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The dial indicator needs to be exactly at a 90* angle relative to the tooth it's contacting, and also right at the edge of the tooth. You have it out at the edge, but it's not 90* angle. Remeasure with it at 90* and see what you get. You need the dial indicator as square as possible to the gear face.
EDIT: The laptop screen in your video shows the dial indicator at a 90* angle/
Location: Detroit (the part with no rules or laws)
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Yeah. That's impossible with this dial.
I measured the MSM diff and it was exactly within spec. Also I was using the next tooth down. So this is now set up exactly like the MSM diff.
The only difference is the bearing cap measurement for setting preload. This diff is much harder to spin than the MSM diff and the distances are + .020 out of spec. I tightened it up but it smashed together and I couldn't turn it by hand.
I measured the MSM diff and it was exactly within spec. Also I was using the next tooth down. So this is now set up exactly like the MSM diff.
The only difference is the bearing cap measurement for setting preload. This diff is much harder to spin than the MSM diff and the distances are + .020 out of spec. I tightened it up but it smashed together and I couldn't turn it by hand.
For the backlash, I would remove the boot off your dial indicator if that's what's in the way of getting it square. Or get another indicator, but being at an angle does change the reading you get. I remember seeing that when building my ford diff recently. Having it square will make it read a larger number, so your 15 tho backlash could be 18-20.
Regarding preload, that's the idea there is preload in the bearings when you set it up. On my ford 8.8, the pinion measured about 20 in*lbs of preload on its own. Once the caps were setup for the diff, that added more resistance and it went up to around 28 in*lbs to spin the pinion. This is with new bearings, and a ford not mazda diff but the general idea is the same. If I was reusing bearings I would not set it that tight since old bearings are not going to break in and loosen up like a new bearing does.
What is your plan on this diff, to rebuild it or just try to adjust it to work?
Location: Detroit (the part with no rules or laws)
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Adjust it to work. I'm not messing with bearing preload anymore. If i try to get the number in rage, it gets too tight to turn by hand. They are square between both flats and that's all i'm going to worry about.
I re-squared the indicator as best i could. It's probably only 5* off. The reading is exactly the same as before. The MSM is at .005 and the 3:636 diff is just at .004. This is a huge difference from .015.
I should have bought a lever style indicator instead of a plunger type. That would be way more precise and easier to set.
Ok. Yeah my Ford 8.8 is setup for 10 (spec is 8-12) Most people shoot for 8-10, in my case it took forever to get it to 10 and the pattern looks great at 10 so I kept it. No doubt 15 on a miata diff was way out of spec!
Oh yeah, you are checking the pattern right? Very important thing to do when checking gears, and cost 2 bucks. Preload is for bearing life and supporting parts, but all the adjustments otherwise are putting the gears in the correct position so the teeth mesh correctly. Which checking the pattern will confirm.
Using trig/phys, you only want the displacement in the 90* (y) direction, which is the totaldistance*sin(of the angle from parallel). When at 90*, sin(90) is 1, so you just get the Y displacement, but if it is like 80*, your gauge has to read the sqrt(y^2 +x^2) which is always bigger than just y.
So like pat said, as you get further from perpendicular, your reading gets bigger.
Help me with the math if I am wrong, just bored and started writing
Location: Detroit (the part with no rules or laws)
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This could be a good thing because both diffs are +.001 over spec. I feel safe with the slight angle of the indicator.
I did. The results I got between the 3.6 and MSM diff were a little different.
I have no pics of the 3.6 but here is the MSM diff. The 3.6 had wear more in the middle of the ring gear. Whereas the ring on the MSM diff is more on the inside edge of the gear.
Both have good wear pattern on the pinion gears. Right in the middle with 90% contact.
Im not completely sure what to look for here. So any advice is helpful. I did put the diff back on the carrier already. So I hope it's good.
Also this was a pain in the *** to get off. Do you even have to?
Edit* reading tells me that you want the pattern on the outside because the pinion walks up the ring under load and moves inward. I guess that sounds logical. I dunno
For a pattern, I usually jam something in the case to rub against the diff, so that it takes some torque to spin the pinion over. Basically loads the gears up some, makes getting a good pattern easier/faster. The one in the pic looks like a competition pattern, with it being low vs centered up/down. That's close to how I setup my ford 8.8, mine is slightly more centered but now I can't find any pics... I left the compound on the teeth on my diff.
