LSD option

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brokencase
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Re: LSD option

Post by brokencase »

I think the tricky part is the elongation of the holes (as pointed out in the directions).

I think I would approach this by chucking the LSD assembly in the lathe and attaching a die grinder with a carbide bit to the turret.

I would then index the lathe chuck through the 10 positions and put a stop on the cross slide of the turret so that I could grind all the holes an even amount. Grinding 30 thou off is not too bad, but it must be done evenly.

Also, best to do this with a spare diff. The rest is pretty easy and normal backlash setup.

My old Sport Trac had a clutch pack type LSD like this one, The clutch discs were good for about 100k miles. I think I changed the fluid in the diff once at around 50k. Might have lasted a bit more if I was more diligent. The LSD along with 4wd made that vehicle unstoppable in the snow. I've not had any experience with the other locker or quaife style LSDs, but I liked how the clutch type LSD behaved for street use.

The nice thing about the clutch discs is that when they eventually do wear out you are not immediately obligated to rebuild the LSD. You can just continue on without the LSD action.

I also think the LSD would reduce the loadings on the CV axles by distributing torque more evenly between the two axles, but I'm just conjecturing this.

In any case, if I could get a hold of a spare Scorpio diff on the cheap, I would jump on this project in a heartbeat. $190 for the LSD is very reasonable.
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brokencase
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Re: LSD option

Post by brokencase »

Ooops. my bad... I thought the Auburn lsd was clutch disc based, but it is not. It is friction cone based..which I presume is metal to metal friction.

But the ebay link I posted earlier was to the Eaton style (same 7.5" GM application) which is clutch disc based.

I don't believe the Auburn cone style is still available for this application. Although there may still be old stock still out there.
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Re: LSD option

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brokencase wrote: Sun Mar 12, 2023 10:17 pm I think the tricky part is the elongation of the holes (as pointed out in the directions).

I think I would approach this by chucking the LSD assembly in the lathe and attaching a die grinder with a carbide bit to the turret.

I would then index the lathe chuck through the 10 positions and put a stop on the cross slide of the turret so that I could grind all the holes an even amount. Grinding 30 thou off is not too bad, but it must be done evenly.

Also, best to do this with a spare diff. The rest is pretty easy and normal backlash setup.

My old Sport Trac had a clutch pack type LSD like this one, The clutch discs were good for about 100k miles. I think I changed the fluid in the diff once at around 50k. Might have lasted a bit more if I was more diligent. The LSD along with 4wd made that vehicle unstoppable in the snow. I've not had any experience with the other locker or quaife style LSDs, but I liked how the clutch type LSD behaved for street use.

The nice thing about the clutch discs is that when they eventually do wear out you are not immediately obligated to rebuild the LSD. You can just continue on without the LSD action.

I also think the LSD would reduce the loadings on the CV axles by distributing torque more evenly between the two axles, but I'm just conjecturing this.

In any case, if I could get a hold of a spare Scorpio diff on the cheap, I would jump on this project in a heartbeat. $190 for the LSD is very reasonable.
Sorry for my confusion...Are you saying that rather than using the "spacer", you would cut the flange of the diff that same thickness to avoid using the space? By same thickness, I mean subtract the spacer amount from the diff flange. Maybe that doesn't make sense.
Also, do you want a spare stock diff, or housing?
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Re: LSD option

Post by my8950 »

So, I did locate another option for a LSD that should be more bolt in friendly.
It uses the stock CV’s, and all associated items.
Cost is $1295…

https://3jdrivelineamerica.com/product/ ... l-nxg-lsd/
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Re: LSD option

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my8950 wrote: Mon Mar 13, 2023 10:46 am Sorry for my confusion...Are you saying that rather than using the "spacer", you would cut the flange of the diff that same thickness to avoid using the space? By same thickness, I mean subtract the spacer amount from the diff flange. Maybe that doesn't make sense.
Also, do you want a spare stock diff, or housing?
Spacer is not the issue. I was speaking of the need to elongate the holes 0.030" that bolt to the ring gear. I would do this on my lathe with a die grinder setup on the cross slide. I would jig it so I could elongate each hole an even amount. Not turning anything on the lathe, just using the chuck to hold the LSD housing and index each of the holes precisely.

