17 replies to this topic

[Aridgerunner]

I received a new 3.2 crown wheel and pinion from Mini Spares last week. When I tried to fit the pinion on to the third motion shaft it only went on about 1/4" and stopped.

I questioned this with Mini Spares asking if it was OK to force the gear on the shaft. Their response was that it is OK to do this. I know the nut on the shaft has to be torqued and feel that if the gear is adding resistance the proper torque may not be reached.

Does anybody here have any tips or suggestions on how to proceed.

Thanks in advance.

Bill

[DeadSquare]

How far does it go on, if you try to slide it on, the other way around ?

[Aridgerunner]

It only goes on about 10MM at best. I have tried it both ways and the result is the same.

[nicklouse]

Are you doing it in car or on workbench?

[Aridgerunner]

On the work bench.

[Gaz66]

The problem with forcing it on is it's a lot more difficult forcing it off again!

[Aridgerunner]

Yes! And that's why I'm hesitant to force it. I just heated it with a hair dryer u til it got to hot to touch. That helped a bit but again, if I do that then it's gonna be a bear to get off if I have to remove in the near future. Like maybe later today or tomorrow.

I have pushed it on and off (partially) several times and now there are witness marks on the shaft. I guess the difference in diameter has to be in hundred of thousands of an inch.

I'm not liking this.

[DeadSquare]

Are you certain that the shaft has not, in some way, become damaged ?

 

Assuming the shaft is OK, somebody has a clever tool that can make the splines correct at either end but not in the middle.  If the pinion doesn't fit, it's not fit for purpose and should be returned to Mini Spares. 

 

It is all very well for them to tell you that it is OK to force it on to the shaft, but it is not meant to be forced on and what happens if you get it stuck half on and can't remove it  ?

 

If you were in UK it would be easier, but I would have hoped that Mini Spares' pride would get a replacement to you PDQ, pending you returning the defective pinion.

 

Are the splines showing any sign of where it is binding, if so, do you have access to a suitable diamond needle file that could touch up the splines ?

[Aridgerunner]

I have to believe that the shaft is fine. I can see no indication of damage. And the 3.44 pinion goes on easily without any dragging or binding.

I have attempted to measure the inside diameter across the splines on both the 3.44 and the 3.2 pinion several times. When I do I always find the 3.44 to be just slightly larger than the 3.2. It won't take much of a difference to make the new gear bind up.

I'll go back to Mini Spares now and request an exchange. The only potential problem with that is the replacement might just be from the same lot.

Thanks to all for help.

Bill

[DeadSquare]

I have to believe that the shaft is fine. I can see no indication of damage. And the 3.44 pinion goes on easily without any dragging or binding.

I have attempted to measure the inside diameter across the splines on both the 3.44 and the 3.2 pinion several times. When I do I always find the 3.44 to be just slightly larger than the 3.2. It won't take much of a difference to make the new gear bind up.

I'll go back to Mini Spares now and request an exchange. The only potential problem with that is the replacement might just be from the same lot.

Thanks to all for help.

Bill

Ask them to try the replacement on a shaft.

[Aridgerunner]

That was my plan. And thanks again.

And I will update this post when I get the reply from Mini Spares.

Edited by Aridgerunner, 06 May 2025 - 05:58 PM.

[Spider]

It only goes on about 10MM at best. I have tried it both ways and the result is the same.

 

It'll be the shaft that;s the issue here. The late shafts were a bit 'funny' in how they were made and it seems they was some variation between them. The Pinion locates in the root (or valley) of the spline of the shaft and that's likely where it's binding.Not a place that's easy to get at to correct. Unless you have access to a surface grinder, I think you may need to either live with it or find a better Mainshaft.

[Aridgerunner]

Spider, you are correct. It is binding in the root of the spline. What has me confused is that the cars original 3.44 pinion fits perfectly.

I am fairly certain that this gearbox is a later one. The engine is a Metro engine and I believe the gearbox is original to the engine. But one can never be sure about anything with a car this old (1978).

If I can't get a better fitting 3.2 pinion from Mini Spares then I'll see if a machine shop can reduce the height of the splines in the gear. I'd rather not completely dismantle the trans again to get the shaft machined.

Edited by Aridgerunner, 06 May 2025 - 10:09 PM.

[Spider]

,,,,,,, I'll see if a machine shop can reduce the height of the splines in the gear. I'd rather not completely dismantle the trans again to get the shaft machined.

 

I think it would be considerably cheaper to replace the Mainshaft, if it came to that.

You could have a taper cut on the ID of the pinion, however, I'd first suggest to establish the shape if the shaft, ie, it could be barrelled or tapered or stepped or ?? it might be just one spline,,,,
 

[Ethel]

How about "painting" the shaft end & using the 3.44 pinion to rub down & identify any high spots?