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Allison m20 behind 8v92ti. Stbd oil level low mark when cold. Oil honey color. Idled the engine 1/2 hour periodically running to 1000 rpm. Oil level rose to 1/2 between full and low but foamy oil dip stick. Added 1 qt 40w, oil level at full foamy.I have read that if overfilled will cause foaming, but under filled? Temps: at brass fitting to trans oil filter 125 by infrared. Lower er gauge - 137. Lower helm - 150
Could be getting air through the suction side, over filled or the gear is whipping up the oil. There’s a guard above one of the gears in the trans. If that has shifted this will happen but it’s rarely the issue.Quote:
Originally Posted by Chasemmc
Do u think operating the transmission will damage it?
Typically no but can’t say without knowing what’s really going on
The operating temp at the sea trail was 153 degrees. I'll monitor while operating. It shifts fine. Wasn't there a good Allison shop in Alabama mentioned in the forum. Maybe I can call them, anyone remember the name?
Acadian Marine Transmission ask for Brian. Broussard, Louisiana. His knowledge is amazing.Quote:
Originally Posted by Chasemmc
Thank you, I will give him a call
Brian was very helpful. I will repeat his knowledge for the benefit of the forum.Brian said that foam on the dipstick is due to an air leak on the suction side or low oil level. He said the reason the transmission first presents by not going into forward is that the oil has a more circuitous route than in reverse and pressure is bled off as it travels.He said temperature, while an indicator, is less important than pressure as low pressure allows the clutch plates to slip while underway. He said it should be between 135 - 150 psi. I think the temperature is monitored but not sure about the pressure. He said to add another qt. And see if that stops the foaming. The trans holds 5 qts plus whatever is in the lines and filter.
Has anyone put pressure gauges on their Allison MH-20's and if so where? Where would I find?
mark
Don’t you have them already?Quote:
Originally Posted by Chasemmc