what is wrong with all those gearboxes ?????

[Zebedeus]

Good afternoon,
I have 1.6TD were i swapped the JX-engine for an AAX-engine. When i removed the gearbox it worked OK. (see my post from 2011) and i was a happy liitle bully driver then.
The gearbox has been checked for wearings and came back as ok. I mount the AAZ-engine, mounted the gearbox (ABH 4 speed) and made a test run. Everything OK. I brought it for an MOT-check, came back and half way the 4th gear poped out. SInce that moment this problem remains and it drives me nuts.
I checked the whole gear-lever issue, i made small modefication as advised in the VW Original servicemanual, cleaned and greased it again and i am out of ideas.
The engine runs smooth, no vibrations. Gear shfting is real smooth for all gears the only problem is the 4th gear popping out.

Has anybody a good idea, or even better; the solution

ENjoy your Eastern weekend, hope to hear from you

Greets Hans (PS sorry for my english language but i am Dutch, yeah, yeah, yeah i know ......... cheap )

[Aidan]

if box has been checked out then I'd be looking at gearbox and engine mounts and cup and ball, and all the linkage first and rebleeding the clutch under gravity

but if driven and repeatedly coming out gear then wear will mean gearbox needs parts replacing or special attention to mainshaft and gear displacement issues, the extra torque isn't helping if it is worn, neither swift gearchanging or changing up too soon and lugging on the torque, the gearbox originally designed for petrol engines with higher rev power lower torque tends to wear more in the diesels I find

[Zebedeus]

thanks for your input Aiden,

to set things clear; the ball on the gearstick has been replaced and is about 1300km old, the clutch is new including the needle bearing at the front of the mainshaft.
The problem i so persistent and equal in happening that, in my humble opnion, it has to be something to "produce". You understand ??

When i drive and shift to the 4th gear its changing gears smoothly, softly, no strange noises. When i release the clutch you can feel on the gearstick that the gearwheels grabbed eachother and when the clutch is completely released it runs for any distance from 50 yards to a mile and then with a real hard and short but heavy snatch it pops out,
I tried different revs but its Always the same symptoms.
someone suggest to disconnect the gearshiftrod from the gearbox, tie it up for the moment and switch to the 4th gear manualy with the lever on the gearbox.
Then start the engine and(prefereble on a slope) try to drive a way. If it stays in gear then its most likely the gearstick and alignement. If it pops out then its not your gearstick and/or alignement but is the problem in the gearbox.

What is your opnion about that?

[CovKid]

Makes sense. Would remove linkage from equation and if it still does it, you know its the box. Just remember you'll be gearless once it does this though unless you scrabble underneath and reconnect linkage.

[Oldiebut goodie]

It's not another case of the linkage bracket being refitted to the gearbox on the wrong side is it? Several people have done that and had trouble with the gears.

[Aidan]

as Oldie says...rear bush plate mounts front side of boss on gearbox, if that's the cause it should be jumping out of 2nd too

[Zebedeus]

i knew that issue from the linkage bracket. VW launched a service bulletin for the gearboxes that explanes that when the mounting part on the gearbox thinner is then 14mm it has to made thicker with a nut to 21mm.
This prevent that rubber cover on the gearshaft is being pressed together to much when shifted to the 4th gear. This compressed rubber pulled back the gearshift and it will pops out from its 4th gear (or in some xases second gear)

I was bored last night and started surfing at youtube for short movies on gearboxes. Specialy for Aiden is the next question; the gearlinkers which are moved by the gearlever shaft are supported with two bearings, (for each gearlinker), with a small steel ball in it. it "locks" the linker in its position for the selected gear.
If, again IF, this small steel ball in one of those bearing is missing or defected the gearlinker will be held in its placce with only one bearing and i suppose that this is not enough.

It;s a wild gamble but as a retired service engineer i have seen the most silly things happen in the real world

[Aidan]

you are correct the linear ball bearings the selector forks run in can be an issue, they are made of pressed spring steel and have a tendency to crack and drop usually a quarter of the inner shell though they often continue to function just fine but if any of the ball bearings come out then the motion can become less than linear and if two slider bearings on the same fork shaft are poor it could be part of the problem, I have to swap generally 2 per box to get a nice shift when reassembled. Unfortunately the new bearings having been made at the end of the press tools' life are often a sloppy fit on worn shafts so good used early ones can be better solution to "pooh" shift
the slider bearings are fitted into the case before the shafts and forks so to replace them properly requires full strip down though I see plenty where one has been bodged in from the end, some ingenious solutions
obviously any parts found on drainplug magnet over the years can paint a picture - the case part of the slider bearing doesn't usually do too much damage, it just depends on it's route to the magnet but the balls can do damage if picked up by crown and pinion or usually 1st gear on a four speed as the ball won't slip under the gear as clearance to case is close so it gets picked up and taken through the gear teeth and the ball and the gears are both hard but the foreign object is 100 times bigger than the gap between the gears so something has to give

[Zebedeus]

Thanks a lot Aiden for your reply. It offers me a lot to think about. First I will drain the gearbox oil and see if that has some suprises. Maybe on the magnet sticks a small steel ball

Then i have to dismount the gearbox which will be no problem. I have to read the english manual to open the gearbox but as far as I know i do not need to make any adjustment after i removed the differential. If i keep that together then the adjustent between diff-wheels will not be changed.

I hope i can ask jou for advice here when got myself in the famous barbwired Canoe

Again, thanks for the information. Enjoy your weekend with the family

Greets Hans

[Zebedeus]

Hello,

For my problem is at this moment no solution available. I put it on a hold for now and will come back if i know the magic word "Solved !!"