Transmission rebuild and synchro related questions
01-15-2007, 12:28 AM
#1
Transmission rebuild and synchro related questions
Hello to all!
i have decided to take my 6 spd transmission apart and rebuild it. The car is a 2000 A6 2.7t.
The problems i had were the following:
- 2nd gear would take a while to engage if i would not rev match perfectly
- 3rd and 4th gear would grind a little most of the times i shifted to these gears.
Since i pulled my engine i decided to take care of the transmission too so the grinding does not make long term damage.
All the gears engage smoothly with the engine off or if i keep the clutch pedal pressed, so the slider gears are all fine.
Now, what puzzles me is the following: 2nd takes a while to engage but does not grind, 3rd and 4th engage faster but grind. Which of these indicates a bad synchro? Now that i have the gear cluster apart from the trans, i could see that the synchros for 3 and 4 sink into the hub more than the ones for 5 and 6 (which work fine). I will measure the seating gap for 3 and 4 when i'll pull that hub.
So if the 3 and 4 synchros are worn, then what causes 2nd to engage so slowly?
Also, anybody know any pricing on the new synchros? I noticed the 1-3 synchros are coated in molybdenum and 4-6 are plain brass.
What else should i do while i have the transmission apart? I'm at 92k now but honestly i am very surprised on how well the transmission looks inside and i'm pretty sure once i replace the synchros it should be like new.
Thanks in advance!
i have decided to take my 6 spd transmission apart and rebuild it. The car is a 2000 A6 2.7t.
The problems i had were the following:
- 2nd gear would take a while to engage if i would not rev match perfectly
- 3rd and 4th gear would grind a little most of the times i shifted to these gears.
Since i pulled my engine i decided to take care of the transmission too so the grinding does not make long term damage.
All the gears engage smoothly with the engine off or if i keep the clutch pedal pressed, so the slider gears are all fine.
Now, what puzzles me is the following: 2nd takes a while to engage but does not grind, 3rd and 4th engage faster but grind. Which of these indicates a bad synchro? Now that i have the gear cluster apart from the trans, i could see that the synchros for 3 and 4 sink into the hub more than the ones for 5 and 6 (which work fine). I will measure the seating gap for 3 and 4 when i'll pull that hub.
So if the 3 and 4 synchros are worn, then what causes 2nd to engage so slowly?
Also, anybody know any pricing on the new synchros? I noticed the 1-3 synchros are coated in molybdenum and 4-6 are plain brass.
What else should i do while i have the transmission apart? I'm at 92k now but honestly i am very surprised on how well the transmission looks inside and i'm pretty sure once i replace the synchros it should be like new.
Thanks in advance!
01-15-2007, 06:42 AM
#2
AudiWorld Super User
You may be best advised passing your questions straight to a transmission.....
specialist.
They should be able to supply the new synchro rings as well.
I would say that 2nd being slow to engage but not grating would still be caused by a worn synchro. Usually 2nd is the first to wear because it does the most work. The speed difference between 1st and 2nd is the gratest change and by 5th to 6th, you hardly need a synchro at all you could just de-clutch and the dogs would just engage straight away.
Have a good look at the shaft to see there is no wear which would cause the hub to stick - this is highly unlikley though.
The 6spd is never a nice box, it is just adequate I think - to be kind. The 5spd was far nicer box to use but we all want that extra gear.
Do a search because there were some issues with the 6spd and second gear being pushed along the shaft if the change from 1st was really pushed in too hard. I think there may be a mod you can do to prevent this from happening. The post about it was from late last summer I think. It is well worth finding while the box is apart.
They should be able to supply the new synchro rings as well.
I would say that 2nd being slow to engage but not grating would still be caused by a worn synchro. Usually 2nd is the first to wear because it does the most work. The speed difference between 1st and 2nd is the gratest change and by 5th to 6th, you hardly need a synchro at all you could just de-clutch and the dogs would just engage straight away.
