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Hey Fellas,
I know there is somebody out there that has done lots of ring and pinion swaps and can give me some insight. Anyway, I had a 3.42 in a 10 Bolt GM, and I switched to a 4.10. Anyway, backlash came out within specs (010), preloads all checked out, careful I was as I have done these before but this time, this one had a high pitched table saw sound even when coasting, accel, decel, after the short test drive of a few miles I took it back home and pulled the cover off to see what happend. Backlash was still good, pinion not not loose, nothing obvious, no broken anything, but the pattern, well its weird because its got a place of none contact. Please gear wizards tell me what happend, and if my R and P is scrap metal… coast and drive side images, please share thoughts…(and the pattern before the drive was centered on both sides before test drive)
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It looks like you are missing shims. Without seeing the pinion it is hard to tell if it is just a worn out pinion or shims.
Ring 1 it seems to be hitting dead center but, a little shallow aka too high up on the gear. It also is not making full contact across the gear face length wise while it is a decent amount I would expect a little more, which is why I am wondering if you have the wrong sized pinion or if it is worn out.
Ring 2 you are hitting too deep and way off to one side. Also once again you do not seem to have the amount of contact I would expect to see across the gear face.
It should look more like this:
it was a brand new ring and pinion. 30 thousands shim on the pinion side. Very close to what was there before. Yes, the loss of contact is what makes me wonder
Here was the ring gear pattern during assembly. It only went a few miles before I came back.
I have also included a picture of the pinion head.
Its at 30 presently. I intitally set it up with a 32 and it wasn’t balanced. Notice the picture before it was run the pattern is right in the middle.
Here is a pretty comprehensive guide on setting it up: Differential Installation Instructions
From what it says heel to toe cannot be changed without machining work. He also goes on to say in some cases it cannot be fully achieved. It also has pictures of acceptable patterns.
I will take each measurement 3 times. If i get one that is way off I will remeasure and use the 3 most accurate or similar measurements and average them. I start with factory shim settings. The way I have always done it is to measure the gear engagement marks aka the gap from heel to engagement, toe to engagement, engagement to top land, engagement to root. Do this on 4 teeth of the gears and average it. I then also take all my other measurements. Do this again after installing the smallest shim for the pinion. Subtract from first measurements. Then remove the pinion shim do it again for the smallest shim for the ring gear. Subtract from first measurements. You now have a way to add or subtract shims on paper. Then you play around with the numbers on paper. Once you find the shim settings for both that are within specs you pick the one with the most gear engagement. You will normally have 4-5 different shim settings that will be within spec. This is the way I have done it. Funny thing is normally it is close to factory shims with maybe one added or subtracted to take up for wear.
Make sure when you do the painting you paint quick so it is as wet as possible to give you the most well defined marks. The way you have it I am wondering if that might be part of the issue.
Before teardown,always measure the backlash and write that down.There is also a depth gauge set up for the pinion.They say not to reuse the crush sleeve,you can and is possible.Called hammer it out,the new crush sleeve is 100% impossible to crush down most of the time.Synthetic gear lube tears up ring and pinions,Royal Purple’s synthetic gear lube is well known for this.I know a guy that builds and fixes race cars that has seen this and he kicks Royal Purple’s synthetic gear lube off the side for this reason.
OK, first off do not reuse crush sleeves any time you are switching the R&P, you are never going to get anything right doing it like that. Synthetic gear lube also does not tear up gears if they’ve been set up and broken in properly, I’ve run it in plenty of stuff anf never had an issue.
But back to the gears at hand…
I haven’t laid hands on any of this and I believe that a huge part of gear setup is feel so take all this with a grain of salt…
First off the fact that both of your first pictures seemed to show a drastically different coast pattern heel to toe at different spots on the same gear is not a great sign. To me that indicates either a parts or install issue that has the pinion loose, the ring gear off center or some kind of thickness/machining rule or even a problem with the carrier.
Did you press the ring gear onto the carrier or pull it on with the bolts? Did you check the pattern in different spots on the ring gear when you did the initial install? Was it consistent around the gear then? How about the backlash? Was it the consistent around the gear? What was the backlash number you got? Also, what did the drive side pattern look like? New carrier or the old one?
I don’t think the gears are dead but there is very likely an issue with something. Clean them up and look to see if there is any galling or heat damage, if not they should still be OK after proper setup.
If it were mine I would go back to square one and remember that with gears one change effects all the other measurements. If you move the pinion or ring gear to get the pattern right it can change the backlash and you may need to move the ring gear. Do it again from the start and, if at all possible, do it out of the car.
Good luck and keep us posted, gears can be super frustrating.
I replaced it all inside with a better grade of gear and all new timken bearings. Pinion depth was measured with a tool ,backlash at 10 6 measurements around the ring gear all appropriate tools used. 30 inch pounds for pinion rotational torque. Switched from a crush sleeve to a shimmed solid spacer. 10 inch lb on the Carrier preload. Now I have red line Synthetic Shockproof in it, and its still noisy, just not as bad. One said since an F body has a torque arm that transfers noise and vibration across the car aftermarket gears are always going to be loud. Another person pointed out aftermarket gears such as the motives 3.90s I put in have a different pitch that makes them stronger but louder. Changed the fluid and it looked clean. Totally baffled. Originally broken in with Lucas 80/90 but now have the red line in it.
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