XK 140 JLE gearbox doesn't fit to overdrive anymore

After having removed my gearbox (JLE31276) from the overdrive (28/1390) some weeks ago (synchromeshes on 2nd and 3rd were no good or better: not good enough) I started yesterday to re-assemble gearbox and overdrive.

Problem: everything went fine until the gearbox and overdrive came to about half an inch from fully home. Springs were all in the correct positions and the oil pump plunger was already on the cam ("pump operating eccentric").

I noticed that the 2 nuts on the long studs were getting very heavy to turn (heavier than the normal spring tensions). Took the overdrive off again and removed the 8 springs and the oil pump cam, so that nothing would be in the way. Tried to mate overdrive and gearbox once more: same result, it stops about half an inch too early and I can’t get any further. Tried turning the mainshaft and outgoing overdrive shaft, but nothing helps.

Checked that the splines were all in line (noticed that by turning the large wheel (apparently named “Sliding member”) inside the rear casing, I could align the splines deep in the housing. I also noticed that there is (deep down) some kind of bush to accept the end of the mainshaft.

No idea why I can’t go in all the way. This all worked fine when I assembled the two during the restoration some years ago and it all functioned well (apart from the synchromeshes of course …).

Does anybody have any idea why I cannot get the mainshaft all the way down in the overdrive unit?

Bob K…

Just a thought, are you assembling the unit horizontally or vertically?
If the former try the latter?

Robin,

Started with vertical: the overdrive in the vice and positioning the gearbox from the top. But after the unsuccesful first attempt also tried horizontally. Didn’t make any difference, unfortunately…
Bob K.

Damn thats me tapped out then, :frowning:

From ancient memory of doing this with my Triumphs and Healeys, it’s just a case of realignment and trying again. It can take ages, like mating clutch and gearbox. Or it can just drop in. Do not be tempted to pull together on the threads if it doesn’t want to go, you’ll break something.

I’ve only done this once about 30 years ago, but I recall you can only turn the main shaft one way, not the other, because of part #17 in this picture, which is a one-way sprag clutch.
image
Keep turning it the right way and it should go in, though of course you have to compress the springs, which is why they give you a couple of long studs.
But my recollection is that I put the whole OD case together first, compressing the springs without the added complication of the main shaft, then slid it on to the main shaft in the main gearbox case, while turning the shaft.

Thanks everybody. Will give it another try. Must have been very lucky, many years ago, when it fitted first time! Also found this advice: http://www.netbug.net/blogmichael/2015/01/24/laycock-de-normanville-overdrive-installation-tool/ for an Austin Healey overdrive. Although my problem is not so much related to the oil pump plunger, the story also recommends to use a dummy mainshaft to align the splines first. All I have to do now is find a dummy shaft … But apparently it is a known problem which is quite reassuring in itself. Will keep you informed.

Bob K.

Yes, case closed (literally)! Just like Roger said, after another 10 attempts, every time realigning the three splined sections deep down in the overdrive, the gearbox suddenly dropped in all the way (still with springs and oil pump cam removed). Then, without touching the overdrive keeping, the splines aligned (with overdrive in vertical position ), I removed the gearbox again and replaced the 8 springs and oil pump cam in the overdrive and placed the (very heavy!) gearbox on the overdrive. It went in just to the point where the 8 springs made contact. After tightening the two nuts I could now go down all the way and place the other 5 nuts.

Thanks for your advice. Bob K.