V8 Roadsters Cadillac Getrag Differential. INSTALLED.
 

I've had this in my car for about a month now and have just been lazy and busy to post.

V8R kit
CTS 3.23 w/LSD

I'll post more details as the thread progresses. Overall I love it.

https://lh4.googleusercontent.com/-p...0119151632.jpg

V8 Roadsters link.

Getrag Differential Conversion - V8 Roadsters

Supposedly there are a few of these kits out there, but I haven't seen anyone say anything so I figured I'd just start this thread so if anyone had any questions, they could ask here.

I also have a 3" Artech exhaust sitting on the floor waiting to be installed. Did it need to be modified to fit?

Which ratio did you get and how do you like it? I assume it's paired with the MSM 6-speed?

Subframe braces waiting to be installed in that pic?

Thanks,
--Ferdi

As all of Abe's kits are 1 offs (or at least they used to be), I can't tell you for certain you'll be ok. But the CTS diff is known for being smallish and as you can see from the pic, my ARTech setup was really nicely routed.

Yes, paired with the stock MSM 6 speed and 3.23 ratio.

Subframe braces are now back on the car and fit without issue as well.

wow, thats a super clean installation. What ratios are available for it?

As from the V8R website.

We utilize the Getrag in our road course and street cars. When sourcing the Getrag look for the 2006-2008. The later models have casting and seal updates. G80 series limited slip
GM part numbers:
3:23 - 25978162
3:42 - 25873500
3:73 - 25873497
3:90 - 25968531

I think the most common with the LSD are the 3.23 and 3.73

I'd kill to have a 3.23 R&P. Just not desperate enough to spend that much money to do so. 3.63 is "good nuff'"

Ok, so this comes with the axles too? As in buy the kit, buy a getrag diff, and bolt it all in and go?! If so I'm sold!

They way I rationalized it to myself was this.

I spent $500 on a 3.63 R&P, but sat on it for a while because I don't have a local gear shop around here that I trust enough to pull my diff, put it back in and hope it works correct.

Also figure around $1000 for the labor to swap out the gears.

So I sold it, and ran my 4.10 for another year or so which isn't that cool w/260-270whp.

Then I found out V8R was going to start making the kit which was about $1700 for everything you need; diff mount, PPF adapter, drive shaft and axles w/abs. All I had to do was find a diff and they go for around $300 pretty regularly in ebay.

So around $2000 to pretty much just bolt everything together and I sold my stock parts for $1000.

So total out of pocket was $1000 plus my time.

I actually have my car on the lift trying to install this kit now.

Did you notice that the CVs were different in length? Mine appear to be the same length from spline to spline.

V8R has not produced instructions for this kit yet (ugh) but according to the differential section in FM's V8 conversion the driver side should be 1/2" shorter than the passenger.

Regardless of which CV I use I am finding that the driver side upright does not want to bolt back in easily. The CV seems to be fully compressed with the bottom bolt holes still about 1/4" away from aligning. When I push a bit and get it bolted up the hub does not rotate freely and it's clear that the CV is binding. The passenger side dropped right in and is not having issues when the driver side parts are uninstalled.

Charlie,

I actually didn't even read that bit about the sides being different length until I was reading around after I already finished the install. So I never measure them.

I just put it together and didn't have the same issue as you.

Pretty awesome stuff. Saw this on m-s.com. Nice to have an option down the road.

Mine is going in Sunday. I got a newer diff that has the extra ribbing and had to do some grinding on the diff case to get the ppf to clear.

I too had to grind ribbing off of the diff case, and I found that the PPF needed some additional cutting outside of the template. My diff was out of a 2006 CTS.

Edit: Here's a video of the issue I am currently having with my kit. It's a bit dark, but you can hear the CV become fully compressed and see how far in the upright still needs to go. I took the upright off of my car and measured it and it seems to be in spec. I also put the upright back into the car without the CV and found that it fit fine.

OK, I'm not the only one then. I ran into the same issue myself having one of the newer diffs.

For those curious, the diff used for this swap was used in the 2004-2007 CTS. The early one 04/05 is considered weaker and came with not as good seals from the factory. The 06/07 diff had revised webbing to make it stronger and newer design seals.

The strength issue I don't believe applies to us as our cars are 2000lbs lighter but I'm not sure about the seals. I think if you're buying used either the seals have probably been replaced, or you can change them out yourself.

Also this diff was used on other cars like the STS, SRX and maybe others with varying years. The hardest part of this swap was figuring out exactly which diff I was looking for. I even accidentally originally ordered a FRONT LSD from an AWD STS. Luckily the eBay seller fixed their mistake and paid for shipping back.

Charlie,

I couldn't tell for sure from your video, but are you sure you've tightened the axle nut down all the way? If's it's not, I can see that causing extra length that might be causing the binding.

I cleaned the splines out of my hubs really good with a wire brush and WD40, and then put a lot of antiseize in there during the reinstall of the half shafts and it was still super hard. I took the 1/2" impact to them and they took a lot of torque to get them to pull through the hubs all the way.

Shane,

Thanks for the reply. I tightened the axle nuts with my 3/4" ratchet and socket with the wheels on the ground. I may need to get the nuts tighter, but I did tighten them until they stopped. The hub is new on the driver side and the CV seemed to slip in smoothly.

I put the car back together making sure to use the (slightly) shorter CV on the driver side. I took a couple more pics, one with the car in the air and one with the weight on the wheels. I apologize as I am not the best photographer.

Looking at your picture, it appears that your driver side CV is a bit more pushed in than the passenger side, but it seems mine is pushed in even more so. See the bellows of the CV boot and how compressed they are on mine? I'm not positive but I think the CV is adding resistance to the drivetrain.

When you spin one of your rear wheels, what happens? Spinning one wheel on mine causes the other wheel to spin too (same direction) as well as the driveshaft. I'm conflicted as to whether the resistance in the drivetrain is from the clutch based LSD or if it's being caused by the CV.

Edit: Talked to Steve at V8R and he walked me through a few checks and the CV play is within spec. Will update with my experiences on Sunday once I get the car back together.

I'll take some pics today. I need to do a little more clearancing on the PPF and I'm thinking about making an extra brace for the front of the diff. My pinion still deflects up and down more than I'd like. I'd like to see others experience when more of these get into people's cars.

When I spin one of my wheels, the other wheels spins the same way as does the drive shaft. This is what I believe to be normal behavior for a clutch type LSD and it is what Corvettes have done since the 60s.

Any update? I took these on saturday.

Something else I thought of... Are you sure the axles are all the way into the diff?

What direction did you have the gap on the circlip when you installed the new axles? The gap is supposed to be UP.

https://www.miataturbo.net/attachmen...ine=1425338433
https://www.miataturbo.net/attachmen...ine=1425338433

You added a washer between the ppf and the v8r mount? I could barely get the mount between the ppf rails. Don't think I could get a washer in there. Did you clearance to make it fit?

I opened up the end of the PPF to allow just a little more space to slide it in. I didn't like how the adapter fits into the PPF. It's too small to sit flush and too big to actually slide into the hole. With the washer, at least it has a flat surface between the two instead of rolling around in the hole.

EDIT: I don't think it really matters. Mine still moved around a lot and I ended up making this.

https://lh3.googleusercontent.com/-s...0228151559.jpg