Before You Pull That MGB Engine…Read On

If you own a late model MGB, it’s likely that you can pull the gearbox, replace the clutch, check the rear main bearing for oil leakage, and/or replace the rear main seal with much less effort than you might be led to believe. These are all those wonderful jobs that start with that dreaded phrase: “First remove engine from car”. Not necessarily true. I have worked out the following procedure on my daughter’s ’79 MGB, and it should work on most later model “B”s without overdrive. Since pulling the engine is a time consuming, knuckle-bruising adventure that can be difficult on both yourself and the car, take the opportunity of checking this procedure out. Almost all of the following steps are required in the old “remove engine” sequence anyway, so you won’t be out much time if your set-up doesn’t accommodate the new idea. If you have an overdrive gearbox, all bets are off.

The rationale behind this procedure is: get the gearbox clear of the body of the car without bending anything or moving the engine. The major problem is that the height of the bell housing runs smack into the firewall when you try to scoot the gearbox back, so you can’t get the shaft clear of the clutch assembly. Or can you? Here’s the way around the problem, in a step-by-step sequence.

1. Clean the entire region that you will be working in, especially the area of the gearbox and housing. Try to get as much dirt, grease and grit out from the area between the gearbox and the car itself. Then clean it again. Disconnect battery. Disconnect gear shift lever. Put a clean, lint-free rag on top of gearbox remote control unit (what you just took the control lever out of). Put the car up on jack stands, firmly supported all around, with enough clearance underneath to lie on your creeper/back and work comfortable under the gearbox. Give yourself some room here.

2. Remove clutch slave cylinder. Remove starter motor, tucking wires up out of the way. (I always use a wire tie for this—it’s cheap, fast and works super.) Remove exhaust system attachment to gearbox. Some cars may require removal of the exhaust system from the rear of the catalyctic converter on back. Remove gearbox to engine mounting bolts. Drain gearbox. Remove drive shaft. Disconnect speedo cable (another wire tie here). Disconnect 4th gear vacuum advance wiring (that makes three wire ties, but who’s counting?). Remove gearbox mounting. Disconnect backup light switch wiring (that’s four).

So far, all of the steps are covered in the gearbox removal section of most workbooks, and in greater detail. Now, we get on to the new lifestyle.

3. Pull gearbox back a half inch or so from the engine, so that it rotates around the shaft freely.

4. Rotate gearbox so that the remote control is turned toward the right hand (passenger) side of the drive tunnel.

5. Support the underside of the gearbox with an appropriate jack (to take the weight off the shaft).

6. Carefully, noting which bolt comes from where (different lengths!) remove the six bolts holding the remote control assembly cover from the gearbox housing. To do this you have to work by sense of touch, since the bolts are up on top, between the gearbox and the car body. I have small fingers, so I can get my socket wrench up in there without damaging my knuckles. If you have big hands you may have to fashion a special short depth socket by cutting about a third off, leaving just a half an once or so of socket to grab the bolt. Sockets are cheap, compared to engine removals.

7. Wiggle the remote control cover loose or lightly tap and pry at appropriate, safe points. Use care here, since there is a paper gasket between the cover which can often be saved with tenderness. Remove the cover. Stuff another lint-free, clean rag into the opening.

8. Now, remove the jack supporting the weight of the gearbox, rotate the gearbox so that it is approximately upside down (watch for some gear lube coming you way—extra rags are handy), and reposition the gearbox jack back under the gearbox again. Slide gearbox (with jack supporting) back away from the engine. You will find a range of several inches backwards travel before coming to the firewall. If there is not enough room, keep rotating the gearbox until you have enough clearance.

9. When the shaft end clears the clutch housing (possible sudden drop of front end of gearbox—care needed here), you can lower the gearbox free of the car. Congratulations! You now have a clear shot at all those good things that the manuals say you can’t reach without removing the engine!

10.Assembly Is the proverbial reverse of the foregoing, with a cautionary note regarding the paper gasket between the remote control unit and the gearbox (namely, don’t forget it or you may get a leak), and of course, to fill the gearbox with the appropriate fluid.

I have used this procedure on three different occasions—one clutch replacement one rear main seal job, and one replacement of the gasket between the engine and the rear mounting plate (a source of oil leakage sometimes confused with rear main bearing wear). I have never pulled the engine out or even loosened the engine mounts, and have accomplished the job, start to finish, in three and one half hours.

By Dr. Bud Laird

 (Mike Goodman’s MG Service in Los Angeles and John Twist of University Motors in Grand Rapids, Michigan have confirmed the practicality of Dr. Lairds technique and use it regularly when undertaking clutch jobs on 1968-’80 non-overdrive MGBs. This procedure will not work on 1963-’67 MGBs or on later model overdrive gearboxes due to insufficient room in the transmission tunnel area. It is extremely important that the back of the engine is properly and safely supported. John Twist has constructed a special crossbeam that rests in the fender mounting bolt area and secures to the rear of the cylinder head. Mike Goodman uses a telescoping jack and a full car lift to enable the mechanic to walk under the car. A number of variations are possible, just be certain that the engine is well supported and that you have room to safely maneuver under the car. —Ed)