shift shafts seals leaking

[81dave]

Hello all ! New to this awesome site ! I need advice on 1981 GMC C1500 w 3-speed manual (maybe Muncie) . After the truck has sat for seven years I have noticed gear oil leaking/hanging from the shift shafts . This model does have the side access cover . The rear output seal has a drop hanging from it also . Would an additive such as Lucas Heavy duty oil stabilizer be a good idea ?  Now that I am beginning to drive it again do you think that the gear oil will make the seals become pliable and stop leaking ? I have found some shift shaft sleeves online that appear to be able to be driven onto the shafts without taking off the cover but that makes me wonder what would happen inside the tranny if I went that route . Any experience would be much appreciated ,

[Captkaos]

Are you wanting additive to solve the leak?  If so I wouldn't.  The took straight gear oil. 
How bad does it leak?  If you are planning on replacing the oil, I would just drain it and pull the cover and replace the seals, it shouldn't take a long time.
If you want to R&R in the truck you will need a fine pick to get the current seal out and a way to get the new one in without damaging it.

[81dave]

Thank you for the advice Captkaos , much appreciated ! Yes , I was hoping the Lucas oil treatment might stop the seals the from dripping . It says on the bottle it can be used for that . I don't believe it makes them swell so much as just plugs up the gaps . From the info that I have found about replacing the seals , I think that I could possibly do that . Going into the tranny does make me nervous though and I would be doing it in the driveway in cold weather , making for a tougher job for an older guy like myself . Once I have the cover off I believe the shifter yokes would have to come off to allow access the seals . Do you have any experience on replacing the seals and any problems I might run into getting the yokes etc. to line up when reinstalling ? Do you know if the "shift shaft repair sleeves" ( they appear to be driven in from the outside and form a lip seal onto the shaft , but I may be wrong on this ) might work .They supposedly are to repair scratches and gouges in the shaft itself I think . They say that they would still use the same size seal . My worry on trying that would be 1.) What would be happening to seal on the inside of tranny , and if the seals support the shaft itself , Holding it in alignment . 2) I sure wouldn't  want to be knocking something loose into the tranny to get stuck or jamming something up .
 I do want the repair to be a good one , I certainly can't afford to repair or replace the tranny at this point .
Advice much appreciated .
 

[81dave]

I forgot to answer on how bad they leak . They are forming drops onto the shafts . Noticed this when I was adjusting the shifter linkage . They do not leak onto the driveway though . No puddles or spots . I have just began to drive it again after sitting for a long time . It was cold when I was adjusting the linkage and I was having to move them back and forth a lot . They may have been cold and stiff or just dried out . The tranny is full of gear oil though .

[DnStClr]

Once the seals have dried up they become vulnerable to leakage when the transmission gets heated up and pressure builds inside the case. The best option is to replace the seals. I wouldn't be afraid to add the Lucas oil til warmer weather. Then plan on new seals.

[81dave]

Thank you DnStClr , That may be what I will try , keeping a close eye on the gear oil level of course . I am just driving it enough at this point to keep everything stirred up , 5 or so miles a week on city streets . Replacing the rear output seal seems pretty straight forward to me . Opening the access cover and replacing the shift shaft seals has me a bit nervous though . It seems simple enough on paper , its just that I have no experience inside tranny's . Would I just have to pry out the old seals with a pick and push in the new ones with a blunt object ? Are there any special tools that I may need to take the shift yokes on and off or to push the seals into place  ? Thanks again !

[Captkaos]

I would just pull the cover off and replace them outside of the truck.

[DnStClr]

NAPA has  a tool for shift shaft seals and it's cheap. P/N  BK 7769250.  I copied this instruction from Hotrodders website- to explain the use of the tool.
"The remover tool slides over the shaft, tap it lightly with hammer then put wrench on it and screw it in, works like an EZ OUT. Then the tool has a bolt you screw in, it pushes on the end of shift shaft and pulls the seal right out. It comes with a driver to install the new seal. Just take's a few minutes. Before you install new seal make sure there isn't any burrs on shaft,where the threads end and the shaft starts. Also use a little light grease on shaft slip seal on tap in with the driver."
And here's an image...

 

[81dave]

Thank you DnStClr and Captkaos , for your replies and advice . I really appreciate you going to all the trouble and time to look up and send the much needed info on the seal R/R tool DnStClr. I apologize for my slow reply but I have been away from my computer for a long time over the Thanksgiving holidays . I am going to look further into the tool to see if it might work on a manual tranny , if not I will be removing the cover to replace the seals when the weather warms . The tool certainly is affordable and might be just what I need . Again , Thanks to you both .
81dave