Layshaft won’t seat

[Lastminuteracin]

Trying to slide the gearbox into the housing on an MK9. Stops about an inch short. After an hour or so of frustration I take the Layshaft out thinking the reverse idler won’t seat right. I leave reverse on the shaft and try to slide it in. Problem is the Layshaft doesn’t want to slide through the needle bearing. It goes in just far enough to engage the coupler and then just stops. A lite tap with a rubber mallet and it goes in a hair but then it’s hell to get out. Both the race on the shaft and needle bearing appear to be fine. I had it together when I mocked up the car originally. Now that it’s for real it’s a no go. I thought about polishing up the shaft a bit in the lathe but figured I’d ask the collective first. I don’t see how I could have misalignment with the input shat or the coupler. Thanks.

[Steve Demeter]

Sometimes the coupler will fall off the input shaft. Ask me how I know. If it fit before it should still fit. I would NOT polish anything but search for something not aligned correctly or like the coupler off the input shaft. One suggestion, take all the gears off the layshaft and see if it will go in. If so then something is probably amiss with the gear stack

[Lastminuteracin]

All the gears were off by the end. The coupler is there. I did monkey with the clutch linkage before I started the gear box install.. I’m still engaged in the disc but wonder if it slipped down a bit messing up the alignment at the gear box end.

[J Leonard]

Did the gearbox get installed without the layshaft in? Pilot bearing/bushing OK?

[Offcamber1]

by any means but...

If you have two gears very close to one another in ratio and accidentally swap two of them on the same shaft it won't seat like that.

with old gears and worn markings it is very easy to do. Count the teeth if you think this might be it.

Yes, I have the t-shirt!

[scotty82]

Jim

make sure you did not install the coupler backwards . one end is counterbored as a relief for the way the spines are machined on the layshaft .
try to slide the layshaft in by itself. no gears or driver .
the only other thing is the input might be too long in the pilot .

[Rick Iverson]

Dude, a wealth of knowledge.

Call me tomorrow, I need some parts, ASAP.

Jim

make sure you did not install the coupler backwards . one end is counterbored as a relief for the way the spines are machined on the layshaft .
try to slide the layshaft in by itself. no gears or driver .
the only other thing is the input might be too long in the pilot .

[Lastminuteracin]

After research, I have the older large front Layshaft bearing. It’s held in with a bolt through the case. The end of the bolt is turned down so it indexes into a hole in the bearings outer race. Ends up the washer on the bolt was a hair too thin. There by squishing the bearing just a tiny bit. A little thicker washer and the shaft slides right in as it should. Building my first car from a box of parts has been very challenging but so far very rewarding. I’m going to know this thing inside out by the time it’s done. Thanks for the advice. More questions to come.

[Robert J. Alder]

Great job of analyzing the problem. (Buy the way, been there done that on that set screw.) People ask me how I know how to do all the stuff on my FFs and Hewlands. Easy. "After screwing somthing up three times, then I'm an expert."

Welcome to the elite club of experts.

[scotty82]

Very common . just a hair to long and it will lock up the layshaft. Good find Jim

[Lastminuteracin]

So now I'm down to that dreaded last 1 inch problem. I just can't get the last splined hub to index on the shaft. The coupler is in correctly with plenty of depth for the shaft to go in. I started by removing the reverse idler to take that out of the equation. Nope. I went so far as to strip all the gears except that last hub. I was able to get it up and seat that way. I assumed I could figure out which way I had to manipulate it in that state and use that technique. Did it a couple times using a pick and figured I can do it now. Reassembled the gear stack and now with the limited visibility and fat fingers I just couldn't get it to go. I do have a dummy aluminum tube the gear stack slides on if that makes a difference. Probably spent 3+ hours total before I gave up. So much other stuff left to do I moved on for now rather than get more frustrated.

[Robert J. Alder]

So now I'm down to that dreaded last 1 inch problem. I just can't get the last splined hub to index on the shaft. The coupler is in correctly with plenty of depth for the shaft to go in. \

1" would imply having trouble with the last "hub" (which carries the 3rd/4th dog ring) to slide on. [The dreaded last 1/2" probelm is more common, getting the 4th gear to slide on.] You might pre-test sliding the hub on to be sure that it goes on the main shaft easily, albeit only when it is lined up perfectly.

Aside from getting your pinky (if you can) or a pick in there to move the hub (usually raise the hub becasue it can slip "down" a bit and not be centered) so it's centered to the main shaft, I'd suggest not pushing too hard. Rather, lift one rear wheel just off the ground. While wiggling the tire (to move the main shaft, gently push in the cluster. Maybe back off pushing just a very tiny bit and do some more gentle pushing and wiggling. [Ditto for the last 1/2". Don't push too hard, just wiggle the tire (and thus the main shaft) to let it slip on.]

You do have three hands, don't you?

Sometimes if pushing too hard when stabbing the cluster, wiggling the main shaft (via the wheel) just moves the "pinched" hub or gear with it, thus preventing it sliding on. Being more gentle lets the shaft move and the hub or gear to not move until it find a happy alignment with the splines.

[scorp997]

Could also be the reverse gear installed backwards on the pinion stack. My first time doing a gear change this happened to me and I couldn’t figure out why the stack wouldn’t seat. The way the fork wraps ‘over’ the reverse gear seemed counter intuitive to me.