Have a good look at the shaft to see there is no wear which would cause the hub to stick - this is highly unlikley though.
The 6spd is never a nice box, it is just adequate I think - to be kind. The 5spd was far nicer box to use but we all want that extra gear.
Do a search because there were some issues with the 6spd and second gear being pushed along the shaft if the change from 1st was really pushed in too hard. I think there may be a mod you can do to prevent this from happening. The post about it was from late last summer I think. It is well worth finding while the box is apart.
01-15-2007, 07:11 AM
#3
AudiWorld Super User
First, are y;ou sure that it had been running GL4 fluid, not GL5? The latter will render the syncros
ineffective but not harm them. No exp. with current Audi x'missions but much with other ZF manuals.
Check clearance between syncro and mating gear. If syncro face hits gear face syncro cone clutch will be ineffective. Have machined 0.020 off face of syncros to increase this clearance with dramatic results.
Check clearance between syncro and mating gear. If syncro face hits gear face syncro cone clutch will be ineffective. Have machined 0.020 off face of syncros to increase this clearance with dramatic results.
01-15-2007, 09:12 AM
#4
Is the 01E 6 speed made by ZF or Getrag? No one has been able to definitively answer this question.
Thanks for whatever info you can provide! I have found all the info I want for the ZF Tip tranny, but nothing related to the 6 speed manual gearbox.
01-15-2007, 09:13 AM
#5
I was using the redline mt90 and after the rebuild i will fill with motul 300
About machining the synchros... i don't know if i want to go that route. I called the dealer, and it costs $80/synchro so i will get all new ones for 2,3 and 4.
Now, as far as the machining goes, what if i do that on the new ones? Will that make them work longer? It would make sense that way since the worn ones will still work if machined.
Also, i am assuming you mean that i have to machine the face that is oriented towards the sliding gear, to allow the cones to touch and create friction.
Is the 0.020 in inches or mm? i guess it is in inches but i'm not too much of a machining person. good thing my dad is
I know in the manual is says that if there is less than 0.5mm clearance when you place the synchro ring in the hub, then it needs to be replaced. Just added it here for general info.
Now, as far as the machining goes, what if i do that on the new ones? Will that make them work longer? It would make sense that way since the worn ones will still work if machined.
Also, i am assuming you mean that i have to machine the face that is oriented towards the sliding gear, to allow the cones to touch and create friction.
Is the 0.020 in inches or mm? i guess it is in inches but i'm not too much of a machining person. good thing my dad is
I know in the manual is says that if there is less than 0.5mm clearance when you place the synchro ring in the hub, then it needs to be replaced. Just added it here for general info.
01-15-2007, 09:17 AM
#6
Well, as far as info goes, i can post a ton of pictures on how to take it apart and ...
what to expect.
It would be nice to have a guide on how to fix these transmissions and i could not find anaything like that on the forum.
I took mine apart with not too much hassle (contrary to what others said) and i have to pull a few more gears until it's all apart.
I'm a computer scientist but still, it did not seem like a complicated job, a lof of the trans comes apart nicely if you do things in the right order WITH the right tools.
I also took a lot of pictures along the way to ilustrate how everything goes together.
It would be nice to have a guide on how to fix these transmissions and i could not find anaything like that on the forum.
I took mine apart with not too much hassle (contrary to what others said) and i have to pull a few more gears until it's all apart.
I'm a computer scientist but still, it did not seem like a complicated job, a lof of the trans comes apart nicely if you do things in the right order WITH the right tools.
I also took a lot of pictures along the way to ilustrate how everything goes together.
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01-15-2007, 10:32 AM
#8
Well, so far i could get by with normal but high quality tools. The only time i needed
a special tool was when i had to pull an inner race for the mainshaft which is accessed through the rear ot the transmission. Very bad location and impossible to get to. After i'm done i'll post all the pics.
I will post a list of all the tools that i used after i'm done.
I will post a list of all the tools that i used after i'm done.
