Re-seal a 6-Speed Transmission

[Scud]

Here’s the basic process of removing, disassembling and resealing a leaky transmission. Two years ago, this was in the “do not attempt” category for me. But now that I’ve done a few with help from other members, I figured I should share what I learned – because the best way to really learn something is to teach someone else.

 

Ready, set, remove transmission. Some pre-steps required. The frame is strapped to the ceiling by ratchet-straps (not shown) to enable “crabbing” the frame. 

 

[Scud]

Step two, break the tranny.

• Remove input hub (special tools needed, see reassembly for picture).
• Remove shift pre-selector.
• Then the rear cover. Some soft mallet and leverage required, especially around the locator pins, which probably have a lot of adhesive in them. When the rear cover is out, you can remove the shift arm shafts and the arms.
• Then the gear stack comes out of the main case – but not until you have removed the speedo gear. This case will also be stubborn around the locator pins. I used carpenter shims to drive the cases apart – a steel screwdriver can cut into the aluminum, but I still had to use a wide screwdriver for leverage in a few spots. 

[Scud]

 

Keep your stuff organized; there’s a lot of it.

 

Clean the adhesive off the bolt threads. Clean the breather. Where is the little washer that goes at the bottom of the speedo drive gear? If you don’t know, it’s probably still in the main case and you don’t want it to fall into a bearing.

 

This is a good time to refer to the Lucky Phil shift improvement thread if you are inclined to do stuff “while you’re here.”

 

This is a also good time to decide whether you are going to replace any or all of three oil seals:  Input shaft, output shaft, gear selector shaft. Actually the time to decide that is probably before you start so you would have the seals on-hand. I didn't replace any seals or mess with the pre-selector, because this tranny only has 5,000 miles on it.

[Scud]

Clean up all the mating surfaces. I use a flat blade and a little oil – followed by a scotch-brite pad to remove all the old adhesive. I use a pick around the locator pins, which have a lot of goo on them.

 

Try to work so debris and dust falls away from gears or bearings – or cover them while you work.

 

[Scud]

We should not tolerate rusty output shafts….

 

[Scud]

OK – nervous time. Reassembly. Do I have all the right tools? Is everything clean? What adhesive am I going to use? What torque settings for two different size bolts?

 

It’s a good idea to dry fit the parts a couple times before applying the adhesive. The shop manual shows this step with a special tool that holds the case upright in a vise. I borrowed one from Andy once and it was very convenient. But you can lower the case over the gear stack instead.

 

 

Note that you cannot lower the gear stack into the case, because one of the shift selector gears will fall off.

 

I used Threebond 1184 (after a final quick-clean with alcohol). This is a very stringy grey adhesive – super strong stuff and about the same color as the transmission cases. Originally, this tranny had unsightly dark red-brown adhesive lines on it.

 

Permatex Right Stuff also comes in grey (or black) and is very good. It cures faster than the Three-bond, so it's really good for just doing the pre-selector with the tranny in the bike. You can ride after 30 minutes. 

[Scud]

 

Gears are in the case.  Did you remember the bolt that goes in from the other side?

 

I think the leak in this one was caused by the bolt at the 8-oclock position. It was very loose on disassembly and that’s where the leak was coming from. There’s no way to access that bolt without removing the rear cover.

 

No anti-seize compound needed. The bolts get bathed in gear oil.

[Scud]

Put the shift arms (which you kept organized in exactly the right locations) onto the grooved gears and make sure you can slide the gears back and forth. Then put the shaft in through the case and into the arms. Note that one end of the shaft is threaded. This is helpful for disassembly too.

 

 

Then put the rear case on and insert the clutch pushrod, throwout bearing and cylinder. Sorry, I didn't take a picture of this step, but you can see that it's on in the next photo. 

[Scud]

Get the transmission in neutral by disengaging all the gears – by sliding the selector arms. Make sure the pre-selector is in neutral. Dry-fit it to be really sure. Are you sure yet? You don’t want any adhesive on till you’re sure.

 

 

Are they both in neutral?  Really?  Are you sure?

[Scud]

Put the input hub back on. Special tools required. But you already have the special tools, cuz you used ‘em when you removed the gear. Torque to spec and fold one tab of star washer into a slot on the ring nut to lock it. You might want to use a new star washer, but I think that as long as you don’t fold the same tab twice that you can re-use the star washer.

 

[Scud]

Admire your work. A six-speed V11 tranny is a thing of beauty.  I only painted the rear case, because it was peeling badly.

 

How long are you supposed to wait to put oil in? Read the directions on your adhesive.  Then put the tranny in and go riding (some other steps required).

 

 

I swore I was gonna remember to attach the ground cable to the tranny...  but I didn't.

 

Shoulda put the cable with all my other stuff on the table. Now I have to pull one of the bolts out and re-torque it over the cable (after scraping the paint off that spot).

[Chuck]

Egg sellent, Scud. I've been wondering what was in that black thing behind the motor..  

[LowRyter]

 

[nobleswood]

Great documentation Scud!

 

I've always had a difficult time figuring out how all the parts mesh together.

 

Only ever took apart the engine & transmission on an original Mini. It never ran again !

 

Did you find /photograph wear on the gears while you were in there ? Still learning about what is acceptable.

[footgoose]

as above ^^ excellent documentation Scud! What about the shaft seal? Wasn't a problem?