Un1 input shaft - is it normal to be removed

Hi there I've searched the forums but cannot seem to find the answer sorry if its been posted before! I have removed the un1 to have a look at the clutch I noticed that I could pull the input spline out (around 20mm)is that normal? I immediately pushed it back in afterand it seems to be operating the output shafts just fine - I cannot seem to remove it again?

Randy V

Lifetime Supporter
If memory serves correctly, the UN1 has a two piece input shaft. There was at least one vendor here that sourced heavy duty one piece shafts. Perhaps check with Andy at Tornado Sports Cars..
I've got a pair of freshly rebuilt (by Chris Cole) UN1 gearboxes that have done 0 miles since rebuilt and although you can tell the input shaft isn't rigid - it has a small amount of side to side movement in all radial directions - it can't be pulled in or out at all.
They are both standard input shafts and not the one piece design.

Howard Jones

So I am a little worried about how much movement you are getting on the input shaft. You saying that your have about 20mm or 3/4 inch in and out on the input shaft. I believed that this is a collar and pinned system. I was correct and it should not move anything like that much.

Watch is video and at the 1:40ish point you can see that the input shaft goes into a collar and the shaft is pinned to it. I think you will need to investigate further to be safe. Sorry...………...

Hi Howard, thank you for that in depth response, the input spline seemed to pull out (possibly more than 20mm if I pulled further) but when I slid it back in I have been unable to take it out again? Could it be possible that it is the single shaft which doesn't require a pin and simply slid out of place?
The input shaft of the UN1 in my car can be pulled out. It is not glued in nor fixed with a pin. Actually it should be glued in but it seems to work anyway. Due to the horizontal play of 5mm, the shaft floats between the pilot bearing and the gearbox.
The car was driven for years and on the track as well. I couldn’t identify any wear or problems so I decided to keep it that way.

Howard Jones

The single piece shafts, I have Chris Cole pieces in mine including the 1 piece shaft do not have any radial (my "in and out" correctly stated) play in it at all, none.

If it's not designed to be pinned then what is the hole for? Does it only hold the splined coupler onto the driven gear stack shaft and the input shaft is free to pull out? Is that what we are experiencing? The point is I think it would be very helpful if one of you guys in Europe that knows for sure would let him/us know. I would hate to have a good gearbox damaged for lack of complete information. I know mine didn't move more that a .1" or two in and out when it had a two piece shaft in it. It did have a bit of lateral play. These are pretty old gearboxes at this point and I am sure there are different configurations as well as many different states of wear. How's that old adage go. "Plan for the worst, hope for the best"

Another consideration is if the shaft jams in the out position it may/can load the thrust bearings in the engine and result in a worst situation. That would be a one in a lot type of failure but I would want to be certain if it was mine.

What happened to lock it in place after it was pulled out? Possibly a piece ( it may have had since broken into 2 or more pieces) of the original pin dropped back into the hole and thus it won't move anymore. The question is really what is going on in there and if it had a pin in it what happened to the pieces if it broke? All important information, especially if it is a good running gearbox. Like I said, it would be a shame to damage it unnecessarily.

Maybe call Chris Cole and ask?
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I think I will take the box apart to be on the safe side! Don't want a pin loose in there, thanks for the informative replies