Think You're a Gearbox Expert?

[Lakeland997]

On my rally car I've been experiencing crunching when changing into 2nd gear. On most down-changes and even up-changes when the oil was cold.
This week I pulled the engine out and stripped the box down.

Here's the components for my mainshaft just before I assembled them the first time round.
Can the eagle-eyed amongst you you spot what's wrong here that caused my problem?

IMG_0885.jpg

[mk1coopers]

Absolutely no good at boxes , are the synchro's smooth on the inside rather than stepped or is it just the photo

[Lakeland997]

If you mean the baulk rings, nope, they were brand new and perfect.

[floormanager]

3 pins but only two springs?

[Lakeland997]

Nope, two springs and three pins is correct.

[Spider]

On my rally car I've been experiencing crunching when changing into 2nd gear. On most down-changes and even up-changes when the oil was cold.
This week I pulled the engine out and stripped the box down.

IMG_0885.jpg

In part, I think you've answered your own question there.

Worn Hubs will also do it, mind you, many are out of spec these days out of the (new) box! They do also have a finite speed at which they'll shift, not matter how good all the parts are.

[Lakeland997]

The synchro hubs are also new Spider but we're getting closer...

[ianh1968]

How about:
It's a 3 synchro first instead of a revesre?

Ian

[GraemeC]

Hub centre in the wrong way round?

[ianh1968]

... no!

Maybe the reverse is back to front on the hub?

Ian

[ianh1968]

Hub centre in the wrong way round?

We were typing at the same time...

I am sure that the "sticky out" bits in the middle of the hubs are both supposed to point the same way...

Ian

[Lakeland997]

First prize to Graeme (just too late Ian)! A great engineer as well as a great driver... makes me sick!

Yes the First/Second synchro hub centre is fitted the wrong way around. The raised part in the centre is a slightly different height on each side (about 2mm higher on the other side). This meant that the baulk ring was not pushed onto second gear before the dogs engaged.

I would like to place the blame elsewhere but no... I assembled it that way. Lesson learnt, posted here in the hope that none of you guys make the same mistake.

[GraemeC]

I have come close to doing the same - hence why I focussed on on the hubs! I think you can be safe in the knowledge you weren't the first and you won't be the last to fall into that trap.

[floormanager]

can you post the incorrect part with arrows?? Good bit of fun!

[Lakeland997]

Can't do arrows I'm afraid but here's a correctly assembled part (image courtesy of Minispares).
You should just be able to see that the ridge around the hole in the very centre is more raised than mine (although it's subtle)

image.axd.jpg

[floormanager]

wow, not much difference there; hats off to Ian and Graham for seeing that

[rich@minispares.com]

I'm sad enough to have spotted that straight away......


Always remember 'tall to tall' when you do the hubs!!!!


You should have really spotted it when you rotated the box once it was built and the detents where in as they would have pulled the hubs into the right positions (which would have shown the error up)....


....but i guess you know that!

The other mistake you can make is to assemble the hubs one spline out so it wont get any gear once the box is built.....I did this years ago - this is when I learnt to always 'in and out' the hubs to check when fitting them!

[ianh1968]

If you visualise the "sticky out" bits in the middle of both hubs
pointing the same way, this will make it easy to remember...

The 3rd/4th hub also has a nose which sticks out in the centre of
the hub, just in case you can't work out what I'm on about.

If you have the 1st/2nd hub on the table in front of you with the
toothed part at the bottom, there is a long plain section of the outer
at the top. The slightly bigger nose of the inner points upwards.

If you have the 3rd/4th hub on the table in front of you with the
long plain section of the outer also at the top, the much bigger
nose of the inner section should also point upwards...

At least that's what I think, totally from memory and not looking
at my spare gearbox in the loft or at any pictures.

Ian

[Lakeland997]

I'm sad enough to have spotted that straight away......


Always remember 'tall to tall' when you do the hubs!!!!


You should have really spotted it when you rotated the box once it was built and the detents where in as they would have pulled the hubs into the right positions (which would have shown the error up)....


....but i guess you know that!

The other mistake you can make is to assemble the hubs one spline out so it wont get any gear once the box is built.....I did this years ago - this is when I learnt to always 'in and out' the hubs to check when fitting them!

The difference between the two sides is so small Rich that the box rotated fine and all the shift rods lined up. Gearchange quality was good too... except for the crunchy second.
All is not wasted however as the strip down has allowed me to fit the Minispares steel baulk rings this time as they were out of stock when I built it originally.
I also had another reason to pull the unit... to take out the 649 cam and put in an SW8 that will hopefully be better for the mixed use the car is getting.
Oh and change the clutch I burnt out... because of the 649
Oh and change the pushrods and adjuster screws that were excessively worn... because of the 649

[locrep]

I was wrong on what I was going to post..