So you go around to each hole and grind a few thou off. Stop, test fit ring gear, if no fit then go around again and grind a little more off each hole. Repeat until ring gear bolts on. Then check total runout with dial indicator to make sure all is well.

I want a spare stock Scorpio diff to do this on, then I would just swap the LSD modified diff into the car. If all goes well I can then hand off my old diff to the next guy who wishes to attempt this.
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Re: LSD option

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brokencase wrote: Mon Mar 13, 2023 10:31 pm
my8950 wrote: Mon Mar 13, 2023 10:46 am Sorry for my confusion...Are you saying that rather than using the "spacer", you would cut the flange of the diff that same thickness to avoid using the space? By same thickness, I mean subtract the spacer amount from the diff flange. Maybe that doesn't make sense.
Also, do you want a spare stock diff, or housing?
Spacer is not the issue. I was speaking of the need to elongate the holes 0.030" that bolt to the ring gear. I would do this on my lathe with a die grinder setup on the cross slide. I would jig it so I could elongate each hole an even amount. Not turning anything on the lathe, just using the chuck to hold the LSD housing and index each of the holes precisely.

So you go around to each hole and grind a few thou off. Stop, test fit ring gear, if no fit then go around again and grind a little more off each hole. Repeat until ring gear bolts on. Then check total runout with dial indicator to make sure all is well.

I want a spare stock Scorpio diff to do this on, then I would just swap the LSD modified diff into the car. If all goes well I can then hand off my old diff to the next guy who wishes to attempt this.
Ok, I got it now...I was getting lost with the lathe section. I have a Scorpio and XR setup, I'll compare to see if I can find any differences.
Are you going to Carlisle again this year?
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Re: LSD option

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Not sure I can make it. I made it in 2020 but now I am on a hiatus and caregiving for my 96 year old father. He does not want to go into assisted living. Mentally he is 100% but he has pulmonary fibrosis so he is on oxygen and is prone to falling. Normally I could count on my elder brother to cover for me but he is getting his knees replaced and will be in physical therapy until July. I might be able to get a neighbor to cover for me to make a short cameo appearance for a few hours.

I'm just above Philadelphia, so it only takes me about 1.75 hours to make the drive out there. I'll see if I can make arrangements and will send you a PM.

I see that I have to buy these to do this job...if I'm tearing a diff down...I'm putting in new seals.
https://www.ebay.com/itm/171290404880

The pinion seal is available domestically, do you know of anyone who sells the side seals domestically?

$70 for a set of seals from UK.. Half of it is shipping. We need to make a new trade agreement between ourselves and Europe.

I can buy an item from temu.com (from China) for $10 and it is free shipping. It gets here in about a week to ten days.

Something tells me the problem is not on our end but on the EU end. But if we and our European Allies are to compete with China then there must be free trade between ourselves first and foremost. Elect me for POTUS and I'll make it happen. I will re-vitalize our Atlantic facing ports.

Yeah I know...getting off the soapbox...

Anyhow definitely in the mode for this. I recently re-did the seals and bearings in my late brother's Triumph GT6 diff. (which is also ISR diff btw)
Of course installation was much easier as the body is off the frame.

Naturally if any others are interested in this I am happy to grind a few LSD diffs once I have established the method on my lathe. Maybe work out an exchange... As far as I know this issue is the same for XR4ti and Scorpio as they both have the 7.5"

I think I could machine the spacer and oblong the holes for around $100. The end user being responsible for the final fitting. Instructions provided.
otherwise, If they are incapable, suitable instructions for their local diff rebuilder?
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Re: LSD option

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One thing I am wondering about adapting the GM Eaton LSD is the fitting of the ring gear to the unit. The grinding of the holes we have discussed and I am OK with that.

