Hey there, hoping someone on the forum can help solve my issue.
If you're following the builds forum, I'm the guy trying to make a mid engine supercar out of an Audi A4 B7 quattro. You can look over it to see more details about the car and what has been done so far here.
The problem I am encountering now, is that the car will only shift when the engine is off. With the key out you can slide through the six gears just fine, but as soon as you fire up the engine it will not go into gear. No matter how hard you push, the only thing that happens is the rpm's drop a tiny bit and you can feel the gears start to grind. Again, with the engine running and the clutch to the floor, the shifter won't go into any of the gears. As soon as the engine is turned off however, it shifts beautifully.
While initially just thinking it needs a clutch adjustment, I remember now that in the junkyard we put the car up on blocks so that all the wheels were off the ground. Running the car off the ground with no wheel resistance, putting the clutch to the floor, and shifting then letting the clutch out in each gear worked just fine and turned all wheels. But then with the car and all wheels on the ground, the only way to get the car into gear is by, with the key out, putting it into gear, and then starting the car with clutch in. Then it works just fine and turns all the wheels as you let out, except it won't come back out of gear, even while stomping the clutch to the floor.
Some older forums said this might be a pilot bearing issue? It won't go into gear while running, but when you start it in gear it works but then won't come back out of gear.
One last thing is I believe that the transmission has no fluid in it. The scrapyard says they drain engine and transmission oil, so could that be the cause? But apparently the car came into the scrapyard because of this issue, and when it probably would have had fluid in it.
Any help appreciated
The input shaft of the Trans is not coming free from the engine.
Either pilot bearing is seized, or the throw out bearing is not disengaging the clutch. Or, the clutch is borked and causing the issue.
Any way you look at it, you are separating the engine and trans...
Unless, you are super lucky and it just needs bled (hydraulic) or adjusted (cable / linkage).
In reply to wvumtnbkr :
Are either of those two bearing replaceable? I found a throw out bearing from RockAuto and a pilot bearing on eBay, or would those require more than average tools, i.e a hydraulic press? I have all the time and can get speciatly tools if it is doable.
Also the car shifted fine when in the air, only with a load does it bind. Is the bearing an explanation for that? Not well versed with transmissions.
This is honest advice...
I would watch some YouTube videos on how an automotive clutch works.
Yes, the bearings are replaceable.
So is the clutch.
It could also be anything in the actuation of the clutch mechanism. You won't know until you understand how it works and you dig into it.
I do not think I could use enough words to explain how it works as easy as just searching YouTube.
Good luck!
Make sure the slave rod pushes the fork when you depress the clutch pedal.
Both the pilot bearing and the throw out bearing can be easily changed with the tools in your garage.
To remove the pilot bearing, you can pack the center with grease and put a rod through the center. Could be a ratchet extension or something close in size to the bearing ID. The idea is that the grease has no way to go and will push the bearing out.
The throw out slides out, no tools needed.
My guess is that its either a hydraulic problem or the disc/pressure plate are bad. I doubt the bearings are the problem (especially the pilot), but I've been wrong before.
In reply to Slippery :
I am on Vancouver Island in B.C, so anything within about 500km I can get.
It definitely seems more like a linkage problem than a bearing, I had a mechanic out there with who thought it all sounded and shifted good when it was in the air. A new clutch kit is only a couple hundred dollars though so I can replace that easily if it isn't simple.
In reply to wvumtnbkr :
Thanks for the tip, watching some youtube videos got me up to speed on clutches. I am gonna check the easier solutions first, like the slave cylinder and linkages, but if worst comes to worst it's gonna be bearings.
Slippery said:
Make sure the slave rod pushes the fork when you depress the clutch pedal.
I guess the only way to see that is disassemble the foot well until I find the base of the clutch pedal and follow the lines through the fire wall. Is there a chance the clutch could be mechanical or even electric?
If it is hydraulic and it doesn't use a hydraulic throw out bearing,it will have a slave cylinder and clutch fork. These items are on the transmission, not at the clutch pedal.
B7 looks like it still has a slave cylinder external to the trans. You should be able to remove it and see if it's functioning properly. Usually when they are bad, they are leaking everywhere. You can put it in a clamp, the clutch pedal should be VERY hard. If not you still have air. If that all checks out it's likely an issue with the clutch fork, or if it's a junkyard setup everything could just be siezed together. To get to all that you have to pull the motor or trans, unfortunately.
