Gearbox identification

[alexander]

Evening
My car has always had gear change problems, with help from the forum I did manage to get the change a little better but it still requires effort to select gears with second being the most difficult.
The car did come with a couple of spare gearboxes, the one I looked at today had the following stamping
J 7177 R 1812 with AM stamped above the last 7.
At 90 degree to the above is the number 50001 with K stamped under it.
My question is this a Jowett box or a meadows.
Thanks
Dave

[David Kemp]

I can't tell you what they should be, as my Meadows cases had Jowett components inside.
Best thing to do I found was open the case & look at the gears. If rough machined they are jowett, if smooth machined Meadows.
Have a look at my post Jupiter restoration.

[Keith Clements]

Usually difficult gear selection is caused by the the set up of the selector rods. However, wear in any one of many places can make it impossible to get easy selection.
It is more difficult on a Javelin than a Jupiter to get to the the adjustment and so on the Javelins I have worked on I increased the size of the inspection cover.
Swapping boxes without a full inspection of all components is likely to give more issues.
Usually a lot of patience is required for set up. You need to understand how the system works whilst homing in on the optimum position for both adjustments.
Whilst doing this you may identify wear in the selector shaft hole in the casing, or the gear change mechanism which are the cause. In the former I have used shim steel to take up the wear as a temporary fix.
The casing will have 5 digit number if Meadows and J followed by 4 digit number if Jowett. The 50001 is a casting number..

[alexander]

Thanks Both
I will enlarge the inspection cover as I do think there is more play in the selected shaft than should be and that will allow me to see what’s going on. I will check over the spare gearbox as the selectors and gears look new with no wear signs, and working on the assumption that if I have a good spare I won’t need it. Nothing like wishful thinking.
Dave

[alexander]

After lots of hours trying to improve the gear change I’ve taken the selector housing off and found wear on both selector bars, the gap in both for the operating lever are worn down and the notches for the plungers are also showing a lot of wear.
I have the selector housing off my spare gearbox with no wear showing on the selector bars, would it be better to fit the whole selector housing with bars or just replace the selector bars.
Thanks again for advice
Dave

[Keith Clements]

I would check out the unworn box for other issues because if there is wear in one place there is likely to be wear elsewhere meaning that your worn box may have other issues such as jumping out of gear.
The unworn box may have been removed because of a major problem, so inspect carefully.
JT has some good advice on how to do this.
But hey you could just try the swap as it might prove what needs fixing.