Gearbox on Jav and Jup.

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I have started this thread because Scott and I did some investigation of the pile of gearboxes that I have and have come up with more questions than answers. This post is also in the Josephine rebuild thread but let us start discussion in this thread.

Josephine performed well carrying Scott and me on our tour of Europe.
In particular the distributor performed well carrying us up those mountain passes and topping 150 kph on the motorway.
But I am just reflecting on what Scott and I did just before setting off.
We changed the gearbox which had been jumping out of third and the rebuilt one we fitted jumped out of top. Probably adjustment, so will see if I can reproduce the issue on the little humps we call hills in Britain.
But to fill some time because of our early return following Chris and Sharon up through France, poor Scott was sent to the Gulag to have a look at the assortment of gearboxes we disassembled at the Resto show.
We also tried to think what might have caused Chris's Jav issue of the gearbox seemingly braking itself in second when torque was applied. No joy there but we did find a lot of conundrums when sorting through my collection of gearbox bits.
We consulted the parts books and tech notes and this thread showing different types of lock plunger 50129 on 1st/2nd synchro ring. But then found at least three sorts of sliding dog 50033. There is the Meadows with recessed faces and electric pencil part numbers. There is the recessed Jowett and the flat faced Jowett which was a different height, 45.81 mm rather than 42.66. What is the reason for the different height and lack of recess and does it matter which type of box they are fitted into?



Also confusing were the two recesses on some mainshafts which seemed to serve no purpose. These pics are taken showing the two holes opposite each other but in different positions along the shaft. What is the purpose of these recesses?


The box we were re-assembling had been rebuilt by JCS and had a meadows 3rd/4th synchro which I swapped for a Jowett one as it was a Jowett box and all other gears were Jowett. The synchro showed signs of overheating. Can Meadows gears be successfully fitted into a Jowett box?
Another box we dismantled with the intention of clarifying the synchro ball arrangement only added to our confusion. We then noticed that some 1st/2nd sliding dogs had no holes drilled right through, others one and others two. So what goes in those straight through holes? In the Meadows there is a plunger and spring, but others had a cylindrical plunger some with two rounded ends and some with one flat end. This box had an extreme amount of travel on the 1st / 2nd assembly. My worry there is that an over enthusiastic engagement of first would pop all the synchro balls out. This box also had the wrong washer fitted in the input shaft causing this severe wear.

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Now gearboxes., As I've told Scott it pays to not strip too many boxes at same time as bits and mods were ongoing and they don't all fit each other. And it's easy to get the various interlocks all mixed up.
Firstly, 1st and 2nd. There are two main shafts, the early Meadows and later J cars with the longer hub. Also the Jcars ones are not all sized well and it pays to keep the hub and outer sliding sleeve together. If you have a worn outer, make sure the new one has a similar interlock and make sure it slides easily on hub. Some were matched fits!?! Meadows stuff is generally interchangeable with meadows as there sizing was ok! There are about 3 types of interlock, and they don't interchange!
3rd and top . The majority of meadows and Jcars gears are interchangeable except for the final J cars PE box which had an interlock fitted on 3rd/top. This is a good box, the best, but they didn't make many. J boxes with big numbers usually.
The mainshaft had two indents for the interlocks and the hub had 4 blank holes and 2 right through for interlocks. The 4 had a small disk in bottom of the blind drilling to give more pressure on the 4 balls doing the work of the original 6!
What to look for with jumping out of 3rd are wobbly gear fits on mainshaft buses, perhaps some shim between bush and shaft.
But main cause is tapered teeth on input shaft and top gear and 3rd and its mate. Also don't use worn synchros as if the gap for 3rd /top gets too wide the balls can pop out!! Also don't try the gears on the bench without bolting a plate against the front bearing!!!Because they sure as hell will pop out .
Bear in mind the saga with Early j boxes in 51/2 with Mr Mayall trying to fix boxes on the floor for production . It wasn't till R&D got involved and a gear grinders bought that it got sorted ! Too little too late. But saying all that it's a strong box when the centre washer is replaced and needle rollers fitted to lay shaft/input gear. Any more question just ask. Maybe you can transfer this to JT
Neil

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The 3rd/top interlock setup on late mainshafts. The interlock pin is just a pin with ball each end, nothing weird. The main thing is the hub has 4 springs and two right through holes for the pins to engage into the dimple in mainshaft. Now this is made happen by the outer sleeve which is matched to the hub with a cutaway tooth halfway in. There are two half teeth and they are opposite sides and from opposite ends., This is to lock the hub while the outer sleeve carries on to engage the synchro teeth of respectively 3rd/top gears. The whole exercise is to stop the inner hub going too far and engaging synchro hub of say 3rd and the outer teeth of top. This has the effect of locking the gearbox solid at about 40 mph which scares the shit out of everybody!?!
The surprising thing was that all the gearboxes up to this last version had got away with this not happening. There were a few cases early on of something like this happening at the wharves when some cars were being sent o/seas but few RECORDED cases after that? Politics I guess?! Any way that's my explanation. Remember the 4 springs left to do the job of 6 had flat discs at base of drilling to load up the springs. Poke a scriber in and compare depths to see if still in .

