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Discussion Starter · #62 ·
Well, the original transmission finally gave out, the rear bearing slowly went out, my wife and I were enjoying a little get away, I left my GT in the parking lot overnight and found a good sized puddle underneath the transmission, I cleaned up what I could before leaving. I was able to wobble the driveshaft where it went into the rear seal, evidently there got to be so much play in that rear bearing that it became impossible for the rear seal to seal. 4th gear was the only gear that became more difficult to get the shifter into towards the end.

I got all I was going to get out of the original transmission. It lasted me over 30 years of trouble free driving until this festered into its end. It may be that the rear bearing is all that went wrong with it? Or a symptom of an additional problem? I put it on the shelf for a rainy day, I’m not sure how involved replacing the rear bearing is or weather I’ll ever fuss with it but the linkage or something might come in handy some day.

I swapped it out over this past weekend, my first transmission replacement (engine in car) I had the 73’ transmission fixed up & on the shelf ready to drop in.
Since I had such a devil of a time lining things up when I had the engine out on the floor, lining it up & getting the bolts started on the newly helicoiled female bell housing threads. I dreaded the day I had to do that with the engine in the car.

I used the directions from the FSM step by step. I’m glad that I raised the car up from the rear so I could rotate the drive shaft and I had plenty of room to bench press the old one out/new one in. I took my time, not rushing it took me a total of 7 mostly trouble free hours, when you figure at least an hour or more was spent looking for the wrench or whatever it was that tried to get away during the process. Thanks to MICAH1’s suggestion from an old thread see post 19 things went MUCH smoother, using 4-M10x1.5x50mm double end studs I used the red Locktite and snugged the down into the bell housing where hopefully they will never come loose. Locktite is an anerobic bonding chemical that will not properly react with aluminum and create the permanent bond but since I had the helicoils installed I think that it will hold. I also recommend using the 4- 15mm small wrench hex nuts along with the 10mm lock washers. As it was I took my 15mm wrench, cut it in half and ground off the top and sides in order to get at the lower passenger nut. A standard 17mm nut would be more difficult to manage. I was able to see & get the top two bolts through the shifter opening using the swivel extension with the 15mm deep socket. I figured there was a reason Opel used the 15mm bolt heads. In the end I was glad to have those little buggers. I used gear oil RTV on the gasket between the gear box & bell housing and let it dry after assembly for 24 hours.

I added 140 weight (note, I live in a southern climate) Sta-lube gear oil to about 1/2” below the plug (2 -2-1/2 pints) & took it out last night and it shifts into all 4 gears smoothly and checked underneath a few hours after the test drive, so far no drips. So far so good. The odometer read something like 83,000 miles on it so that could possibly mean 183,000 miles? If it’s anything like my first one they seem pretty tough. This was a good way to go, when it’s time it made the upcoming clutch replacement, much less intimidating.
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