Changing rear seal in Allison trans-How difficult

[ron6785]

Have oil leak in Port Trans, assume its the rear oil seal. Anyone had experience in how difficult it is to change??? Has anyone changed the output seal with the boat in the water???

[yachtsmanbill]

Both the M and MH models have a bearing cover that unbolts to change the seal... The center nut is pretty darn tight on the coupling, and you'll probably need a puller for that part too. The seal is the easy part. Check the seal area on the coupling for a groove as well. That can be cut for an undersized seal or sleeved for a standard. What caused the failure?
Mis-alignment probably?? ws

[REBrueckner]

Yes, check the shaft to tranny alignment before reassembly.

[SKYCHENEY]

For clarification, is it the output seal of the transmission or is it the rear main of the engine that's leaking into the transmission?

[ron6785]

For clarification, is it the output seal of the transmission or is it the rear main of the engine that's leaking into the transmission?

. Sky, I assume its the output seal as the oil is leaking down the trans coupling shaft. I did detect a slight vibration at over 1300RPMs this summer.

[ron6785]

Yes, I'm sure I have an alignment problem as I developed a slight vibration at over 1300 rpms this summer and fall put over 2000 miles since I noticed it so thats the probable cause.

[SLIDELLBIGAL]

Its probably just wear and or the seal got hard over time. The coupling is tight on the output shaft so alignment will not wear the seal unless the splines on the output shaft are loose. If it was the rear seal on the engine, the oil level in the clutch would be climbing and the oil in the clutch would turn black like the engine oil.

[ron6785]

Its probably just wear and or the seal got hard over time. The coupling is tight on the output shaft so alignment will not wear the seal unless the splines on the output shaft are loose. If it was the rear seal on the engine, the oil level in the clutch would be climbing and the oil in the clutch would turn black like the engine oil.

Yes, It isn't the rear engine seal because the oil is going down on the trans and no loss of oil on the engine side. As I mentioned, I have a slight vibratrion at over 1300 rpms however the vibration doesn't seem to increase at higher rpms, which seems strange.

[GJH]

Check the Hydreco pump, which is mounted above the trans. They are known for having gaskets and seals go bad. The oil leaks down onto the trans and then the coupling, and it can lead to the conclusion the seals are bad on the trans. I had two different mechanics jump to that conclusion.This is exactly what happened to me recently, and and the mechanic I hired to do the work luckily caught it before going through the whole drill of pulling the coupling apart, pushing the shaft back, etc. If this is the same in your case, go ahead and have the pump rebuilt with all new o-rings and gaskets; they have a bunch of them and you might as well get 'em all done.

[Nonchalant1]

If it's the pump, it's an easy job. Mine came apart into a center block and 2 covers, and only had to replace the 2 bid o-rings as those are the only seals or gaskets. Very simple bulletproof pumps.

Doug