# MF40 Instant Reverse Problem



## Jowo (Jan 8, 2017)

After recently restoring an MF40, the gears would grind when attempting to shift, indicating a warped or sticky clutch pack. I split the tractor and replaced the discs and plates in both packs. After reassembling the tractor, the transmission worked flawlessly with no grinding and smooth engagement into forward and reverse. After about 30 minutes, and numerous forward/reverse cycles (allowing engine to idle down before engagement), I lost reverse. I checked the system pressure and it was steady at 156 psi. I then checked pressure after engaging the forward clutch and it dropped momentarily and returned to 153 psi. But, when I engaged reverse, the pressure dropped and never recovered, indicating a loss of pressure integrity in the rear pack. I split the tractor again, pulled the packs and immediately found a large circumferential crack extending 2/3 around the rear clutch pack cylinder (at the base). 

I have found replacement parts ($$$) and am prepared to put the transmission back together. Obviously, I don't want the new cylinder to fail the same way, and have been unable to determine the cause of failure. I found no indications of anything assembled incorrectly and it worked perfect, initially. It seems the failure would indicate excessive pressure within the cylinder, but the system pressure has always been within limits when tested. 

If anyone has any ideas/experience they would share that might assist me with this issue, it would be appreciated. Thanks for your help!


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## sixbales (May 18, 2011)

Howdy Jowo,

Welcome to the tractor forum.

What is the actuating pressure on the clutch pack cylinder supposed to be? Check your manual. If 150 psi is too high, you will have to make adjustments. On Ford tractors, they use shims to adjust the regulator pressure. Probably the same on MF's.


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## Jowo (Jan 8, 2017)

The actuating pressure is supposed to be 150 psi min and 160 psi max. Yes, Massey's pressure is adjusted the same way, but you add the shims to increase the pressure. Either way, the pressures have always been within the proper range when checked. Did Ford have the same transmission? I noticed that a few of the parts referenced a Ford part number. Thanks for the feedback! I noticed you are in Tomball, I'm between Katy and Brookshire.


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## sixbales (May 18, 2011)

Well Howdy Neighbor!! Good country out that way. 

Your pressure is good. I'm wondering if your clutch pack exerts an axial force on the tube?? Is there an adjustment mentioned in your manual? You might check with your MF dealership.


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## shona13 (Aug 12, 2011)

G'day Jowo.
I received your request from Jim( MF in WA)
I have not rebuilt the mf 40 shuttle shift for some time but I do not remember anything complicated about the job.
Just reading my MF Service manual to jog my memory.
Does it look like a FRESH failure ie is the metal clean , Is there any sign of violence !! Physical damage like a part that has failed and got stuck somewhere, Hydraulically there is nothing that would cause the clutch drum to fail.
Keep me posted and if need be I can send you some pages from the service manual.
regards.
Hutch.


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## Jowo (Jan 8, 2017)

Thank you Sixbales and Hutch for your feedback. The clutch pack showed absolutely no indications of physical damage, either mechanical or corrosion/pitting. The best that I can tell, the break all looks fresh. I can clearly see one face of the failure, particularly at the initiation point and it appears to be a clean, fresh break. With that said, after I receive the new cylinder and have a chance to compare them, I plan to cut the old one to get a better view of both faces. It is clearly a brittle tensile failure with the classic 45 degree fracture plane.

I agree with your comment, Hutch, that the transmission is not complicated and should not fail due to hydraulic pressure. At one point I considered the possibility of a pressure spike (stuck regulator piston), but I calipered the cylinder and calculated the maximum tensile stress that the cylinder wall could experience. As it turns out, the stress at maximum pressure is less than 1000 psi, and the tensile strength of the material should be well over 100,000 psi. So, pressure itself should not fail the cylinder, particularly at the point that it failed as it had a much larger cross section than other parts of the cylinder (there are many other parts that would fail first, such as the aluminum piston or seals). This should answer your question, Sixbales, concerning axial force. Yes, the cylinder walls are under axial stress when the hydraulic force is exerted against the piston (compressing the clutch plates and discs), but the force is minimal. The only "adjustment" would be the hydraulic pressure itself.

This all seems to point back to the material itself, and whether there was a defect in the material, or possibly in the original heat treatment. It seems odd that it would fail when it did, but I can not come up with any other explanation. I doubt that I would be able to determine that, for certain, without costly lab analyses. My main reason for submitting the OP was to make sure that this was not a common failure with this type of transmission, and that no one (the few that have worked on these transmissions) had seen this type of failure previously.

Thanks again for everyone's feedback. If anyone has any further thoughts or suggestions, it would be appreciated.
John


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