I'm just trying to identify if it is an internal problem and if it is what the most likely fault is - pinpointing helps prior to dismantling more so in modern boxes - in days of old you could just take a plate off and check sequences before dismantling.
Pugman406 wrote:Rite then, just tried it with engine off, went in 1st no probs, but wudnt go in 2nd first time round, so thats a new one!
That's quite normal since the second gear has to realign as the hub annulus slides over.
This test gives clues on where to look when dismantling since as I described it could be a number of faults causing the same problem. Oh - there is some emphasis on oil spec here but the fact is it rarely is the problem - but it could well have caused the problem to arise through wear or even contamination - in other words the damage has been done - gear oils are different to engine oils in that they are more resistant to pressure. It is also likely the box has run it's time. When a box wears it leaves tiny bits of metal circulating and it's this that knackers up the needle rollers. This said manufacturers tend recommend leaving the oil in for life because more cockups were made by people putting the wrong oil back in than any damage bits would do. More so when the gear oil shares the same compartment as a final drive ( differential Gear). Only use the recommended grade and type.
Last edited by Longintooth on Sat Dec 13, 2008 7:49 pm, edited 3 times in total.
From what I have to work on I would put the problem down to two strong possibilities - the needle rollers that support the first motionshaft and the mainshaft are defective or the second gear needle rollers - the former is the most likely. This support is directly within the third and fourth gear hub. When in direct drive ie 4th the shaft will be turning one to one with the mainshaft and so will have no effect on the drive. However, when engaging first, the hub will have a lot of work to do to spin the mainshaft the tiny amount that is required to push past the baulking ring of the first gear. This baulking ring is what stops the first gear and and then the clever bit to push past the teeth on the baulking ring which is designed to block the engagement until it actually stops turning, then kick it back to allow entry. If you have ever tried to engage first when the vehicle is moving you will know how very hard it is or impossible above some speed. I would always recommend drivers to learn double clutching to match the gears throughout the range up and down - it will double the life of the box and is very useful if you have to drive home with a broken clutch cable or hydraulic loss.
If you have a faulty synchro, you will have selection problems, worn teeth on the synchro ring or hub means that the synchros are turning at different speeds, therefore giving difficult selection.Synchro means synchronisation, that means as I said each gear turning at the same speed to allow smooth selection.
Worn bearings will produce noise, either on tickover, which will disappear when the clutch is depressed...first motion shaft now stopped turning....or, noise in first gear as you move off and increase speed.
I suggest changing the oil for a semi synthetic 75 grade, or as I said earlier, select second gear, then move into first gear before moving off.
Double de-clutching won't work in first gear.It works in the same way as a synchro ring or hub in that it helps to equalise the speed of the cogs to make gear selection easier.
You are right on all comments,however ,if the oil spec is and has been correct then this would not be the cause. So you may be suggesting that a different spec will help but only if the clutch is dragging badly and turning the first motion shaft which would crash reverse. The correct grade for the 406 is EP gear oil 70-80SAE now if that is incorrect everyone will have the problem according to your hypothesis and this is not the case. Now we don't know if there is a bearing noise or not and if it is the first motion shaft to mainshaft support it will start by being sticky because the needles will run across the shaft similar to a one way sprag at first before being really noisy. The syncros may be perfectly ok and doing their job but that is the reason it won't go in - otherwise it would crash because the baulkers are worn. So I conclude that there are more than one hub or bearing holding the mainshaft cluster gears so that the hub pushers on the 1st gear can't push past the baulk ring but it does when the engine is off - biggest clue since there is always some drag due to the clutch drive plate sticking on the shaft and with it stopped it just allows the hub to push past. I've had 1000's of boxes apart from 16 speed twin splitters with Delta shafts,automatics to these little dinky minis and you do get a pattern emerging from that experience - don't you think?
I wasn't suggesting double clutching into 1st !!!! - we're discussing a problem selecting 1st from a start and yes if 2nd can be selected first then 1st or change the oil spec - he can do it but that has not solved the problem and it will deteriorate further. I can select 1st gear with ease in any weather and it's as sweet as can be.
Oh and thanks for clearing up what synchro meant, I'll remember that - are you still at college?
Actually, I have been in the car trade 38 years, the last 28 of which running my own car repair business.
Well, we may both be wrong about the fault experienced by our friend, it could be just a simple linkage problem, we'll never know unless we get the car to drive and therefore be able to check it out ourselves.
You're quite right and I hope you have not taken offence - I use a tried and tested formulae I produced to target specific problems and it works to a 90% success
rate because almost all gear trains use the same basic systems - but in the end it is down to getting dirty. If you read the current article on the other post you may or may not agree. In almost all gear train problems it boils down driver abuse at some stage and the misuse of Syncromesh no more so than in heavy goods vehicles.
