Gearbox/Intermediate shaft query

[Matt No VAT]

Have an interesting little problem on the go at the moment.

I have a engine and box ready to go back in the car but for the intermediate shaft problem.

In normal conditions the intermediate shaft is inserted into the gearbox and the two flanges/driveshafts rotate in opposite directions, mine does this but when the shaft cover and oil seal (with the 4 x 13mm bolts) on the intermediate shaft side is tightened up the pair of flanges/driveshafts seem to lock and rotate in the same direction. Plus the speedo cable drive is rotating when its in neutral?? Hmmmmmmmm

I took the original gearbox/flanges/ cover & seal off and these were fine when fitted to the original moved them to the new engine and have the same problem?

Tried it with two different gearboxes with the same result. The only thing I've not moved is the intermediate shaft support/engine mount bracket. But when the shaft is fully "home" without the cover bolted up the shafts/flanges rotate in the correct directions.

When the oil seal cover is bolted on, there is a bearing inside and the outer shell of this moves laterally to allow oil flow (i presume) but I'm stumped as it seems to be being pushed too far to the right and when the cover is tightened up it locks against the ring and I'm back to square one!

Is there a secret to fitting these that I'm missing out on?

TIA:confused:

Forgot to add, I have two intermediate shafts, the original and the one I got from Dave W, using either results in the locking up effect? (spent 3 evenings on this now with no joy)

[rutthenut]

Matt, are you sure this is actually a problem, or just confusing behaviour? It confused me, anyhow!!!

Obviously, both wheels should rotate in the same direction when driving the car. But if the car is in gear, and jacked up (or unit out of the car), turning one wheel would force the diff to work and make the other wheel turn in the opposite direction. You've obviously seen that working as you would expect - possibly whether in gear or in neutral.

But if the gearbox is in neutral, it would probably be easier for the diff to turn 'en masse' rather than to overcome the friction and effort needed to turn the spider gears etc. In that case, the wheel on the other side would be expected to turn in the same direction. This will only apply when the gearbox is in neutral (of if you have a very low compression, low friction engine!).

The speedo drive is surely adding to the confusion, as it should always turn when the driveshafts rotate, regardless of whether the car is in gear or not - otherwise the speedo would read zero mph if selecting neutral when travelling at any speed.

Note that the speedo drive is controlled by the rotation of the diff, and hence the driveshafts, as opposed to the rotation of the gearbox shafts. So hopefully that means that seeing the speedo drive move is something you should expect, at least when both wheels (and hence the diff) are rotating in the same direction, which would equate to some sort of road speed.

If the wheels are spinning in opposite directions, with the diff being stationary due to a gear being engaged, I suppose the speedo drive should not move, as there would be no real forward (or reverse) movement on the ground should this happen.

Having said all that, I'm not sure if you have another problem with the oil seal cover and bearing. I've no idea about that (assuming both original and new intermdiate shafts are the right length).

You really do seem to be having more than your fair share of problems though Matt. Hopefully all will come good soon enough!

[Matt No VAT]

Yes, one obstacle after another.... these things are certainly sent to try us!

Many thanks for the pointers, its useful to have others throw ideas and explanations around!

Whats most confusing about this is that I had left the engine with the blown head gasket out of the car alone. So I had a working example on the garage floor as a kind of reference.

The gearbox I attached to the newly rebuilt engine requires just the intermediate shaft assembled (I thought this would be easy!)
The original engine when in neutral had both driveshafts rotating in opposite directions when spun by hand - with very little friction or resistance.

The new engine however locked them and required much more effort to spin the driveshafts.

As a test I swapped the gearboxes over and hey presto it locked - I might try putting the new gearbox on the old engine and see what happens?

Failing that I think I'll just lock the garage up with two V6 engines and three gearboxes on the floor and never go back in there again!

I must have been a real sinner in a previous life...or maybe it was this one?

[AndyH]

Matt,

I've just re-built the gearbox on mine, and I hate to say it, but I didn't see the problem you're describing.

Rotate one shaft and the other contra rotates. In neutral you should be able to grab both shafts and spin in the same direction (i.e.you're turning the whole diff.)

There is a shim on the output shaft bearings.... This is only on one side (on mine it was the intermediate shaft side.) It's not very obvious... it looks like it could be part of the bearing.

It's there to set the clearances across the bearings / diff assembly... I can only guess that this is too thick and is causing the whole diff assembly to bind.

If you've not changed anything, then this should not be a problem, but if you've changed a bearing or seal plates then this could be the cause of it going tight when you torque up the bolts.

This does not explain why it's happening on two different gearboxes though, unless you happen to be swopping the seal covers between gearboxes and you've just been unlucky that the combinations you've tried in both gearboxes causes the diff to be tight?

Andrew

[Matt No VAT]

Hi Andrew,

Hmmmm what you describe is what I was hoping my refit would be like.

I'll be having another bash at it tonite and see what goes - but I've checked both the shims on the intermediate side and they are identicle. Both the bearing plates are the same dimensions (I've checked)

I've not changed anything on the gearbox, internally. Hence the confusion!

Oh well back to the drawing board (and the garage which is more like a sauna these days!!)

[Matt No VAT]

Today I have discovered the following:

When In doubt go down the pub and then on for a curry!!

Its amazing what 3 pints of Guiness, a curry and a couple of bottles of Cobra can do for you!!

I came home and thought "One last try" with the whole gearbox and shaft game! And I have learnt more about the V6 engines.

I fitted a shaft to a gearbox that was exhibiting this strange locking up crap, while it was on the floor....worked perfectly!! A-ha.......Progress!!!

Q: So whats not in the setup now that could affect this?

A: The Rear engine mount bracket / Intermediate shaft support

The crux of the matter is there are two types rear engine mount brackets, although they look identical and have the same casting number (A 164 296) there are also some smaller numbers stamped into them - these stamped numbers are tiny compared to the casting numbers but they seem to be crucial.

Ones which will caused (me) a problem have 22 and 04 stamped into them.

Ones which work fine have 1C and 02 stamped into them. When I fitted this, everything slotted together perfectly and worked properly first time.

I am presuming the stamped numbers denote either auto or manual (but I'm guessing at that, as I hear theres a difference in the intermediate shaft on autos and manuals)

The good news is that if you have a complete donor car then your probably not going to run into this problem as the engine and box come together as a unit.

However, if like me your building up an engine from scratch with engine and box from different donor cars, learn from my endeavors!! Especially if your going to mate an auto engine to a manual box, as I'm thinking that my newly built up engine was originally attached to an auto and hence run into this problem. So get the rear engine mount and the intermediate shaft with your manual gearbox while your at it.

Who knows?? who cares?? - I'm off to go and drink beer to excess! :D

[chris.richard]

FWIW, when I was struggling to sort this problem out, I couldn't even get the transfer shaft to go into the manual box / differential splines with the auto engine mount in place.

[Matt No VAT]

That'll be coz the auto intermediate shaft is a few thou greater diameter, plus there are a couple of other subtle differences.

But I'm having a day off from cars/engines as I've just finished work (another 21hr stint)

ZZZZZZZZZzzzzzzzzzzzzzzzzzzzzzzzzzzz

[chris.richard]

Sorry, I was meaning with the manual shaft, but the auto mount.