Triumph Repair: layshaft wont fit, spitfire 1500, ebay

Question
QUESTION: I am wrapping up the rebuild of my Spitfire 1500 transmission. I am using the laygear and reverse from another gearbox. The bearings and shafts are installed, and as I go to insert the layshaft, it slides into one end, but doesn't line up on the other end. Are the laygear and shaft mated to the individual gearbox? Obviously I must take it apart again, and if they are mated using the other gearbox should solve the problem. Your expertise on this would be very helpful.

ANSWER: Hi Tom,
You need to count the number of teeth on each gear that you switched. If the number of teeth are the same it should fit. It is difficult to lift the laygear up into place to get the other end of the shaft to line up and I have tried several methods. Sometimes I was able to reach down and lift the lay gear up while wiggling each gear on the main shaft to engage. Another way is to put a piece of rope or wire around the laygear and lift with that and a third method is to turn the box upside down and rotate the mainshaft back and forth to get each gear to engage and allow gravity to help get the laygear in place.
The layshaft thrust washers on each end were always a problem and you had to keep the tabs in place when doing all of this. Some mechanics made short shafts to hold them in place when installing the laygear, then removing each short shaft when the laygear was inplace making it easier to slide the layshaft through. I used a heavy grease to hold mine inplace although on some I threatened to make a couple of short dummy shafts too when I would get a difficult one.
Howard

---------- FOLLOW-UP ----------

QUESTION: I have the gearbox from the vehicle and one I bought on eBay. I guess it's possible the gearbox on the car was not original. There was a different number of teeth on the reverse gear in both gearboxes--so the laygear and reverse gear are mated. Perhaps there are some other differences. The difference wouldn't have to be much, since the layshaft misses the other side hole by about 1/16 inch. I pried out the new input shaft bearing, and it sounds like it's ruined. Those must not be as durable as I thought.

Answer
Working in several dealerships and in my own shops over the years I have built many boxes and I have put many together using parts from other boxes even not knowing what year they were, by just a little measuring and close examination and counting teeth. A pair of gears that were used and came out of different boxes can give you a slight wine in that gear but still work well and in time they usually quit wining. When I would get one that did make a little noise, I made sure to change the gearbox oil several times.
You can't use two gears that have a different number of teeth because they change the diameter of the gear. The only time I seen a gearbox that could change only one gear with a different number of teeth was in a Harley motorcycle. They did it by changing the shape of the teeth on one gear. I have never run into a car that had tried it. If you change out both opposing reverse gears it should work. But measure carefully and count the teeth on both opposing gears. If you got both boxes you can measure between the holes in the case between the reverse shaft and the main shaft to be sure. That measurement should be the same on both boxes.
let me know,
Howard