Bulvot

I'm in the middle of a timing belt job, and the wear on the passenger cam gear looks like it is bad enough to warrant replacement. The oil pump gear as well, in my opinion. However, this is the first time that I've done a timing belt job on a 928, so I would appreciate any input on the condition of the gears. Unless convinced otherwise, I plan to replace both cam gears, the oil pump gear and the crank shaft gear. The motor was rebuilt within the last 10k miles, but it was 10 years ago. I'm a bit disappointed in the condition of the gears, given the rebuild, but that predates my ownership.

I haven't removed the belt yet because if I am going to replace the gears, I want to measure the timing as it is now. The motor has custom cams in it and I don't know how the engine builder set the timing. It runs really well, so I would like to measure and duplicate the timing rather than disassemble it and set it to factory specs. And, I don't have the right tools to measure the timing yet. So, the belt stays on for now.


Passenger Cam Gear:





Driver Cam Gear:





Oil Pump Gear:

linderpat

Agree. You should replace them. That passenger gear looks pretty worn. Also, never replace just one; if doing that job, replace them all at the same time. Maybe the prior owner did not do that during the rebuild? Also, add the year of your car to your signature so we know what we are looking at. I can tell it's a 32 valve motor because each side has a rotor, but it could be anything from an 85 to a 95 GTS.

Ducman82

crank gear will prob be just fine. they are steel. Rarely wear. i would replace them all at once for sure.

ROG100

Small signs of wear - if this is not a daily driver I would say they would last another iteration of the belt. You can always take a peek every year.

Kevin in Atlanta

Cam gears look fine - no cupping. If it were me I'd have them dry-film lubricant coated. They should be good for another 40k miles.

buccicone

Rob Edwards

I think the driver's side gear is ok, but I don't like those two or three teeth on the passenger side where most of the coating is already gone. At the very least get them DFL-1 coated but my bias would be to replace the passenger gear. Is the oil pump gear aluminum or steel?

Bulvot

Thanks for the input. I can see where you guys are coming from that it should be good for a bit more. That is good advice, especially if I were on a tighter budget with this project. But, I would like to err on the side of new parts, just to be safe. There is enough "maybe" and "probably" and "should" to warrant new parts in my opinion. If everyone was saying "those have no significant wear, you're seeing things, don't bother replacing them", I would rethink my understanding of what wear looks like on the 928 cam gears. But, given that they have some clear wear, and that the wear is uneven between the two cam gears, I'm going to start over with new on all gears that the timing belt goes on.

Now, if only the clutch replacement will be as easy as the timing belt job has been so far!

Roger, I sent an email to you regarding these parts and some other things.

Bulvot

My assumption is that that the oil pump gear is aluminum, it sure looks like it, but I haven't confirmed that yet.

And, it is a 1987 S4.

Kevin in Atlanta

If you replace the cam gears I'll take the used ones off your hands,

Bertrand Daoust

+1.
I would worry a bit more with the passenger side gear.
Just looked at it in a year or two.

GregBBRD

No question. It is.

Bulvot

Bertrand, I will probably hold onto the old cam gears as spares and look into having them recoated, if that's an option. I've been slowly building up my inventory of spare parts in case they are no longer available in the future.

Greg, I'll refrain from getting out a magnet now that you've confirmed that the oil pump gear is aluminum

I'm ordering all new gears. That way there will be no guessing, and no requirement for more frequent than normal checks.

My biggest worry with respect to the 928 is that the vendors, service providers and product developers will be NLA in the future. We have some really amazing ones who are active on here and extremely helpful. When they go away and we can no longer procure their services, we'll all be much worse off.

GregBBRD

Ah. Someone smart enough to see the writing on the wall and realize how little things affect the big picture!

I'm continuing inventing and making pieces that grealty improve these cars...perhaps at a faster rate than ever before.

After the recent theft and copying of my crankcase oil separator that fits below the filler neck by Potdog, I've decided to not release any of my new pieces to the general public. The only way someone gets the new pieces is if they are installed in my shop....end of story!

I have new oil contol pieces that will completely eliminate oil in the intake system for an S3. More cost effective (and more efficient) oil separators for the S4 and GTS models. More efficient, more cost effective, greatly improved syncros for 928 transmissions. A new single disc clutch coming down the pipeline. I'm not going to release my A/C system to the public, anymore....only will be installed, in house. My intake system will never be sold to anyone that doesn't have one of my engines.

The list goes on and on.
​​​​​​
​​​I'm completely done releasing brand new products to the general public.for some inmoral crook to copy, without any of the developmental and testing costs.

Go ask Potdog what he's inventing, on his own. Good luck with that!

skpyle