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Discussion Starter #1
Hi all,

I am installing an Eaton Truetrac into a 8.5" 10 bolt diff, all seems to be going well so far. The gears were replaced with Richmond ring and pinion around 50 miles ago - car didn't see much use before being taken off the road to rebuild things. I have installed new bearings with the existing gears, using set up bearings of the same manufacture for pinion depth.

Backlash comes in around 10 thou. I have applied yellow paint to check the settings, and would like someone more knowledgeable than me to advise me on whether this is ok. Any help is greatly appreciated.

Cheers

Andrew
615499


615500
 

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More for Less Racer
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Pic #1 both drive and coast look bad.

Pic #2 drive side looks a lot better, but we cannot see the coast side?
 

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Discussion Starter #3
Pic #1 both drive and coast look bad.

Pic #2 drive side looks a lot better, but we cannot see the coast side?
Hi, thanks for replying. The pics are off the one test - I took a shot of the one side in each pic, so the coast side of pic 2, is pic 1. Hope that makes sense!
 

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When you take the pattern are you loading the gears as best you can? I put on a leather glove and put resistance on the ring gear. Patterns should be opposite each other. Adjust pinion shim to make this happen.
 

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the coast pattern looks like the pinion is too far away.
hard to tell with used gears.
we're the gears quiet before? are they going in the same housing?
 

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Discussion Starter #6
When you take the pattern are you loading the gears as best you can? I put on a leather glove and put resistance on the ring gear. Patterns should be opposite each other. Adjust pinion shim to make this happen.
I've tightened the pinion nut to take play out of the pinion. I have to turn the ring gear with a spanner on one of the bolts. It's not that hard to turn though... I'll try playing around with the pinion depth.
 

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Discussion Starter #7
the coast pattern looks like the pinion is too far away.
hard to tell with used gears.
we're the gears quiet before? are they going in the same housing?
The gears had very little use in the car - I drove maybe 50 miles with them before taking it off the road. They were installed by a local mechanic years ago, and I vaguely remember there being a bit of noise, but I think I assumed it was because they needed to be broken in. Same housing, the only thing different is the Truetrac and new bearings.
 

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If this us an aftermarket gear, the checking distance should be etched on the end of the pinion gear. 99% of 8.5 differentials will use the same shim under the rear pinion bearing. The nut should be tightened to obtain 20 inch pounds resistance to turn with new bearings lightly oiled. The carrier without the ring gear will need to be shimmed to achieve 40 inch pounds to turn in new bearings lightly oiled with the caps torqued. THEN you can install the ring gear and commence the shim swap side from side to side but never change the total thickness of the carrier shims combined. If you take .040 off of one side, it goes into the other side. Again, aftermarket gears will be etched with the desired backlash on the ring gear. I have yet to see anything above .007 and no tighter than .005. THEN you can apply the checking die or marking grease to see where you are. I suggest a bit tighter on the backlash on manual transmission setups with sticky tire launches planned. Automatics will be fine with target backlash. It isn't hard, just time consuming. Years ago, I set a 12 bolt on the money that was quiet. The next one I did was a 4.56 again on the money and it had a slight whine on coast. Everything was textbook correct. It didn't wear out prematurely. Tighter backlash was worse, loose was better so we left it loose an extra .002 as it was an automatic.
 

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Discussion Starter #12
If the bearing preload is set correctly it should be a little difficult to turn it.
This I am unsure on, how to set the preload without using the new crush sleeve. Is it just a matter of Holding onto the ring gear while turning the pinion? I'm using set up bearings...
 

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Discussion Starter #13
If this us an aftermarket gear, the checking distance should be etched on the end of the pinion gear. 99% of 8.5 differentials will use the same shim under the rear pinion bearing. The nut should be tightened to obtain 20 inch pounds resistance to turn with new bearings lightly oiled. The carrier without the ring gear will need to be shimmed to achieve 40 inch pounds to turn in new bearings lightly oiled with the caps torqued. THEN you can install the ring gear and commence the shim swap side from side to side but never change the total thickness of the carrier shims combined. If you take .040 off of one side, it goes into the other side. Again, aftermarket gears will be etched with the desired backlash on the ring gear. I have yet to see anything above .007 and no tighter than .005. THEN you can apply the checking die or marking grease to see where you are. I suggest a bit tighter on the backlash on manual transmission setups with sticky tire launches planned. Automatics will be fine with target backlash. It isn't hard, just time consuming. Years ago, I set a 12 bolt on the money that was quiet. The next one I did was a 4.56 again on the money and it had a slight whine on coast. Everything was textbook correct. It didn't wear out prematurely. Tighter backlash was worse, loose was better so we left it loose an extra .002 as it was an automatic.
Thanks for the detailed info. I am putting in a Truetrac , so I need to fit this before ring gear, and test rotation torque? The pinion is tested with no crush sleeve?