As seen in the instructions below on the original diff the ring gear is interference fit on the inside edge of the carrier.
To me, this seems essential to maintaining concentricity of the ring gear. Those instructions I posted from the IMON list earlier do not discuss this. It seems the original poster is relying only on the bolts to maintain concentricity.

It would seem to me that it would be highly unlikely that these two diameters would be the same due to the difference in applications between the two.

If the diameters of the inside of the Scorpio Ring gear vs. the Eaton Diff are different then one should machine a thin ring to take up any difference between the two. If you do this then the criticality of elongating the 10 holes precisely/evenly becomes less of an issue.

I've marked in red the the surfaces I am referring to...what are the diameters of the scorpio ring gear vs. the eaton diff?
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Re: LSD option

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The Eaton style LSD on ebay ($190) comes with new carrier bearings. Looking at rockauto for Camaro and Scorpio applications indicates that the bearings are the same for both applications which is good news in light of the fact that the IMON poster indicated he had destroyed a bearing while removing it.
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Re: LSD option

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brokencase wrote: Wed Mar 15, 2023 2:16 pm The Eaton style LSD on ebay ($190) comes with new carrier bearings. Looking at rockauto for Camaro and Scorpio applications indicates that the bearings are the same for both applications which is good news in light of the fact that the IMON poster indicated he had destroyed a bearing while removing it.
Interesting and helpful that the bearings should be the same.
Since I took apart one of the carriers that I have last weekend, I can try to remove the ring gear and measure.
However, that isnt going to tell us the diameter of the part on the actual center section.
I'm wondering if there is a way to find a drawing on that part from a GM vehicle, even if it isn't posi, just a 7.5" center section should have the same size...???

You could even ask the sale on ebay is my guess...Maybe they can measure it? even fron China, mm's are mm's...
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Re: LSD option

Post by DPDISXR4Ti »

Good job digging up that 25+ year-old thread from JChristou@aol.com. I think he was the first one to "discover" the possibility of using the GM 7.5 in our differentials. I recall he used the Auburn initially and then later upgraded to the Quaiffe.

The thing I also recall is that his approach seemed more involved than what Grayson did using the Eaton 7.5. I don't recall that the Eaton needed the spacer or elongating the mounting holes. I never did this swap myself, so just spouting off memories which may or may not be correct.
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Re: LSD option

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DPDISXR4Ti wrote: Thu Mar 16, 2023 11:01 am The thing I also recall is that his approach seemed more involved than what Grayson did using the Eaton 7.5. I don't recall that the Eaton needed the spacer or elongating the mounting holes. I never did this swap myself, so just spouting off memories which may or may not be correct.
I do see mention of ring gear spacer, but not elongated holes.
Something else that I just had pop in to my mind, there are two GM diff's, one is for 3.08 and lower ratios, another is for 3.23 and higher.
Possibly that is the reason the holes would need to be elongated, because this guy used the 3.08 and lower ratio diff? Just a thought...
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Re: LSD option

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They make a spacer for the ring gear for the GM 7.5" differential.
Here...
https://www.speedwaymotors.com/7-1-2-In ... ,7534.html

It states the inside diameter of the spacer is 4.640" Only dimension I could find, wild shot in the dark
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Re: LSD option

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my8950 wrote: Thu Mar 16, 2023 11:15 am I do see mention of ring gear spacer, but not elongated holes.
Something else that I just had pop in to my mind, there are two GM diff's, one is for 3.08 and lower ratios, another is for 3.23 and higher.
Possibly that is the reason the holes would need to be elongated, because this guy used the 3.08 and lower ratio diff? Just a thought...
I don't believe so since he indicated that he had to elongate the holes "inward". I do see the distinction between 3.08 and lower at rockauto but nowhere does anyone offer an LSD for the 3.08 and lower diffs.

Pretty sure the Auburn unit (an all the others) was for 3.08 and higher.
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