FJ40 H42 4 Speed 16 Spline Output Shaft Wear Evaluation

[Ackcruisers]

I’m in process of swapping a J30 for an H42. The 4 speed and tcase are from a 12/79 FJ40 with 90k miles. I separated the tcase to inspect the transmission 16 spline output shaft and found normal wear. I’m likely going to run it but wanted to get a second opinion.

 

[Skeet]

Depends on how much play there is with the gear on the shaft in its position

 

[Ackcruisers]

Depends on how much play there is with the gear on the shaft in its position

I see with your build you opted for output shaft replacement. The tcase input gear was smooth without any noticeable play before engagement. I’m wondering what an acceptable amount of wear is (and how to measure) per FSM.

 

[Skeet]

I didn’t notice any symptoms of wear when driving prior to tear down either. But I bet if I put it back together unchanged and was looking for it then, I would.
You can slide the gear to the unworn area of the shaft and feel how much wear there is in the gear alone, then slide it into place and feel the combined wear. With a new shaft and gear there is zero play. Once there is play between the two, the wear accelerates exponentially since it now has clearance to hammer together on every engagement.
Of course it took decades to get the wear that is there so it won’t fall apart overnight either.
I don’t believe there is a tolerance called out in the FSM. It’s your call.

 

[Ackcruisers]

I didn’t notice any symptoms of wear when driving prior to tear down either. But I bet if I put it back together unchanged and was looking for it then, I would.
You can slide the gear to the unworn area of the shaft and feel how much wear there is in the gear alone, then slide it into place and feel the combined wear. With a new shaft and gear there is zero play. Once there is play between the two, the wear accelerates exponentially since it now has clearance to hammer together on every engagement.
Of course it took decades to get the wear that is there so it won’t fall apart overnight either.
I don’t believe there is a tolerance called out in the FSM. It’s your call.

Thanks for the tip. Much appreciated. I slid the tcase input gear first over the seated area and rotated it. Did the same on the un worn area. Went back and forth to gauge and compare. There was no rotational difference I could feel however, there was a slight auditory difference. I appreciate the idea of exponential wear once play is present. I’ll have to think about my next step.

 

[FJ45 67]

Thanks for the tip. Much appreciated. I slid the tcase input gear first over the seated area and rotated it. Did the same on the un worn area. Went back and forth to gauge and compare. There was no rotational difference I could feel however, there was a slight auditory difference. I appreciate the idea of exponential wear once play is present. I’ll have to think about my next step.

I’m in a similiar position, what did you decide to go ? and how did it turn out ? There is an aftermarket gear available with a longer drive spline ?

 

[numby]

There is an aftermarket gear available with a longer drive spline ?

For the split case - yes. Check Terrain Tamer for earlier one-piece case. I thought they were discontinued.

 

[Ackcruisers]

Installed it without replacing gear. No issues whatsoever. Quiet and smooth.