4 speed transnission help NAA

Anonymous-0 · Jul 14, 2014

Does the transmission need to be removed from both the engine and the rear end to be disassembled? I believe that the spline on a gear of the main shaft are failing.
Unless some one has another opinion. When the tractor is in first gear with a load on it when you ease off the clutch the tractor will start to move and then it will pop and roll backwards then thy to do it again. With out a load it is fine second gear is also fine.

Last the ring and pinion broke while in first gear and locked the tractor up, I believe this also broke the transmission, but I can not see any damage leading me to think it is the spline on the main shaft or inside a gear.

John Smith8N · Jul 14, 2014

Yes, it has to be removed to be disassembled. Look for a worn mainshaft under the first gear (7100), a worn oversize bore in the first gear, or more likely a combination of wear on the mainshaft and the bore inside the gear. Also look for too much end play in the mainshaft or worn dentals on the first gear and/or the sliding coupler that engages it. All of the above can make it jump out of gear under a load.

Dave Boys · Jul 14, 2014

John - the transmission is not popping out of gear.
After the pop and the roll backwards it tries to go
forward again. Then repeats, unless there is not a
load on the tractor. Which is what was making me
think the splines inside the gear.

JMOR · Jul 14, 2014

I'm not John, but just doing late night reading and I'm sure John will be back with always excellent advice. Meanwhile, I believe you will find that first gear(7100) has no splines to shaft, but the coupler does.

Dave Boys · Jul 14, 2014

I believe the gear the coupler slides on is splined as is the
shaft. That is where I think the damage is.

John Smith8N · Jul 14, 2014

(quoted from post at 03:08:04 07/15/14) John - the transmission is not popping out of gear.
After the pop and the roll backwards it tries to go
forward again. Then repeats, unless there is not a
load on the tractor. Which is what was making me
think the splines inside the gear.

As JMOR said there are no splines inside the gear, just the coupler. Since it works fine in second gear, that eliminates everything else in the drive train. I'd suspect the countershaft gear which drives the 7100 gear may be missing about half it's teeth.

JMOR · Jul 15, 2014

(quoted from post at 23:16:22 07/14/14)

(quoted from post at 03:08:04 07/15/14) John - the transmission is not popping out of gear.
After the pop and the roll backwards it tries to go
forward again. Then repeats, unless there is not a
load on the tractor. Which is what was making me
think the splines inside the gear.

Click to expand...

As JMOR said there are no splines inside the gear, just the coupler. Since it works fine in second gear, that eliminates everything else in the drive train. I'd suspect the countershaft gear which drives the 7100 gear may be missing about half it's teeth.

ohn you are a thinker & experienced! Since third and 1st share the same coupler it then you reason that coupler must be OK, leaving the gear that drives it as the cornered suspect. I missed that! Darn it. :wink: Far down in the dark & maybe submerged would be hard for a man to see.

4 speed transnission help NAA

Anonymous-0

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