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T-Series first gear alignment
- Thread starter saltiga
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My sons name is Paul so you must be a good bloke. The first gear is not going far enough to the right for full engagement i dont have another gearbox to compare the fork position with.( I have contacted a guy who says he has an mg y box and hope then to compare with) I will post pictures of first gear, neutral ,then in 2nd Saltiga
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As Paul states, it's hard to analyse it without a hands-on inspection.
Looking at the wear pattern on both first gear and layshaft, it appears that it's been running like that a long time. Position on the mainshaft is determined by the cut-out position on it for the detent balls in the collar. My WAG (Wild Arse Guess) is it's been like that from the beginning. I'd replace the bronze fork(s) and press on. But it's been so long since I've been in a T-series box I don't recall if that's how they are normally. If you get to eyeball another unit, you'll have a better idea of what's "normal".
Looking at the wear pattern on both first gear and layshaft, it appears that it's been running like that a long time. Position on the mainshaft is determined by the cut-out position on it for the detent balls in the collar. My WAG (Wild Arse Guess) is it's been like that from the beginning. I'd replace the bronze fork(s) and press on. But it's been so long since I've been in a T-series box I don't recall if that's how they are normally. If you get to eyeball another unit, you'll have a better idea of what's "normal".
Yes I am thinking along those lines all i need is another g/box which i think is coming or a kind TD owner to measure theirs. It does not surprise me if the indents are out. When i recond the oil pump on the engine the slave gear (a new one) would not fit in the opening, the body had been machined .005inch smaller than the driven gear opening , the easy way out was to tale .007inch off the gear fitted together and now have 60lbs at idle and the pressure relief must be working at 65psi saltiga
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First gear is held in place with the fork, it doesn't have an interlock (spring loaded ball), I agree it's been that way for a very long time and possibly since new. These things were pretty much put together by hand so a miss alignment might have been in there from the beginning. I need to look at a exploded view of the transmission. PJ
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Make sure the stops and fork are in the proper position on the shaft, like I said before, it's tough to to analize without having it on hand. Now saying that, for as long as it's been that way, I wouldn't worry about it, just drive the heck out of it! 
PJ
View attachment 63365
PJView attachment 63365
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Paul said:
Apologies! As stated; been too long since a T-series crossed the bench. Looked at an MGB 3-synchro box diagram, it's the same... I'll claim oldtimers' disease.
...but would still say replace the fork(s), Laygear bearings and if galled, the layshaft, along with remaining bearings/seals then re-assemble and drive.
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I agree Doc, having it down this far, a complete rebuild would be the way to go, but now until things get straightened out on this Chinese virus thing, some folks might not want to spend that kinda money and keep it in reserve. Different strokes!
The 1st /2nd gear fork is made of steel, mine has a .010 clearance.and can be built up with weld. the first gear is held in by the fork and the ball and spring on the shifter shaft, the fitting of another spring , ball and another indent into the 1st/2nd gear shifter shaft will also help. the position of this is in the machining hole for the interlock balls between 3/4 and 1/2 shafts. I have a suspicion that the out of alignment of the first gear will tend to wear the teeth on first gear into taper as evident on this gearbox it also wears the first/second slider as evident in the slider gear spline. now if this is the case then jumping out of first gear will be more of a possibility. the gear wearing in the center will tend to leave a shoulder of unworn gear helping it to stay in gear this of course is supposition. A close look at the first gear teeth shows this taper the best I can measure its about .020inch, the wear on the slider shows the first gear has been a sort of rocking motion also adding to first gear jumping out of mesh
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Okay, seeing those pix it appears the incomplete engagement has tapered the teeth of the first gear, I'll assume the laygear exhibits the same? That doubles the angled load as result. That would effectively induce a sort of side-load on the gear, inducing the "rocking motion" you describe. Wear on the shaft splines worsens, the ramp effect increases and the result is popping out of first gear on load.
None of that is good news.
None of that is good news.
Yes, the lay-gear is also tapered, its hard to measure but i have about .005inch taper wear on most of the teeth. My thoughts are, if this is common with td/tf gearboxes its why many complain of first gear problems i have the MG Y box now but the first gear and lay-gear are missing. Can any one give me the measurement of the neutral to first gear selector shaft indents, mine measure .670inch This is also hard to measure accurately but its in the ball park. I will be replacing lay-gear, first and slider. Has any one used the rebuild lay-gear?? Saltiga