Back in July, I hopped into my 69 Spider to go for a ride with my son. While still in the garage, I put the transmission into 5^th in order to jiggle things around and line up the teeth for reverse gear. I pulled the shift lever rearward and it wouldn’t budge. Huh! I cajoled, fumed and fussed to no avail. Just once, I succeeded in getting the transmission out of gear but it immediately got stuck again when I re-placed it in 5^th. I checked what I could at the top of transmission, finally deciding that it had to come out of the car.

Having never had an Alfa transmission apart and wanting the car back in service, I decided to take it to a local Alfa shop for repair. About a week later, the shop reported that they had succeeded in getting it out of gear but didn't know how they did it and that it appeared to work properly. Being thusly reassured, I paid the ransom, brought the transmission home, and played with it before reinstalling. I found that it would intermittently get stuck in 5^th but could be jiggled out. So much for professional help.

I armed myself with what information I could find on my CarDisk CD and started disassembly.

Unlike this Alfa-provided section of a column shift transmission, the shift lever is gimbal-mounted at the top of the shift tower, at the rear of the transmission. There are three shift rods, and the far end of the shift lever pushes one rod at a time forward or back in the top of the transmission case. Each shift rod has its own shift fork. Looking at them from right to left, the shift rods control the gears (1^st-2^nd), (3^rd-4^th) and (5^th-reverse). The shift rods have a clever mechanical interlock to prevent more than one rod being out of neutral at a time. Each rod also has three notches machined into the top (near the front) to engage with a spring-loaded steel ball.

These balls and notches are what holds the shift lever in position or out of position for each gear. The balls and springs are under what appear to be three buttons just behind the bell housing at the top of the transmission. Figure 2 shows the shift rod spring ball detent feature on the left and the interlock feature on the right.

The 5^th and reverse gears are located under the rear housing, so I was hopeful that I would not need to split the casing. I stood the transmission on the bell housing, removed the vents/bushings and, with some help from a wooden mallet, pulled off the rear housing. The 5^th/reverse shift fork pushes on the 5^th gear synchronizer sleeve and simultaneously causes an idler gear for reverse to slide along a shaft. This idler gear is what reverses the output shaft direction so you can back up and uses a bronze bushing to spin on the idler gear shaft.

Now for the inspection. Everything seemed fine when pushing and pulling on the 5^th/reverse shift rod and the transmission slipped in and out of 5^th just fine. Why was it working now? After pulling the spring and steel ball assembly and removing the shift fork, I withdrew the shift rod and could see that the shaft was true and in perfect condition. (You have to be careful not to spill or drop the interlock cylinders.) The interlock and ball detent were clearly not the problem. The 5^th gear synchronizer and sleeve did not seem to cause any hang-ups and the shift fork fit the sleeve properly. I was running out of options but unwilling to close the patient and hope that a miracle had occurred.

While standing there shuttling the shift rod back and forth, I noticed that when 5^th was engaged the reverse gear idler hung about halfway off of its shaft. Examining the bushing, I could see small circumferential scratches near the center that appeared to have been caused by the corners at the end of the shaft. I now knew what the problem was but not why; after all, these transmissions have worked for years. 

My car had come with several spares, including a disassembled transmission. The reverse idler shaft on the spare seemed about 10mm longer and, being able to see both ends, I could tell that it was held in place by a press fit in the aluminum housing. The reverse idler shaft in my car had shifted in the housing so that the idler would hang off the end of the shaft when the transmission was in 5^th. With the transmission sitting vertically on the bell housing, as it was during the mechanic’s and my inspections, gravity kept the idler aligned. When horizontal, gravity caused the idler to cant and hang up on the end of the shaft.

The fix was simple. I split the housing and, through the careful application of a C clamp and appropriately sized sockets, the shaft was pushed back into position. I then used a center punch to stake the housing and keep the shaft in place. Now it was time to close the patient. The application of a very thin layer of RTV to the housing mating surfaces cuts down on the leak potential. The reinstalled transmission shifts as it should.