GT6 Driving the mainshaft bearing into the gearbox case.

I'm currently rebuilding a three-rail gearbox for a GT6 MkIII I'm restoring, and I'm about at the point I can put it all back together after replacing about half the parts in it. Reverse was mostly obliterated, and the syncro teeth on 2nd and 3rd were worn badly from running a while on used up rings, and of course the one thrust washer that's hard to find was in four pieces.

Anyway, I'm contemplating getting this all back in the case and I'm not quite sure how to get the mainshaft and its bearing back in place without the factory tool that mimics the input shaft to hold the mainshaft centered and at the correct depth while you drive the bearing into the case. I see there's a guy currently on eBay selling the correct Churchill tool for $150, and I'll bite the bullet and buy it if I have to, but just wondering if anybody else had any clever method to do it without the tool? I could probably fabricated something, but that might be more trouble than $150 is worth. I could just insert the input shaft first, but I don't really want to be banging on the little roller bearing that fits between the input shaft and the mainshaft.

I wish I could offer sage advice. However, it has been literally more than 20 years since I rebuilt our car's gearbox. What I can say is that I only made one special tool and that was a mandrel to hold roller bearing rollers in place when installing the laygear. I was able to do the other tasks with common shop tools. Hopefully someone with more recent experience will offer better advice.

dklawson said:

I can say is that I only made one special tool and that was a mandrel to hold roller bearing rollers in place when installing the laygear.

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That one was easy to make :joyous:, although I just cut a 5/8" aluminum rod I had instead of actually lathing something down to the ridiculously specific 0.655" the WSM specifies.

I also used the inner race of one of the old bearings to make a distance tube for measuring input shaft end float.

As you said, everything else has so far been just standard shop tools.

I'm not familiar with GT6 gearbox, but isn't it very similar to a TR6 gearbox? The Ohio Buckeye Triumph's web site has some excellent articles on rebuilding TR6 transmissions which also shows how the author fabricated most of the special tools. I followed his lead and fabricated the tools with just a hack saw, Mig welder, and vise. So you may be able to cheaply make something that will do the job.
Bob

One of the guys on the Triumph Experience forum showed me a picture of the tool he built for the job, which was just an aluminum plate with a couple of mounting holes and a threaded hole in the middle for a capscrew that held the mainshaft in its proper place. That'll be easy to fabricate and should do the job just fine.

The TR6 gearbox is a bit different, but the mainshaft/input shaft joint looks basically the same. I'll check the Buckeye Triumph's site, thanks!

Here's my solution to the problem. Not quite as nice as the factory tool, but it only took a few minutes to put together and should get the job done.