TDC (Top Dead Center) for Automatics

In my daily job, I've found myself explaining how to get the TDI engine to TDC if there is an automatic trans, hard to explain over the phone, but I think these photos will pretty much tell the story.... this may seem like basic 101 timing belt... but I'm surprised at how often this comes up....

First off, DO NOT USE THIS FOR TDC:

I've seen where the serp belt pully can shift and end up being off a few teeth! This is OK for getting you in the ball park, but should NEVER be trusted.

You need to look for the mark on the flex plate through the a port in the transmission:


The close up shot of the alignment mark:


You want to "split the circle" on the bottom edge of the inspection port. You will be looking just over the radiator support when you do this:


That, my friends, is TDC. There are other engine/trans combinations that this pretty much works with. Sometimes there can be a lot of surface rust on the flex plate, so it can be hard to see the mark. I've used a screw driver to scrap the surface rust off so I can see the mark in these cases.

Later.

Thanks for an excellent concise, highly useful post.
Link to this was copied onto my personal notepad list for future reference!
And, noting the Ross-Tech sig... thanks for a great product, (Vag-Com / VCDS) highly recommended to own for a variety of reasons if you have a TDI.

Thank you. Very nice photos. Very helpful.

I'm in the process of doing the timing belt on my first automatic (03 Jetta TDI). I use the "VWTDI_TimingBeltChange" video that was produced back in ~2004 and was available for purchase here on TDI club for many years. I also use the "A4TimingBelt.pdf" file authored by DriveBiWire. I noticed when I locked the camshaft with the metalnerd tool, the mark on the flywheel was about middle of the timing window. Per the video, I locked the crankshaft with another special tool while the old timing belt was still on the engine. So the general thought here is that since the car was running (and the car I'm working on was), the timing should be good. However, once we removed the old TB, I had to loosen the crank lock to move the crank to attain the true TDC as you show in your last photo.

I suppose my point is, for those of us that don't do this for a living, it was troubling to me that I had to change the crank/cam relationship from what the engine had already been running with. Some of us just need a little reassurance that this tweaking is acceptable and is what needs to be done to achieve the correct and perfect crank/cam relationship. Sorry for all the ramble...but Mark Twain I'm not.

how do you know to "split the circle"

does it say in the "big red book"?

i know for the manuals there is a little indent mark that you have to line up the "0" on the flywheel.

thanks

Here's what I found.. the instructions aren't exactly precise. Hope this is okay to post.

Combine17 said:

how do you know to "split the circle"

does it say in the "big red book"?

i know for the manuals there is a little indent mark that you have to line up the "0" on the flywheel.

thanks

Click to expand...

Is there is an "O" on the manual flywheels? Since when? I don't see that when I do timing belt work. Ive done a fair amount of manuals and autos.

No the manual has a line, and a pointer in the middle of the hole like the picture above.

-J

I'm aware that this is an old thread, however I disagree with the original post...the timing mark on the ALH balancer cannot "slip" as it's one solid mass with the central bolt flange....only the central mass ring that is pressed in with a rubber sleeve can "slip" ....however the older 1Z/AHU pulley can slip as it's a different construction than the ALH/PD balancer, also the bentley shows the bottom of the wide oval level with bottom of the rectangular hole not split by it .... zombie thread rant over

awesome, thanx for the info!

"jimbote" beat me to it,

Now I get to reply to an 11 year old thread and say thank you! Wasn't sure which direction of the automatic was where this mark needed to be, but now I know. Need to changing the timing belt on a Beetle I bought to fix and flip (I've only ever changed timing belts on cars with manual transmissions).

KKennedy said:

Thank you. Very nice photos. Very helpful.

I'm in the process of doing the timing belt on my first automatic (03 Jetta TDI). I use the "VWTDI_TimingBeltChange" video that was produced back in ~2004 and was available for purchase here on TDI club for many years. I also use the "A4TimingBelt.pdf" file authored by DriveBiWire. I noticed when I locked the camshaft with the metalnerd tool, the mark on the flywheel was about middle of the timing window. Per the video, I locked the crankshaft with another special tool while the old timing belt was still on the engine. So the general thought here is that since the car was running (and the car I'm working on was), the timing should be good. However, once we removed the old TB, I had to loosen the crank lock to move the crank to attain the true TDC as you show in your last photo.

I suppose my point is, for those of us that don't do this for a living, it was troubling to me that I had to change the crank/cam relationship from what the engine had already been running with. Some of us just need a little reassurance that this tweaking is acceptable and is what needs to be done to achieve the correct and perfect crank/cam relationship. Sorry for all the ramble...but Mark Twain I'm not.

Click to expand...

Even though this is an old thread and an old post, but if someone else comes across it...

I've found this same thing on cars I've worked on (that were new to me, and I'm changing the TB out of an abundance of precaution, like I do on EVERY TDI I buy that I plan to keep) - if the cam and crank are off like this, that's where I'll use the metalnerd tool for popping off the camshaft sprocket, lock the camshaft in place after removing the vacuum pump, and then using the Sprocket Buster, ever so slightly advance the belt so that the timing mark on the flywheel is where it's supposed to be. Sadly, on my most recent change, I had no timing mark, because the previous owner used some crappy XTD $100 clutch, but everything else I've owned had the proper mark. Same thing when I reassemble. The IP is timed, but the 13mm bolts not totally snugged up, the camshaft is in time, and once I get the TB tensioner back to spec, I can usually get things perfectly timed the first time, because if I need to move the crankshaft so the mark is at TDC, the cam and crank are already at TDC, and you're good.

Just because the car was running before and the cam and crank were a little off, doesn't mean you should keep things that way. There's a small margin of error these will accept, bu I like getting things done right so there's no problems down the line.

i take it that mark is only relevent to pre bew autos.

benshaw said:

i take it that mark is only relevent to pre bew autos.

Click to expand...

Good question. I could check someday, if I get around to it, as I have a BEW auto.

BEW BHW and BRM are all TDC'd with the crank lock tool installed on the front of the engine. Not with a flywheel mark...

Windex said:

BEW BHW and BRM are all TDC'd with the crank lock tool installed on the front of the engine. Not with a flywheel mark...

Click to expand...

Thank you! That's what Ive been wondering. Should be tackling my TB change this coming week. Even though this was an older post, the timing is perfect!