5 speed transmission leak

[SDkvrd]

5-speed Gearbox appears to have been leaking for a while due to a failed control rod o-ring. Looks like I need to replace No. "4-5" as shown in the schematic. Never taken a tail shaft housing off one of these. The rear drive flange could be finicky, but it can't be much different than an L-series gearbox. Any helpful hints?

U20 trans schematic.jpg

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[jrusso07]

It is finicky for sure. I used a big dead blow plastic hammer and a short 2x4 and pounded it to separate. Had transmission standing up with bell housing sitting on a couple of 2x4s so that input shaft isn't in contact with floor. Tail piece up in the air.


I put a long, 3/4 " dia. wooden dowl in the speedo gear mounting hole to hold grand while removing rear nut.

Had to bang on tail shaft mounting flange for a while before it separated. DO NOT attempt to pry the tail shaft off. Housing is soft!

[SDkvrd]

Thanks for confirming my fears. I might just be tempted to take it to the local transmission guy if I can't persuade the parts to separate on their own.

[notoptoy]

This is doable, use the tabs on the tailshaft only to break it loose. Don't pry or whack on anything else with anything but a rubber mallet.
Loosen the screws, give a couple of whacks with the rubber mallet around the base, then use a dowel or extension to focus any serious pounding onto these two tabs indicated in the photo.
Anything stronger than a rubber mallet on the tailshaft and you risk cracking it or punching a hole through. As noted above, never pry between the two surfaces, it's soft, and if you don't do major damage, it'll likely never seal again.

[SDkvrd]

and getting that control rod out to replace the o-ring, a similarly delicate procedure involved I assume?

[notoptoy]

It's been a while since I did it, but I believe the control rod slides right out as you remove the tailshaft housing. Not a problem at all, but of course remove the pin at the back before removing tailshaft. Also remove the speedometer drive gear. And a note, the vent is plastic and can easily be broken as after 40+ years it can be brittle.

[mraitch]

While you have the tranny out, check to see if the shifter springs are broken - they are NLA from Nissan, but you might be able to find something similar.

[SDkvrd]

While you have the tranny out, check to see if the shifter springs are broken - they are NLA from Nissan, but you might be able to find something similar.

Maybe early Z car 70-71 gearbox parts would work? I'll have to check it out when the case is apart. Thanks to everyone for all the good advice!

[sunbeam590]

There are 3 o rings you will need to replace, the one on the selector shaft 5 and there are one each end of the monkey motion shaft 6-7 you will need to make a stepped drift up to drift out the support tube to get at these, I managed to break off the breather while getting the tail shaft housing off, I will replace it with a metal one .

[SDkvrd]

Thanks sunbeam590! I'm going to be extra careful to not break off the breather. I hope those o-rings are still available

[sunbeam590]

Any bearing service centre, or parts shop, will have the o rings,