redline7921

Hello everyone. I have posted a few photos of a gear pattern I ended up with. I am not an expert and am looking for some one who can provide feedback on what needs adjustment to get the correct pattern. I have some ideas, but I prefer to see what you all say so my ideas don't skew yours.

Thanks in advance.

Noahs944

You are pretty close.
This top photo you took doesn't matter because the concave side is the non-driven side.


This convex side matters as it driven from the pinion. Pretty close to perfect. The thing to remember is gears want to blow apart. So you might want to error on the side of gear contact slightly tighter than centre. I have limited diff experience but I'd start with slightly more pinion depth and then re-check.


What type of paint is that?
I ask because we seem to have consistent pattern (lower on this photo appear perfect but upper less than perfect -like the pinion is high), was everything bolted tightly? In a pinch I've used Engine assembly lube. It doesn't dry & crack like that yellow paint is.

Noahs944

Have you watched this video? Seems like a gooder, mate! Best of luck to you.

redline7921

I used the Mopar iron oxide gear marking compound. I have tried Prussian blue but you can't see the pattern well, so the yellow stuff works a lot better.

I think there was some gear oil remaining on the drive side causing the pattern to be inconsistent in some spots.. I may do it again. Everything was torqued to spec, the hard part is loading the gears.

I am checking because somehow 1st gear synchro cracked on me (it was brand new) - the ring and pinion check is a while I am in there thing.

With the current setup I get some growl during coast from 3000rpm to 2500rpm, so I think I need some adjustment, but am not sure what way. The backlash right now is .008"(.2032mm). I think I should reduce backlash slightly but I was more concerned about required adjustments to pinion depth, if any.

I have watched the vido attached, thanks. I find reading the gear pattern is the challenge.

I appreciate all the feedback.

Noahs944

Growling can be caused by bearings. Were you able to visually inspect them?

redline7921

All the bearings are brand new. I replaced both pinion bearings and both carrier bearings about 1000km prior. With the new install preload was as per the workshop manual. The load now is almost non existent. The growl becomes louder as the tranny warms up. Do to expansion maybe?

Noahs944

not torque tube or wheel bearings, eh?

redline7921

Have the Constantine bearings in the torque tube, new as well. Wheel bearings at front almost new. Rears original but the car only has 75k miles. Sound goes away when the load from coasting is removed either by pushing the clutch in or by giving a little gas. Definitely tranny related. I think it is the ring and pinion that needs slight adjustment.

Since these are used gears, should I not look at the coast side since it would be worn less? Somewhere I read that, but there is a lot of info almost too much.

In theory increased pinion depth would move the coast pattern towards the heel and the drive side towards the toe. Is that what you are suggesting I do from your post earlier?

Noahs944

Redline,
It sounds like you are doing some amazing things to your car! I'm proud of you!

Honestly I'm not knowledgable enough to be giving advice (I keep waiting for someone else to chime in), perhaps I should withdraw my earlier comments.

I have learnt that in the case of used gears, it's recommended to take a pattern before & then try to match that pattern after (because the r&p will have the most surface contact and therefore be stronger).

Here I have read what you are talking about (reading coast side on used gears):
https://www.ringpinion.com/Content/B...h-Patterns.pdf

Noahs944

Sorry, I was treating this diff like one of our truck differentials at work (different configuration). I haven't tore into one of these Audi units yet.

If what you say is true then I would have suggested pulling the pinion out to give the drive side more heel. But a true expert should really pipe up.

Did you match the backlash to what it was before & try to match the pattern to what it was? If not, and you wipe the yellow paint off, you might be able to see the original wear pattern, and just try to match THAT.

-I can't figure out why the r&p would effect your first gear syncro.



Makes no sense to me.

AZ520

I would give a quick check to you rear axle bearings and cv axles just to rule them out. I had a hard time locating a bad left rear axle bearing. I only discovered it after removing the rear disk, hub and axle. It's very important to pull the hub and have the axle un-bolted because It felt fine with just the caliper removed and spinning the disk by hand or running the with the wheel off the ground. I thought it was coming from the transmission for sure. My 2 cents.

KevinGross

I'd say your drive-side pattern looks okay. But honestly after many years of setting up Porsche transmissions with blueing (Prussian Blue) before I got the factory tools, I'd say that reading set-up from patterns doesn't work very well.

Carl's video is quite correct in what he says about the effect of changing depth and backlash, which is cool. Things do move under load, which is why an unloaded blueing is not reliable. He doesn't mention whether he's working with a spiral bevel versus hypoid pinion gear design, alas, and I'm not sure the difference that would make.

The factory pinion depth (S3) almost never has to change when installing new pinion bearings. I check it every time. But unless I am dealing with a 968 or 944S2 gearbox that the factory set up wrong, I almost always measure well within the factory's .05 tolerance.

Your first gear synchro didn't crack because of the r&p set-up. It broke either because it was damaged during installation (unlikely) or because you dropped the clutch drag racing your car (happens all the time...).

Backlash should be 0.10 to 0.20 measured per the books, at 95 mm from axis (per the book, 79 mm from the tool face plus 16 mm for the radius of the tool). Good luck!

redline7921

I will check the CV joints and rear bearings to be sure.

The synchro is unrelated. I had been living with the noise for a while (since I did the rebuild), but for some reason one day last week the synchro failed. Figured while I was in there I might as well have another look at the ring and pinion , see if I can't make it run silent.

I unfortunately did not look at the before pattern or measure backlash. Probably because it was all new, learned my lesson there.

First time I had it back together I had the backlash at .12mm (the minimum from the manual) but the pinion was further out and the noise was over a greater rpm range (3500 down to 2000). Drive was silent as it is now.

The only adjustment for the pattern in the photos was pinion depth, increased by I think .2mm.

​This change made the noise only happen from 3000-2500, so a range of 500rpm vs 1500 before. A positive, but still not perfect. I don't want to tear this thing apart again, as much as I enjoy working on it.

I can now have the transmission removed and apart in 3hrs lol

My car is all stock, just trying to keep it in tip top shape and not have any nagging issues.

Again, thanks for the suggestions, I will try them and see how it turns out.

Alex

Noahs944

At work (again, on hiway truck mechanic), we have a trick for diagnosing front wheel bearings that might be in rough shape: while the front end is jacked up, spin the wheel & with the other hand on a near-by component (in this case a brake chamber) if you feel vibrations on the chamber, it's an indication of damaged bearings.

redline7921

Here is the pattern that I ended up using, but with a backlash of 0.165mm. I will post more photos with obvious incorrect patterns for reference.

From the first post I reduced pinion depth by 0.0206 mm. This turned out to solve the noise coming from the tranny during coast from 3000-2500rpm, and things are running smooth.

Thanks everyone for their input.