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Series gearboxes - what to look for?

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Hi, 

Going to look at a 2nd hand series 3 gear box and over drive combo. Over drive described as good and gear box as 'notchy'. 

Nevr bought a gear box or over drive before so would be greatful for any advice that can be offered. Both are currently in the vehicle so can be driven. 

 

Many thanks 

Richard 

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You can check the oils and see what colour they are. A clear golden appearance is of course much better than mucky and dark.

The overdrive will likely be noisy whatever the condition, but they tend to continue working in this state. I've known 3 series overdrives in my time. They have a habit of spraying oil out of the breather in the top cover plate. It is no more than a plate with a hole, with a split pin in the hole. Consequently they do lose oil, so make sure it hadn't been run dry.

The main box should engage and change gear freely. The series 3 box is full synchromesh in forward gears, so expect no bad crunching on gear changes.

Worn boxes will rattle quite a bit when you ease of the accelerator and go to overrun, but I have known good ones that are fairly quiet.

Also when entering overrun, check it doesn't jump out of gear. Weak detent springs or worn gears can cause this to happen. 

Hope this helps.

 

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On 1/4/2019 at 4:23 AM, mickeyw said:

You can check the oils and see what colour they are. A clear golden appearance is of course much better than mucky and dark.

The overdrive will likely be noisy whatever the condition, but they tend to continue working in this state. I've known 3 series overdrives in my time. They have a habit of spraying oil out of the breather in the top cover plate. It is no more than a plate with a hole, with a split pin in the hole. Consequently they do lose oil, so make sure it hadn't been run dry.

The main box should engage and change gear freely. The series 3 box is full synchromesh in forward gears, so expect no bad crunching on gear changes.

Worn boxes will rattle quite a bit when you ease of the accelerator and go to overrun, but I have known good ones that are fairly quiet.

Also when entering overrun, check it doesn't jump out of gear. Weak detent springs or worn gears can cause this to happen. 

Hope this helps.

 

Yep, my Superwinch made Fairey type howled from new.  It almost sounded like a spooled up turbo.  I used some fittings and silicon hose to make remote breathers for the transmission, including the overdrive, which stopped a lot of the oil loss and mess.

The notchiness could be worn baulk rings or just a clean and adjustment of the detent balls and springs or rotation of the selector shaft needed.  I have a rebuild guide on my blog (click the sig below) and you'll be able to see how they work.  I doubt it's anything serious.

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