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MG MGA - Gearbox dismantling

I have got as far as the speedo drive is out, the rear cover plate off and the interlock plate out. I have removed the bolts / nuts holding the rear extension on, and am trying to separate the front from the rear. So far I can only get about 1/4" daylight and no more. Is it necessary to remove the drive flange from the rear? The manual does not mention it.
Art Pearse

Went to Barney's site. Answer is yes!
Art Pearse

I now have the drive flange off (1600 box), and 1" of daylight.

Next problem - "Rotate the remote control shaft to move the selector lever out of engagement with the selector slots. Then the rear housing may be pulled off to the back. If you have trouble here, refer to removing the top spacer plate (repeat over and over) and the speedometer drive spindle." I cannot rotate the remote shaft enough to disengage the selectors. What is the trick? The tower spacer plate is off and speedo drive is out.
Art Pearse

Further to the above - presumably the gears should be in neutral? Does the remote shaft lever retract above the top selector, below the bottom selector, or between the two selectors? I can't make it do any of these 3 possibilities! Help!!
Art Pearse

Sorry there are 3 selectors; reverse, 1/2 and 3/4, but you know what I mean, which way does it come out?
Art Pearse


I just finished my tranny and am still about as much of an amature as you. If I understand, you want to disengage the shaft and lever from the selectors so you can seperate the front and back housings. I found that aligning the selectors so that the "U" space in each selector is on top of the other, then by rotating the lever downward through the open space it
can be disengaged.

One other caution, remove the shafts and block in one piece so that the ball & springs do not fly apart.

Barneys site is great help but still questions came up for me and I needed help.

Good luck
J. Hudrlik

Hi Art. Push the tranny back together, then put the gearbox in neutral. Then try pulling the two halves apart. You will notice that when the gearbox is in neutral that all the selectors where the gear lever joins, are in alignment. At this point you can jockey the gear lever so its "stub" that is within the selectors can be moved out of contact with the 3 selectors. The rear extension should then just slide off. Hope this explanation is understandable. If you can get your hands on a Hanes manual for the MGA, it has a pretty good section on transmission overhaul, with pictures. If you have any questions, please email me at Cheers, Glenn
Glenn Hedrich

Finally got it, but it is not so simple as you say Glenn. Just being in neutral did not permit the lever to rotate far enough down to clear the 3/4 selector. Had to push the case back until the studs were clear (which automatically pulls it into gear) and then there is a bit more movement by rotating the case. At least that's what I THINK happened!
Art Pearse

Hi Art. Seems no two transmission cases are exactly cast exactly identical, so sometimes extra "manipulation" of the rear housing is necessary, a twist here, a pull there and off it comes. When you pull out the shifter shafts, be sure NOT to remove them from the steel block that is attached to the aluminum front housing. If you do, springs and balls will fly out and get lost. unbolt the steel block, and pull it off along with the shafts. Additionally, when you have the 3 steel shifter shafts out, run the appropriate bronze shift forks up and down each shaft to check for burrs. Burrs on the shafts will prevent the tranny from shifting properly. The burrs are usually found where the bronze shift forks are held to their shafts by pointed end bolts. The bots often displace metal causing burrs to form on the shafts. 100 grit wet/dry sandpaper and some elbow grease seems to take such burrs off nicely. Have fun Art! Glenn. Hey do you think spring will ever get here? lol
Glenn Hedrich

Hi Glenn. Thanks for the tip about the balls and springs. That sort of thing is your worst nightmare. Actually, I can't seem to budge the guide block from the case, but I think I will just leave it in place with the rods as there seems to be no work required there. I don't quite get your bit about the burrs. If the set screw causes a burr (and it will!), it will be in a place where no sliding takes place.
I have got the reveres gear and shaft out. Which way do you drift out the layshaft - fronwards or rearwards? And do the needles stay in place inside the laygear?
Art Pearse

Now I know why I had trouble. The pinch bolt on the remote shaft, holding the selector lever was sticking through about 1/16", fouling on the case and preventing enough downward rotation for the lever to clear the selectors. Can't think I'd be the only one to have this situation. I will grind it flush B4 ass'y.
Art Pearse

The detent block sits on two dowel pins. Place a sharp knife blade behind it and tap into the joint with a hammer to separate the parts.
Barney Gaylord

Hi Art. The burr(s) can make selector fork removal and re assembly difficult. Sorry, meant to say that burrs elsewhere on the shafts can make the tranny difficult to shift. I shaft burr can prevent the forks from sliding properly. It is worth checking all 3 shafts as described before assembling the forks onto the shafts. Glenn
Glenn Hedrich

This thread was discussed between 08/03/2010 and 18/03/2010

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