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MG MGA - transmission rebuild problems

I have just attempted a rebuild of my 1957 MGA transmission, using the instructions provided by the "MG Guru." The transmission shifted in all gears before I took it apart, but the usual things were worn. All was disassembled, renewed, and reassembled according to the instructions and photos. Everything looks like the photos, but the transmission doesn't work.
Shifting it into 1st gear position is smooth, with the full range of movement. The problem is that transmission then is locked. That is, nothing will turn inside of it, and I can't turn the input shaft by hand.
It is impossible to shift into the second gear position. The selector shafts don’t move.
Third gear position also cannot be shifted into, either. Looks like the same problem as second: in both cases shaft movement should be forward, but it seems to be limited by the detent block.
The fourth gear position is easy to reach – smooth shift and full movement. However, the transmission now seems to be in neutral. I can turn the input shaft by hand, and the output shaft doesn't turn with it. The 3-4 gear sliding hub didn't move, either, when I made the shift.
The reverse position is easily reached, again: smooth shift and full range of motion. The transmission then is locked, like in the first gear position.
I can only conclude that there is something really wrong with my reassembly. The only thing I can think of to do is to take everything apart, down to the last spring and ball, and start all over again. Does anyone have any suggestions that might help me out? Many thanks in advance for your comments.

Mike Whalen
M.E. Whalen

I think you've managed to install the 3/4 synchro backwards, or a fork or summat. The thing sounds like it is in third gear when it's supposed to be in neutral. When you shift to 4, you take it out of 3rd, so it is in neutral. Any other gear locks it because it IS in third, and he will not turn in two gears!
Did you take the detent block apart? Seems that the third gear detent/interlock may be locking it out of other gears, but then it should not go into first either. Been too long since I've done it, but fix the "constant third" first.


FRM
FR Millmore

I REBUILT THE SAME TRANSMISSION, 1957. I HAD IT APART AND TOGETHER 3 TIMES BEFORE GETTING IT RIGHT. ON THE FIRST TRY I HAD A PROBLEM SIMILAR TO THE ONE YOU DESCRIBE. MY PROBLEM WAS THAT THE FRONT LAY GEAR THRUST WASHER HAD FALLEN DOWN AND WAS NOT ON THE LAYGEAR SHAFT. IT WAS JAMMED BETWEEN THE LAYGEAR AND THE HOUSING AND BOUND THE LAYGEAR SO IT WOULD NOT TURN FREELY. ONCE THIS WAS CORRECTED EVERYTHING TURNED OK.

MY SOLUTION TO GETTING THE FRONT AND REAR LAYGEAR WASHERS ALIGNED AND ON THE SHAFT WAS TO TAKE THE OLD, WORN OUT SHAFT AND GRIND A GOOD TAPER ON ONE END. THIS MADE PICKING UP THE THRUST WASHERS EASY. I PUSHED THIS "TOOL" ALL THE WAY IN AND MADE SURE THE LAY GEAR TURNED FREELY. THEN, JUST SHOVE THE OLD SHAFT OUT WITH THE NEW.

SOUNDS LIKE YOUR PROBLEM MAY BE DIFFERENT?
H Speer

Mike, -- My first thought was with FRM on this one. It sounds like the 3-4 hub might be installed backward, although it is supposed to be nearly impossible to actually close the case mating joints in this condition. With the 3-4 hub backward there is commonly about 1/8-inch interference in the fit, so if you get the main and rear housings bolted together the front cover cannot be installed. And if you then tighten the bolts on the front cover it makes the shafts bind up, and I think the 3-4 hub will be permanently locked in 4th gear position.

If you actually have it all bolted together, and the shafts turn freely, then I would be inclined to think the 3-4 hub is properly assembled. My next guess would be the set screw securing the 3-4 shift fork onto the control rod is not in the indexing hole in the rod, and the fork is out of position on the rod.

Position of the 3-4 hub and the 3-4 fork are easy to check through the side cover. My first suggestion is to reset position of the 3-4 fork on the shift rod. Loosen the fork set screw, set the 3-4 sliding hub to central neutral position, set the 3-4 shift rod to central neutral position (using the shift lever), then tighten the set screw into the fork again. Lemme know if that fixes it.
Barney Gaylord

Barney -
Maybe so, but various additional errors could compound this. Missing TW for 2/3 bushes, missing circlips on 1st or third motion shaft bearings - seen that one!
Hard to figure that you could actually not have the setscrew in the index hole for the fork, but I have seen them with the wrong screws = regular bolts.
It has to be one or the other though.

Mike has something muddled: "Third gear position also cannot be shifted into, either. Looks like the same problem as second: in both cases shaft movement should be forward,"
>>> The movement for 2 & 3 is in opposite directions.

FRM
FR Millmore

Barney, you were correct. All it needed was to have the selector forks repositioned with the shift lever in the appropriate gear position. It seems to shift ok now. Thanks to everyone for their comments!
M.E. Whalen

This thread was discussed between 12/12/2009 and 14/12/2009

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