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Allison 4000 Transmission Leak

 

I noticed an occasional small drop of "oil" on the floor beneath the back of the transmission.  It concerned me so I had mechanics and technicians look at it.  I had checked fluid level, no detected loss. 

Mike Rodgers checked and found nine bolts at about one quarter the spec torque required so he tightened them to specs.  They then soaped and pressure cleaned the tranny, I drove and then crawled under several times to monitor the clean surfaces.  The fluid seep around two bolts was visible, the tightening did not solve.  Maybe more than the two bolts were involved, there are quite a few more than nine there.

Took the coach to Stewart and Stevenson.  When I got there, about 100 miles, and parked, we noted the leak had increased from a drop or two, so timely to have looked at this. S & S took it apart and found three gaskets of the retarder plates needing to be replaced. 

Photos of the bolts that were loose and the seep around them are attached.  Maybe it would have continued many miles just leaking a little but that would have worried me. 

 Transmission Leak

Transmission Leak

Transmission Leak

Transmission Leak

Maybe check these every, oh, 140,000 miles?  Mike 2001 U320 40'

Retarder And P3 Planetary, Retarder Valve Body Module — Exploded View

Retarder And P3 Planetary, Retarder Valve Body Module — Exploded View

Retarder And P3 Planetary, Retarder Valve Body Module descriptions

One of the methods for finding a leak is interesting; "The Powder Method. Clean the suspected area, apply an aerosol-type white powder, such as foot powder, to suspected area, operate vehicle under normal conditions, visually inspect suspected area and trace the leak path over the white powder surface to the source. Dick, 2003 U320 40'

Troubleshooting Charts For Allison Transmissions AT / MT (B) / HT / V

© Barry Brideau 2003-2017