As the posters above mentioned, you are looking for the slave, which is on the transmission. Its highlighted in yellow below.
The throw out bearing is the bearing the green arrow is pointing at and the fork is the marked by the red arrow.
The fork pivots on the opposite side of the input shaft, so could be that the pin is damaged there as well. My money is on the clutch itself though :).
These pictures are off of an ebay transmission, I think its the one you have.
Leviathan888 said:
In reply to Slippery :
I am on Vancouver Island in B.C, so anything within about 500km I can get.
I miss Grouse Mtn :). Might be going back this summer.
Junkyard b7? I say slave cylinder.
In reply to Slippery :
Yeah, as you pointed out in the photos it must have something to do with that fork sticking or TO bearing.
After reviewing in my head everything about that clutch and why it worked in the air but not the ground, I have come to the conclusion that the clutch is always on a tiny bit. Even if the clutch is stuck engaged 5%, as soon as you take it out of gear the tranny spins up to speed with the engine and it won't go back into gear. It worked in the air because with no wheel resistance, just pushing into gear without the clutch grinds the gears a little bit but quickly hooks up and spins the wheels. The friend who watched the wheels when I had it up off the ground says he thought it kind of looked like that, making me think either something is lodged in the bell housing keeping the clutch from fully disengaging, or the fork is worn through. Gonna check the both cylinders and whatever of the fork I can access, but it looks like I might have to drop the transmission and look at the clutch.
Apparently this B7 was brought into the junkyard because of the clutch issue, meaning it was probably checked out at a dealership. Hopefully a mis-diagnosed slave cylinder issue, but I'll probably end up replacing the clutch.
The clutch is always engaged, unless you depress the pedal, which causes the tob to push against the pressure plate and decouple engine and transmission.
When the engine is off, nothing is rotating, so you can shift until you are blue in the face without touching the clutch pedal. Once you turn on the engine, you have the flywheel spinning at 700 or so rpms ... no way you can shift it unless the clutch disengages it.
I doubt its your bearing.
Investigate, its a VERY simple system ... dont just buy parts unless you want to spend money.
In reply to Slippery :
I mean even with the clutch to the floor and engine running, there still is some amount of connection between the engine and transmission. Which doesn't really sound like a bearing so later today I'll check the cylinders and fork. With the car running and in neutral, even stomping the clutch doesn't allow you to go into any gears. As you manually start to press through the threshold of the the gear you can feel grinding, making me think depressing the clutch doesn't fully disengage engine from transmission. Maybe I am misunderstanding you?
Yes, we are all saying that the transmission isn't disengaging from the engine.
However, there are about 5 reasons (at least) that could be causing that.
In order from worst to simplist...
1) clutch failure. Sometimes parts of the clutch get wedged together and won't allow the clutch to release.
2) hydraulic system failure. This means that the system isn't transferring the force to the pressure plate to release the clutch.
-If the car uses a hydraulic throw out bearing, this can fail as well. Otherwise, a NON hydraulic throw out bearing will just make noise and not cause your issue.
-clutch fork. This transfers the force and motion of the slave cylinder to the throwout bearing and hence to the clutch pressure plate.
3) pilot bearing failure. This means that parts of the pilot bearing are stuck to both the crank and Trans input shaft. (Rare, but can happen).
4) the hydraulic system has air in it and just needs a simple bleed to get it to function.
Your transmission is definitely still engaged to your engine. It's the why that we don't know yet.
I would also like to reiterate....
Don't buy anything until you know what the issue is!
If it was me, I'd be doing this (in this order).
1)Check the clutch fluid reservoir. If very low or empty, add fluid. Check for leaks.
2) look at the slave cylinder.
2b) have somebody press on the clutch pedal and see if the slave cylinder is moving. If it is, see if I can boroscope the bellhousing to see what's going on in there. If it's not, bleed the system.
3) if none of that works, I'd be splitting the engine and Trans from each other. The problem WILL be obvious once you get it all apart.
That list is exactly what I intend to check. Although it doesn't sound right, I think I might have read somewhere that the clutch runs off the brake fluid reservoir?
The master likely gets its fluid from a shared reservoir with the brakes in OE form. Lord knows what you have done in your chassis, likely separate.
Most cars, even with a perfectly running clutch, will still spin the driven wheels when in the air and the clutch pedal depressed. That does not mean anything here.
