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Jeremy, Technician
Category: Construction and Road Equipment
Satisfied Customers: 3318
Experience:  ASE Medium/Heavy Duty Technician, Hydraulics, Brakes, Electrical Certified
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Fiat Allis 945B wheel loader. Allison model TT4720. Driving

Customer Question

Fiat Allis 945B wheel loader. Allison model TT4720. Driving full rpm down trail when trani seemed to go to neutral. No trans oil pressure in any gear, yet low reverse still works. Removed charge pump to filter line, lots of oil, filled a 5 gallon pail in about 20 seconds. What is the most likely problem?
Submitted: 9 months ago.
Category: Construction and Road Equipment
Customer: replied 9 months ago.
Up until that point trans worked very well, although I did feel stall rpm was too high when oil was hot. Also less than 100 hrs on trans oil and filter change but oil seems quite dirty for such low hrs
Customer: replied 9 months ago.
Could it be the clutch cut off valve stuck that is activated by the left foot brake? Could that valve cause that even though I did not operate the brake at that time?
Expert:  Jeremy replied 9 months ago.

My name is ***** ***** I will assist you with your question today.

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i don;t normally work on these, but I can give it a shot. Do you still need assistance?


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Customer: replied 9 months ago.
I still need assistance, the loader is still broke down out in the field. It is an older loader and the transmission is not electrically controlled in any way. I am hoping something external has failed, because it is a huge job if the trans must be pulled. In fact, the loader would not be worth the cost of a new trans and labour. Thanks Brian
Expert:  Jeremy replied 9 months ago.

Thanks for the reply. With you still getting the 1 reverse, most likely it needs a rebuild due to the clutch plate discs being warn. As you said, this isn't a electric transmission, it is all mechanical which uses the friction discs. However, it could be the pump in the trans since you lost the upper reverse. t would still need to be pulled and if going that far, a rebuild kit with the friction discs would be wise to do since you appear to have had slippage based on the comment that you had higher RPMs.

Customer: replied 9 months ago.
I still have a bit of hope for it. Why would the clutches just suddenly, completely quit grabbing when there was next to no load on it . It quit suddenly, just like as if it was shifted to neutral. Also I always thought it was the torque convertor worn because of the higher stall speed when oil was hot. I don't think its the pump because as I said when I removed the line I got about 5 gals of oil in about 20 secs at its slowest idle speed. This trans has an external main pump. What about the clutch cut off circuit? When it was used the pressure did drop to zero while the brake was on and yet reverse still worked with it activated. I could be wrong, but I feel you should familiarize yourself more with this particular trans before advising me it needs a rebuild. Although it probably does, I want to be absolutely sure before I tie into it. This trans weighs 2000 pounds and would be a huge undertaking. I know there aren't many Fiat mechanics left but I was hoping maybe some of the older guys would have worked on one. Thanks Brian

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