1170 update Why the tranny went BANG

[Ron Sa]

Apparently in low range, 3rd gear, under high load, slipped free of the fork and rapidly slid toward 4th causing a split second but very hard gear grind to occur. I interpreted this sounding like a loud bang.
The first pictures show the driven gears with low range 3rd and 4th on the right. The second picture shows these drive gears are a cluster--- having the weight of a hefty hammer.

Comparing the two forks that hold the two slideable drive cluster gears, the groove-engaging tabs are missing off the 3rd - 4th -7th -8th fork seen closer up. I measured the gear groove's flange which measured 3.013 inches. I had a 3-inch OD washer which fit nicely in the damaged fork. Apparently, the fork's tabs had experienced rapid wear rather than an overload break.

 

[wore out]

I wonder, is there a worn bearing or other issue that would force the gear to want to move and wear the fork so badly?

Is there anything amiss that should be directing (splashed) lube to that area?

Or is this a common wear point?

 

[J Hamilton]

I'm glad you have kept us updated on what you found as I have been following what you have posted because I own an 1170 myself

 

[Eagle Doc]

Back in the day we had some 930/1030s that would not stay in third gear. We were able to replace the 3rd/4th gear on the sliding gear shaft and fix the problem. The 30 series detent spring was not strong enough to hold the gear from working out of gear. The 70 series shift fork is secured to the shift rail when in gear but if the gear is trying to creep toward neutral it slowly wears the fork. Maybe Mel or Rod can explain the better.

 

[Ron Sa]

Eagle Doc is correct. The four range gears have more than a ball detent. There is a lock for each of the 4 range gears. See the picture.








Most of us have probably experienced gears pushing hard enough to overcome the ball detent and slip out of gear. Typically, no harm done--maybe over rev the engine.

.
Some Allis tractor models had the reputation of not staying in gear. At least one of my brothers B John Deeres had a habit of slipping out of 3rd.

I have driven a few old trucks that occasional slipped out of a gear'

 

[Ron Sa]

Regarding shifter fork wear, perhaps mEl and others could share their experience and observations.

I am going to look closer for the mode of failure. If the contact tabs wore thin and finally broke, a rough, thin break area should be noticeable. First observation, the entire remaining surfaces look machined. When the replacement arrives, I will get some close-up pictures of the failure and also the used replacement. My CaseIH dealer says new forks are not available.

If 3rd gear wore the fork thin by pushing hard towards neutral, the flange porting of the groove would have experienced the force and caused the wear. If 4th gear wore the fork thin by pushing hard towards neutral, the casting side of the groove and fork would be experiencing the force. If the picture is correct, for 4th gear an unmachined portion of the gear would soon start contacting the fork and cause a much different wear situation. Only 3rd gear could slip thru the fork.

Do bad gear sets that slide always push towards neutral? Just curious.

 

[1370rod]

Over the years I have seen quite a few badly worn shift forks and tractors that jumped out of gear under load. The reason I believe is many, maybe a gear that is not machined perfectly or loose bearings or worn shafts, maybe even a fork that was not tempered properly. Some of the time everything looked great but they still jumped out of gear. If the problem was bad enough a gear change was needed to correct the problem even though everything looked good. The early 2470's were gear jumpers, Case told us to replace the gears even though they used shift collars and that cured the problem. Some never did jump out, why the difference? I believe it was on the ninety series were some jumped out of gear, these had shift collars, not sliding gears. Anyway Case changed the angle on the collar engaging teeth on the gear to cause the collar to move towards the gear when under load. This fixed the problem but would cause some shift fork wear also. A worn out fork in a older tractor is not uncommon and yet some tractors with thousands of hours show little or no wear for no explainable reason. Rod.

 

[jim on van isle]

I had the same wear on the shift forks last year on our 970. I had the tractor split to repair the power shift & noticed a lot of end play on that shaft in the first drawing. There was a lot of shims behind the retaining washer that went against bearing #6 in the drawing. With those extra shims, the shaft moved excessively & I thought that might be a reason for the gears to move & ride on the forks. I put 2 shims back in & got .010 end play which seemed more reasonable (book called for 2 shims).I changed one gear & both forks with used ones which had way less wear than the old ones. This tractor has been apart before at one time so I thought the extra shims could have been a mistake. Thanks. Jim S

 

[mEl]

Jim, very early Power Shift tractors came without those shims and when the plate was tightened it loaded the outer edge of the bolts as the plate bowed under torque causing the heads to pop off the cap screws, consequently Case came out with a PUP to address the problem, the shims were added to effectively bring the shaft end out far enough that there was clearance between the plate and the face of the gear. It was a fix as fail. A couple thousandths clearance was all it needed but your ten is good. I was never sold on Case's bolts so I used Bowman Products bolts in the next hardness range and cleaned and dried then treated those bolts with Red Loctite.

This post was edited by mEl on 02/16/2022 at 04:45 am.