A mechanic had set the new Richmond gears up when I had the car on the road, maybe 10 years ago. It hadn't been driven much before I took it off the road - we're talking less than a hundred miles. I decided to upgrade to the Truetrac, and as I had sandblastered the diff casing to clean it to paint. I decided it best to replace the bearings in case of grit getting in. Initially, I just put back the existing pinion shim but couldn't get a decent pattern (this was the pictures I took at the start of this thread). I had bought the Ractech pinion depth checking tool, but after getting the average of a dozen or so measurements and doing the math, the shim required was .015", not the .035" of the original. Ugly pattern. I have been playing around with the shim thickness to try and get a better pattern. Backlash on the ring gear says .008". This is the latest pattern I have - getting a bit better, but still the shape isn't good. I'll have a go this weekend with trying to set the carrier to get to 40 inch pounds. When rotating the ring gear, I usually just move the ring a short distance on the pinion, back and forth 3 or 4 times. Not sure if this is the best option - sometimes I think the paint gets onto the pinion and then transfers back onto the ring gear and distorts the pattern...
 

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Don't use the crush spacer when doing trial assemblies. Save it for the final assembly. As for the differential bearing [preload, just get it as tight as you can. There isn't a good way to measure it. If the pinion bearing preload is set to around 19-21 then turning the ring gear against the pinion will give enough load on the gears to do a pattern check. Don't turn the pinion, turn the ring gear.
 

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You can AFTER your pinion depth is correct. You have to sneak up on it with a pipe wrench with a cheater bar on the yoke to hold it and a 3/4 drive breakover with a cheater on it or use a 4 to 1 torque multiplier. The amount of torque required may be north of 300 ft lbs. Try to hit 20 inch lbs by being brutal. People use an impact to do get the sleeve to crush but they won't know if they went too far until the turning resistance is too much. Then when they back it off to get the correct resistance, the nut backs off at some point.
 

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Don't use the crush spacer when doing trial assemblies. Save it for the final assembly. As for the differential bearing [preload, just get it as tight as you can. There isn't a good way to measure it. If the pinion bearing preload is set to around 19-21 then turning the ring gear against the pinion will give enough load on the gears to do a pattern check. Don't turn the pinion, turn the ring gear.
A bolt with a nut thru a ring gearless carrier is how I measure carrier turning preload.
 

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Diff bearing preload = (Total preload measured at pinion flange - preload measured with pinion alone) * gear ratio
 

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Discussion Starter #19
Don't use the crush spacer when doing trial assemblies. Save it for the final assembly. As for the differential bearing [preload, just get it as tight as you can. There isn't a good way to measure it. If the pinion bearing preload is set to around 19-21 then turning the ring gear against the pinion will give enough load on the gears to do a pattern check. Don't turn the pinion, turn the ring gear.
Thanks - that makes a lot of sense. I'm feeling a lot more confident about attacking it over the weekend.
 

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Discussion Starter #20
You can AFTER your pinion depth is correct. You have to sneak up on it with a pipe wrench with a cheater bar on the yoke to hold it and a 3/4 drive breakover with a cheater on it or use a 4 to 1 torque multiplier. The amount of torque required may be north of 300 ft lbs. Try to hit 20 inch lbs by being brutal. People use an impact to do get the sleeve to crush but they won't know if they went too far until the turning resistance is too much. Then when they back it off to get the correct resistance, the nut backs off at some point.
Thanks. I have seen a few videos of the crush sleeve being installed. Definitely looks to be tricky, and I am not looking forward to doing it alone, with the diff out of the car. General consensus seemed to be to avoid using an impact wrench.
 
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