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gearbox and overdrive

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bob hughes

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I have just done a daft thing, having drained most, but not all of the oil out of the gearbox, I tipped it up on end for a few minutes whilst I considereed how to replace the bell housing- the over drive end to be exact. I am now mindfull of one of our comrades who's box only lasted 500 miles then packed up, possibly due to disturbed sludge. So with that in mind, and the box on the bench I am steeling myself to have a go, but I will also need to clean out the overdrive as well. As I have little to no knowledge of gearboxes and overdrives how difficult is it going to be for a novice armed with the Healey manual.I guess that there may have been a quarter of a pint left lying around when I tipped it up so, as I see it, I may not need to strip the gears off the shafts if they can come out in one go, not sure about the overdrive though, any ideas would be most welcome
 
Getting the OD appart is easy, not so back together. I'd waste so chaep oil a dry to rince stuff through. It may not be as bad as you think.
 
I have been into some serious consultation with gearbox and overdrive specialists and the costs were ramping up. taking your point about a rinse out, I contacted a local gearbox guy - just your average joe, who asked why was I was about to waste money, try a rinse first using a litre of diesel, on the basis that if there were bits in the diesel on drain down then he would open up everything, so I have left it with him to get on with and I can concentrate on tidying up the gearbox bay. I will know by Friday which way to go and if the worst comes to the worst at least his rates are lower than the any of the specialists I have been talking to. I will let you know how I get on.
 
There shouldn't be a lot of sludge in the OD or transmission. After all, there not being subjected to the contaminates in the engine. I haven't heard of using diesel fuel as a cleaner, but I have heard of using mineral spirits as a good flusher. Or as others have said just flush with cheap oil.
 
I am not an expert but here goes. I assume you have taken the top cover off of the gearbox. If you have sledge in the bottom of the trans. then you have sledge in the bottom of the overdrive and you might consider going further. If the bottom of the gearbox is relatively clean I would not flush with anything but I would re-fill with Red-Line MT-90 (I think that is correct). If you decide to go further I suggest you Google "the wire trick" You will be facing that procedure if you separate the gearbox from the overdrive. The real problem for me was the alignment of the shaft into the back of the overdrive. If you decide to separate the two units I will then suggest alignment procedures as you will need to see what I am referring to. The process of taking the overdrive itself apart scared me and I saw no reason to proceed as the overdrive, once exposed, was very clean. I hope this helps and if you want to talk 530 587 4700 PDT. Bob
 
Chaps
Thanks for all the advice, it may not come to a strip down yet. I know of the problems in mating the gear box and the overdrive, but hopefully I will not have to face it. I will let you know the findings in the next 36 hours.
 
Well, its back from the garage with a clean bill of health, so say. I have painted it all up and during this process I turned it upside down and fluid started to drain out from the solinoid area ( removed incase of damage ). So I have just removed the drain plug on the overdrive and drained the last of the oil/diesel mixture out and cleaned the deposites away from the magnetic spacers below the strainer, ( you can see confidence in the clean bill of health fast disapearing here ). Some unhealthy looking pieces of metal also came out from this area along with a fine deposite of presumably dirt & iron filings or something like that, so I am going to flush it myself, can't trust anyone these days.
 
Bob Hughes said:
Well, its back from the garage with a clean bill of health, so say. I have painted it all up and during this process I turned it upside down and fluid started to drain out from the solinoid area ( removed incase of damage ). So I have just removed the drain plug on the overdrive and drained the last of the oil/diesel mixture out and cleaned the deposites away from the magnetic spacers below the strainer, ( you can see confidence in the clean bill of health fast disapearing here ). Some unhealthy looking pieces of metal also came out from this area along with a fine deposite of presumably dirt & iron filings or something like that, so I am going to flush it myself, can't trust anyone these days.
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Hi Bob,
In my experience, flushing is probably not necessary. Maybe even a bad idea. It would be normal for a bit of worn metal to collect in the bottom. The less it is disturbed, the better.

There are a couple of places where loosened junk from flushing could cause problems. The operating valve plunger (spindle) has a tiny hole in it's side which could become plugged. The operating valve ball has both upper & lower seats which could become fouled & not properly seal. These parts are accessable from the brass plug near the top right front of the OD.

The oil pump non return valve could become fouled & not properly seal. This valve is accessable under a brass plug under the solenoid cover.

The operating valve travel/solenoid adjustment is quite critical & may need to be reset. The shop manual method of inserting a pin through the right hand lever & clamping the operating lever is often not accurate on an older unit which has some wear. I would go by the "measuring ball lift method" as outlined in the below reference:
https://www.britishcarforum.com/lore/article.php?id=073

Information on the electrics is shown here:
https://www.britishcarforum.com/lore/article.php?id=064

Lastly, I would fill the transmission with 30 wt motor oil, or 20W-50 motor oil, or RedLine MT90 oil. I have found the RL to provide noticeably better shifting but it is expensive. It may take a few miles of driving to get trapped air out of the hydraulic circuits, but everything should be self bleeding.

Good luck,
D
 
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