Welcome to our Site for MG, Triumph and Austin-Healey Car Information.


MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Cannot select reverse when running

Hi all, thanks for looking. Im a new keen owner to MGs (had 67 moggy saloon previously). New car grinds when attempting to select reverse with the engine running. The rest of the gears run through fine. I can switch everything off and then select reverse, switch on and off i go (backwards). Coming out is not a problem, but forget going back in. Its engine off again.

Im getting mixed vibes about gearbox or clutch being at fault. With the forward gears being synced surely this is heading towards a clutch clearance problem?

Is the clutch accesible without an engine out?

Cheers, Nath
Nathan Whitfield

It may be a clutch hydraulic problem which is easier to fix than thr clutch. The slave cylinder id the usual suspect. Lots in the archives.
Welcome to mGB ownership, they are bit livelier than a Morris Minoe :-)
Stan Best

This is a clutch issue, not a gearbox issue. The clutch is not clearing properly. It could be that the clutch plate is worn, but most likely it is the hydraulic system as Stan says. Lie on the floor with a ruler so that you can see the clutch slave cylinder. Get a helpful assistant to press the clutch pedal right down to the carpet. The pushrod coming out of the slave cylinder should move about half an inch. If it much less than this, then in most cases the slave cylinder needs replacing.

If the car can still be driven OK, then for now you can get around it by pressing the pedal, selecting a forward gear, then keeping the pedal down move the lever to reverse. The synchromesh on the forward gear will stop the rotation of the cogs so that you can then get into reverse silently. But eventually you will have to fix it.

If it is simply the slave cylinder, then that can be replaced without major surgery, although there isn't a lot of room to work on the hose, and bleeding the clutch afterwards gives some people a lot of trouble. Look up reverse bleeding in the archive. If the clutch itself needs attention then it is an engine out job as the clutch is sandwiched between the engine and the gearbox, as it is on almost every car except the classic Mini, 1100, 1800, Allegro, Metro, etc.
Mike Howlett

I have to say that if the clutch is dragging as seems to be the case then while selecting a forward gear will allow the synchro to stop the gears turning enough to select a gear, as soon as you take it out of that gear the cogs will immediately start turning again and it will still grind when selecting reverse, even if you have kept the clutch pedal fully down. If it *doesn't* grind doing it that way, then it is simply that you are selecting reverse too quickly after pushing the clutch pedal down. I have an intermittent dragging problem on my V8 which is something in the bell-housing not hydraulics, so I've had quite a bit of experience with this, and baulking in 1st and 2nd.

Worn linkages and clevis pin at the pedal end will cause a low biting point and potentially this dragging as well as air in the hydraulics. It's just possible that the slave cylinder seals are on the way out and pulling in air as you release the pedal, but as it is back-pressure from the clutch arm that pushes the piston back into the cylinder, and not the release of the pedal pulling it back, this is pretty unlikely. However it still leaves the question of how air has got into the system, if that is indeed what has happened.

If, however, like mine the biting point when it doesn't drag is normal, and the dragging/grinding in reverse is intermittent, then you will be stuck with it until you pull the engine. In the meantime if the grinding is so severe that you can't select reverse with the engine running, then switch off (or don't start yet), select reverse, and restart with the clutch still down.
PaulH Solihull

After depressing the clutch pedal, first select 4th, then go from 4th into reverse. That's what I have to do to avoid crashing the gears.
Brian Shaw

I'll say again, selecting a forward gear before reverse *will* stop the cogs spinning if you are trying to select reverse too soon after putting the clutch down. If the clutch is dragging they will simply start spinning again when you take it out of the forward gear.
PaulH Solihull

excellent help all, thankyou very much. and yes after some driving and testing (and some worsening in symptoms) im looking at clutch issues...we now have an increasing in difficultly to select even forward gears, but when you do with the clutch still hard to the floor we creep forward and even could stall if i ride the clutch at the lights!. I need to get this car in the air and have a good look underneath.

Keep you posted. MGs over Bullnose anyday

Nathan Whitfield

This thread was discussed between 31/07/2011 and 23/08/2011

MG MGB Technical index

This thread is from the archives. Join the live MG MGB Technical BBS now