I just finished a 6 conversion on a '73 914. My 901 gearbox was completely rebuilt using using my gears and the '73 side shifter with a 914-6 main case, intermediate plate and ring and pinion. I built the shift shaft to clear the -6 heater boxes, closely aligning the shaft at the side shifter to duplicate the geometry of the stock shift rod. Shifting was fine through 4th gear but sometimes would not engage 5th although it felt like it went in. Finally, the shifter locked in the 5th gear position but no gears were engaged, as if in neutral.

After removing the side shifter assembly and realigning everything, I made some fine adjustments to the shift rod, rechecked the geometry at the side shifter in all gears and reassembled everything. Shifting felt very smooth and positive in all gears without the engine running. On the first test run, it shifted easily into 4th but when the clutch was released, the gears were not engaged (neutral) and the shifter was locked up now in the 4th gear position.

The shop that rebuilt the gearbox pulled it apart after the first lockup but couldn't find anything wrong.

Has anyone ever encountered this condition? A friend told me he had heard of welding an extension to the side shifter lever arm that extends inside the box. I've owned this car for 30 years and never seen this problem before. I'll be forever grateful to anyone who has a solution.

I'll try to post some pictures of the shift rod and side shifter as it is in the car.

Thanks,

Ron

4th-5th gear shifter fork may be misadjusted, bent, or put on backwards.
Front or rear bearing may be bad.

If you lock it in between gears as you have,,,,remove the custom shifter rod setup you have and see if you can shift it by hand right at the tranny.

You say that you used the 914/6 main case with the 73 sideshifter.
How did you do the conversion?
May not be square to the main shaft...

Sure sounds like the shifter forks are misaligned though...that will get you stuck betwen gears...at least that is what it feels like.
In reality, it the main shifter piece that is not properly engaging the 4-5 shifter fork...all the way...it just requires a simple adjustment, but you need to do this in either a jig, or I have a tranny with a huge cutout so I can access the shifter forks to adjust them.

Ask your tranny rebuilder how he adjusts the shift forks...you must have the shifter rods, and both gear shafts properly supported to ensure you adjust the shifter fork square.

All that being said...its about 1/4 of play side to side....you can do it by trial and error.

I would pull the gear stack and check all the bolts to make sure they are tight...and adjust the shift forks again.
Rich

Rich, Oops, you're absolutely right. It is a 914 side shift main case. I probably misunderstood the rebuilder. The intermediate plate had the boss for the throttle belcrank.

Thanks much for the reply. I'm confident the info will be very helpful in resolving the issue.

After the first lockup and the gearbox was inspected, I reinstalled it and tried shifting gears by hand at the tranny before installing the shift rod and everything seemed to work just fine. Once the tweeked shift rod was hooked up, I shifted through all the gears with the engine off, checking the position of the sideshift lever for each gear selection and everything looked and felt normal. I should have run through the gears with the engine running while still on the stands but didn't. The problem only seems to show up under driving conditions. I'm pretty sure the shift rod is not the problem (all new bushings throughout and good alignment).

Thanks again.

Ron