Allison Aft Seal Swap Out

[neildeb2]

Just wrapping up changing out the leaky aft seals on my Allsison MH-30 transmissions (port and starboard). If anyone else wants to try it feel free to call me. I learned a lot doing it. It's not that hard. Maybe this is old hat but it was new for me. I'm happy to share detailed info on how to do it. Neil 360-305-9384

 

[SKYCHENEY]

I changed an output seal on one of my M20s. Its an easy repair.

 

[Dragonten]

Pardon my ignorance. What is the aft seal? Curious to learn.

 

[Captain Ralph]

Pardon my ignorance. What is the aft seal? Curious to learn.

The out-put shaft of the clutch/transmission behind your engine.
Rear seal may have been a better descriptor.
Allison MH is the mfg and model of the clutch/transmission.

 

[Dragonten]

Got it thanks.

 

[zigzag930]

Neil,

Is this seal between the engine and the transmission or on the rear of the transmission facing the prop shaft?

J

 

[rsmith]

The problem typically is the wear groove on the coupling. I chucked up the couplings in my little atlas lathe and just ran some emrycloth on them to try to polish out the grooves but they still drip. Only when sitting running they’re dry as a bone if I had it to do over I would have had one of those cheater sleeves slid on.there are 2 seals I faced both in to keep the oil in. Didn’t help. I had to break and tighten the nut with a cold chisel couldn’t get anything else in there. I asked a DDA guy first said that’s what they all do it’s the only way to get the nut tight enough.

 

[neildeb2]

It's the set of 2 seals on the output side of the transmission.

 

[SKYCHENEY]

I pulled the shaft back and had enough room to get a socket in there. Pulled out the output flange and seal and installed the new seal and slid the flange back in after cleaning up the mating surface. But, again, mine were M gears, not the MH.

 

[rsmith]

I pulled the shaft back and had enough room to get a socket in there. Pulled out the output flange and seal and installed the new seal and slid the flange back in after cleaning up the mating surface. But, again, mine were M gears, not the MH.

With your heavy equipment you probably had that 400lb torque wrench. That was over 25 years ago and 7000 hours of hard running haven’t falle off yet. But It would have been nice to have the torque wrench.

 

[SKYCHENEY]

With your heavy equipment you probably had that 400lb torque wrench. That was over 25 years ago and 7000 hours of hard running haven’t falle off yet. But It would have been nice to have the torque wrench.

Yes, I had the big torque wrench.