Location: Detroit (the part with no rules or laws)
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Well, I think i fixed it. It still has a slight "whirl" sound, but it's way quieter than before. I can also feel a very slight vibration. But talking to a few people they're telling me that the gear noise may never go away due to the way it had been previously worn in. And the stuff i feel could be from the stiff poly bushings in the diff carrier. That and i'm just super paranoid, usually i just turn the radio up and forget about it.
Chatted with Fiata Abarth dude for a while. He was super in love with his car, he couldn't stop talking about it. In fact, he didn't ask a single question about mine or even mention it. He never even took notice to the fact that i was pouring E85 in it. I usually get a couple people at least say to me "hey, you know that's e85 not gas right".
Pictures!
Pathetic excuse for some performance videos... It's impossible to drive this car while holding a phone / camera / whatever, i gave up trying to 1-2 shift. It looks slow judging by the gauge. But if my calculations are correct, 90mph on the gauge is a little over 110.
Well, I think i fixed it. It still has a slight "whirl" sound, but it's way quieter than before. I can also feel a very slight vibration. But talking to a few people they're telling me that the gear noise may never go away due to the way it had been previously worn in. And the stuff i feel could be from the stiff poly bushings in the diff carrier. That and i'm just super paranoid, usually i just turn the radio up and forget about it.
...
Well I'm glad to hear that! The one thing you might can try to quiet the diff even further, is a 75-140 oil for it. That's a common thing to do on high stress, or noisy diffs. On fords 8.8's they spec both weight oils depending on if it's a car or truck. So some guys switch to thicker oil for heavy duty use, and note the gears and diff are quieter with thicker oil. But overall it sounds like it's much better, I couldn't hear it at all in your video, before it sounded supercharged!
Location: Detroit (the part with no rules or laws)
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Originally Posted by patsmx5
Well I'm glad to hear that! The one thing you might can try to quiet the diff even further, is a 75-140 oil for it. That's a common thing to do on high stress, or noisy diffs. On fords 8.8's they spec both weight oils depending on if it's a car or truck. So some guys switch to thicker oil for heavy duty use, and note the gears and diff are quieter with thicker oil. But overall it sounds like it's much better, I couldn't hear it at all in your video, before it sounded supercharged!
I am using 75-110 currently. But I do have a jug of 75-140 here too. I may drive this for 50 or so more miles and change the fluid out. Im betting the plug is going to have some metal on it.
He never even took notice to the fact that i was pouring E85 in it. I usually get a couple people at least say to me "hey, you know that's e85 not gas right".
"There is a difference? Huh. Whatever, the car really likes it!"
I am using 75-110 currently. But I do have a jug of 75-140 here too. I may drive this for 50 or so more miles and change the fluid out. Im betting the plug is going to have some metal on it.
Thanks again for all the help.
No problem! Glad it's working much better for you.
Location: Detroit (the part with no rules or laws)
Posts: 5,677
Total Cats: 800
Another season in the books. The 3.636 lasted out the summer. I'm having really strong feelings of selling off the diff and running Pats 4.1 MSM diff. My engine really doesn't like anything under 4000rpm and being able to take it well into 8000rpm i feel like i can get away with it. Since it's not a daily and basically just a fun today to blast around in i don't know if i'm going to be bothered by the short gears.
I went and found a companion for it to hunker down with over the winter.
12,000 original miles.
Unfortunately, it's my daddy's. And now the NB is spending all winter outside.
Location: Detroit (the part with no rules or laws)
Posts: 5,677
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So, i'm on the fence about this 3.636 diff.
It's great for highway pulls, awesome in fact. Great for driving around town. But i want to go fast. I'm seriously tempted to toss this MSM diff in and call it. Would there be any interest in a 3.636 diff if i were to sell it off? (no pumpkin, and it does have a little whine, i don't think it is going away).
Also, i was doing my annual spring time maintenance. Found this. I believe i've had this turbo mounted to this manifold for what, 5 years now? Maybe more. Even Nord-lock can back off over time. Everyone check your ****!
05-29-2017, 01:41 PM
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