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Rodbr

Gearbox issue-reverse gear

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I had my overdrive box rebuilt by a well known chap. he advised me that the box would free up after about 1200 miles. The box is notchy and superb but for a small issue.

When selecting reverse,                    it doesn't!!!!

The lever goes over as if to select but on releasing the clutch I get nothing. The selector seems to go over centre and past the selection location. The other gears are tight and excellent. no issues at all, 

no nasty noises and overdrive works firmly as requested with mid range pressure set up, snappy but not break a halfshaft. I hate a lazy slow overdrive selection.

I must presume that there is some sort of stop to put reverse selector in the correct position but I'm unsure where it would be.

It's not a major issue but can be embarrassing after the third or forth failure to select reverse.

Advice would be appreciated.

Rod

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Sounds to me like the reverse gear is not being moved when the selector shaft is, maybe the "Fork - reverse selector" is loose on the shaft.

https://www.moss-europe.co.uk/external-gearbox-tr2-4a-1953-67.html

Item 53 on this page.

If you can get the remote gear change assy off the box you should be able to see whats going on.

Bob.

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Hi Rod,

I agree with Bob.  The selector fork #53 engages with sub selector fork #65   Fork 65

 this  moves the small reverse gear cluster back and forth.

It sounds like the forks are not interacting.

 

Remove the GB top cover and you should see the problem. It is easy (Ho ho ho) to sort - assumng that is the problem.  Should have been found on the bench.

 

Roger

Edited by RogerH

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This could be granny sucking eggs stuff.....

Have you tried easing the clutch up a small amount whilst moving the stick rearwards.  I had a 3 synchro box that sometimes refused to go into reverse and that technique worked.  The stick goes a long way rearwards to fully select reverse.

Also, the early car gearbox requires the stick to be lifted to get it on the reverse selector rod, later cars have a ramp that the stick wil slide up on.  The square sided reverse selector is preferred by the racers as it reduces the risk of reverse engagement when changing gear in a spirited fashion.

 

Cheers

Peter W

Edited by BlueTR3A-5EKT

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Hi There,

Bob and Roger This is what i thought of but it would not be an intermittent issue if it was sliding surely.? if the forks were not interlacing surely it would go into reverse the once as it would not come back out of reverse

Hi Peter,

That method does help.

Considering who built the box it was built as a fast road box with competition overdrive set up. The reverse detant is a very positive lift and select. The gates are as new square with no wear at all and as said notchy which is what i wanted.

It has occurred to me that I installed the anti lever vibration fix as the gear lever buzzed badly and was irritating. That issue was sorted by the "fix" can't think that it would cause this issue but!!!!!!!!!!!

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Hi Rod,

you didn;t mention     'intermittent'.

 

Ignore selector fork etc if intermittent.

 

Roger

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Not so, it can be intermittent, the will always be some friction between the shaft & the fork. The reverse gear itself has no "detent" it is free to slide on its shaft, the only thing which positions it is the selector shaft via the fork.

If the gears are all lined up then the gear would take no effort to move into mesh, if however the cogs were not in line (Peter's scenario) then the shaft would move leaving the gear behind.

Bob

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Hi guys I am reluctant to start again removing the tunnel given the previous issues with overdrive solenoids at this time. been in and out of there more times than fiddlers elbow.

Can you confirm the the reverse selector is held to the shaft with a roll pin? if that has broken in place it might have enough friction to allow selection.

I perhaps am not describing things well enough in that the lever seems to go past the engage position. It may just be my perception i will lay around and see what I can find. I can get it into reverse and it works with no gronchy noises it just takes a few attempts but reverse gear is meshing properly.

Another thought ! could this occur if the gearlever spring and plunger, which I don't see on the diagram, is mangled or worn. I did not get a gearlever with my refurbed gearbox and used the one I got with the car. I used Stuarts method of holding in position with a tiewrap (yes i did get it out afterwards.)

The retaining through bolt that provides a pivot for the gear lever in the housing (part 19) on the above diagram has to enter through the lever obviously but! does the lever only go in one way round as it must have machined limits of swing left to right in the lever ball? For avoidance of doubt i am using TR3a one piece ish lever.

I appreciate all input on this 

Thanx 

Rod

Edited by Rodbr

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The fork is held onto the shaft by a taper "wedgelok" screw:

image.png.05e836d72580e73410d9480d29e0311d.png item 76 below

https://rimmerbros.com/Item--i- GRID200093 

As is the gear lever end of the reverse selector shaft (there are 5 such screws in the box - two at the gear lever end 1/2 nd & reverse, and 1 for each selector fork.

I don't think any of the points you raise above re the base of the gear lever would explain what is happeneing.

Bob.

Edited by Lebro

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