Gearbox Update/Questions

[TWebb]

To the sages out there...

As expected, 3rd gear is completely gone. Not a tooth left on the layshaft gear. As expected, the matching gear has some damage, so at a minimum this pair will need to be replaced.

As this was supposed to be a brand, spanking new gearset, we have yet to determine the cause of the failure. The failure occurred on an upshift from 2nd the 3rd. This was the 5th session on the new gearbox. The "B" spec motor only puts out 150 at the crank.

A secondary issue was the inability to get the 3rd/4th dog ring to engage with 4th gear. There is not sufficient throw to allow engagement. When in the neutral position there is more daylight between 4th and the dog ring than between the dog ring and 3rd.

The gearbox was not built by me. I paid to have a "pro" assemble.

Go easy. I am not a gearbox expert by any means.

Any ideas?

[rgh0]

If I understand correctly you have a straight cut dog selection gear set that 3 rd gear failed stripping its teeth in its fifth race / race meeting and also damaging the 3rd layshaft gear. Is it a quaiffe gear set ? Is the rest of the box casing standard i.e original iron and not aluminium or magnesium. Was any wear or other issue with the failed gear or other gears or the bearings. I presume the proble with selecting 4 th gear was seen on dismantling after the failure. what oil were you using

Hard to comment on cause at this point and really need to close up photos of the teeth where it has broken to comment further.

cheers
Rohan

[TWebb]

Rohan,

I was hoping you might reply. This was the 5th session of the first weekend on the gearbox.

Quaiffe ultra-close gearset in a new aluminum Tony Thompson case. Gearbox will be torn down next week. I will get photos. The builder indicated all new components went into the build...at least I paid for all new parts.

Redline Lightweight Shockproof.

[TWebb]

I'm guessing by your comment that there is an issue with the aluminum case or that special care/machining needs to go into the build if using aluminum??

[rgh0]

It looks like a manufacturig defect in either the case or the gear set but need to see the failure details to have more definitive conclusions. If the guy who built it is stripping it down try to be there when he is doing it to ensure you see the parts as they come out.

cheers
Rohan

[TWebb]

ok. Thanks

[promotor]

Two possible things to look out for -
1) spacer behind the rear mainshaft bearing incorrect / missing together with incorrect bearing carrier causing misalignment/floating of mainshaft gears in relation to the cluster gear:
2) interlock plungers missing (one, some or all) - gear tooth breakage is a classic symptom of selecting two gears at once.

Dog boxes while simple in operation have a few bits that are fiddly to get right regarding the gear thrust rings on the mainshaft and the ball bearings that help to stop the thrust rings from individually rotating.

[2cams70]

I’m no expert in dog boxes but looking at the general wear patterns on those parts they don’t look “brand spanking new” to me. I don’t know how much you’ve used it since installation however. Surprised it’s using what appear to be general application stamped circlips and not hardened precision ground ones which OEM’s typically use in transmissions

[steve lyle]

I’m no expert in dog boxes but looking at the general wear patterns on those parts they don’t look “brand spanking new” to me. I don’t know how much you’ve used it since installation however. Surprised it’s using what appear to be general application stamped circlips and not hardened precision ground ones which OEM’s typically use in transmissions

Tim didn’t post his pics yet, those are from promotor of his box. Notice no stripped teeth. I’ve see his box - Tim’s pics will be much uglier!

[2cams70]

I’m glad I’ve got you to remind me whenever I get mixed up with who posted what Steve. Unfortunately I’m not as sharp as I used to be although some would probably argue I never was that sharp. I made the same mistake with your post about your carb. issues. Anyway I await the next installment with pictures of the carnage.

[promotor]

I’m no expert in dog boxes but looking at the general wear patterns on those parts they don’t look “brand spanking new” to me. I don’t know how much you’ve used it since installation however. Surprised it’s using what appear to be general application stamped circlips and not hardened precision ground ones which OEM’s typically use in transmissions

They're the original Quaife circlips but as you say, they have a stamped look/feel to them. They're different to the Ford ones but only slightly - they have a little extra protrusion on the back face to help with surface area in contact with the hardened steel spacer.

You're right about the wear - but when I got asked to assemble it I said "it's quite worn and some bits haven't been treated too kindly, are you sure?" the reply was "don't worry about it" so I did as I was told!

The downside to the dogbox is that the dogs release quite a lot of material from crashing the dogs - a magnet is an extremely good idea in one of these.

[promotor]

I’m no expert in dog boxes but looking at the general wear patterns on those parts they don’t look “brand spanking new” to me. I don’t know how much you’ve used it since installation however. Surprised it’s using what appear to be general application stamped circlips and not hardened precision ground ones which OEM’s typically use in transmissions

Tim didn’t post his pics yet, those are from promotor of his box. Notice no stripped teeth. I’ve see his box - Tim’s pics will be much uglier!

Tim / Steve. I'm sorry to say I'm looking forward to seeing the damage but I do feel your pain, it's not nice to have expensive things fail.
Interested to know whether the cluster is rebuildable or is a one-piece item as that'll be cheaper if you can rebuild the cluster rather than have to buy the whole unit.