How to piece together a ZL1 differential swap - lessons learned from the battle

[dentnshell]

With an auto you will need something from DSS for from the the ZL1 HD kit
22960156

the Tranmsision lengths are different.. You can not use a ZL1 Manual or Auto driveshaft. GM made the 22960156 for just such an application... It is a 2 piece just like stock. Of course you will then also need a new transmission flange.

Just follow the first post.. everything is listed there.

[hammdo]

Sorry guys for the late reply. The tool I had (black) was for the SS/Z28 diff axle seals. The blue version is for the pinion seal on the SS/Z28 diff...

-Don

[dreksnot]

Driveshaft is dependent on your tranny, not the diff. The diff is the same both the manual and auto (it's just different gears, 3.23 or 3.73).

So, you'll be needing the auto (length) OEM driveshaft, or go with the 1pc DSS.

[kyrebel]

I'm putting a ZL1 manual 3:73 cradle in my automatic SS and can buy a ZL1 automatic driveshaft fairly cheap.will the length work with the SS 6L80? I have heard that the ZL1 6L90 is longer.i know I will need the ZL1 flange for the tranny.Also on the fence about using the 3:73 with the Procharger 625 RWHP vs the 3:23.Any opinions?

[dentnshell]

Originally Posted by kyrebel

I'm putting a ZL1 manual 3:73 cradle in my automatic SS and can buy a ZL1 automatic driveshaft fairly cheap.will the length work with the SS 6L80? I have heard that the ZL1 6L90 is longer.i know I will need the ZL1 flange for the tranny.Also on the fence about using the 3:73 with the Procharger 625 RWHP vs the 3:23.Any opinions?

You will need a custom driveshaft or the ZL1 HD upgrade shaft - part number is in the instructions. the ZL1 auto does have a longer transmission. GM made a special driveshaft just for this upgrade.
The 3.73 and 3.23 are the same differential just different internal gears.

The 3.73 may work with the procharger as it builds boost more like a turbo. There is no way I would do it with the SC. I have no personal experience with the procharger. I would personally choose the 3:23 if I had the choice.

[kyrebel]

thanks dentnshell.i got a deal too good to pass up with the 3:73 complete cradle and may end up trying to trade it out for one with a 3:23 or just put a 3:23 r&p in it or hell I may even try it just didn't want to do it twice.what gear you running in yours?is yours A6 or manual?

[dentnshell]

Auto. The best part of the upgrade has been the much tighter clutch pack. The car hooks so much better with little to no wheel hop. The swap is not bad at all. I highly recommend solid subframe bushings while you are doing the swap.

[Infern0]

Originally Posted by dentnshell

This would have been awesome two weeks ago! I just completed my swap this past weekend.

I will add that I went ahead and purchased
Two differential Rear Axle seals... Might as well do it just in case. P/N 20964013

Prob a dumb question, but looking this up in gmpartsdirect it mentions this as seals (plural). Does anyone know if this means if qty 1 comes as a pair?

[dentnshell]

From a guy who has now purchased three - screwed up one, because I did not use the tool. One seal per package.

[-Im.z2ight-]

Sorry for the new guy question but whats the bonus of going zl1 diff?

[dentnshell]

Originally Posted by -Im.z2ight-

Sorry for the new guy question but whats the bonus of going zl1 diff?

Unless you have the power to destroy a standard diff or axles... Not much except extra weight.

The ZL1 differential is about 70lbs heavier. It is cast iron and has a much larger ring gear. The axles are larger in diameter and are designed to reduce wheel hop. The Zl1 diff has a much tighter clutch pack. So for me a trutrac or posimod wasn't needed. Also the extra weight is in a great location to help me hook up. The ZL1 has a built in oil cooler if you choose to use it. The stock ZL1 pumps transmission fluid through the differential cooler to help keep it cool for track use (fluids don't mix)

In short it is bigger, heavier, and stronger. If you need stronger then you need it or a similar solution. If you don't need stronger, then it is not for you.

[Infern0]

Originally Posted by dentnshell

Unless you have the power to destroy a standard diff or axles... Not much except extra weight.

The ZL1 differential is about 70lbs heavier. It is cast iron and has a much larger ring gear. The axles are larger in diameter and are designed to reduce wheel hop. The Zl1 diff has a much tighter clutch pack. So for me a trutrac or posimod wasn't needed. Also the extra weight is in a great location to help me hook up. The ZL1 has a built in oil cooler if you choose to use it. The stock ZL1 pumps transmission fluid through the differential cooler to help keep it cool for track use (fluids don't mix)

In short it is bigger, heavier, and stronger. If you need stronger then you need it or a similar solution. If you don't need stronger, then it is not for you.

Damn good answer lol.

Thanks for the answer on the seals too, Dentnshell lol! Ordering a third I know had to be frustrating. I got this to hopefully help with the occasion.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[dentnshell]

That driver might work, but due to the lip I am not sure I would use it. I found the correct one on eBay. 30 bucks. Pretty much idiot proof. I did one successfully using 1/4" socket extension and being ginger around the perimeter. The second seal I tapped one too many times and dented it. It is a tight fit. To change the seal is $45. Plus $60 in fluid. Taking out the axle. Which is pulling the brake caliper. Tie rod trailing rod and hub. After messing one up. I am am glad I had the correct tool for the replacement.
My dealer offered a loaner if I left my first born child. Might be worth a trip to check.

[-Im.z2ight-]

Going ago twin turbo at what point should I go Zl1 rear end?