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MG TD TF 1500 - MG TD Gearbox Freeze

The recent full restoration of my mg td 9677 included replacing the gearbox (second gear had been lost), replacing the clutch/pressure plate/thrust bearing, and also replacing the clutch linkages on the side of the sump. Now a problem has come up that has me stumped.
Sometimes when I stop in Neutral, let go of the clutch, then depressing the clutch again to try putting into FIRST - I am unable to select any gear. The gear lever can be moved around in the neutral gate, but I cannot put it into a gear. I have found this happens more often when the car's suspension has articulated quite a bit, like when parking with the left rear up high - say on a curb, or when going down a steep driveway and turning LEFT. (when the front right wheel goes in and the left rear articulates inwards). The only way to get her into gear again is to push the car onto a curb or ramp to the RIGHT. Letting me think that something is twisting the drive train.
I have checked the prop shaft for adequate movement in the splines, the diff hangers for not fouling the diff, the gearbox extension and selector shafts, fitted new anti-chatter bushes and things I thought would be the obvious. Please can someone give me some suggestions?
Ivan de Clerk

Does turning the engine off make any difference when it is jammed? If you haven't tried that, turn it off when it jams and try it then. If the clutch was dragging it wouldn't go in to any gear.
George Butz

Thanks George. Tried switching off and putting her into gear. Still nothing. Tried pumping the clutch as well. (Clutch pedal freeplay is about half and inch, and starts taking about an inch from the floor). The clutch would be suspect, but with the engine turned off, one should still be able to push it into a gear.
Ivan de Clerk

Ivan, did you open up the gearbox? Or, did you just replace the throwout bearing without taking the cover off the gearbox? There are a couple of balls in the gearbox whose function is to prevent the selection of more than one gear at a time.
Bud Krueger

Hi Bud. No I did not open the box. Only removed the remote extension, and reworked that. On the other side, I replaced the thrust bearing, pressure plate and clutch plate. What I can do is when she freezes up again, to remove the remote extension (4 bolts) and look at the selectors underneath. These are the selector shafts which have the springs and bearings I presume? You're giving me hope though ... This could be the right track.
Ivan de Clerk

Ivan,

The springs and balls are under the main cover on the side adjacent to the remote extension. A ball goes in each hole, and a fairly long spring goes on top, and then the cover.

warmly,
dave

Dave Braun

I agree with Dave. I had the same problem with a TC gearbox (same ball/spring arrangement). A previous owner had replaced the springs with shorter, lighter springs that didn't keep the balls in place. If I put the car in neutral before coming to a stop sometime, reverse could move forward and jam the shifter. It would also happen when I was trailering the car with the transmission in neutral...the balls would jump out at a bump and the shifting forks would shift.
Gene Gillam

Ivan, the attached image shows the two balls that I spoke of. Their lack can cause the problem that you speak of. It's easy to lose them when working on the gearbox (don't ask how I know). It's not easy to replace them if they're missing. I'm not an expert on the subject, but I think that an early gearbox may allow the selector shafts to be removed without removing the gearbox. Later gearboxes have a circlip on the outside of the gearbox that wouldn't allow this.

Bud Krueger

Bud, great picture. Very possibly the problem in this area. I know how the balls pictured fall out - I'll never tell either. Another gearbox trick is to loosen the shift fork and spacer thingy (on the rail with the spacer at the front) then slide the rail back and stupidly stare as the spacer fall into the bottom of the gearbox. You are correct- the earlier TD does not have the circlip on the 3/4 rail and you can pull them out to the rear- don't know the car # but later than 10835. Ivan, when you pull the remote cover, check that all three selectors are tight on the rails. Very important- the later circlip was added to keep the 3/4 hub from comming apart when the rail/shift fork moved too far back- I would avoid popping that rail backward without the shifter cover on. Push and pull on each, and try to engage more than one gear- if one rail is foreward or back, none of the others should move much-just a bit of play-(due to the interlock balls in Bud's photo). If they do (ie you can engage two gears at once)there is a problem with the interlock balls as in the photo (one or more are missing). Carefully take the top cover off. there should be three springs sticking up in the back. Remove them, and using a magnet pull the ball over each rail out to make sure they are there. Then you can loosen the lockbolts on the shift forks and the spacer (don't let it fall in), slide the rails back and out, and inspect for lack of balls (that is generally very, very bad), etc. Read the shop manual too. George
George Butz

Super picture Bud. I misspoke from memory, and forgot the balls also had to go between the shaft locations for a total of five balls!

warmly,
dave
Dave Braun

Bud, thanks very much for the picture. Sorry for the time delay, I am now back. What Gene mentioned above (thanks Gene) is actually what happens - I come to a stop and put the car in Neutral, then no gears.
First thing will be to try to find out if there is excess play, so when it happens again I'll pull off the remote extension to see if the reverse gear shaft has moved forward. I could do this on the side of the road, (its very quite here in our suburbs) then try to force the shaft rearwards with a screwdrive. I should have all the gears back. Thanks George for the your instructions.
Ivan de Clerk

That's it. I've found the reason why the gearbox freezes up. I drove around with some tools waiting for it to hapopen again, and when it did, off came the selector shaft. The reverse shifter shaft had moved slightly forward, blocking everything else. It could be moved freely and I could feel no detent. The ball bearing was not getting pressed down into the cut-out in the shaft. When home, I opened the top gearbox cover and removed the springs carefully, the balls were all there, but when touching the reverse shaft ball, it went down as it should have. I checked the springs and the picture attached shows the problem, the one on the left is the reverse shaft spring. When the PO inserted it, it must have been pinched or something and the end that was psuhing on the ball opened ever so slightly.
In went the new springs, cleaned the gasket muck away, made new ones, installed everything and all is fine again. Thanks George, Bud, Dave and Gene for responding, you've been a great help.

Ivan de Clerk

Nice work, Ivan!

warmly,
dave
Dave Braun

I can only say I am astonished at the rapididy with which this seemingly difficult problem was solved. And thanks to Ivan for giving us the solution in picture form. Truly a wonderful bunch of knowlegable people on this BBS.
Cheers,

Bob
R. K. Jeffers

This thread was discussed between 31/03/2009 and 11/04/2009

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