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MG Midget and Sprite Technical - Changing Gear Noise
I have a problem with my midget on changing gear.
When the engine is cold no issues slips in and out of gears without any problems.
After around 30min or so first to second and second to third predominately (sometimes third to fourth but rare)a strange squealing noise can be heard once the gear has been selected on releasing the clutch. The noise only disappears when a higher gear is selected.
I have also noticed if the rpm is running slightly higher in the selected gear as well. It is not all the time but it is a bit of a lucky dip as to when it occurs.....
I had the slave cylinder replaced last year and I bled this using a ezibled but don't think this is the problem.
|J D Brynes|
|What engine is it? A series or Triumph.|
|It is the original 1275cc engine....|
|J D Brynes|
|Others will know better but clutch is my first thought.|
Questions/thoughts that come to my mind -
. do you drive the car often?
. when did this first start?
. was the clutch fluid completely changed with the slave?
. have you checked the g/box oil level?
. when was the g/box oil last changed?
. have you tried going up a hill and accelerating hard?
. have you tried double-pressing or pumping the clutch on gear changes?
|I'm not too familiar with the A series boxes but my pondering has led me to wonder about the bearings/bushes the assorted shafts in the box run in. Could it be that they are either loosening in their housings or tightening on the shaft journals (or both)or as the temperature rises and then spinning up? |
The things that led me to this are the relationship to temperature and the occurrence of the noise as the clutch is engaged and the gears come under load.
Without wishing to dispute Nigel's insight I don't know what in the clutch would do this unless it were slipping very noticeably.
Someone with a better understanding of the 1275 gearbox will no doubt be more helpful, but it's my best guess so far.
(I hope I'm wrong because it would be a nasty problem).
BTW good points about the gearbox oil Nigel.
|As Nigel says, check the g/box oil level. If it's low I'm wondering if the needle roller bearing between input and output shafts is overheating, maybe some needles seizing, then rubbing against the shaft(s). You don't want that. In top gear the noise would disappear as the shafts are locked together. The clutch release bearing would be a preferred candidate but it doesn't sound like that. But I'm guessing.|
|Interesting comments Bill. Excuse my ignorance but I can't think why the clutch thrust bearing would do it since it seems to be only when the clutch is engaged and the bearing unloaded. Unless I'm missing something fundamental which is not unlikely!|
|Does the squealing noise occur only when the clutch pedal is depressed?|
If yes, then the thrust bearing may have seen better days.
Sorry, I meant it probably isn't the clutch release bearing but it would be a "preferred" fault as it would be easier to rectify, although the g/box would still have to come out.
|See what you mean Bill. Having had a chance to look at the manual in between cooking, cocktail mixing and splicing new ropes for the fishing boat (on my day off) I'm sorry to say the needle bearing looks a likely culprit to me.|
Sorry JD. I hope you find an easier fix.
When you say the noise dissapears when the higher gear is selected , do you mean
When you select 4th gear
When selecting a higher gear than the one you were in
If it's never there in 4th you can almost be certain that there is something in the gearbox making the noise
If it's during the actual changing of the gears it 'could' be noisy synchro rings caused by very low oil level in the g/box
If it's as you are starting to let the clutch out it could be the spigot bush in the back of the crank running dry
|Some years ago my clutch/ gearbox started making a really loud screeching noise. It occurred on gearchange and sometimes persisted for several minutes after each gear change. It started after I had been through several floods. At the time I had the standard clutch arrangement, but with a roller release bearing.|
Given that I thought I would almost certainly have to remove the engine and gearbox to sort it out anyway, I decided there was nothing to loose in spraying some sort of cleaning fluid wherever I could reach inside the bell housing with an extended spray nozzle. I started with brake cleaning fluid and then applied long squirts of WD40. I used this because it is light and non-oily - I didn't want to exchange the squealing noise for a slipping clutch!
Somewhat to my surprise the noises all stopped, it didn't slip and worked fine for some 1000's of miles before I later stripped it down to fit a concentric slave system.
|I think more info is needed. I do like simple and effective solutions like Guy's (if it turns out to be appropriate in a case like this).|
Things like checking (and if necessary or due) changing the g/box oil are easy, cheap and quick to do. Certainly checking the g/box oil and topping up if necessary are primary basic steps even if they're not the direct cause or solution taking them will help.
I've no real insight, no mechanical knowledge just, if I can remember, experience. The problem is I can't remember the individual problems and solutions, the solutions are mostly made by others anyway, and all gets jumbled in my mind because I don't really understand it all.
I did have my Spridget clutch both stick on and slip during the same journeys a couple of years back and when the clutch was took out it was broken in a good few places but not the (replacement MGA competition) release bearing.
This thread was discussed between 31/12/2016 and 02/01/2017
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