kmggoober

We have recently bought a 1976 AC 7080 and it randomly makes a noise in the rear end. It is a high pitched vibration noise. It does it on and off for seconds at a time. Everything functions correctly. Thanks

Live Oak

Welcome to Tractor Forum kmggoober. Not a lot of information to go on there. For starters have you checked the level of and verified the condition of the oil in the rear end. When it makes this noise, have you noted exactly what it was you were doing at the time? The 7080 was a pretty high hp tractor for its time rated at 181 hp. What has this tractor been used for in the past. This might shed some light on the wear and tear this machine has on it and why the rear end might be making noises.

kmggoober

The fluid levels are all fine. It does sound to me like some kind of hydraulic noise though. The tractor has 4000 original hours on it and was primarily used for its drawbar. Moving the 3 point up and down makes no difference.

johndeere

I do not remember what type transmission shift variation the AC had?Does it have a high side and low side of each gear choice.Low and High range sort of a torqe amplifier?If so does it do it in both ranges or just low or high?

johndeere

It could be a plate your hearing.If so it could come loose and hit the gears and then you really have a problem.

tractorblogger

Oh! OH! I know the answer to that one. The 7080 had a 20 forward speed transmission. 5 speeds with a high and low range. Then what Allis called over and under for each of those 10 speeds. The over/under was very much like the TA, only Allis used 2 buttons on the floor instead of the lever as IH did.
So I guess that still leaves the question, does the tractor make the noise is only the under, only the over......or both?
I am curious as to the cause of the noise, so perhaps this will help get the ball rolling again.

Pat
Farm Tractor Blog

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kmggoober

problem found. dont know the whole story but the hydraulic pump was blocked off by something and it would push a bit of fluid untill it sucked all it could get out. when the pump wasnt under load it would make that sound.