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I’m not Gary and in no way comparable but it looks to me like your pinion in the first 2 pictures is a little too deep into the ring gear.
Are photos 1/2 and 3/4 of different set ups? Photos 3/4 look to be a different pattern (possibly a little better) than 1/2. Photos 3/4 look like you pulled the pinion back a little.
But - no expert. Set up a Chrysler 8-3/4” once. But, I’ll help keep you up at the top and maybe Gary will see it.
I’m not Gary and in no way comparable but it looks to me like your pinion in the first 2 pictures is a little too deep into the ring gear.
Are photos 1/2 and 3/4 of different set ups? Photos 3/4 look to be a different pattern (possibly a little better) than 1/2. Photos 3/4 look like you pulled the pinion back a little.
But - no expert. Set up a Chrysler 8-3/4” once. But, I’ll help keep you up at the top and maybe Gary will see it.
Hi Dan Thanks for your help......Look at the pics.....I labelled them with 035 and 030. 035 is the top two photos. and I think those look best. I did try 025 and didn't like the pattern.
By any chance did you try a shim under .030, say .027? The fact that you appear to have a reasonably full tooth pattern on both the coast and drive side would tell my novice mind that you may be pretty close. In my project it was a pretty narrow range of pinion depth where both sides were getting full tooth contact and neither was running into the root or off the crown and neither was too close to the toe or heel. Another pattern on the shallower side of .030 shim would probably help tell you if that really is optimum or if you might benefit in going a little shallower. Gary will also probably tell you to slowly rotate the gears and listen for any slight ticking or other metallic noise to indicate their might be some light clashing of the pinion and ring teeth, indicating they are not mating smoothly.
Forgot to ask - have you tried to find a cause or fix for the runout? I think .003” on the ring gear will create some issues - maybe noise, not sure.
Last edited by DansYellow66; 01-24-2024 at 04:48 PM.
I did try a 025 but didn't like the way it looked. It's odd to me that 35 looks closer to the center than the 030. you would think the 030 would bring it closer to center.
The runout is on the case. I think .003 is within max. allowable.
It may be a bit better centered from toe to heel on the .035 pattern but my understanding is that is less important than being centered between the root and the crown. The .035 pattern looks to me to be getting into the root of the teeth - both drive and coast.
I suspect the .025 pattern was starting to get out on the crown a little and look a little irregular. My experience was the shallower pinion depth moves the pattern slightly to the outside (heel) but not much. I think with some gears the pattern from heel to toe is just going to fall where it falls once a good gear impression pattern is achieved that is not into the root or going off the crown.
Sounds like you did 3 patterns right and probably have bracketed the optimum area around .030. Hope Gary chimes in to help.
Hi Brian,
I am still around although I post more pictures on FB these days.
035 is thicker than most GM gears used, however every gear set and housing is different so that alone can't rule out 035" but the pattern is low to the root on both sides of the gear. The 030 may be more in line with a sharper pattern.
I don't recall if you have the original gears in the diff or if you bought used GM gears? Good GM gears usually show a better coast pattern than I see with either of those. If the gears were original to the housing, what was the shim in place?
I don't like either set of patterns but again that may be from loading on patterning or the paste consistency. How do they mesh and sound turning the gears? There should be a nice smooth mesh, no clunking.
I keep lash with used gears at 006-008"
003" variance in the lash through 360* is pushing the limit. I like it under 002". That may be gear wear and those patterns show wear. RIng gear run out is different and usually is from either mounting the RG with a burr or other issue or a posi case flange with runout. That can be from a gear failure.
So, I would go back over the pattern, see if you can get it sharper. Confirm the lash thru 360*, check the RG for runout as that can cause lash to change but usually more drastic than 001"
For comparison here is an original set of GM gears I set up. Clearly you can see the coast is equal root to crown, drive shows wear. The gear set is in use and quiet as these are from a few years ago.
Hi Brian,
I am still around although I post more pictures on FB these days.
035 is thicker than most GM gears used, however every gear set and housing is different so that alone can't rule out 035" but the pattern is low to the root on both sides of the gear. The 030 may be more in line with a sharper pattern.
I don't recall if you have the original gears in the diff or if you bought used GM gears? Good GM gears usually show a better coast pattern than I see with either of those. If the gears were original to the housing, what was the shim in place? Original shim was 030. I did take a pattern before disassembling.These are original GM gears but unsure if original to the case.
I don't like either set of patterns but again that may be from loading on patterning or the paste consistency. How do they mesh and sound turning the gears? There should be a nice smooth mesh, no clunking. There is nice even mesh, no noise. Maybe a little more oil in the paste (too thick?). Your paste looks like is splattered so thinner and run with a drill? Before I took it apart, it was smooth as well.
I keep lash with used gears at 006-008"
003" variance in the lash through 360* is pushing the limit. I like it under 002". That may be gear wear and those patterns show wear. RIng gear run out is different and usually is from either mounting the RG with a burr or other issue or a posi case flange with runout. That can be from a gear failure. I ran the dial indicator on the carrier to get the 003 runout measurement. I was very careful about burrs and used a stone on all mounting surfaces. And yes when I cleaned everything up without any oil on them after disassembly, they did a appear worn.
So, I would go back over the pattern, see if you can get it sharper. Confirm the lash thru 360*, check the RG for runout as that can cause lash to change but usually more drastic than 001" Will do. Do you run a drill on the pinion to spin for pattern checking?
For comparison here is an original set of GM gears I set up. Clearly you can see the coast is equal root to crown, drive shows wear. The gear set is in use and quiet as these are from a few years ago.
I vary the paste consistency depending on the stage I am in.
I don't run them in with a drill, all hand work.
If the 030 was good while in the car I would go back to it.
Trying to get a textbook pattern on used gears will usually lead to frustration and mistakes. If you change the pattern of a worn in gear set to get a better-looking pattern you may then introduce gear whine that wasn't there before.
The pattern I show would not be one I used if the gears were new, yet if I tried to bring up the drive, then the coast would be off, and it would have whined.
If the gears are original to diff that is what I would do. There should be a date code on both the R&P. The unknown if the gears were bought used from ebay or other sites is, you don't know if they are a matched set or not. Some sellers will say anything to make a few bucks at the buyer expense.
Let me see if I can reply, as I am in Da Nang, Viet Nam....
IF, I recall, when checking pattern, ref shop man, you "load" the pinion by wrapping a rag around it, hold tight and move the ring to give a sharper pattern.
This dampens the back lash some what to give a better pattern. Did you do this?
Let me see if I can reply, as I am in Da Nang, Viet Nam....
IF, I recall, when checking pattern, ref shop man, you "load" the pinion by wrapping a rag around it, hold tight and move the ring to give a sharper pattern.
This dampens the back lash some what to give a better pattern. Did you do this?
Aloha,
Rene'
That will work. I have done that with an old leather belt, rag, etc. I made a fixture I use now that works great but for a one time build, the rag or belt will work.
Thanks for your assistance Gary, you speak and we all learn!
Absolutely. I have half a notion to grab a plane ticket and pitch a tent outside Gary's house for a couple of weeks and see what he can teach this old feeble mind about setting up diffs.
01-19-2024, 01:36 PM
Read My Gear Patter Please Gary
