi, It's been a long while since I've done a LT77 box rebuild, but I think the mainshaft needs to
come through a bit more. I have found an old Haynes manual for a RR that actually describes
how to. It says that the circlip holds the shaft in position. Your first photo looks like the circlip
isn't touching the bearing, so is something missing on the mainshaft build up to allow that gap
and so not bring the mainshaft through far enough? I hope that reads OK.

Colin
 
#3
Thanks Colin.

The mainshaft isn't poking through quite as much as it should, as the selective washers aren't fitted in the front cover yet - I'm hoping they will turn up today. It seems odd that there is nothing between the bearing and the circlip, but everything seems to be where it should be and I've got no parts left over! The 4x4 versions are slightly different, so that may explain the difference with the circlip locating the shaft.

Looking at the TR7 parts manual, here:
http://www.tr7.co.uk/pdfs/Triumph_TR7_& ... Manual.pdf
On page 30, the circlip CCN120 fits straight after the bearing, which is what then influences the positioning of the 5th gear assembly on the mainshaft. It does seem a bit strange that there's a gap between the bearing and the circlip, which wasn't there when I did the 1st gear bush endfloat check with the spacer, as per the workshop manual. I'll have to have a closer look later.
 

ghce

Well-Known Member
#4
Cant help much on the technical side however I love the quality of your photo's, what camera are you using?


EDIT I see now a Canon A590IS :oops: should have looked for the EXIF data first




Graeme
 

unstable load

Well-Known Member
#5
I am going to go all anorak on you now, but my first Supervisor in aviation always told me that circlips go on with the 'sharp' edges towards the load.
From your first picture, I'd say you need to flip the circlip so the sharp edges are facing outwards, allowing them (in theory) to grip better and not
expose the slightly rounded face to the risk of camming out under load. :D
 
#6
ghce said:
Cant help much on the technical side however I love the quality of your photo's, what camera are you using?
The wife's - don't tell her! :D

I've now worked out what I've done - the circlip was in the wrong groove! On closer inspection this evening, I could just make out the groove next to the bearing, so the circlip is now hard against that. The 5th gear assembly is now in the correct place and the circlip fits on the top of the 5th gear synchro support plate.

Thanks for the circlip tip - I'll remember that one for future reference, I'm not taking the 5th gear assembly apart again now :mrgreen:
 
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