5 speed gearbox selector problems

[firelizard]

Hi,
I have a 2002 Passat B5 130 TDI with a 5 speed manual gearbox.

The gearchange is intermittently difficult in most gears (especially 1st, 2nd and 4th) with gear changes sometimes being impossible with some gears under certain conditions. Sometimes you can complete a journey with no significant problems.

1 month ago it had a new clutch and dual-mass flywheel (the clutch plate was worn and flywheel was contaminated with something). This did not cure the gearbox fault.

The gearbox has last week been stripped, cleaned and rebuilt by a gearbox specialist who maintains that there is no wear in any of the components and that the gearbox has no fault (the car has done 150k miles) but he did change the oil (he maintained that it had hypoid oil in it). This has also made no difference. His next suggestion is to change the synchro rings, which I'm not happy doing given that they have already been checked as okay and there is no guarantee that this will cure it either !

The symptoms are:

1st gear:
If I can't select 1st gear from stationary, usually putting the gear into neutral, releasing the clutch and trying again fixes this problem.

Today, I selected first gear and with the clutch in for about 1 minute at a junction I was aware that it was stuck in 1st gear (couldn't put it into neutral). When the clutch was released and the car moving again, 2nd gear selected as normal.

2nd Gear:
2nd gear sometimes crashes on down selection after which you can sometimes only select forward gears after putting the gear into reverse.

3rd and 5th gears always seem okay.

4th gear is frequently difficult to select.

It seems worse when the car has been driven for a few miles (cold oil works better).

Under heavy acceleration, change up always seems smoother with few if any problems. Problems always seem to be worse when decelerating heavily with the clutch depressed and changing down.

The gear lever has about 3mm free vertical movement due to wear in the plastic ball housing mechanism. My local VW dealer service department doesn't believe that this could be the cause of the gearbox problems.

I have noticed that the gear lever moves a little when accelerating/decelerating. Also the gear lever selector measurement from the front of the plastic gearlever housing (under the gear lever gaitor) to the metal housing can only be adjusted down to 48 mm when the Haynes manual suggests a measurment of 43 mm. This suggests that the gearbox is 5mm further forward than it should be (gearbox and engine mounts are ok though) or the Haynes manual is incorrect

I'm beginning to think that the problems are related to the clutch being depressed and the input shaft/synchro mechanisms.

I'd appreciate any suggestions !

[towcestervag]

if the gearbox crunches on way down it sounds like baulk rings
most of the gearbox specialists i know now say to put engine oil in box as hypiod seems to break down

[firelizard]

Changing the oil to new GL5 spec gear oil hasn't improved it at all. I did consider putting Redline MTL in it ,as it seems to be recommended in other forums but didn't as the container suggested that it is not recommended for normal automotive applications due to much reduced friction. I was concerned that it could have made the synchro mechanism worse as they do rely on a certain amount of friction to bring the two gears up to the same speed.

There have been some later recalls on VW models to change the gear oil but not for my car/year.

The car has done 140k miles with no gear change problems previously.

[towcestervag]

i know passats suffer from 1st gear selection when stationary as mine does a little
but otherwise the gearboxes are good
but you said it crunched on way down into 2nd so that seems like baulk rings and the gearbox specialist should of known that from you and should of seen wear

[martin1810]

"Today, I selected first gear and with the clutch in for about 1 minute at a junction I was aware that it was stuck in 1st gear (couldn't put it into neutral). "
That is a clutch fault. It is possible that the slave cylinder or master cylinder are worn and letting fluid pass the seals. So your foot was still on the clutch but the clutch was released as the fluid pressure had leaked away. I would change both cylinders.

[firelizard]

Thanks . I'll check for clutch fluid leaks over the next few days.

I've found that by double declutching (say 5th gear, into neutral, release cluch, depress clutch into 2nd) it stops it crashing in 2nd gear on changedown. This would seem to suggest synchro problems.

[martin1810]

You may not see any leaks if the fluid is getting passed the seals but staying in the cylinder. Double declutching may work because you are pressing the clutch more than once and helping to keep the pressure on the clutch plate. Your description does sound like synchro rings but surely the gearbox repairer would have noticed if they were worn.

[firelizard]

Presumably if the clutch master or slave cylinder seals are worn a simple test would be to put the car in first with the clutch depressed and the handbrake off and see whether the clutch engages after a while.


I would also have expected the gearbox repairer to have actually fixed the problem rather than returning it in the same state that it went in! They have promised to remove the box and replace any parts necessary (no labout cost for removal and refitting) but the during the last conversation I had with them, they asked me what I want them to look at next, suggesting thay they don't know what they are doing.

[martin1810]

Gearbox repairers are rarely interested in fixing cars. Most stick to checking the box only. In fact many don't even have facilities to remove the box. They get someone else to do that and they just check the box. I am surprised they didn't change the synchro rings whilst it was apart. Maybe they didn't inspect it properly.

[firelizard]

What surprises me is the fact that they failed to notice that the problem was still there when the car was returned. You'd expect them to first confirm that there is a problem, repair it then check it works.

Having driven around a bit I've noticed that it you do a fast gear change it's generally ok, suggesting the synchros are having problems bringing the two gears up to the same speed when they differ greatly (e.g. on deleleration). I'm fairly convinced it's synchros now. Thanks.