Downshift thump in Allison 647

[luvrbus]

Another thing that will cause a hard shift coming out of lockup is low idle speed,trimmer spring adjustments control the shifting a 740 can be made to shift smooth as any on the market  


good luck

[akroyaleagle]

I replaced my 740 with a new one from Allison because I thought it was slipping.

The new one shifted hard. Bob Ware in LA installed a shift kit. The 740 has shifted smooth as our cars since (1996).

Seems the cost was around $140 installed then.

I too was offered the 15-45 option by the transmission installer (Clif's Eagle Specialty Shop Goodletsville,TN).
I was actually told to use whatever the engine used to avoid putting the wrong fluid in. I'm the only one that services my bus so think that's a pretty remote chance. However, I'm getting older.

Most of my life has been spent in aviation. I do not believe oil has the same heat properties and viscosity as transmission fluid. That's my personal take and I don't see any advantage in going to oil.

[luvrbus]

Joe, I spoke with Bob Ware not long ago he retired from S&J Chevrolet after Roger Penske bought the company that guy taught me a lot about making the Allison shift smooth one of my hero's for sure

good luck

[gmbusguy1]

Hey Guys, if you would open your hymn books ( the Allison service manual) you can read about how the acceptable fluid is either syntec, ATF or motor oil of the correct CF rating and Viscosity depending on the service application and temperature

Chris

but then am I singing to the choir?