Thought I would do I write up on a differential brace I fabbed up to stop this problem...

Many are probably aware of the differentials on the C6's (especially 2005) being on the weak side when you start throwing power at them. I had already purchased an installed the ECS diff/trans brace. This brace helps prevent the diff from rotating upwards which is acting to split the diff from the trans. Unfortunately it does nothing to prove t the back end from blowing out due to the axial load of the pinion gear (acts against rear of the differential).

So, I decided to do a little fabricating of a diff brace of my own design that strengthens the rear of the differential. I started with measuring out the bolt spacing and diameter of the rear cover, location of the fill plug, and overall width between the side covers. I then drew up a simple design in CAD to upload to Send-Cut-Send. Below is the CAD design minus a few details I added later.

After getting back the main piece from Send-Cut-Send I fabbed up the two side arms and some additional tabs on the top to mount tie rods that go from the rear up to another bracket mounted to the transmission/diff junction.



Below is the additional piece that mounts at the transmission/diff junction.

And a couple photos of it mocked up with the tie rods before sending to the powder coaters.



There were two additional "brace" points that I added to the rear to assist the differential "ears" and prevent those from cracking. I used an old pair of C6 spring mount pads that I cut the old rubber off and mounted some rubber pucks to. These thread into the mount and brace against the subframe.

A couple other details - I did have to grind off the stamped flange from the diff cover to ensure the brace mounted flat against the cover. Additionally I had to get longer cover bolts for both the rear and side covers to account for the extra thickness.

I haven't driven the car yet as I'm finishing up the 418 LS3 with an LS7 top end. Just need to finish up the fuel system and I'll be back on the road. I'm expecting ~600whp, so this brace will give me some extra insurance to avoid some of the horror stories others have experienced with the '05 diffs. I'll report back after driving it for awhile.

 

Might save the case, but you still have the problem of the pinon gear on the long unsupported output shaft of the trans, that starts the problem with the shaft flex as gear is trying to climb up and over the ring gears, with too much torque in the first place.

Hence problem is, and always will be, that GM did not put a bearing mid point of the trans output shaft in the diff case, to combat the long shaft from flexing in the first place.


And on later diff cases, then did add more internal webbing to strength the cases, but did not solve the shaft defection from pinion to ring gear load in the first place.

 

You are correct that it's not a 100% perfect fix that will prevent any failures. If you throw enough power at anything it will eventually fail. And, you're right, the transmission shaft would benefit from a mid shaft bearing support. But, the transmission output shaft is still supported by a bearing with a carrier mounted to the rear of the case. As the pinion wants to climb there will be a bending moment that will put radial load into the bearing, which puts load into the case causing it to flex. If the shaft undergoes enough flex it will eventually fail, but a stronger case will aid in the support of the rear bearing and prevent the flexing of the shaft.

 

Do you wish to share your 3D file? I would like to order something similar from Send Cut Send, I was just about to take measurements to do this exact thing.

 

Sure thing, here is the link to the Onshape file. I ended up only using the main/large piece that goes on the back of the diff to have send-cut-send make. I made the two side pieces, the three top pieces, and the gussets/pad support holders from cardboard templates. Let me know if this link doesn't work for you.

https:/cad.onshape.com/documents/35880a3054e89e06a6d4db38/w/8e6c009c8f69803decf57286/e/fde4ab5840441c31eb3341ef?renderMode=0&ui State=69a1b2cc7cb43b0835ac7f48

 

You are the man, If you ever want to go rear mount turbo, I have a bracket I designed and ordered from Send Cut send. I am happy to share the file.