Here ends the lesson, Neil.

Thanks, Neil. This box must have been rebuilt without the two pins and 4 balls. I will have to find some and put in. Keith.

https://jowett.net/gallery/d/60192-1/Drawing+29.pdf This drawing of the mainshaft has a recess added on modification J dated 29/2/52 but it seems to be only one.

The mods to 1st/2nd seem to be captured in this drawing https://jowettnet/forum/download/file.p ... &mode=view

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Hi again Keith, was thinking about your comment about the gearbox that dragged in 2 nd gear. I've had this happen when the 1/2" studs at bottom front of the case are screwed-in too far . There is one which is machined shorter to stop it pushing the large Bronze thrust washer against the front large gear end of the cluster. This will reduce the clearance and make the cluster hard to turn or lock it solid even. It is important to check this point before assembling a gearbox and I usually fit the studs with Loctite as they are below oil level and can leak oil.
I also was not clear on the 3rd/top interlock pins. They are just a rod with round ends but the length is important. It's wise to trial fit them with no springs and ensure they do what they're supposed to before final assembly. That goes with 1st/2nd as well .
Another potential oil leak is the end of the layshaft into the box front. If loose oil will pass. I smear loctite in front hole on assembly to seal that point, again which is below oil level. Have fun! Neil

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The 3/4 driving dog and sliding sleeve Scott and I took out of the J9143 JCS rebuilt box composed of a Meadows sleeve ( that had two of its teeth ground out to drive the interlock pins) and a late J box dog with the two drilled through holes. What is worse is that 3 of the holes were 15.2 mm deep and the remaining one 12.5mm deep and that hole did not seem to have a disc in it. No discs came out of the synchro spring holes.
So I then sorted through the dozen sets of parts I had and could not find another dog with two holes, although I did find 6 sleeves with ground out teeth. So I am now in search of dogs with two holes to match the surplus of sleeves without teeth....no jokes please.

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After a morning updating the JCC website as a result of changes at the AGM and then continuing the preparation for the major update of jowett.net, I stopped when there was a power cut and went down to progress investigation of gearboxes.

From my stock I chose the two latest gearboxes I had which had not been dismantled. J8305 was very manky but succumbed exposure and then to thwart my attempts refused to release its woodruff key in the operating shaft. I even tried putting a hole through the shaft from the opposite side and managed to get 8 mm in before hitting some very hard steel that even a cobalt drill would not touch. Another 2 mm would have allowed a pin to be used to push the key out. So the grinder was employed to get the shaft out. How it was fixed is beyond my comprehension because I first clamped it with an engineers' clamp then wacked it with a chisel, I also tried some heat...all to no avail.
The 3/4 dog and sleeve moved on the mainshaft indicating that there were no interlocks. On disassembly this proved to be the case with no recesses in the shaft.

J9101 on the other hand had a 3/4 dog and sleeve that would not move easily on the mainshaft. I did not push too hard in case the balls flew out. Tomorrow I will continue disassembly to see if there are plungers and discs in the synchro lock holes. I suspect there are and the mainshaft will have recesses.

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Another morning continuing the JowettTalk and JowettGallery upgrade, followed by fixing Amy's side gate that had falling down in the gales and then back to gearboxes.
I continued the dismantling of J9101. Thankfully the Woodruff key came out using a hefty blow on one end of it. They should come out in a sort of circular motion which this one did. I could not get the cage bearing off the end of the mainshaft. It had worn so much into it, there was a ridge 2 mm deep preventing removal. The play in the input shaft indicated something was wrong. Also the bad bearing had worn the synchro, so if nothing else the mainshaft and input shaft are scrap.

Note how the bearing was not close up against the mainshaft end and hanging over the edge at the front. Where should it sit and how is the distance controlled?

The washer was heavily worn inside the input shaft.

The worn and an unworn synchro.

But now to answer the question. No ..this mainshaft had no dimples and the 3/4 dog had 6 normal synchro holes. Perhaps some swarf from the mangled shaft had locked the dog on the mainshaft.

So what series of gearbox numbers did have the two interlock pins?