i really dont see how it could go into 3rd and not 4th....
on my 1275 the shift arm does both gears, if neither worked
i would expect a loose shifter fork, but with just one gear
not working i would suspect a stuck ball bearing or at worst
a stuck synchro not letting it go in...
ive just put mine back together (2nd time out) a few weeks
ago, so im pretty fresh on the subject..
does it pop out of gear when using 1,2,3..hows reverse?...

dont be scared, its not toooo intimidating and there
is alot of info available for rebuilding it... ....z

I didn't realize you could put MMO in your ears

heh...
Like I said: Never underestimate the POWER!!

I love the MMO idea. I'll do it.
Never pops out of any other gear. Reverse works fine but it is a bit hard to find sometimes. Remember, I've only driven it 5 miles since I got it home. It's not going far with no brake lights. That'd be really great if it would free up on it's own.
BTW now that there's oil in the gearbox, it's leaking. My guess is it slowly leaked until gone and the PO never noticed as he only drove it occasionally for very short trips.
What about running something more aggressive in it for a brief bit, like.....I don't know diesel fuel or something. Maybe that's a really bad idea.
There's a 5 speed on ebay. Maybe I should buy that. I have dibs!

maybe drain it, rinse with water(hose), spray it good inside
with citrus cleaner, go through the gears to loosen stuff,
maybe even start the car for a few minutes,wait, rinse well, let dry, then fill with oil....

thats what i did, but i took mine apart to do it....
just a suggestion....shouldnt hurt nothin.

if u cant flush the problem u will have to pull
the motor....not too bad with a small lift.
i pulled mine in less than 2 hours last time ....z

I can relate to your brake issue. When I bought my Mini, I later learned that 1/2 of one wheel cylinder was all that was stopping the car! 12.5 percent of the brakes were working! All fixed now.

Unless you have overfilled it, there are very few spots it can leak from. From the picture you posted it looks fairly clean under there and that should help in locating the leak. The first thing I would do is place a piece of cardboard under it to locate the area it is actually coming from (front, center, rear, right or left side) and then get under there and visually inspect it. There are a couple of plugs near the center, bottom of the tranny, if either of these is leaking it also may help localize your 4th gear problem as they are access plugs for detent installation, the one being level with the drain plug being a detent ball that rests between first and second, and third and fourth. The other is for the reverse gear detent. other than these two plugs, the drain and the side cover gasket are the only other potential leaks at the middle. If the leak is coming from the front of the tranny, the only potential leaker would be the front cover plate (which would require tranny removal to access!). Towards the rear, a leak would have to come from the gasket between the main gearbox and the control lever assembly (again requiring removal to remedy) or from the rear seal (which would most likely indicate an over-filled tranny!). Good luck and keep us posted on what you find!

Hopefully your brake-light issues are electrical, which may be more of a pain to trace, but actually easier to remedy than mechanical problems! I would venture to say from what you have posted that they are electrical, and a methodical tracing of potential trouble spots will track them down too!

How can you overfill it? Aren't you supposed to fill it until it runs out the fill hole? That's what I did anyway. The leak is academic at this point, getting 4th to work with an easy fix is the goal, it's almost certainly coming out anyway so than the leak issue will be addressed.
I'm going to try the MMO.

Can you remove the detent plugs from underneath and see what's going on? I'll do some more looking at the books.

[quote=jvandyke
Can you remove the detent plugs from underneath and see what's going on? I'll do some more looking at the books. [/quote]

I am pretty sure that you can

I think that you can remove one (the one for reverse), but not the other as it lies between two of the shift rods and is inserted during assembly after inserting one rod and prior to inserting the other. Regardless, a liberal a liberal squirt of MMO in the bores for the detens could not hurt and could help a great deal.

PS: Overfilling the tranny can be accomplished if the car is jacked up at the rear while filling the tranny. The excess oil will drain from the rear at the output shaft when the car is lowered!

Well, I don't think the simple fix is going to help.
Drained the gearbox and the drain plug had a fair number of metal shavings in it. I put the MMO in it anyway for kicks.
Sounds, acts and is beginning to look, like she's baked.
So I watched a smooth case tranny go on ebay for $100, should I hold out for another ribbed case, chase a Datsun 5 speed? Is the one on ebay worth the $350+ is at right now?
Or just save my $$ to rebuild mine?
I should probably stop testing mine, probably just ruining more parts.

I vote for a straight swap for a ribcae. The ribcase is more robust than the smooth case. While the 5 speed is nice - you're quickly north of $1500 and you have to modify the body and that will lead to a restoration and then you will be like me - 4 years into a 2 year project.

Buy a ribcase - take an afternoon to swap them and go drive!

Yeah - Get a Rib Case.
Fastest way back to driving!

Driving is what it's all about, I have an MGC that's been 20 years on jack stands. Man I still remember driving that baby down the AlCan doing 125 mph...

Driving - get a good rib case - swap it in & drive!

Where to find one......???

Put the word out to the local British car clubs.