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I chose this diff for my BEC. Since it's out in the open air, I took it apart and welded up some holes as well as a bracket for a disc brake.

I don't remember how tight it was when I got it (used). But I'm finding it very difficult to rotate the axles now that I'm going for final assembly. I've shimmed the cover (right pic) up with .003" shims sitting on the lands on the left pic to allow me to tighten the four large bolts and still be able to spin the internals.

I'm sure things distorted a bit during welding. I think the cap is kind of convex now.

I sharpied the ends of the smaller internal gears as well as the area on the caps that they rub on to try to get a feel for what was going on. You can see one gear and is making heavier contact (sharpie gone). Also note the wear marks on the cap would also indicate a bit of convexness.

In the pics the cap is flipped horizontal from the left and I've color coded which marks line up with which. Also the orange color is where I've placed shims.

On the cap there is a very small "pocket" (not visible) machined or ground around where those gears hit as if that is a final fine tune on the original assembly.

Any thought's on how tight those gears should be axially? 0.001" interference or clearance? I'm thinking if I can turn it by hand that's too loose. But then again, if there's no clearance, no grease will get to those surfaces.

Do you think putting shims in it (as I've done but bigger to cover more area) is an ok way to tune that tightness?

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"It ain’t what you don’t know that gets you into trouble, it’s what you know for sure that just ain’t so."
"Sometimes I sits and thinks, sometimes I just sits." - Satchel Paige

Use plasti-gauge to check all including the thrust washer. Do not rotate.

Recheck with the cover bolted-on 180. Let us know the results for each position.

Check the condition of the blind side of the gears and thrust surface depth.

Measure the lengths of each gear and return to original position.

I think the cover pockets are just wear since the gears are much harder than the cover.

Better not to swap positions of the gears since a wear pattern has already been established but it might be ok to do so. I’d probably end mill the cover pockets for minimum clearance rather than try to shorten the gears then return the gears to a smooth enough finish that won’t grind through the cover. I would not shim the cover due to the thrust washer.

Too bad you didn’t check end play before welding on it. Splash lube 75/90 wt. I would ask torsen tech for general end play spec, Colorado diff if they ask. I would not discuss the project or what you’ve done to it. I’m guessing .005” nominal end play. Too loose is better than too tight.

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Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

Oh, plastigauge, I forgot about that stuff, thanks. My first attempt with the plastigauge wasn't a great result. It confirmed that the cap was very convex. I mounted the cap in my mini lathe, clamped on the journal and used the same journal to indicate it in. It took a good .005" to get it flat.

I had measured the length of the small outer gears before and was amazed at how close they all were to each other, within a thou with an old calipers. I kind of dread taking it apart again, as it's kind of a puzzle to get back together.

I plastigauged it again, and the gauge was mostly crushed on the small outer gears, but barely touched on the large inner. But I didn't put any brass shims in around the bolts. So I regauged it again with the .003" brass shims. Then I started to get some readings. With the .003" shim I was getting plastigauge measurements from .002 to .0035. So I would definitely say it's got an interference fit right now.

I mounted the cap in the lathe again to take 3 or 4 off the outer section and leave the center high in an attempt to tighten up the center fit.

After looking at Eaton's site, I found instructions for on-vehicle testing. I interpreted it to mean you should be able to rotate it somewhat freely under light load.

It does turn smoother now with a flat cap, but I think I'll try to see if I can mill those "clearance" pockets back into the cap.

No pics tonight, camera was acting weird.

_________________
"It ain’t what you don’t know that gets you into trouble, it’s what you know for sure that just ain’t so."
"Sometimes I sits and thinks, sometimes I just sits." - Satchel Paige

You could also try a small amount of valve lapping compound on the gear ends, have the shimmed cap facing down so no compound migrates into the gears, then rotate the assembly back and forth to check the progress on the cap. It may be too slow of a process without a way to rotate the axle with a motor, belt, and a bearing rest to support the axle against the belt load. If this works well, remove the shims and repeat to help equalize end play across all the gears. You'd be rotating the output with no load diff to the input and the other output will also be rotating the same way, so there should be no issue with the diff being without oil, but I'd keep the speed low and monitor the case heat with your hand. It should not get hot except the end cap should be warm.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

I don't know if this is typical for all Torsens but the Type 1s I dealt with several years ago had timing marks on each gear. If you didn't assemble everything in the correct orientation, it bound and locked.

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-Andrew
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