670 Super Diesel Ampli-torc problems

[WNY Molines]

I went to use our 670 super diesel yesterday to spread a load of manure and it acted completely normal.I parked the tractor for an hour or so and went back to use it, and the two speed AT would not engage the high side. When I push the lever forward it will just stay in the low side. last night, I pulled it in the shop and adjusted the torc to make sure there is plenty of pressure to engage, however the torc still will not work in the high side. Tractor acts completely normal otherwise and has never done this before. No strange noises or anything, and the lever clicks forward just as it should. Is there a common failure in these units? I have never dealt with one if these before and the only thing I can think was maybe there is a problem with splines on a shaft or a hub but I would think a problem like that could be heard. Thanks in advance for any replies.
 

[G706]

I had the same problem on a M670. The tabs on the clutch plates all sheared off. That can happen to the PTO. too. Over time the tabs wear out and break off. It can also happen if the tractor is allowed to overspeed in low range and high range is engaged quickly to slow the tractor down. The more common problem is that low range doesn"t work because the sprag clutch is worn out. Look through the adjustment access hole with a light and see if you can see the ampli torc clutch. Should be able to see if the tabs have broken off. Have to split the tractor to fix it.
 

[WNY Molines]

It looks like the only way to fix it is going to be to split the tractor then. We bought it a couple years ago at an auction and it would slip in low occasionally since we've owned it, but I would always usually just leave it in high. I'll probably end up putting all new clutch plates in it at that point and going through the sprag assembly so the high and low sides both work when I'm done. I was hoping it wouldnt be this bad because the only other tractor we have to put on the spreader is a Ford 7000 that I have all restored but I guess thats the way she goes.
 

[JOCCO]

Welters should have the parts to fix it although not cheap!!! Get a good book (and now videos) on how to rebuild one. I tend to agree with 706 on what happened. There is a couple different type of low range clutches i suspect you have the later one. If you sent it out it could cost up to $2000 to fix!!!!! OH ONE MORE THING I HAVE SEEN THE BRONZE SHIFT FORK ON THE LEVER MESS UP. tHE GOOD NEWS IS YOU WILL STILL HAVE TO SPLIT IT!!!!!
 

[rpllr]

I would say it"s the sprag if it"s a later one we had the same problem in a vista
 

[WNY Molines]

I"m pretty sure there arent any problems with the shift fork. When I had the cover off to adjust the AT, I checked to make sure locking the lever forward engaged everything as it should. as far as I can see, the lever is engaging just as it should. I dont think it is a problem with the spragues that has caused the high side to fail because the spragues are used during an underdrive situation right? The torque is working through the low side no matter what the position of the lever is. Am I somewhat correct in this assumption? I am more used to Fords dual power than the AT on our minnie. On another note...the tractor is a 1966 model year.Thanks for the replies
 

[jack bycraft]

Having had this happen many times to our 602, the tabs of the friction plates are all broken off. The sudden demise is when the last tab broke off. One should always shift to high by slowly dragging the clutch up so as to get all of the plate tabs against the driving surface of the cage. This is contrary to the manual but we found it works.
 

[G706]

As Jocco says Welter"s is the place for parts 417-498-6496. Their prices are as reasonable as you can find. Be sure to get a seal for the front cover and a new pilot bushing. The clutch plates are available from A&I Products which helps with the price. Welter"s can answer any questions you have about the repair. Get an M670 overhaul manual from Jensales or an IT Manual. The IT manual is ok, it cover all MM tractor models, but Jensales has the actual Moline factory repair manual.