Clutch less overdrive selection on my 74 GT is smooth and slick but deselection results in a hefty * to the transmission. I counter this by dipping the clutch but I am concerned that this not normal.
Although previously owning a couple of B's these were non OD cars so I have no experience of what is "right"
I had a big Healy a few years back and remember the OD on that being totally seamless going in and out so I guess I expect the MG to be similar.
I have checked the oil and it looks like clean engine oil and up to the full mark but obviously can't tell if it's the correct 20/50 spec.
Before I dive in and change the oil and check the filter screen any pointers to look for, or does this unit sound normal?
Best rgds
Dave
Overdrive deselction *
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David Wicks
- Posts: 29
- Joined: Sat Sep 24, 2016 9:02 am
- Forename: David
- Surname: Wicks
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David Wicks
- Posts: 29
- Joined: Sat Sep 24, 2016 9:02 am
- Forename: David
- Surname: Wicks
- MGCC Member: Yes
Re: Overdrive deselction *
The forum will not let allow the word * so I am subbing snatch
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Peter Cresswell
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- Joined: Fri Oct 31, 2014 10:05 am
- Forename: Pete
- Surname: Cresswell
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- Location: Stone, Staffordshire
Re: Overdrive deselction *
Hi David,
I have delayed responding to your query so others who have come across the problem may have some idea of the cause. But now after a couple of weeks, no luck!
I do know (because my B does this and one I had in the past had a similar problem) that it is much more common to have one the engages and disengages 'lazily'. It seems it is quite rare to have one that disengages abruptly - if I have read the * correctly! Hence I think the lack of other responses.
I have never taken an overdrive apart, but a friend of my has recently overhauled one as an upgrade for a Jensen Healey he has restored. I asked if he had any ideas about what would make the overdrive release abruptly, and he thought it might be either the cone clutch lining is worn or one of the clutch springs has broken. However to dismantle and overdrive successfully (and put it back together again) requires access to several special tools which he made. The overdrive he worked on was similar to the earlier D type overdrive used on 3 synchro MBGs rather than the LH type on 4 synchro Bs, but thought the principle in essence was the same. He used Overdrive Spares in Rugby (see http://www.odspares.com/ ) and said they were very helpful and happy to chat over the phone about problems.
So based on the recommendation above I would suggest you contact Overdrive Spares and have a chat. If the problem is serious, parts can be quite expensive so you quickly get up to the same price as specialists charge for reconditioned units and also bear in mind they are difficult to strip down without the special tools.
I have delayed responding to your query so others who have come across the problem may have some idea of the cause. But now after a couple of weeks, no luck!
I do know (because my B does this and one I had in the past had a similar problem) that it is much more common to have one the engages and disengages 'lazily'. It seems it is quite rare to have one that disengages abruptly - if I have read the * correctly! Hence I think the lack of other responses.
I have never taken an overdrive apart, but a friend of my has recently overhauled one as an upgrade for a Jensen Healey he has restored. I asked if he had any ideas about what would make the overdrive release abruptly, and he thought it might be either the cone clutch lining is worn or one of the clutch springs has broken. However to dismantle and overdrive successfully (and put it back together again) requires access to several special tools which he made. The overdrive he worked on was similar to the earlier D type overdrive used on 3 synchro MBGs rather than the LH type on 4 synchro Bs, but thought the principle in essence was the same. He used Overdrive Spares in Rugby (see http://www.odspares.com/ ) and said they were very helpful and happy to chat over the phone about problems.
So based on the recommendation above I would suggest you contact Overdrive Spares and have a chat. If the problem is serious, parts can be quite expensive so you quickly get up to the same price as specialists charge for reconditioned units and also bear in mind they are difficult to strip down without the special tools.
Pete
1969 MGB Roadster
2020 MG HS Exclusive
2007 Mercedes SLK
Plus 34 other cars since 1965
1969 MGB Roadster
2020 MG HS Exclusive
2007 Mercedes SLK
Plus 34 other cars since 1965
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David Wicks
- Posts: 29
- Joined: Sat Sep 24, 2016 9:02 am
- Forename: David
- Surname: Wicks
- MGCC Member: Yes
Re: Overdrive deselction *
Thanks for the reply Peter,
So it seems I have a "rare" problem, my unit is the later LH by the way.
To update, I have now drained the oil, checked and cleaned the strainer and replaced the oil with good quality 20/50 stuff. To me the oil was pretty dirty considering it was from the gearbox - quite black and almost like used engine oil. Not what you would expect from a reputed 24K mile car.
Anyway back to the problem, The OD selection is now slicker but it will still j**k coming out of OD top on a trailing throttle, for example slowing for a roundabout at around 40 mph. If the power is kept on, for example accelerating up hill or overtaking, then it is reasonable but not seamless or slick like an auto box or a manual 5 speed.
I guess I can live with it though, thanks for your research and tips on getting a fix but I simply couldn't justify a unit overhaul financially for what is a relatively minor thing - unless of course it develops into a major issue.
During reading up on the issue I noticed that the earlier OD needs a vacuum relay to prevent deselect unless the accelerator continues to be pressed. That is interesting as it suggests that the early type OD was j***y but needed a smoothing or delaying mod.
Anyway, thanks again for your input.
Best Regards
David
So it seems I have a "rare" problem, my unit is the later LH by the way.
To update, I have now drained the oil, checked and cleaned the strainer and replaced the oil with good quality 20/50 stuff. To me the oil was pretty dirty considering it was from the gearbox - quite black and almost like used engine oil. Not what you would expect from a reputed 24K mile car.
Anyway back to the problem, The OD selection is now slicker but it will still j**k coming out of OD top on a trailing throttle, for example slowing for a roundabout at around 40 mph. If the power is kept on, for example accelerating up hill or overtaking, then it is reasonable but not seamless or slick like an auto box or a manual 5 speed.
I guess I can live with it though, thanks for your research and tips on getting a fix but I simply couldn't justify a unit overhaul financially for what is a relatively minor thing - unless of course it develops into a major issue.
During reading up on the issue I noticed that the earlier OD needs a vacuum relay to prevent deselect unless the accelerator continues to be pressed. That is interesting as it suggests that the early type OD was j***y but needed a smoothing or delaying mod.
Anyway, thanks again for your input.
Best Regards
David