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MG MGA - Gearbox removal

My question is this...can the gearbox on an MGA 1500 be removed leaving the motor in place? Is it possible to drop the gearbox from the rear end and remove it?
Stephen Lofaro

No.
Barney Gaylord

Yes it is possible to removed the gearbox with the engine in place but no, it can't be removed downwards it has to come up through the car. This means removing most of the interior to get the floorboards out to allow the cover to come off.
Malcolm Asquith

Surprisingly section A18 and F1 of my original workshop 1600 workshop manual (Issue 6) says remove engine and gearbox forward as a single unit but only after removing floor, transmission tunnel and gearbox remote control. It makes it sound very easy! I have never heard of anyone doing it this way.

I have always removed both engine and gearbox forward but after splitting, and hence without dismantling the interior. Although it may be possible to take out just the gearbox up through the cabin I think it is a lot easier to remove the engine first rather than remove floors/transmission tunnel.

Paul
Paul Dean

Easiest and quickest way is to remove the complete engine and gearbox together.

Remove the bonnet (hood)
Remove the radiator
Remove the fanbelt pulley on the front of the crankshaft (put it in first gear, then undo the starter dog with big spanner and Birmingham screwdriver)
Undo the propshaft at the gearbox
Remove the gear lever
Obviously, disconnect all the cables and pipes.
Remove the single bolt fixing the gearbox to the chassis, and remove the nuts/bolts from the two engine bearers
Take the engine out

It does need to come out at quite a sharp angle, so make sure your hoist has plenty of height.

David
D Brown

PS
Ever tried juggling a gearbox back on to an engine while underneath a car?
David
D Brown

What is a Birmingham screwdriver?
Art Pearse

A hammer. Be sure not to use a right-handed one when you really should be wielding the left-handed variety. Although the latter are much harder to come by these days - bloody EU!

Alex
Alexander R

Did I really say first gear?-
Of course I meant fourth.
David
D Brown

David

It is interesting that you take them both out forward together after removing only the gear lever. Why on earth does the workshop manual say remove floor/tunnel/remote/etc as if it is trivial! Perhaps the author just sat in an office at Abingdon writing the manual.

I have always split them in the car and removed forward, but perhaps you have better lifting gear. I re-install in same way. Reconnecting gearbox in car is only slightly fiddly.

Paul

PS Photo of manual page attached. Readable at second attempt.


Paul Dean

I was swapping MGA engines when I was 19 or 20, and I'm glad I didn't read the Workshop Manual before I did it. R&R of the engine by itself is a POC. Frankly it would be downright stupid to pull the gearbox out if you only needed to pull the engine for engine or clutch service.

For engine installation just jack the gearbox up until the bellhousing hits top of tunnel, and insert the engine. Aligning the clutch splines is maybe a 2-minute jiggle, quicker once you get the hang of it. You must use a clutch alignment tool to center the clutch disc first.

R&R of the gearbox is also a POC. Remove tunnel center carpet section only (might be some staples in the floor), remove tunnel cover (8 screws), remove shift extension assembly (4 bolts). Disconnect speedometer cable and remove one bolt from the gearbox mount. For the 1600, disconnect the propshaft front flange (4 bolts). For the 1500, drain the oil first (because it will run out the back when propshaft is disconnected). The gearbox then pulls right out the front, with or without the engine.

Pulling engine alone requires only a small tilt to align with the raised gearbox. Pulling engine and gearbox together requires a very large tilt, almost standing it on end, and high lift with lots of ceiling clearance. You really need a tilt-leveler mechanism for that operation.

As to instruction in the Workshop Manual, I recon the book was written before the first car left the factory. Very early production MGA (first 500 cars or so) did not have a removable tunnel cover, so you had to remove the tunnel to get the gearbox out. The factory also liked to treat the gearbox as part of the engine, calling the assembly the "Power Unit". It was pre-assembled before it went into the chassis, and before the body was installed.

Field service people had an entirely different view of the situation. It was intuitively obvious from the git-go that it was easier to cut a large hole in top of tunnel than to remove the tunnel. It was commonly flame cut, then the plug was later tack welded back in place and covered with carpet. Field mechanics jumped on the factory real early on and caused them to redesign the tunnel to have a removable top cover. I suppose the book was never revised, because R&R of the floor and tunnel still applies to the early production cars.
Barney Gaylord

No one has mentioned that it is easier if you raise the rear of the car first.
David Werblow

The writers of the workshop manual were writing it for the MG franchised workshops, with a proper car lift, lights, the lot. They also assumed that the cars had nice, shiny new screws securing the floor, seats and tunnels. Plus one mechanic for the nut and another for the bolt.
Things are different when the seats and floor are secured with fasteners that haven't been touched for fifty years. Or even ten years.
Another puzzle - why put that really useful access hole in the transmission tunnel for the bolt securing the gearbox to the chassis if you're expecting the tunnel to be removed?
David
D Brown

There is no "access hole in the transmission tunnel for the bolt securing the gearbox to the chassis" (unless someone added the hole aftermarket). If you put the bolt in wrong end around during restoration, then it won't come out without removing the tunnel (or cutting the head off the bolt).
Barney Gaylord

Glad I didn't read the manual either - but then most operations are unnecessarily complicated when they don't need to be!

I never take the top off the tunnel - just take the gearlever gaiter off and spring out the big circlip and lift the lever out - the extension can stay on the box.

I always pull engine & box out together except when just doing a clutch change.
Chris at Octarine Services

Oh Barney!
How embarrassing!
I now have to reveal that I DO have an access hole, because I replaced the gearbox mounting bolt the wrong way round (body off) and didn't notice until the next engine-out weekend. There is, of course, enough space for a stress-free withdrawal when it's the right way round.
Sorry
David
D Brown

When you pull the shift lever out you most likely lose the anti-rattle ball from the rear lever on the remote shift shaft. Do you have some devious method of re-installing that ball when reinstalling the shift lever? If you leave out the ball and/or spring, the hand lever will exhibit a resonance vibration right around highway speed (about 3500-4000 rpm), and the buzzing will drive you batty.

The little anti-vibration ball has a tendency to wear a vertical groove in the back side of the small ball on the hand lever. About 15 years ago I replaced the ball with a brass button, 1/4" diameter and I think a bit more than 1/4" long. No more wear, and I have never had to replace a brass button, but it will still be lost when the hand lever is removed. I haven't figured out how to put it back in place without removing the remote shift extension assembly, which is why I recommend removing the extension assembly and leaving the hand lever assembled.
Barney Gaylord

The only reason I pull gearboxes out of MGAs is to replace them with Ford type 9 boxes so I have generally no need to worry about that little ball.

If the box is coming out to be rebuilt then like you I replace the ball with a brass bucket & spring like the MGB one - that will stay in place with a dab of heavy grease.
Chris at Octarine Services

I've pulled the transmission out through the disassembled cockpit, I've removed the engine separately, and I've the removed the engine and gearbox as a unit. Next time, I'll probably do it with the body off.

What always puzzled me was why MG put the floorboards over the gearbox tunnel's flange instead of the other way around. I suppose maybe the tunnel contributes marginally to the stiffnes of the chassis that way. Seems like being able to remove the tunnel without removing the floorboards would make removal of the gearbox through the cockpit much easier.
k v morton

This thread was discussed between 08/08/2013 and 21/08/2013

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